- Email: [email protected]
Resolving local dynamics of dual ions at the nanoscale in electrochemically active materials
Journal Pre-proof Resolving local dynamics of dual ions at the nanoscale in electrochemically active materials Junxi Yu, Boyuan Huang, Aolin Li, Shanshan Duan, Hongyun Jin, Ming Ma, Yun Ou, Shuhong Xie, Yunya Liu, Jiangyu Li PII:
S2211-2855(19)30867-5
DOI:
https://doi.org/10.1016/j.nanoen.2019.104160
Reference:
NANOEN 104160
To appear in:
Nano Energy
Received Date: 6 September 2019 Revised Date:
27 September 2019
Accepted Date: 30 September 2019
Please cite this article as: J. Yu, B. Huang, A. Li, S. Duan, H. Jin, M. Ma, Y. Ou, S. Xie, Y. Liu, J. Li, Resolving local dynamics of dual ions at the nanoscale in electrochemically active materials, Nano Energy (2019), doi: https://doi.org/10.1016/j.nanoen.2019.104160. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
Resolving local dynamics of dual ions at the nanoscale in electrochemically active materials Junxi Yua,b,1, Boyuan Huangb,c,1, Aolin Lia,1, Shanshan Duand, Hongyun Jind, Ming Mab, Yun Oue, Shuhong Xiea,*, Yunya Liua,*, and Jiangyu Lib,* a
Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education, and School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan, 411105, China. b Shenzhen Key Laboratory of Nanobiomechanics, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen Guangdong, 518055, China. c Department of Mechanical Engineering, University of Washington, Seattle, WA, 98195, USA. d Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan, 430074, China. e Hunan Provincial Key Laboratory of Health Maintenance for Mechanical Equipment, Hunan University of Science and Technology, Xiangtan, Hunan, 411201, China.
Abstract: Electrochemical conversion is typically studied at macroscopic scale, and it is quite challenging to probe local electrochemistry at the nanoscale, especially those involving multiple ions. Through a series of atomic force microscopy experiments, we demonstrate that two competing ionic strains arising from molar volume changes and electrochemical dipoles in a dual-ion system can reveal themselves in distinct relaxation behavior, enabling us to decouple their respective contributions and thus measure local diffusivity along with activation energy. Using soda-lime float glass as a model system, we observe a fast relaxation corresponding to diffusion of Na+ and a slow relaxation associated with electrochemical dipoles formed between Na+ and non-bridging oxygen. Assisted by simulations, we determine the local diffusivity of 5.64 × 10
m /s and activation energy of 0.55eV for Na+ at 100oC. The study provides a
powerful tool to resolve local dynamics of dual ions, which can be applied to study a variety of complex energy conversion and storage systems. Keywords: Dual-ion system, ionic dynamics, relaxation, electrochemistry, electrochemical strain microscopy
1 *
These authors contributed equally to this work To whom correspondence may be addressed. Email: [email protected], [email protected] and [email protected]
1
With the ever-increasing energy demand of the world, it is imperative to develop highly efficient energy conversion and storage systems to boost the deployment of renewable energy resources [1,2]. Dual-ion batteries (DIBs), with the demonstrated potential to meet the requirements of electric vehicles (EVs) and grid-scale energy storage station [3,4], have emerged as an exciting new electric energy storage solution thank to their high working voltage, long cycling life, low cost, and enhanced safety and sustainability [5–7]. While conventional singlecation batteries such as lithium-/sodium-ion batteries (LIBs/SIBs) rely on the intercalation of single ions in both cathode and anode to achieve electrochemical conversion [8], the salt in electrolytes of DIBs provides both cations and anions involved in the electrochemical process, making it possible for DIBs to operate at higher voltage that favors enhanced energy density [9]. Indeed, the appealing concept of DIBs has led to promising applications in lithium-ion batteries [10–12], sodium-ion batteries [13–15], calcium-ion batteries [16], as well as potassium-ion batteries [7,17] in recent years. Nevertheless, DIBs are significantly different from conventional LIBs and SIBs [8,18], and further development of DIBs requires a better understanding of their fundamental electrochemical process involving dual ions, especially at the nanoscale. Electrochemical conversion is typically studied at the macroscopic scale based on measurement of potential and current [19,20], and it is quite challenging to probe the local current down to the nanoscale [21,22]. In response to the emerging nanostructured electrode materials for LIBs and SIBs, electrochemical strain microscopy (ESM) has been developed, capable of mapping local ionic activities with nanometer resolution [23]. It has since been applied to study a wide range of electrode materials and solid electrolytes [23–28], including amorphous Si anode in an all-solid thin film LIB [23], selected layered LiCoO2 cathode [24], micro- and nano-crystallized LiFePO4 cathode [25], LiNi1/3Co1/3Mn1/3O2 cathode within an allsolid state thin film LIB [26], fresh and aged LiMn2O4 cathodes [27], as well as Li1.4Al0.4Ti1.6(PO4)3 solid-state electrolyte [28]. Nevertheless, ESM probing is currently limited to the single-ion systems, and the local electrochemical process involving multiple ions remains largely unexplored. In fact, the interplays between dual ions, especially their competing dynamics, make the local probing as well as its analysis and interpretation quite challenging, while the information is critical for a wide variety of electrochemically active systems ranging from halide perovskite solar cells [29–31] to ion-gated functional oxides [32]. We thus seek to
2
develop experimental techniques as well as analytical tools that are capable of resolving local dynamics of dual ions in electrochemically active systems. To this end, we notice that both cations and anions migrate under an electric field in a dual-ion system, inducing not only the Vegard strain arising from molar volume change [33,34] but also electrochemical dipoles that result in electrostriction [35,36]. In particular, when ion concentration changes, the volume of the solid expands or contracts in a similar way as thermal expansion or contraction, resulting in Vegard strain [33,34]. For a system with dual ions, opposite charges migrate under an applied electric field in opposite directions, resulting in the formation of electrochemical dipoles and the corresponding electrostrictive strain quadratic to the induced polarization [35,36]. These two processes are intimately coupled and closely related to the local dynamics of dual ions. As a result, if we can differentiate Vegard strain from electrostriction, especially their dynamic behavior, then it will be possible to decipher the local dynamics of dual ions at the nanoscale. Here we use soda-lime float glass as a model system to prove this concept. The system is electrochemically active, especially at elevated temperature, with relatively mobile Na+ and immobile O2- interacting with each other [37,38], providing us a clean model system for the study and analysis. Through a series of experiments, we demonstrate that these two competing electrochemical strains in dual-ion systems can indeed reveal themselves in distinct relaxation behavior under electric excitation applied via scanning probe, enabling us to decouple their respective contributions and thus measure local diffusivity as well as activation energy at the nanoscale in excellent agreement with macroscopic measurements. The study thus provides a powerful tool to resolve local dynamics of dual ions at the nanoscale in a wide variety of electrochemically active systems. RESULTS AND DISCUSSION Electrochemical strains We consider soda-lime float glass and fused silicate shown in Fig. 1 as our model systems [39]. Fused silicate contains bridging oxygen (BO) linking two neighboring tetrahedra of SiO4 (Fig. 1d), providing strong bonds between the smallest structural units of the network [38]. Soda-lime float glass, on the other hand, possesses negatively charged non-bridging oxygen (NBO2-) that provides a relatively weak connection to the network modifier cations such as Na+ (Fig. 1a), and thus the network is depolymerized [40]. Therefore, soda-lime float glass with 3
positive Na+ balanced by negative NBO2- can be regarded as a dual-ion system, wherein Na+ is much more mobile than NBO2- [37,38,41–43], while fused silicate is electrochemically inert [37] that serves as a control for the comparison.
Fig. . 1. Characteristics of local electrochemical strain of (a-c) soda-lime float glass and (d-f) fused silicate. (a, d) Schematic microstructure of soda-lime float glass and fused silicate. (b, e) Single-point first- and second-harmonic electrochemical strains versus excitation frequency. (c, f) First- and second-harmonic electrochemical strains versus excitation voltage, each averaged over 10 spatial points with error bars; note that there is no second-harmonic response observed in fused silicate. Our ESM experimental setup is schematically shown in Fig. S1a, wherein an alternatingcurrent (AC) voltage is applied to the sample via a conductive scanning probe microscopy (SPM) tip to induce fluctuation of local ionic concentrations, resulting in Vegard and/or electrostrictive strains that can be measured via photo-diode. Note that Vegard strain is linear to the electric field that can be measured through first harmonic response, while electrostriction due to electrochemical dipoles is quadratic that can be measured via second harmonic response [35,36], as schematically presented in the Fig. S1b and c, enabling us to decouple these two distinct yet closely related mechanisms. We first perform ESM measurements of soda-lime float glass and fused silicate at room temperature of 35oC. ESM amplitude of soda-lime float glass under a 10V
4
AC versus the excitation frequency at a representative point is shown in Fig. 1b, and it is observed that second harmonic response is higher than first harmonic one. This trend at a single point is confirmed by ESM amplitude versus excitation voltage averaged over 10 spatial points with negligible error bars (Fig. 1c), revealing consistently that the second harmonic quadratic response dominates the first harmonic linear one. When fused silicate is probed, on the other hand, no meaningful second harmonic amplitude is observed throughout the sample (Fig. 1e and f), and only first harmonic response is found to be present. The defining difference between these two types of samples is the presence of relatively mobile positive Na+ in soda-lime glass, and thus under AC voltage, both Vegard strain and local electrochemical dipoles will be induced under the probe [35,36], with second harmonic electrochemical dipoles dominating. There is no such electrochemical dipoles formed in fused silicate due to its lack of mobile ions, resulting in no measurable second harmonic ESM response. We thus investigate the dual ions in soda-lime glass in our subsequent studies, focusing on the dynamics of its electrochemical strains.
Fig. 2. Relaxation dynamics of local electrochemical strain in soda-lime float glass measured at 35oC. (a) Schematic DC profile for relaxation measurement. (b, d) ESM amplitude
5
and phase versus time corresponding to the DC profile. (c) Zoomed-in relaxation curves after removing negative and positive DC.
Relaxation dynamics The local electrochemical strain measured via ESM correlates with both concentration and diffusivity of respective ionic species [25], and thus we resort to relaxation study to resolve local ionic dynamics of soda-lime glass. Here a direct-current (DC) voltage is imposed on top of AC to induce longer range redistribution of Na+ ions underneath of the probe, as schematically shown in Fig. 2a. After the removal of the DC, Na+ relaxes back to its original equilibrium distribution, and the local dynamics can then be inferred from the time constant associated with the relaxation of ESM amplitude, as observed in Fig. 2b. Importantly, the DC applied induces electro-migration of Na+ over a longer range (in comparison to AC), and thus polarizes the sample over a larger scale. This induced apparent local polarization linearizes the quadratic dipolar electrostriction [44] that exhibits itself as first harmonic response in addition to Vegard strain, both of which relaxes back to the equilibrium after removal of DC. The second harmonic response, on the other hand, is not expected to exhibit relaxation, as detailed in Note S1 and confirmed by our experiment. Furthermore, no relaxation is observed in fused silicate (Fig. S2), consistent with its lack of ionic mobility. Two important observations can be made on the relaxation behavior in Fig. 2b. First of all, ESM amplitude increases under both negative and positive DC, with the increment more prominent under the negative DC, and after removal of either negative or positive DC, the ESM amplitude drops and relaxes back to the equilibrium. This observation again suggests that the local electrochemical strain measured by ESM arises largely from electrochemical dipoles instead of Vegard strain, since Vegard strain exhibits opposite variation under different DC polarities. In particular, negative (positive) DC increases (decreases) the concentration of Na+ under the probe, resulting in increased (decreased) Vegard strain and thus the corresponding ESM amplitude increases (decreases) [25,45]. Electrochemical dipoles, on the other hand, are induced by both negative and positive DC, and the difference lies only in the polarity of the ESM phase instead of its amplitude [39]. Indeed, the phases of ESM response under negative and positive DC are opposite to each other, as seen in Fig. 2d, wherein the phase under negative DC 6
is the same as that in equilibrium in the absence of DC, while the phase under positive DC jumps by 201o, close to the complete phase reversal of 180o. The data thus confirms the dominant dipolar nature of the local electrochemical strain. More interestingly, we notice that after removal of negative DC, the ESM amplitude decreases monotonically, while upon removal of positive DC, the amplitude decreases initially, and then bounces back, as exhibited by the portion shaded by green color in Fig. 2b. This difference can be seen more clearly from relaxation curves zoomed in Fig. 2c, wherein the reversal of ESM amplitude after initial decrease is highlighted upon removal of positively DC. Associated with this amplitude reversal, the corresponding phase is reversed as well (Fig. 2d), dropping by 196o and thus recovers the original phase at equilibrium. These observations are new and have not been reported in literature, to our best knowledge, and they are highly consistent and repeatable, as detailed in Fig. S3. Understanding the corresponding mechanisms may help us resolve local dynamics of dual ions that is otherwise very difficult to do. Local dynamics of dual ions The reversed trend in ESM amplitude after removal of positive DC as exhibited by Fig. 2b and c indicates that there are two distinct electrochemical strain mechanisms competing in soda-lime float glass, and the obvious candidates are electrochemical dipoles and Vegard strain. Both of them are induced by ionic migration, and thus intimately coupled, though Vegard strain is related to molar volume change associated with ionic redistribution, while electrochemical dipoles are due to charge separation, resulting in electrostriction. We can then rationalize different relaxation behavior under different DC polarities as follows. Under a negative DC, positive Na+ moves toward the SPM tip, increasing local ionic concentration and thus associated molar volume, and simultaneously polarizing the local region with upward electrochemical dipoles, as schematically shown in Fig. 3a. Both processes increase electrochemical strain and thus corresponding ESM amplitude, as experimentally observed in Fig. 2b, and upon removal of the DC, the amplitude drops monotonically and relaxes back to equilibrium. Importantly, the positive electrochemical dipoles decrease (increase) under a positive (negative) voltage during an AC excitation cycle, similar to Vegard strain that contracts (expands) under a positive (negative) voltage, and thus these two strains are in phase with each other. Under a positive DC, on the other hand, positive Na+ moves away from the tip, decreasing local ionic concentration and thus 7
associated ESM amplitude, while simultaneously polarizing the local region with downward electrochemical dipoles, as schematically shown in Fig. 3c. These two processes have opposite effects on the ESM amplitude, and because electrochemical dipoles dominate, the overall effect is enhanced ESM amplitude, although to a less extent in comparison to that under a negative DC, as experimentally observed in Fig. 2b. Upon removal of the positive DC during relaxation, electrochemical dipoles decrease while ionic concentration increases under the SPM tip, resulting in crossover as observed after the initial drop in ESM amplitude. Note that the negative electrochemical dipoles increase under a positive voltage during AC excitation, opposite to Vegard strain that contracts under a positive excitation, and thus their phases are reversed, as observed in Fig. 2d. The relaxation behaviors observed thus clearly reveal two distinct ionic strain mechanisms, enabling us to resolve local dynamics of dual ions. To this end, we model the observed relaxation behavior using exponential functions with two distinct time constants τ1 and τ2 corresponding to these two competing processes, 0,
=
−
+
−
+
,
(1)
which fits relaxation curves well under both negative and positive DC. For negative DC shown in Fig. 3b, the relaxation can be decomposed according to Eq. (1) into a faster process (blue curve) with time constant of τ1=0.200s and a slower process (red curve) with time constant of
τ2=1.243s. For positive DC shown in Fig. 3d, the relaxation is decomposed into a faster process (blue curve) with time constant of τ1=0.222s and a slower process (red curve) with time constant of τ2=1.271s. The time constants under different DC polarities for both faster and slower relaxations match each other well, validating the proposed competing mechanisms that take place under both negative and positive DC. The faster relaxation corresponds to Vegard strain that is directly related to the ionic concentration of Na+, while slower relaxation is due to induced electrochemical dipoles resulted from readjustment of negative NBO2- in response to redistributed Na+, which takes longer time though over much shorter distance. Importantly, for relaxation curve after either negative or positive DC, the overall ESM amplitude is largely contributed by the slower relaxation process, i.e. electrochemical dipoles, as evident by Fig. 3b and d, fully consistent with the observation that second harmonic response dominates first harmonic one in Fig. 1. The decomposition thus makes it possible for us to determine the local diffusivity of faster ion.
8
Fig. 3. Local dynamics of dual ions in soda-lime float glass. (a, c) Schematics of microscopic mechanisms associated with electrochemical dipoles and Vegard strain induced by negative and positive DC biases. (b, d) Relaxation curves after removing negative and positive DC (black, left axis), and their decompositions into faster and slower relaxation processes (blue and red, right axis). Local diffusivity The relaxation time constant is closely related to the diffusion of Na+ back to equilibrium distribution upon removal of DC, and in order to determine the local diffusivity from relaxation curves, we resort to numerical simulation for comparison and calibration with experiment, as detailed in the Note S2. A probe with an applied voltage ! is in contact with soda-lime float glass, resulting in a localized electric potential distribution shown in Fig. 4a, which is highly concentrated underneath the SPM tip. Dirven by this electric field, Na+ migrates away from the tip, governed by [46–48] "# "
=$⋅&
'#
#/#()*
+
+,
-.
12
/$ / − /0 + -. /$! ,
(2)
wherein D, c, cmax and cs are diffusion coefficient, ion concentration, maximum ion concentration and baseline ionic concentration, As, z, and ϕ are coefficient regulating equilibrium concentration, charge of ions and electric potential, and R, F and T are ideal gas constant, Faraday’s constant
9
and absolute temperature, respectively. This results in ionic distribution shown in Fig. 4b under 1V, wherein the concentration of Na+ is reduced under the SPM tip. Upon removal of DC, Na+ diffuses back to its equilibrium distribution, and the variation of Na+ concentration right underneath the tip with respect to time is simulated. With appropriate choice of diffusivity & = 5.64 × 10
m /s at 100oC as reported in literature for
Na2O·Al2O3·2SiO2 glass [43], we observe excellent agreements between computed relaxation curves and measured faster relaxation process after both negative and positive DC, as shown in Fig. 4c and d. We thus conclude with confidence that the local diffusivity of Na+ measured by ESM is 5.64 × 10
m /s at 100oC, consistent with macroscopic measurement. Since Vegard
strain of NBO2- does not contribute to the observed relaxation, it is also determined that its diffusivity can be neglected at 100oC.
Fig. 4. Local diffusivity of Na+ at 100oC. (a, b) Simulated 2D mappings of electric potential and Na+ under a tip bias of 1V. (c, d) Faster relaxation curves measured after negative and positive DC, in comparison to simulated relaxation of Na+ concentration.
10
Fig. 5. Local activation energy of Na+ in soda-lime float glass. (a, b) Relaxation curves after application of negative and positive DC bias of 40V at different temperatures. (c) Time constants of faster and slower relaxations versus temperatures, after negative and positive DC biases. (d) Arrhenius plot of the diffusion coefficient versus the inverse of temperature, yielding corresponding activation energy. Activation energy The accurate measurement of local diffusivity of Na+ at 100oC also makes it possible to determine its local activation energy, and thus we measure relaxations of soda-lime float glass from 35℃ to 100℃. Typical relaxation curves after negative and positive DC are shown in Fig. 5a and b, which are in good qualitative agreement with relaxation behavior observed at room temperature, with more data presented in Fig. S4. It is noted that the relaxation accelerates with increased temperature, indicating higher diffusivity, and the crossover after removal of positive DC occurs earlier and becomes more prominent (Fig. 5b). These curves are then fitted by Eq. (1), and the corresponding time constants for faster and slower relaxations are plotted versus 11
temperature in Fig. 5c. Note that time constants decrease with temperature as expected, and their values after negative and positive DC are highly consistent with each other at each temperature for both faster and slower processes, validating the proposed mechanism. More interestingly, we plot the Log of diffusivity with respect to the inverse of temperature in the form of Arrheniustype plot [45,49] in Fig. 5d, which is fitted very well by the linear curves, yielding local activation energy 34 of ~0.55 eV and ~0.58 eV for faster and slower relaxation, respectively, which is good agreement with the macroscopic value of 0.63 eV for Na+ reported in literature [43]. Importantly, the faster and slower ionic activation exhibits very similar activation energy, indicating that the biased tip activates Na+ first, and then electrochemical dipoles forms after slight adjustment of short-range NBO2- distribution. Discussion Electrochemical strain microscopy (ESM) was originally developed to probe local lithium ion activities in batteries [23], bridging an important gap between macroscopic electrochemical measurement and nanostructured electrodes. Many electrochemical systems, however, involves multiple ions, substantially complicating the experimentation and analysis. While our study was motivated by DIBs, its potential applications are not limited to them. Indeed competing ionic dynamics not only occurs in DIBs for energy storage, but also in resistive switching for data storage [50–52], in halide perovskite solar cells wherein ionic defects are prevalent [53], and in emerging functional oxides such as HSrCoO2.5 wherein H+ and O2- are utilized to tune its structure and properties [32]. The abilities to resolving local dynamics of dual ions in these diverse functional materials and systems for energy conversion, storage, and information processing, especially in a quantitative manner, are invaluable to understanding their microscopic mechanisms. Vegard strain is inevitable in battery electrodes during charging and discharging, which is usually undesirable and impacts battery cycling performances and reliability. In dual-ion systems, the effects of electrochemical dipoles also cannot be ignored. What we demonstrate here, however, is that with careful experiment and analysis, we can take advantage of information rendered by Vegard strain and electrochemical dipoles, enabling us to resolve local ionic dynamics at the nanoscale by ESM, which is otherwise very difficult to do. First and second harmonic measurements give clear indication on which mechanism is more dominant, while 12
relaxations after negative and positive DC make it possible to decompose their respective contributions in a quantitative manner. In combination with numerical simulation, the local diffusivity and activation energy can then be precisely determined. While we demonstrate this concept in a clean model system where the two ionic processes have quite different time scales, we believe the method can be applied to study a wide range of energy materials and systems involving multiple ions, even when their respective time scales are not much separated. We are currently studying halide perovskite solar cells, wherein the dynamics are much more complicated, though the essential trend still holds, and soda-lime glass gives us a clean benchmark to guide their study and analysis. METHODS Materials The soda-lime float glass and fused silicate glass investigated were obtained from Edmund Co., and the samples were cleaned before experiments using the following protocol: 10 min of sonication in acetone followed by water rinsing, 10 min sonication in ethanol followed by water rinsing, and a final 10 min sonication in distilled water. After the final sonication step, the glasses were dried with compressed clean nitrogen gas. Electrochemical strain microscopy The first and second harmonic point-wise measurements were conducted on an Asylum Research MFP-3D-Bio atomic force microscope and carried out in air. Relaxation studies and variable ESM studies were performed on an Asylum Research Cypher ES atomic force microscope under nitrogen flow. We used conductive cantilevers (FMG01/Pt, ~60 kHz and ~3 N/m) for all measurements. Each cantilever was calibrated by the thermal fluctuation method. The glass samples were placed on a built-in heating stage provided by Asylum Research to measure the temperature dependence of ESM response. Variable temperature ESM measurements were conducted at least 20 min after changing the temperature in order to ensure the temperature stability during the measurements. Simulation The ions diffusion equation (2) was deduced from thermodynamics theoretical (see Note S2). The tip-induced electric filed has been estimated using image charge model [54]. The 13
computation was two-dimensional (2D), and its numerical simulation was implemented by custom written MATLAB code. The boundary conditions of the ionic diffusion equation are periodic boundary along x direction and there is no ionic flux along y direction boundaries. The finite difference method and fast Fourier transform are used to solve diffusion equation. The simulation size is 100 nm × 100 nm with 128 × 128 mesh. ACKNOWLEDGEMENTS We acknowledge National Key Research and Development Program of China (2016YFA0201001), National Natural Science Foundation of China (11627801, 51772254, and 11772286),
Shenzhen
Science
and
Technology
Innovation
Committee
(KQTD20170810160424889, JCYJ20170818155200084, and JCYJ20170818155813437), Key Area R&D Program of Guangdong Province(2018B010109009), the Instrument Developing Project of Chinese Academy of Sciences (No. ZDKYYQ20180004), and Huxiang Young Talents Plan Project of Hunan Province (2019RS2037). REFERENCES [1]
J.B. Goodenough, Evolution of strategies for modern rechargeable batteries, Acc. Chem. Res. 46 (2013) 1053–1061.
[2]
J.B. Goodenough, K.S. Park, The Li-ion rechargeable battery: A perspective, J. Am. Chem. Soc. 135 (2013) 1167–1176.
[3]
J.-M. Tarascon, M. Armand, Issues and challenges facing rechargeable lithium batteries, Nature 414 (2001) 359–367.
[4]
M. Armand, J.-M. Tarascon, Building better batteries, Nature 451 (2008) 652–657.
[5]
M.L. Aubrey, R. Long, A dual-ion battery cathode via oxidative insertion of anions in a metal-organic framework, J. Am. Chem. Soc. 137 (2015) 13594–13602.
[6]
B. Ji, F. Zhang, X. Song, Y. Tang, A novel potassium-ion-based dual-ion battery, Adv. Mater. 29 (2017) 1700519.
14
[7]
K. V Kravchyk, P. Bhauriyal, L. Piveteau, C.P. Guntlin, B. Pathak, M. V Kovalenko, High-energy-density dual-ion battery for stationary storage of electricity using concentrated potassium fluorosulfonylimide, Nat. Commun. 9 (2018) 4469.
[8]
M. Li, J. Lu, Z. Chen, K. Amine, 30 years of lithium-ion batteries, Adv. Mater. 30 (2018) 1800561.
[9]
M. Wang, Y. Tang, A review on the features and progress of dual-ion batteries, Adv. Energy Mater. 8 (2018) 1703320.
[10]
W. Li, Q. Ning, X. Xi, B. Hou, J. Guo, Y. Yang, B. Chen, X. Wu, Highly improved cycling stability of anion de-&intercalation in the graphite cathode for dual ion batteries, Adv. Mater. 31 (2018) 1804766.
[11]
C. Jiang, Y. Fang, J. Lang, Y. Tang, Integrated configuration design for ultrafast rechargeable dual-ion battery, Adv. Energy Mater. 7 (2017) 1700913.
[12]
G. Chen, F. Zhang, Z. Zhou, J. Li, Y. Tang, A flexible dual-ion battery based on PVDFHFP-modified gel polymer electrolyte with excellent cycling performance and superior rate capability, Adv. Energy Mater. 8 (2018) 1801219.
[13]
M. Sheng, F. Zhang, B. Ji, X. Tong, Y. Tang, A novel tin-graphite dual-ion battery based on sodium-ion electrolyte with high energy density, Adv. Energy Mater. 7 (2017) 1601963.
[14]
G. Zhang, X. Ou, C. Cui, J. Ma, J. Yang, Y. Tang, High-performance cathode based on self-templated 3D porous microcrystalline carbon with improved anion adsorption and intercalation, Adv. Funct. Mater. 29 (2019) 1806722.
[15]
L. Fan, Q. Liu, S. Chen, Z. Xu, B. Lu, Soft carbon as anode for high-performance sodiumbased dual ion full battery, Adv. Energy Mater. 7 (2017) 1602778.
[16]
N. Wu, W. Yao, X. Song, G. Zhang, B. Chen, J. Yang, Y. Tang, A calcium-Ion hybrid energy storage device with high capacity and long cycling life under room temperature, Adv. Energy Mater. 9 (2019) 1803865.
15
[17] B. Ji, F. Zhang, N. Wu, Y. Tang, A dual-carbon battery based on potassium-ion electrolyte, Adv. Energy Mater. 7 (2017) 1700920. [18]
C. Delmas, Sodium and sodium-ion batteries: 50 years of research, Adv. Energy Mater. 8 (2018) 1703137.
[19]
M. Ma, K. Zhang, P. Li, M.S. Jung, M.J. Jeong, J.H. Park, Dual oxygen and tungsten vacancies on a WO3 photoanode for enhanced water oxidation, Angew. Chemie - Int. Ed. 55 (2016) 11819–11823.
[20]
M. Ma, B.J. Jin, P. Li, M.S. Jung, J. Il Kim, Y. Cho, S. Kim, J.H. Moon, J.H. Park, Ultrahigh electrocatalytic conversion of methane at room temperature, Adv. Sci. 4 (2017) 1700379.
[21]
A. Eshghinejad, E. Nasr Esfahani, P. Wang, S. Xie, T.C. Geary, S.B. Adler, J. Li, Scanning thermo-ionic microscopy for probing local electrochemistry at the nanoscale, J. Appl. Phys. 119 (2016) 205110.
[22]
A. Eshghinejad, Y. Ou, J. Zhao, S. Adler, E.N. Esfahani, Scanning thermo-ionic microscopy : Probing nanoscale electrochemistry via thermal stress-induced oscillation, Micros. Today 25 (2017) 12–19.
[23]
N. Balke, S. Jesse, Y. Kim, L. Adamczyk, A. Tselev, I.N. Ivanov, N.J. Dudney, S. V. Kalinin, Real space mapping of Li-ion transport in amorphous Si anodes with nanometer resolution, Nano Lett. 10 (2010) 3420–3425.
[24]
N. Balke, S. Jesse, A.N. Morozovska, E. Eliseev, D.W. Chung, Y. Kim, L. Adamczyk, R.E. García, N. Dudney, S. V. Kalinin, Nanoscale mapping of ion diffusion in a lithiumion battery cathode, Nat. Nanotechnol. 5 (2010) 749–754.
[25]
Q.N. Chen, Y. Liu, Y. Liu, S. Xie, G. Cao, J. Li, Delineating local electromigration for nanoscale probing of lithium ion intercalation and extraction by electrochemical strain microscopy, Appl. Phys. Lett. 101 (2012) 063901.
[26]
J. Zhu, L. Lu, K. Zeng, Nanoscale mapping of lithium-ion diffusion in a cathode within an all-solid-state lithium-ion battery by advanced scanning probe microscopy techniques, ACS Nano 7 (2013) 1666–1675. 16
[27]
S.Y. Luchkin, K. Romanyuk, M. Ivanov, A.L. Kholkin, Li transport in fresh and aged LiMn2O4 cathodes via electrochemical strain microscopy, J. Appl. Phys. 118 (2015) 072016.
[28]
S. Duan, H. Jin, J. Yu, E.N. Esfahani, B. Yang, J. Liu, Y. Ren, Y. Chen, L. Lu, X. Tian, S. Hou, J. Li, Non-equilibrium microstructure of Li1.4Al0.4Ti1.6(PO4)3 superionic conductor by spark plasma sintering for enhanced ionic conductivity, Nano Energy 51 (2018) 19–25.
[29]
J.B. Goodenough, Electronic and ionic transport properties and other physical aspects of perovskites, Reports Prog. Phys. 67 (2004) 1915–1993.
[30]
C. Eames, J.M. Frost, P.R.F. Barnes, B.C. O’Regan, A. Walsh, M.S. Islam, Ionic transport in hybrid lead iodide perovskite solar cells, Nat. Commun. 6 (2015) 7497.
[31]
B. Huang, G. Kong, E.N. Esfahani, S. Chen, Q. Li, J. Yu, N. Xu, Y. Zhang, S. Xie, Ferroic domains regulate photocurrent in single-crystalline CH3NH3PbI3 films self-grown on FTO/TiO2 substrate, Npj Quantum Mater. 3 (2018) 30.
[32]
N. Lu, P. Zhang, Q. Zhang, R. Qiao, Q. He, H.B. Li, Y. Wang, J. Guo, D. Zhang, Z. Duan, Z. Li, M. Wang, S. Yang, M. Yan, E. Arenholz, S. Zhou, W. Yang, L. Gu, C.W. Nan, J. Wu, Y. Tokura, P. Yu, Electric-field control of tri-state phase transformation with a selective dual-ion switch, Nature 546 (2017) 124–128.
[33]
Vegard L., Die Konstitution der Mischkristalle und die Raumfullung der Atome, J. Mater. Sci. 17 (1921) 17–26.
[34]
N.W. Dention, A.R., Ashcroft, Vegard’s law, Phys. Rev. A. 43 (1991) 3161–3164.
[35]
Q.N. Chen, Y. Ou, F. Ma, J. Li, Mechanisms of electromechanical coupling in strain based scanning probe microscopy, Appl. Phys. Lett. 104 (2014) 242907.
[36]
J. Yu, E.N. Esfahani, Q. Zhu, D. Shan, T. Jia, S. Xie, J. Li, Quadratic electromechanical strain in silicon investigated by scanning probe microscopy, J. Appl. Phys. 123 (2018) 155104.
[37] E.L. Williams, Diffusion of oxygen in fused silica, J. Am. Ceram. Soc. 48 (1965) 190–194.
17
[38]
M.A. Lamkin, F.L. Riley, R.J. Fordham, Oxygen mobility in silicon dioxide and silicate glasses: a review, J. Eur. Ceram. Soc. 10 (1992) 347–367.
[39]
R. Proksch, Electrochemical strain microscopy of silica glasses, J. Appl. Phys. 116 (2014) 66804.
[40]
K. Stefan, W. Lothar, A. Sharafat, J. Bo, Trends in effective diffusion coefficients for ionexchange strengthening of soda-lime-silicate glasses, Front. Mater. 4 (2017) 13.
[41]
R.J. Ryder, G.E. Rindone, Internal friction of simple alkali silicate glasses containing Al kaline-earth oxides: II, interpretation and discussion, J. Am. Ceram. Soc. 44 (1955) 532– 540.
[42]
F. V. Natrup, H. Bracht, S. Murugavel, B. Roling, Cation diffusion and ionic conductivity in soda-lime silicate glasses, Phys. Chem. Chem. Phys. 7 (2005) 2279–2286.
[43]
Z.G. Tyurnina, N.G. Tyurnina, S.I. Sviridov, Diffusion of sodium ions and electric conductivity in glassy and crystallized Na2O·Al2O3·2SiO2, Glas. Phys. Chem. 41 (2015) 579–581.
[44]
A. Gruverman, O. Auciello, H. Tokumoto, Imaging and control of domain structures in ferroelectric thin films via scanning force microscopy, Annu. Rev. Mater. Sci. 28 (2002) 101–123.
[45]
Q.N. Chen, S.B. Adler, J. Li, Imaging space charge regions in Sm-doped ceria using electrochemical strain microscopy, Appl. Phys. Lett. 105 (2014) 201602.
[46]
R.P. Buck, Kinetics of bulk and interfacial ionic motion : Microscopic bases and limits for the nernst-planck equation applied to membrane systems *, J. Menbrane Sci. 17 (1984) 1– 62.
[47]
E. Bohn, T. Eckl, M. Kamlah, R. McMeeking, A model for lithium diffusion and stress generation in an intercalation storage particle with phase change, J. Electrochem. Soc. 160 (2013) A1638–A1652.
18
[48]
S.Y. Luchkin, J. Schröder, D.C. Lupascu, H.N.M. Thai, A.L. Kholkin, M.-A. Keip, H.-Y. Amanieu, D. Rosato, Electrochemical strain microscopy time spectroscopy: Model and experiment on LiMn2O4, J. Appl. Phys. 118 (2015) 55101.
[49]
S. Yang, B. Yan, J. Wu, L. Lu, K. Zeng, Temperature-dependent lithium-ion diffusion and activation energy of Li1.2Co0.13Ni0.13Mn0.54O2 thin-film cathode at nanoscale by using electrochemical strain microscopy, ACS Appl. Mater. Interfaces 9 (2017) 13999–14005.
[50]
A.Q. Jiang, C. Wang, K.J. Jin, X.B. Liu, J.F. Scott, C.S. Hwang, T.A. Tang, H. Bin Lu, G.Z. Yang, A resistive memory in semiconducting BiFeO3 thin-film capacitors, Adv. Mater. 23 (2011) 1277–1281.
[51]
G. Zhong, F. An, Y. Bitla, J. Wang, X. Zhong, J. Yu, W. Gao, Y. Zhang, C. Tan, Y. Ou, J. Jiang, Y. Hsieh, X. Pan, S. Xie, Y. Chu, J. Li, Deterministic, reversible and nonvolatile low voltage writing of magnetic domains in epitaxial BaTiO3/Fe3O4 heterostructure, ACS Nano 12 (2018) 9558-9567.
[52]
T. Jia, Z. Fan, J. Yao, C. Liu, Y. Li, J. Yu, B. Fu, H. Zhao, M. Osada, E.N. Esfahani, Y. Wang, Y. Yang, Z. Cheng, J.-Y. Li, H. Kimura, Multifield control of domains in a roomtemperature multiferroic 0.85BiTi0.1Fe0.8Mg0.1O3–0.15CaTiO3 thin film, ACS Appl. Mater. Interfaces 10 (2018) 20712–20719.
[53]
J. Li, B. Huang, E.N. Esfahani, Touching is believing : interrogating halide perovskite solar cells at the nanoscale via scanning probe microscopy, Npj Quantum Mater. 2 (2017) 56.
[54]
W.J. Ming, R.K. Zhu, K. Pan, Y.Y. Liu, C.H. Lei, The effective point charge of probe tip in piezoresponse force microscopy, J. Appl. Phys. 124 (2018) 154106.
19
Junxi Yu is a Ph.D. candidate in Materials Science and Engineering at Xiangtan University. Her current research mainly focuses on characterization of energy storage materials based on advanced scanning probe microscopy.
Boyuan Huang received his bachelor’s degree in Nanjing University in 2016. He is a Ph.D. candidate under the supervision of Prof. Jiangyu Li at University of Washington. His research focuses on developing advanced characterization and data analysis methods based on scanning probe microscopy.
Aolin Li is a Ph.D. candidate in Materials Science and Engineering at Xiangtan University. His research mainly focuses on the mechanical-electro coupling in electrochemistry systems.
Shanshan Duan obtained her bachelor’s degree in Engineering from China University of Geosciences (Wuhan) in 2015. She is a Ph.D. candidate at China University of Geosciences (Wuhan). Her current research mainly focuses on lithium ion solid state electrolytes and solid state batteries.
20
Prof. Hongyun Jin obtained B.E. in 2000 and Ph.D. in 2009 from the Department of Materials Science and Engineering, China University of Geosciences (Wuhan). Afterward, he worked as a visiting scholar in University of Washington. His works on nano energy materials, 3D printing and thermal barrier coatings, and he has published over 50 papers in the field. He has got prize in Hubei science and technology in 2011 and 2015.
Ming Ma received his B.S. degree in 2010 from Shandong University (China) and Ph.D. degree in 2017 from Sungkyunkwan University (Korea). Now, he has joined Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, as an associate professor. His research focuses on the fabrication and application of nanomaterials, especially in the photoelectrochemical water splitting field.
Yun Ou recived his Ph.D. degree in Materials Science and Engineering from Xiangtan University in 2004. He joined in Hunan University of Science and Technology from 2014. Then he worked as Postdoctoral Fellow (2016-2018) at Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences. His research interest focuses on fabrication and characterizing low-dimensional materials and multifunctional materials.
21
Prof. Shuhong Xie obtained Ph.D in 2008 from the Faculty of Materials, Optoelectronics, and Physics, Xiangtan University. Afterward, she worked as a visiting scholar in University of Washington. Her works on nano energy materials and multiferroic nano materials, and she has published over 70 papers in the field.
Prof. Yunya Liu received his Ph.D. degree from Xiangtan University in 2010, and is currently a professor at School of Materials Science and Engineering of Xiangtan University. His research interest focuses on the mechanics of materials, scanning probe microscopy, and the correlations between microstructures and macroscopic behaviors of multifunctional and energy materials.
Prof. Jiangyu Li recently joins Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, where he directs Shenzhen Key Laboratory of Nanobiomechanics. Prior that, he was Professor in the Department of Mechanical Engineering, University of Washington. He obtained his B.E. degree in 1994 from the Department of Materials Science and Engineering, Tsinghua University, and Ph.D. degree in 1998 from the Department of Mechanical Engineering, University of Colorado-Boulder. Li works in the general field of mechanics of materials, focusing on advanced scanning probe microscopy and its applications in functional materials.
22
Highlights Local dynamics of competing ions in the electrochemically active dual-ion systems is resolved at the nanoscale Intriguing relaxation behavior of dual-ion systems after positive and negative biases are rationalized by the competing Vegard strain and electrochemical dipole Local diffusivity and activation energy are measured quantitative at the nanoscale, assisted by phase field simulation. The method can be applied to a wide range of energy materials and systems involving multiple ions.
S2211-2855(19)30867-5
DOI:
https://doi.org/10.1016/j.nanoen.2019.104160
Reference:
NANOEN 104160
To appear in:
Nano Energy
Received Date: 6 September 2019 Revised Date:
27 September 2019
Accepted Date: 30 September 2019
Please cite this article as: J. Yu, B. Huang, A. Li, S. Duan, H. Jin, M. Ma, Y. Ou, S. Xie, Y. Liu, J. Li, Resolving local dynamics of dual ions at the nanoscale in electrochemically active materials, Nano Energy (2019), doi: https://doi.org/10.1016/j.nanoen.2019.104160. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
Resolving local dynamics of dual ions at the nanoscale in electrochemically active materials Junxi Yua,b,1, Boyuan Huangb,c,1, Aolin Lia,1, Shanshan Duand, Hongyun Jind, Ming Mab, Yun Oue, Shuhong Xiea,*, Yunya Liua,*, and Jiangyu Lib,* a
Key Laboratory of Low Dimensional Materials and Application Technology of Ministry of Education, and School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan, 411105, China. b Shenzhen Key Laboratory of Nanobiomechanics, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen Guangdong, 518055, China. c Department of Mechanical Engineering, University of Washington, Seattle, WA, 98195, USA. d Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan, 430074, China. e Hunan Provincial Key Laboratory of Health Maintenance for Mechanical Equipment, Hunan University of Science and Technology, Xiangtan, Hunan, 411201, China.
Abstract: Electrochemical conversion is typically studied at macroscopic scale, and it is quite challenging to probe local electrochemistry at the nanoscale, especially those involving multiple ions. Through a series of atomic force microscopy experiments, we demonstrate that two competing ionic strains arising from molar volume changes and electrochemical dipoles in a dual-ion system can reveal themselves in distinct relaxation behavior, enabling us to decouple their respective contributions and thus measure local diffusivity along with activation energy. Using soda-lime float glass as a model system, we observe a fast relaxation corresponding to diffusion of Na+ and a slow relaxation associated with electrochemical dipoles formed between Na+ and non-bridging oxygen. Assisted by simulations, we determine the local diffusivity of 5.64 × 10
m /s and activation energy of 0.55eV for Na+ at 100oC. The study provides a
powerful tool to resolve local dynamics of dual ions, which can be applied to study a variety of complex energy conversion and storage systems. Keywords: Dual-ion system, ionic dynamics, relaxation, electrochemistry, electrochemical strain microscopy
1 *
These authors contributed equally to this work To whom correspondence may be addressed. Email: [email protected], [email protected] and [email protected]
1
With the ever-increasing energy demand of the world, it is imperative to develop highly efficient energy conversion and storage systems to boost the deployment of renewable energy resources [1,2]. Dual-ion batteries (DIBs), with the demonstrated potential to meet the requirements of electric vehicles (EVs) and grid-scale energy storage station [3,4], have emerged as an exciting new electric energy storage solution thank to their high working voltage, long cycling life, low cost, and enhanced safety and sustainability [5–7]. While conventional singlecation batteries such as lithium-/sodium-ion batteries (LIBs/SIBs) rely on the intercalation of single ions in both cathode and anode to achieve electrochemical conversion [8], the salt in electrolytes of DIBs provides both cations and anions involved in the electrochemical process, making it possible for DIBs to operate at higher voltage that favors enhanced energy density [9]. Indeed, the appealing concept of DIBs has led to promising applications in lithium-ion batteries [10–12], sodium-ion batteries [13–15], calcium-ion batteries [16], as well as potassium-ion batteries [7,17] in recent years. Nevertheless, DIBs are significantly different from conventional LIBs and SIBs [8,18], and further development of DIBs requires a better understanding of their fundamental electrochemical process involving dual ions, especially at the nanoscale. Electrochemical conversion is typically studied at the macroscopic scale based on measurement of potential and current [19,20], and it is quite challenging to probe the local current down to the nanoscale [21,22]. In response to the emerging nanostructured electrode materials for LIBs and SIBs, electrochemical strain microscopy (ESM) has been developed, capable of mapping local ionic activities with nanometer resolution [23]. It has since been applied to study a wide range of electrode materials and solid electrolytes [23–28], including amorphous Si anode in an all-solid thin film LIB [23], selected layered LiCoO2 cathode [24], micro- and nano-crystallized LiFePO4 cathode [25], LiNi1/3Co1/3Mn1/3O2 cathode within an allsolid state thin film LIB [26], fresh and aged LiMn2O4 cathodes [27], as well as Li1.4Al0.4Ti1.6(PO4)3 solid-state electrolyte [28]. Nevertheless, ESM probing is currently limited to the single-ion systems, and the local electrochemical process involving multiple ions remains largely unexplored. In fact, the interplays between dual ions, especially their competing dynamics, make the local probing as well as its analysis and interpretation quite challenging, while the information is critical for a wide variety of electrochemically active systems ranging from halide perovskite solar cells [29–31] to ion-gated functional oxides [32]. We thus seek to
2
develop experimental techniques as well as analytical tools that are capable of resolving local dynamics of dual ions in electrochemically active systems. To this end, we notice that both cations and anions migrate under an electric field in a dual-ion system, inducing not only the Vegard strain arising from molar volume change [33,34] but also electrochemical dipoles that result in electrostriction [35,36]. In particular, when ion concentration changes, the volume of the solid expands or contracts in a similar way as thermal expansion or contraction, resulting in Vegard strain [33,34]. For a system with dual ions, opposite charges migrate under an applied electric field in opposite directions, resulting in the formation of electrochemical dipoles and the corresponding electrostrictive strain quadratic to the induced polarization [35,36]. These two processes are intimately coupled and closely related to the local dynamics of dual ions. As a result, if we can differentiate Vegard strain from electrostriction, especially their dynamic behavior, then it will be possible to decipher the local dynamics of dual ions at the nanoscale. Here we use soda-lime float glass as a model system to prove this concept. The system is electrochemically active, especially at elevated temperature, with relatively mobile Na+ and immobile O2- interacting with each other [37,38], providing us a clean model system for the study and analysis. Through a series of experiments, we demonstrate that these two competing electrochemical strains in dual-ion systems can indeed reveal themselves in distinct relaxation behavior under electric excitation applied via scanning probe, enabling us to decouple their respective contributions and thus measure local diffusivity as well as activation energy at the nanoscale in excellent agreement with macroscopic measurements. The study thus provides a powerful tool to resolve local dynamics of dual ions at the nanoscale in a wide variety of electrochemically active systems. RESULTS AND DISCUSSION Electrochemical strains We consider soda-lime float glass and fused silicate shown in Fig. 1 as our model systems [39]. Fused silicate contains bridging oxygen (BO) linking two neighboring tetrahedra of SiO4 (Fig. 1d), providing strong bonds between the smallest structural units of the network [38]. Soda-lime float glass, on the other hand, possesses negatively charged non-bridging oxygen (NBO2-) that provides a relatively weak connection to the network modifier cations such as Na+ (Fig. 1a), and thus the network is depolymerized [40]. Therefore, soda-lime float glass with 3
positive Na+ balanced by negative NBO2- can be regarded as a dual-ion system, wherein Na+ is much more mobile than NBO2- [37,38,41–43], while fused silicate is electrochemically inert [37] that serves as a control for the comparison.
Fig. . 1. Characteristics of local electrochemical strain of (a-c) soda-lime float glass and (d-f) fused silicate. (a, d) Schematic microstructure of soda-lime float glass and fused silicate. (b, e) Single-point first- and second-harmonic electrochemical strains versus excitation frequency. (c, f) First- and second-harmonic electrochemical strains versus excitation voltage, each averaged over 10 spatial points with error bars; note that there is no second-harmonic response observed in fused silicate. Our ESM experimental setup is schematically shown in Fig. S1a, wherein an alternatingcurrent (AC) voltage is applied to the sample via a conductive scanning probe microscopy (SPM) tip to induce fluctuation of local ionic concentrations, resulting in Vegard and/or electrostrictive strains that can be measured via photo-diode. Note that Vegard strain is linear to the electric field that can be measured through first harmonic response, while electrostriction due to electrochemical dipoles is quadratic that can be measured via second harmonic response [35,36], as schematically presented in the Fig. S1b and c, enabling us to decouple these two distinct yet closely related mechanisms. We first perform ESM measurements of soda-lime float glass and fused silicate at room temperature of 35oC. ESM amplitude of soda-lime float glass under a 10V
4
AC versus the excitation frequency at a representative point is shown in Fig. 1b, and it is observed that second harmonic response is higher than first harmonic one. This trend at a single point is confirmed by ESM amplitude versus excitation voltage averaged over 10 spatial points with negligible error bars (Fig. 1c), revealing consistently that the second harmonic quadratic response dominates the first harmonic linear one. When fused silicate is probed, on the other hand, no meaningful second harmonic amplitude is observed throughout the sample (Fig. 1e and f), and only first harmonic response is found to be present. The defining difference between these two types of samples is the presence of relatively mobile positive Na+ in soda-lime glass, and thus under AC voltage, both Vegard strain and local electrochemical dipoles will be induced under the probe [35,36], with second harmonic electrochemical dipoles dominating. There is no such electrochemical dipoles formed in fused silicate due to its lack of mobile ions, resulting in no measurable second harmonic ESM response. We thus investigate the dual ions in soda-lime glass in our subsequent studies, focusing on the dynamics of its electrochemical strains.
Fig. 2. Relaxation dynamics of local electrochemical strain in soda-lime float glass measured at 35oC. (a) Schematic DC profile for relaxation measurement. (b, d) ESM amplitude
5
and phase versus time corresponding to the DC profile. (c) Zoomed-in relaxation curves after removing negative and positive DC.
Relaxation dynamics The local electrochemical strain measured via ESM correlates with both concentration and diffusivity of respective ionic species [25], and thus we resort to relaxation study to resolve local ionic dynamics of soda-lime glass. Here a direct-current (DC) voltage is imposed on top of AC to induce longer range redistribution of Na+ ions underneath of the probe, as schematically shown in Fig. 2a. After the removal of the DC, Na+ relaxes back to its original equilibrium distribution, and the local dynamics can then be inferred from the time constant associated with the relaxation of ESM amplitude, as observed in Fig. 2b. Importantly, the DC applied induces electro-migration of Na+ over a longer range (in comparison to AC), and thus polarizes the sample over a larger scale. This induced apparent local polarization linearizes the quadratic dipolar electrostriction [44] that exhibits itself as first harmonic response in addition to Vegard strain, both of which relaxes back to the equilibrium after removal of DC. The second harmonic response, on the other hand, is not expected to exhibit relaxation, as detailed in Note S1 and confirmed by our experiment. Furthermore, no relaxation is observed in fused silicate (Fig. S2), consistent with its lack of ionic mobility. Two important observations can be made on the relaxation behavior in Fig. 2b. First of all, ESM amplitude increases under both negative and positive DC, with the increment more prominent under the negative DC, and after removal of either negative or positive DC, the ESM amplitude drops and relaxes back to the equilibrium. This observation again suggests that the local electrochemical strain measured by ESM arises largely from electrochemical dipoles instead of Vegard strain, since Vegard strain exhibits opposite variation under different DC polarities. In particular, negative (positive) DC increases (decreases) the concentration of Na+ under the probe, resulting in increased (decreased) Vegard strain and thus the corresponding ESM amplitude increases (decreases) [25,45]. Electrochemical dipoles, on the other hand, are induced by both negative and positive DC, and the difference lies only in the polarity of the ESM phase instead of its amplitude [39]. Indeed, the phases of ESM response under negative and positive DC are opposite to each other, as seen in Fig. 2d, wherein the phase under negative DC 6
is the same as that in equilibrium in the absence of DC, while the phase under positive DC jumps by 201o, close to the complete phase reversal of 180o. The data thus confirms the dominant dipolar nature of the local electrochemical strain. More interestingly, we notice that after removal of negative DC, the ESM amplitude decreases monotonically, while upon removal of positive DC, the amplitude decreases initially, and then bounces back, as exhibited by the portion shaded by green color in Fig. 2b. This difference can be seen more clearly from relaxation curves zoomed in Fig. 2c, wherein the reversal of ESM amplitude after initial decrease is highlighted upon removal of positively DC. Associated with this amplitude reversal, the corresponding phase is reversed as well (Fig. 2d), dropping by 196o and thus recovers the original phase at equilibrium. These observations are new and have not been reported in literature, to our best knowledge, and they are highly consistent and repeatable, as detailed in Fig. S3. Understanding the corresponding mechanisms may help us resolve local dynamics of dual ions that is otherwise very difficult to do. Local dynamics of dual ions The reversed trend in ESM amplitude after removal of positive DC as exhibited by Fig. 2b and c indicates that there are two distinct electrochemical strain mechanisms competing in soda-lime float glass, and the obvious candidates are electrochemical dipoles and Vegard strain. Both of them are induced by ionic migration, and thus intimately coupled, though Vegard strain is related to molar volume change associated with ionic redistribution, while electrochemical dipoles are due to charge separation, resulting in electrostriction. We can then rationalize different relaxation behavior under different DC polarities as follows. Under a negative DC, positive Na+ moves toward the SPM tip, increasing local ionic concentration and thus associated molar volume, and simultaneously polarizing the local region with upward electrochemical dipoles, as schematically shown in Fig. 3a. Both processes increase electrochemical strain and thus corresponding ESM amplitude, as experimentally observed in Fig. 2b, and upon removal of the DC, the amplitude drops monotonically and relaxes back to equilibrium. Importantly, the positive electrochemical dipoles decrease (increase) under a positive (negative) voltage during an AC excitation cycle, similar to Vegard strain that contracts (expands) under a positive (negative) voltage, and thus these two strains are in phase with each other. Under a positive DC, on the other hand, positive Na+ moves away from the tip, decreasing local ionic concentration and thus 7
associated ESM amplitude, while simultaneously polarizing the local region with downward electrochemical dipoles, as schematically shown in Fig. 3c. These two processes have opposite effects on the ESM amplitude, and because electrochemical dipoles dominate, the overall effect is enhanced ESM amplitude, although to a less extent in comparison to that under a negative DC, as experimentally observed in Fig. 2b. Upon removal of the positive DC during relaxation, electrochemical dipoles decrease while ionic concentration increases under the SPM tip, resulting in crossover as observed after the initial drop in ESM amplitude. Note that the negative electrochemical dipoles increase under a positive voltage during AC excitation, opposite to Vegard strain that contracts under a positive excitation, and thus their phases are reversed, as observed in Fig. 2d. The relaxation behaviors observed thus clearly reveal two distinct ionic strain mechanisms, enabling us to resolve local dynamics of dual ions. To this end, we model the observed relaxation behavior using exponential functions with two distinct time constants τ1 and τ2 corresponding to these two competing processes, 0,
=
−
+
−
+
,
(1)
which fits relaxation curves well under both negative and positive DC. For negative DC shown in Fig. 3b, the relaxation can be decomposed according to Eq. (1) into a faster process (blue curve) with time constant of τ1=0.200s and a slower process (red curve) with time constant of
τ2=1.243s. For positive DC shown in Fig. 3d, the relaxation is decomposed into a faster process (blue curve) with time constant of τ1=0.222s and a slower process (red curve) with time constant of τ2=1.271s. The time constants under different DC polarities for both faster and slower relaxations match each other well, validating the proposed competing mechanisms that take place under both negative and positive DC. The faster relaxation corresponds to Vegard strain that is directly related to the ionic concentration of Na+, while slower relaxation is due to induced electrochemical dipoles resulted from readjustment of negative NBO2- in response to redistributed Na+, which takes longer time though over much shorter distance. Importantly, for relaxation curve after either negative or positive DC, the overall ESM amplitude is largely contributed by the slower relaxation process, i.e. electrochemical dipoles, as evident by Fig. 3b and d, fully consistent with the observation that second harmonic response dominates first harmonic one in Fig. 1. The decomposition thus makes it possible for us to determine the local diffusivity of faster ion.
8
Fig. 3. Local dynamics of dual ions in soda-lime float glass. (a, c) Schematics of microscopic mechanisms associated with electrochemical dipoles and Vegard strain induced by negative and positive DC biases. (b, d) Relaxation curves after removing negative and positive DC (black, left axis), and their decompositions into faster and slower relaxation processes (blue and red, right axis). Local diffusivity The relaxation time constant is closely related to the diffusion of Na+ back to equilibrium distribution upon removal of DC, and in order to determine the local diffusivity from relaxation curves, we resort to numerical simulation for comparison and calibration with experiment, as detailed in the Note S2. A probe with an applied voltage ! is in contact with soda-lime float glass, resulting in a localized electric potential distribution shown in Fig. 4a, which is highly concentrated underneath the SPM tip. Dirven by this electric field, Na+ migrates away from the tip, governed by [46–48] "# "
=$⋅&
'#
#/#()*
+
+,
-.
12
/$ / − /0 + -. /$! ,
(2)
wherein D, c, cmax and cs are diffusion coefficient, ion concentration, maximum ion concentration and baseline ionic concentration, As, z, and ϕ are coefficient regulating equilibrium concentration, charge of ions and electric potential, and R, F and T are ideal gas constant, Faraday’s constant
9
and absolute temperature, respectively. This results in ionic distribution shown in Fig. 4b under 1V, wherein the concentration of Na+ is reduced under the SPM tip. Upon removal of DC, Na+ diffuses back to its equilibrium distribution, and the variation of Na+ concentration right underneath the tip with respect to time is simulated. With appropriate choice of diffusivity & = 5.64 × 10
m /s at 100oC as reported in literature for
Na2O·Al2O3·2SiO2 glass [43], we observe excellent agreements between computed relaxation curves and measured faster relaxation process after both negative and positive DC, as shown in Fig. 4c and d. We thus conclude with confidence that the local diffusivity of Na+ measured by ESM is 5.64 × 10
m /s at 100oC, consistent with macroscopic measurement. Since Vegard
strain of NBO2- does not contribute to the observed relaxation, it is also determined that its diffusivity can be neglected at 100oC.
Fig. 4. Local diffusivity of Na+ at 100oC. (a, b) Simulated 2D mappings of electric potential and Na+ under a tip bias of 1V. (c, d) Faster relaxation curves measured after negative and positive DC, in comparison to simulated relaxation of Na+ concentration.
10
Fig. 5. Local activation energy of Na+ in soda-lime float glass. (a, b) Relaxation curves after application of negative and positive DC bias of 40V at different temperatures. (c) Time constants of faster and slower relaxations versus temperatures, after negative and positive DC biases. (d) Arrhenius plot of the diffusion coefficient versus the inverse of temperature, yielding corresponding activation energy. Activation energy The accurate measurement of local diffusivity of Na+ at 100oC also makes it possible to determine its local activation energy, and thus we measure relaxations of soda-lime float glass from 35℃ to 100℃. Typical relaxation curves after negative and positive DC are shown in Fig. 5a and b, which are in good qualitative agreement with relaxation behavior observed at room temperature, with more data presented in Fig. S4. It is noted that the relaxation accelerates with increased temperature, indicating higher diffusivity, and the crossover after removal of positive DC occurs earlier and becomes more prominent (Fig. 5b). These curves are then fitted by Eq. (1), and the corresponding time constants for faster and slower relaxations are plotted versus 11
temperature in Fig. 5c. Note that time constants decrease with temperature as expected, and their values after negative and positive DC are highly consistent with each other at each temperature for both faster and slower processes, validating the proposed mechanism. More interestingly, we plot the Log of diffusivity with respect to the inverse of temperature in the form of Arrheniustype plot [45,49] in Fig. 5d, which is fitted very well by the linear curves, yielding local activation energy 34 of ~0.55 eV and ~0.58 eV for faster and slower relaxation, respectively, which is good agreement with the macroscopic value of 0.63 eV for Na+ reported in literature [43]. Importantly, the faster and slower ionic activation exhibits very similar activation energy, indicating that the biased tip activates Na+ first, and then electrochemical dipoles forms after slight adjustment of short-range NBO2- distribution. Discussion Electrochemical strain microscopy (ESM) was originally developed to probe local lithium ion activities in batteries [23], bridging an important gap between macroscopic electrochemical measurement and nanostructured electrodes. Many electrochemical systems, however, involves multiple ions, substantially complicating the experimentation and analysis. While our study was motivated by DIBs, its potential applications are not limited to them. Indeed competing ionic dynamics not only occurs in DIBs for energy storage, but also in resistive switching for data storage [50–52], in halide perovskite solar cells wherein ionic defects are prevalent [53], and in emerging functional oxides such as HSrCoO2.5 wherein H+ and O2- are utilized to tune its structure and properties [32]. The abilities to resolving local dynamics of dual ions in these diverse functional materials and systems for energy conversion, storage, and information processing, especially in a quantitative manner, are invaluable to understanding their microscopic mechanisms. Vegard strain is inevitable in battery electrodes during charging and discharging, which is usually undesirable and impacts battery cycling performances and reliability. In dual-ion systems, the effects of electrochemical dipoles also cannot be ignored. What we demonstrate here, however, is that with careful experiment and analysis, we can take advantage of information rendered by Vegard strain and electrochemical dipoles, enabling us to resolve local ionic dynamics at the nanoscale by ESM, which is otherwise very difficult to do. First and second harmonic measurements give clear indication on which mechanism is more dominant, while 12
relaxations after negative and positive DC make it possible to decompose their respective contributions in a quantitative manner. In combination with numerical simulation, the local diffusivity and activation energy can then be precisely determined. While we demonstrate this concept in a clean model system where the two ionic processes have quite different time scales, we believe the method can be applied to study a wide range of energy materials and systems involving multiple ions, even when their respective time scales are not much separated. We are currently studying halide perovskite solar cells, wherein the dynamics are much more complicated, though the essential trend still holds, and soda-lime glass gives us a clean benchmark to guide their study and analysis. METHODS Materials The soda-lime float glass and fused silicate glass investigated were obtained from Edmund Co., and the samples were cleaned before experiments using the following protocol: 10 min of sonication in acetone followed by water rinsing, 10 min sonication in ethanol followed by water rinsing, and a final 10 min sonication in distilled water. After the final sonication step, the glasses were dried with compressed clean nitrogen gas. Electrochemical strain microscopy The first and second harmonic point-wise measurements were conducted on an Asylum Research MFP-3D-Bio atomic force microscope and carried out in air. Relaxation studies and variable ESM studies were performed on an Asylum Research Cypher ES atomic force microscope under nitrogen flow. We used conductive cantilevers (FMG01/Pt, ~60 kHz and ~3 N/m) for all measurements. Each cantilever was calibrated by the thermal fluctuation method. The glass samples were placed on a built-in heating stage provided by Asylum Research to measure the temperature dependence of ESM response. Variable temperature ESM measurements were conducted at least 20 min after changing the temperature in order to ensure the temperature stability during the measurements. Simulation The ions diffusion equation (2) was deduced from thermodynamics theoretical (see Note S2). The tip-induced electric filed has been estimated using image charge model [54]. The 13
computation was two-dimensional (2D), and its numerical simulation was implemented by custom written MATLAB code. The boundary conditions of the ionic diffusion equation are periodic boundary along x direction and there is no ionic flux along y direction boundaries. The finite difference method and fast Fourier transform are used to solve diffusion equation. The simulation size is 100 nm × 100 nm with 128 × 128 mesh. ACKNOWLEDGEMENTS We acknowledge National Key Research and Development Program of China (2016YFA0201001), National Natural Science Foundation of China (11627801, 51772254, and 11772286),
Shenzhen
Science
and
Technology
Innovation
Committee
(KQTD20170810160424889, JCYJ20170818155200084, and JCYJ20170818155813437), Key Area R&D Program of Guangdong Province(2018B010109009), the Instrument Developing Project of Chinese Academy of Sciences (No. ZDKYYQ20180004), and Huxiang Young Talents Plan Project of Hunan Province (2019RS2037). REFERENCES [1]
J.B. Goodenough, Evolution of strategies for modern rechargeable batteries, Acc. Chem. Res. 46 (2013) 1053–1061.
[2]
J.B. Goodenough, K.S. Park, The Li-ion rechargeable battery: A perspective, J. Am. Chem. Soc. 135 (2013) 1167–1176.
[3]
J.-M. Tarascon, M. Armand, Issues and challenges facing rechargeable lithium batteries, Nature 414 (2001) 359–367.
[4]
M. Armand, J.-M. Tarascon, Building better batteries, Nature 451 (2008) 652–657.
[5]
M.L. Aubrey, R. Long, A dual-ion battery cathode via oxidative insertion of anions in a metal-organic framework, J. Am. Chem. Soc. 137 (2015) 13594–13602.
[6]
B. Ji, F. Zhang, X. Song, Y. Tang, A novel potassium-ion-based dual-ion battery, Adv. Mater. 29 (2017) 1700519.
14
[7]
K. V Kravchyk, P. Bhauriyal, L. Piveteau, C.P. Guntlin, B. Pathak, M. V Kovalenko, High-energy-density dual-ion battery for stationary storage of electricity using concentrated potassium fluorosulfonylimide, Nat. Commun. 9 (2018) 4469.
[8]
M. Li, J. Lu, Z. Chen, K. Amine, 30 years of lithium-ion batteries, Adv. Mater. 30 (2018) 1800561.
[9]
M. Wang, Y. Tang, A review on the features and progress of dual-ion batteries, Adv. Energy Mater. 8 (2018) 1703320.
[10]
W. Li, Q. Ning, X. Xi, B. Hou, J. Guo, Y. Yang, B. Chen, X. Wu, Highly improved cycling stability of anion de-&intercalation in the graphite cathode for dual ion batteries, Adv. Mater. 31 (2018) 1804766.
[11]
C. Jiang, Y. Fang, J. Lang, Y. Tang, Integrated configuration design for ultrafast rechargeable dual-ion battery, Adv. Energy Mater. 7 (2017) 1700913.
[12]
G. Chen, F. Zhang, Z. Zhou, J. Li, Y. Tang, A flexible dual-ion battery based on PVDFHFP-modified gel polymer electrolyte with excellent cycling performance and superior rate capability, Adv. Energy Mater. 8 (2018) 1801219.
[13]
M. Sheng, F. Zhang, B. Ji, X. Tong, Y. Tang, A novel tin-graphite dual-ion battery based on sodium-ion electrolyte with high energy density, Adv. Energy Mater. 7 (2017) 1601963.
[14]
G. Zhang, X. Ou, C. Cui, J. Ma, J. Yang, Y. Tang, High-performance cathode based on self-templated 3D porous microcrystalline carbon with improved anion adsorption and intercalation, Adv. Funct. Mater. 29 (2019) 1806722.
[15]
L. Fan, Q. Liu, S. Chen, Z. Xu, B. Lu, Soft carbon as anode for high-performance sodiumbased dual ion full battery, Adv. Energy Mater. 7 (2017) 1602778.
[16]
N. Wu, W. Yao, X. Song, G. Zhang, B. Chen, J. Yang, Y. Tang, A calcium-Ion hybrid energy storage device with high capacity and long cycling life under room temperature, Adv. Energy Mater. 9 (2019) 1803865.
15
[17] B. Ji, F. Zhang, N. Wu, Y. Tang, A dual-carbon battery based on potassium-ion electrolyte, Adv. Energy Mater. 7 (2017) 1700920. [18]
C. Delmas, Sodium and sodium-ion batteries: 50 years of research, Adv. Energy Mater. 8 (2018) 1703137.
[19]
M. Ma, K. Zhang, P. Li, M.S. Jung, M.J. Jeong, J.H. Park, Dual oxygen and tungsten vacancies on a WO3 photoanode for enhanced water oxidation, Angew. Chemie - Int. Ed. 55 (2016) 11819–11823.
[20]
M. Ma, B.J. Jin, P. Li, M.S. Jung, J. Il Kim, Y. Cho, S. Kim, J.H. Moon, J.H. Park, Ultrahigh electrocatalytic conversion of methane at room temperature, Adv. Sci. 4 (2017) 1700379.
[21]
A. Eshghinejad, E. Nasr Esfahani, P. Wang, S. Xie, T.C. Geary, S.B. Adler, J. Li, Scanning thermo-ionic microscopy for probing local electrochemistry at the nanoscale, J. Appl. Phys. 119 (2016) 205110.
[22]
A. Eshghinejad, Y. Ou, J. Zhao, S. Adler, E.N. Esfahani, Scanning thermo-ionic microscopy : Probing nanoscale electrochemistry via thermal stress-induced oscillation, Micros. Today 25 (2017) 12–19.
[23]
N. Balke, S. Jesse, Y. Kim, L. Adamczyk, A. Tselev, I.N. Ivanov, N.J. Dudney, S. V. Kalinin, Real space mapping of Li-ion transport in amorphous Si anodes with nanometer resolution, Nano Lett. 10 (2010) 3420–3425.
[24]
N. Balke, S. Jesse, A.N. Morozovska, E. Eliseev, D.W. Chung, Y. Kim, L. Adamczyk, R.E. García, N. Dudney, S. V. Kalinin, Nanoscale mapping of ion diffusion in a lithiumion battery cathode, Nat. Nanotechnol. 5 (2010) 749–754.
[25]
Q.N. Chen, Y. Liu, Y. Liu, S. Xie, G. Cao, J. Li, Delineating local electromigration for nanoscale probing of lithium ion intercalation and extraction by electrochemical strain microscopy, Appl. Phys. Lett. 101 (2012) 063901.
[26]
J. Zhu, L. Lu, K. Zeng, Nanoscale mapping of lithium-ion diffusion in a cathode within an all-solid-state lithium-ion battery by advanced scanning probe microscopy techniques, ACS Nano 7 (2013) 1666–1675. 16
[27]
S.Y. Luchkin, K. Romanyuk, M. Ivanov, A.L. Kholkin, Li transport in fresh and aged LiMn2O4 cathodes via electrochemical strain microscopy, J. Appl. Phys. 118 (2015) 072016.
[28]
S. Duan, H. Jin, J. Yu, E.N. Esfahani, B. Yang, J. Liu, Y. Ren, Y. Chen, L. Lu, X. Tian, S. Hou, J. Li, Non-equilibrium microstructure of Li1.4Al0.4Ti1.6(PO4)3 superionic conductor by spark plasma sintering for enhanced ionic conductivity, Nano Energy 51 (2018) 19–25.
[29]
J.B. Goodenough, Electronic and ionic transport properties and other physical aspects of perovskites, Reports Prog. Phys. 67 (2004) 1915–1993.
[30]
C. Eames, J.M. Frost, P.R.F. Barnes, B.C. O’Regan, A. Walsh, M.S. Islam, Ionic transport in hybrid lead iodide perovskite solar cells, Nat. Commun. 6 (2015) 7497.
[31]
B. Huang, G. Kong, E.N. Esfahani, S. Chen, Q. Li, J. Yu, N. Xu, Y. Zhang, S. Xie, Ferroic domains regulate photocurrent in single-crystalline CH3NH3PbI3 films self-grown on FTO/TiO2 substrate, Npj Quantum Mater. 3 (2018) 30.
[32]
N. Lu, P. Zhang, Q. Zhang, R. Qiao, Q. He, H.B. Li, Y. Wang, J. Guo, D. Zhang, Z. Duan, Z. Li, M. Wang, S. Yang, M. Yan, E. Arenholz, S. Zhou, W. Yang, L. Gu, C.W. Nan, J. Wu, Y. Tokura, P. Yu, Electric-field control of tri-state phase transformation with a selective dual-ion switch, Nature 546 (2017) 124–128.
[33]
Vegard L., Die Konstitution der Mischkristalle und die Raumfullung der Atome, J. Mater. Sci. 17 (1921) 17–26.
[34]
N.W. Dention, A.R., Ashcroft, Vegard’s law, Phys. Rev. A. 43 (1991) 3161–3164.
[35]
Q.N. Chen, Y. Ou, F. Ma, J. Li, Mechanisms of electromechanical coupling in strain based scanning probe microscopy, Appl. Phys. Lett. 104 (2014) 242907.
[36]
J. Yu, E.N. Esfahani, Q. Zhu, D. Shan, T. Jia, S. Xie, J. Li, Quadratic electromechanical strain in silicon investigated by scanning probe microscopy, J. Appl. Phys. 123 (2018) 155104.
[37] E.L. Williams, Diffusion of oxygen in fused silica, J. Am. Ceram. Soc. 48 (1965) 190–194.
17
[38]
M.A. Lamkin, F.L. Riley, R.J. Fordham, Oxygen mobility in silicon dioxide and silicate glasses: a review, J. Eur. Ceram. Soc. 10 (1992) 347–367.
[39]
R. Proksch, Electrochemical strain microscopy of silica glasses, J. Appl. Phys. 116 (2014) 66804.
[40]
K. Stefan, W. Lothar, A. Sharafat, J. Bo, Trends in effective diffusion coefficients for ionexchange strengthening of soda-lime-silicate glasses, Front. Mater. 4 (2017) 13.
[41]
R.J. Ryder, G.E. Rindone, Internal friction of simple alkali silicate glasses containing Al kaline-earth oxides: II, interpretation and discussion, J. Am. Ceram. Soc. 44 (1955) 532– 540.
[42]
F. V. Natrup, H. Bracht, S. Murugavel, B. Roling, Cation diffusion and ionic conductivity in soda-lime silicate glasses, Phys. Chem. Chem. Phys. 7 (2005) 2279–2286.
[43]
Z.G. Tyurnina, N.G. Tyurnina, S.I. Sviridov, Diffusion of sodium ions and electric conductivity in glassy and crystallized Na2O·Al2O3·2SiO2, Glas. Phys. Chem. 41 (2015) 579–581.
[44]
A. Gruverman, O. Auciello, H. Tokumoto, Imaging and control of domain structures in ferroelectric thin films via scanning force microscopy, Annu. Rev. Mater. Sci. 28 (2002) 101–123.
[45]
Q.N. Chen, S.B. Adler, J. Li, Imaging space charge regions in Sm-doped ceria using electrochemical strain microscopy, Appl. Phys. Lett. 105 (2014) 201602.
[46]
R.P. Buck, Kinetics of bulk and interfacial ionic motion : Microscopic bases and limits for the nernst-planck equation applied to membrane systems *, J. Menbrane Sci. 17 (1984) 1– 62.
[47]
E. Bohn, T. Eckl, M. Kamlah, R. McMeeking, A model for lithium diffusion and stress generation in an intercalation storage particle with phase change, J. Electrochem. Soc. 160 (2013) A1638–A1652.
18
[48]
S.Y. Luchkin, J. Schröder, D.C. Lupascu, H.N.M. Thai, A.L. Kholkin, M.-A. Keip, H.-Y. Amanieu, D. Rosato, Electrochemical strain microscopy time spectroscopy: Model and experiment on LiMn2O4, J. Appl. Phys. 118 (2015) 55101.
[49]
S. Yang, B. Yan, J. Wu, L. Lu, K. Zeng, Temperature-dependent lithium-ion diffusion and activation energy of Li1.2Co0.13Ni0.13Mn0.54O2 thin-film cathode at nanoscale by using electrochemical strain microscopy, ACS Appl. Mater. Interfaces 9 (2017) 13999–14005.
[50]
A.Q. Jiang, C. Wang, K.J. Jin, X.B. Liu, J.F. Scott, C.S. Hwang, T.A. Tang, H. Bin Lu, G.Z. Yang, A resistive memory in semiconducting BiFeO3 thin-film capacitors, Adv. Mater. 23 (2011) 1277–1281.
[51]
G. Zhong, F. An, Y. Bitla, J. Wang, X. Zhong, J. Yu, W. Gao, Y. Zhang, C. Tan, Y. Ou, J. Jiang, Y. Hsieh, X. Pan, S. Xie, Y. Chu, J. Li, Deterministic, reversible and nonvolatile low voltage writing of magnetic domains in epitaxial BaTiO3/Fe3O4 heterostructure, ACS Nano 12 (2018) 9558-9567.
[52]
T. Jia, Z. Fan, J. Yao, C. Liu, Y. Li, J. Yu, B. Fu, H. Zhao, M. Osada, E.N. Esfahani, Y. Wang, Y. Yang, Z. Cheng, J.-Y. Li, H. Kimura, Multifield control of domains in a roomtemperature multiferroic 0.85BiTi0.1Fe0.8Mg0.1O3–0.15CaTiO3 thin film, ACS Appl. Mater. Interfaces 10 (2018) 20712–20719.
[53]
J. Li, B. Huang, E.N. Esfahani, Touching is believing : interrogating halide perovskite solar cells at the nanoscale via scanning probe microscopy, Npj Quantum Mater. 2 (2017) 56.
[54]
W.J. Ming, R.K. Zhu, K. Pan, Y.Y. Liu, C.H. Lei, The effective point charge of probe tip in piezoresponse force microscopy, J. Appl. Phys. 124 (2018) 154106.
19
Junxi Yu is a Ph.D. candidate in Materials Science and Engineering at Xiangtan University. Her current research mainly focuses on characterization of energy storage materials based on advanced scanning probe microscopy.
Boyuan Huang received his bachelor’s degree in Nanjing University in 2016. He is a Ph.D. candidate under the supervision of Prof. Jiangyu Li at University of Washington. His research focuses on developing advanced characterization and data analysis methods based on scanning probe microscopy.
Aolin Li is a Ph.D. candidate in Materials Science and Engineering at Xiangtan University. His research mainly focuses on the mechanical-electro coupling in electrochemistry systems.
Shanshan Duan obtained her bachelor’s degree in Engineering from China University of Geosciences (Wuhan) in 2015. She is a Ph.D. candidate at China University of Geosciences (Wuhan). Her current research mainly focuses on lithium ion solid state electrolytes and solid state batteries.
20
Prof. Hongyun Jin obtained B.E. in 2000 and Ph.D. in 2009 from the Department of Materials Science and Engineering, China University of Geosciences (Wuhan). Afterward, he worked as a visiting scholar in University of Washington. His works on nano energy materials, 3D printing and thermal barrier coatings, and he has published over 50 papers in the field. He has got prize in Hubei science and technology in 2011 and 2015.
Ming Ma received his B.S. degree in 2010 from Shandong University (China) and Ph.D. degree in 2017 from Sungkyunkwan University (Korea). Now, he has joined Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, as an associate professor. His research focuses on the fabrication and application of nanomaterials, especially in the photoelectrochemical water splitting field.
Yun Ou recived his Ph.D. degree in Materials Science and Engineering from Xiangtan University in 2004. He joined in Hunan University of Science and Technology from 2014. Then he worked as Postdoctoral Fellow (2016-2018) at Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences. His research interest focuses on fabrication and characterizing low-dimensional materials and multifunctional materials.
21
Prof. Shuhong Xie obtained Ph.D in 2008 from the Faculty of Materials, Optoelectronics, and Physics, Xiangtan University. Afterward, she worked as a visiting scholar in University of Washington. Her works on nano energy materials and multiferroic nano materials, and she has published over 70 papers in the field.
Prof. Yunya Liu received his Ph.D. degree from Xiangtan University in 2010, and is currently a professor at School of Materials Science and Engineering of Xiangtan University. His research interest focuses on the mechanics of materials, scanning probe microscopy, and the correlations between microstructures and macroscopic behaviors of multifunctional and energy materials.
Prof. Jiangyu Li recently joins Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, where he directs Shenzhen Key Laboratory of Nanobiomechanics. Prior that, he was Professor in the Department of Mechanical Engineering, University of Washington. He obtained his B.E. degree in 1994 from the Department of Materials Science and Engineering, Tsinghua University, and Ph.D. degree in 1998 from the Department of Mechanical Engineering, University of Colorado-Boulder. Li works in the general field of mechanics of materials, focusing on advanced scanning probe microscopy and its applications in functional materials.
22
Highlights Local dynamics of competing ions in the electrochemically active dual-ion systems is resolved at the nanoscale Intriguing relaxation behavior of dual-ion systems after positive and negative biases are rationalized by the competing Vegard strain and electrochemical dipole Local diffusivity and activation energy are measured quantitative at the nanoscale, assisted by phase field simulation. The method can be applied to a wide range of energy materials and systems involving multiple ions.