antimony hybrids as advanced anodes for sodium storage

Author’s Accepted Manuscript Top-Down Synthesis of Interconnected TwoDimensional Carbon/Antimony Hybrids as Advanced Anodes for Sodium Storage Chao Wu, Laifa Shen, Shuangqiang Chen, Yu Jiang, Peter Kopold, Peter A. van Aken, Joachim Maier, Yan Yu www.elsevier.com/locate/ensm

PII: DOI: Reference:

S2405-8297(17)30177-0 http://dx.doi.org/10.1016/j.ensm.2017.08.011 ENSM205

To appear in: Energy Storage Materials Received date: 8 May 2017 Revised date: 9 August 2017 Accepted date: 28 August 2017 Cite this article as: Chao Wu, Laifa Shen, Shuangqiang Chen, Yu Jiang, Peter Kopold, Peter A. van Aken, Joachim Maier and Yan Yu, Top-Down Synthesis of Interconnected Two-Dimensional Carbon/Antimony Hybrids as Advanced Anodes for Sodium Storage, Energy Storage Materials, http://dx.doi.org/10.1016/j.ensm.2017.08.011 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. 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.

Top-Down Synthesis of Interconnected Two-Dimensional Carbon/Antimony Hybrids as Advanced Anodes for Sodium Storage

Chao Wu,ac1 Laifa Shen, a1 Shuangqiang Chen, a Yu Jiang,b Peter Kopold, a Peter A.van Aken,a Joachim Maier,a and Yan Yu*ab a

Max Planck Institute for Solid State Research, Heisenbergstr.1, Stuttgart 70569, Germany

b

CAS Key Laboratory of Materials for Energy Conversion Department of Materials Science and

Engineering University of Science and Technology of China Hefei 230026, China c

Institute of Superconducting & Electronic Materials, Australian Institute of Innovative

Materials, University of Wollongong, NSW 2522, Australia. E-mail: [email protected] 1

These authors contributed equally to this article.

KEYWORDS: Top-down synthesis, Carbon nanosheets, Sb nanoparticles, Sodium-ion batteries, Multi-dimensional structure. ABSTRACT: Nanoparticle-based electrode materials have sparked enormous excitement in the sodium-ion battery community because of potentially fast transport kinetics. However, they may suffer from many challenging static and dynamic problems, such as agglomeration of nanoparticles, high contact resistance, volume change, and instability of solid electrolyte interphase. Herein, we develop inter-connected 2D carbon nanosheets in which ultrasmall 0D Sb nanodots are embedded homogenously through a previously unexplored “top-down” strategy. Starting from the laminar structure K3Sb3P2O14, H3Sb3P2O14 nanosheets are exfoliated by ion exchange and then serve as templates for the synthesis of carbon sheets and Sb nanodots. Such combination of multi-dimensional and multi-scale nanostructures in the electrode materials lead to excellent electron/ion transport kinetics and pronounced integrity of the electrode structure on

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cycling, providing a promising pathway for developing advanced electrode materials in terms of reversibility, rate capability and cycle life.

1. Introduction Sodium-ion batteries are of major importance, especially for large-scale energy storage devices, due to low cost and abundant source of sodium.1-5 As for the anode side, commercial graphite shows a limited capacity for sodium storage (31 mAh g-1 using ethyl-methyl carbonate-based electrolyte and 100 mAh g-1 using ether-based electrolyte).6-7 Compared to graphite, Sb-based electrode materials have been identified as promising anode candidates for sodium storage due to high theoretical capacity and very suitable redox voltage range.8-19 However, poor kinetics and large volume change result in a low reversible capacity and fast capacity decay. In principle, nanoparticle-based Sb-based electrode structures can boost sodium storage kinetics because of shortening the chemical diffusion length of sodium. In reality, a multitude of challenging kinetic and structure stability problems, such as agglomeration of nanoparticles, increased contact resistance, and instability of solid electrolyte interphase (SEI) layers.20-25 may be met and prevent their use in commercial sodium-ion batteries.26,27 In order to overcome the above problems, diverse strategies have been proposed to improve the electrochemical performance, including compositing with carbon or other materials16-17 and controlling nanostructure.19,28-29 However, the performance improvement is still limited by these approaches. Two-dimensional (2D) conductive ultrathin materials,30-31 such as nanosheets of carbon, titanium carbide and MoS2, have attracted great attention in recent years due to exceptional physical and chemical properties.32-34 High electronic conductivity and large aspect ratio make them ideal as current-collectors.35 The rational combination of 0D active nanoparticles and 2D current-collector has the potential to overcome the above problems associated with the

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nanoparticle-based electrodes upon cycling. However, there are two major problems to be addressed: i) how to distribute active nanoparticles homogenously on 2D current collectors; ii) how to preserve the homogenous distribution state of nanoparticles without agglomeration on cycling. General approaches are random mixing active nanoparticles with 2D current-collectors or random decorating active nanoparticles on the 2D current-collectors,36 which cannot overcome the above problems. Embedding active nanoparticles homogenously into the 2D conductive materials appears to be a well-suited strategy (Schematic 1), but is also a very challenging one as far as synthesis is concerned. Herein, we develop a novel “top-down” strategy for constructing interconnected 2D carbon nanosheets embedding ultrasmall 0D Sb nanodots (denoted as Sb-NDsCNs). Starting from the micro-sized K3Sb3P2O14 bulk particles, H3Sb3P2O14 nanosheets are available by ion exchange and then serve as templates for the synthesis of the desired Sb nanodots embedding the carbon nanosheets. The special structure design of Sb-NDsCNs provides multiple advantages for overcoming the critical problems associated with the nanoparticle-base electrode materials. The interconnected carbon nanosheets form a 3D electronic conductive network and simultaneously facilitate access of the ions to large surface area due to the 2D structure. On the other hand, the carbon nanosheets prevent the Sb nanodots from aggregating, thus keeping the electrode structure stable and maintaining the extremely short diffusion lengths. As a consequence, the SbNDsCNs electrodes show excellent electrochemical performance in terms of reversibility, rate capability, and cycling stability. 2. Experimental section Synthesis of Sb-NDs⊂CNs

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First of all, K3Sb3P2O14 with lamellar structure was synthesized according to procedure provided by previous study.37-38 0.5g of K3Sb3P2O14 was mixed with 300 mL of HCl solution (4M) and stirred for 2 days for ion exchange. The above ion exchange procedure was repeated for 3 times to obtained pure H3Sb3P2O14 crystal. The obtained H3Sb3P2O14 was dispersed into 30 mL of deionized water by ultrasonic and stirring treatment under the assistance of ethylenediamine (1 mL). 0.25 g of glucose was added into the above solution and the solution was transferred into 50 mL of autoclave with Teflon line. After reaction at 180 oC for 10 h, the solid product was obtained by the filter separation and freezing dry. The obtained product was annealed at 500 oC for 1-2 h in Ar/H2 to achieve the desired Sb-NDs⊂CNs. Synthesis of Sb@carbon 0.24 g of Sb2O3 nanoparticles was mixed with 0.25 g of glucose by grinding. The obtained mixture was annealed at 600 oC for 2 h to obtain the desired Sb@carbon. Materials characterization. The morphology of the as-prepared samples was investigated by field-emission scanning electron microscopy (FE-SEM, Zeiss Gemini DSM 982) and transmission electron microscopy (TEM, JEOL ARM200F, 200 kV). Nitrogen adsorption and desorption isotherm measurement were performed with a Quantachrome Adsorption Instrument. The crystal structures of the asprepared samples were recorded by X-ray diffraction (XRD) (Philips) using Cu Ka radiation. Electrochemical measurement. The electrochemical measurements were carried out in a 2032-type coin-cell. The metallic sodium films serve as the counter electrode with 1M NaClO4 in propylene carbonate (PC) containing 5 wt% fluoroethylene carbonate (FEC) as electrolyte. The working electrodes were made by casting slurry containing active material, carboxymethylcellulose-Na binder, and carbon

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black (super P) with a mass ratio of 8:1:1 on a Cu foil. The diameter of working electrodes is 10 mm. Note that all the capacity values of Sb-NDs⊂CNs and Sb@carbon are calculated based on the mass of active nanodots and carbon. Before the full cell assembly, the Sb-NDs⊂CNs anodes were initially pre-activated in the voltage range of 0.005–2 V versus Na+/Na at 0.1 A g−1 for two times to reach a stable state. The galvanostatic charge-discharge tests were performed on a battery system (Neware BTS). Electrochemical impedance spectrum (EIS) measurements were performed on an electrochemical workstation (VoltaLab 80) in the frequency range from 100 KHz to 0.1 Hz. 3. Results and Discussion The top-down synthesis process for Sb-NDsCNs is described in Figure 1a, involving the following key steps. First, we synthesized K3Sb3P2O14 crystals with laminar structure as a precursors for the Sb nanodots.37-38 As shown in Figure S1, the crystal X-ray diffraction (XRD) patterns are indexed to the pure rhombohedral phase (JPCD card no.01-078-1030). After ion exchange, they are transformed into laminar H3Sb3P2O14 crystals, as confirmed by XRD analysis (Figure 1b). The H3Sb3P2O14 crystals can be easily exfoliated into a manifold of graphene-like nanosheets under the assistance of ethylenediamine. A representative transmission electron microscopy (TEM) image of H3Sb3P2O14 reveals a flexible and corrugated texture (Figure 1 c). It should be noted that ethylenediamine plays an important role in the exfoliation process. It not only improves the exfoliation efficiency, but also enables the stability of the exfoliated suspension solution. As shown in the inset of Figure 1a, no precipitate is observed after standing even after 24 h. The exfoliated H3Sb3P2O14 nanosheets are coated by polysaccharides via a hydrothermal procedure, then freezing-dried and finally annealed to give the desired products.

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During this process, the H3Sb3P2O14 nanosheets act as growth templates for carbon nanosheets. At the end of the process, the embedded nanodots are obtained. The morphology and microstructure of Sb-NDsCNs were investigated by XRD, scanning electron microscopy (SEM), and TEM. XRD pattern of Sb-NDsCNs confirm the presence of pure rhombohedral antimony crystals after annealing at 500 oC. As shown in Figure 2a, the weak diffraction peak at 2θ=26o is corresponding to hexagonal carbon, and other diffraction peaks are indexed to antimony crystals (JPCD card no.01-071-1173). Elemental analysis indicates that the carbon content for Sb-NDsCNs is about 20 wt%. Figure 2b-d displays the SEM images of Sb-NDsCNs with different magnifications. The low magnification image reveals that the 2D thin carbon nanosheets are interconnected 3D carbon networks (tens of micrometers) and that the junctions between nanosheets are well defined. At high magnification, large numbers of nanodots embedded into the carbon nanosheets are observed. TEM images further confirm that these ultrasmall nanodots are homogenously dispersed within the 2D nanosheets with an average diameter of about 10 nm (Figure 2e,f and Figure S2). To our best knowledge, such multi-dimensional and hierarchically organized nanostructure (combination of 0D, 2D and 3D) has not been designed or at least not been reported. High-resolution TEM images display that the characteristic lattice fringes of Sb dots, indicating a high degree of crystallinity. The surface area of Sb-NDsCNs was quantified using nitrogen adsorption measurements. The specific surface area is estimated to be about 74.9 m2 g-1 according to the Brunauer-Emmett-Teller (BET) method (Figure 2g). The carbon sheets are porous with an average diameter of about 6 nm. Raman spectra of Sb-NDsCNs reveal two typical D and G bands around 1383 and 1598 cm−1, corresponding to sp3-type disordered carbon and sp2-type graphitized carbon, respectively.21 The intensity of D band is less than that of G band, indicating

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a larger amount of sp2-type carbon compared to sp3-type carbon, what is favorable for electron transfer and hence for rate performance (Figure 2i). H3Sb3P2O14 nanosheets serve as template to form 2D carbon nanosheets embedded into 0D Sb nanodots, which is a key step for Sb-NDsCNs. During this process, the oxygen and phosphorus are completely removed in the reductive atmosphere (Ar/H2) and the original nanosheets are transformed into ultrasmall nanodots. Interestingly, it is found that Sb-containing phosphates are completely reduced to Sb metal rather than to phosphides. This behavior is different from that of transitional metal (Fe, Co, and Ni)-containing phosphates that were only reduced to the phosphides (FeP, Co2P and Ni2P).39 In addition, we have found that the annealing temperature plays an important role for the transformation of H3Sb3P2O14 into Sb crystals. When the annealing temperature decreases from 500 oC to 400 oC, SbPO4 is observed as impurity phase (Figure S3). However, their nanostructure is preserved, similar to Sb-NDsCNs. The multi-dimensional and multi-scale nanostructure is responsible for the attractive electrochemical performance of Sb-NDsCNs anodes for sodium storage. Coin-cells were assembled with Sb-NDsCNs as working electrode and sodium metal films as counter electrode. Figure S4 exhibits initial cyclic voltammetry (CV) curves at a scanning rate of 0.1 mV s -1. In the first discharge process, two reductive peaks are located around 0.59 and 0.2 V, corresponding to the two step sodium-insertion behavior of Sb nanodots(Sb + χNa  NaχSb; NaχSb + (3-χ)Na  Na3Sb).28, 40 In the corresponding charge process, the two step sodium-desertion reactions occur simultaneously, and thus only one oxidation peak around 0.95 V is observed. After the first cycle, the reduction peaks shift to 0.46 and 0.19 V while the oxidation peak still appears at 0.95 V. This tiny voltage shift is ascribed to the strain change during the initial sodiation process.41 Figure 3a exhibits the initial charge/discharge profiles in the range from 0.005 to 2 V at 0.1 A g-

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1

. They display two discharge plateaus around 0.77 and 0.31 V as well as one well-defined

charge plateau around 0.82 V, consistent with the CV result. The Sb-NDsCNs electrodes deliver a discharge capacity of 750 mAh g-1 and a reversible capacity of 447 mAh g-1, corresponding to a Coulombic efficiency (CE) of 60%. The initial irreversible capacity could be ascribed to the formation of solid electrolyte interface (SEI).28 After the electrochemical activation of the first cycle, the reversible capacity reaches 506 mAh g-1. After a few of cycles, the CE value has exceeded 99%. Notably, the above specific capacity takes account of Sb- and carbon-masses. The pure carbon electrode materials without Sb nanodots were prepared by pyrolysis of glucose precursor under the same condition as Sb-NDsCNs. Figure S5 shows the initial charge/discharge profiles of the carbon electrodes at 0.1 A g-1, indicating that the pure carbon electrode have a very low reversible capacity. If the carbon capacity contribution is deducted, the capacity contribution from Sb amounts to up to 630 mAh g-1 which is close to the theoretical capacity of Sb (660 mAh g-1). The 2nd and 3rd discharge profiles of the Sb-NDsCNs electrodes display different plateau ratios, which is associated to the amorphous transition of Sb crystal with cycling. Figure S6 exhibits the XRD patterns of the Sb-NDsCNs electrodes after one cycle and two cycles. Three main diffraction peaks of Sb nanodots are observed after one cycle, and only the strongest diffraction peak corresponding to plane of (012) is observed after two cycles, indicating that the crystal structure of Sb nanodots goes toward amorphous state. The charge profiles exhibit a single plateau, which is possibly attributed the simultaneous conduction and similar reduction potential of the desodiation process of fully sodiated Na3Sb and intermediate NaχSb. The capacity above 1V could be attributed to polarization in the desodiation process of NaxSb and Na3Sb. Similar phenomenon is observed in the previous studies of Sb/carbon electrodes.28-29 Moreover, the Sb-NDsCNs electrodes exhibit a remarkable cycling

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performance (Figure 3b). After one cycle, the electrodes begin to deliver a stable reversible capacity. They show a capacity of 477 mAh g-1 after 100 cycles with a retention of 94% compared to the second cycle. Compared to the first cycle, the capacity does not perceptibly fade. For comparison, we synthesized carbon-coated Sb nanoparticles (noted as Sb@carbon). As shown in Figure S7, the XRD pattern indicates pure antimony phase, and the SEM image reveals that the aggregated Sb nanoparticles are coated by amorphous carbon. The Sb@carbon electrodes are tested under the same condition as the Sb-NDsCNs electrodes, delivering reversible capacities of 386 and 429 mAh g-1 at 0.1 A g-1 for the first and second cycle. After 100 cycles, the capacity decreases to 153 mAh g-1 after 100 cycles, corresponding to a capacity retention of 40% and 36% when compared to the first and second cycle. This cycling stability of Sb-NDsCNs is also better than previously reported carbon-coated or graphene-supported Sb electrodes.12, 26-27, 40, 42-43 To further verify the cycling stability of Sb-NDsCNs, we cycled the cells for 250 cycles at 0.3 A g-1 (Figure 3e). The Sb-NDsCNs electrodes deliver reversible capacities of 416 and 461 mAh g-1 at the first and second cycle, respectively. After 250 cycles, the charge capacity remains at a value as high as 380 mAh g-1, and yields a capacity retention of 91 wt% with respect to the first cycle. Owing to its special nanostructure, the Sb-NDsCNs electrodes show an excellent rate capability. As shown in Figure 3c and Figure S8, they deliver reversible capacities of 507, 470, 426 mAh g-1 at low current densities of 0.1, 0.3, and 0.5 A g-1, respectively. Capacities of 377 and 271 mAh g-1 are available at high current densities of 1 and 2 A g-1, respectively. All these values are stable and reproducible on variation of the current. Figure 3d exhibits the comparison of rate performance between Sb-NDsCNs and previously reported carbon/Sb composites. The rate capability of Sb-NDsCNs is higher than that of the reported carbon/Sb composites (the

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capacities are compared on the basis of the total mass of Sb and C).28-29, 42-47 Compared to SbNDsCNs, the Sb@carbon electrodes deliver reversible capacities of 427, 332, and 237 mAh g-1 at 0.1, 0.3, and 0.5 A g-1, respectively. The capacities sharply decrease to 163 and 99 mAh g-1 at currents of 1 and 2 A g-1, respectively (Figure S9). When the current density returns to the initial rate, strong fading is noticed. In order to further explore the performance of Sb-NDsCNs, full batteries were assembled using carbon-coated Na3V2(PO4)3 (denoted as Na3V2(PO4)3@carbon) as cathodes and Sb-NDsCNs as anodes. The carbon content of Na3V2(PO4)3@carbon is about 15 wt%. The full battery of Na3V2(PO4)3@carbon//Sb-NDsCNs shows an average voltage output of 2.5 V (Figure 4a), delivering a discharge capacity of 90 mAh g-1, which is calculated based on the cathode mass of carbon and Na3V2(PO4)3. After 50 cycles, the capacity still reaches 79 mAh g-1, demonstrating the good cycling performance for the full battery. In addition, the energy density of the assembled full battery is estimated to be about 192 Wh kg−1 (based on the entire mass of active materials of both electrodes). This value is comparable to or better than values for the previously reported full batteries based on rGO-Sb2S3//Na2/3Ni1/3Mn2/3O2 and STNTO//Na2/3Ni1/3Mn2/3O2 systems.18, 48 The remarkable kinetics and long-term cycle stability of Sb-NDsCNs are attributed to the special architecture, synergistically combining the advantages of 0D, 2D, and 3D (nanosheets are inter-connected) structures. In spite of 0D Sb nanodots (embedded in 2D carbon nanosheets) being separated from each other, they are well connected in terms of electrochemical circuits. In addition to providing electrons, the porous 2D carbon nanosheets allow Na+/electron to quickly access the Sb nanodots. Figure 4b exhibits the CV curves of Sb-NDsCNs at different scanning rates, yielding an apparent chemical diffusion (Dδ) coefficient of about 2.7×10-14 cm2 s-1, calculated according to the Randles–Sevcik equation 49

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Ip= 2.69×105n3/2AC (Dδ )1/2 v 1/2 where Ip is the peak current, n the number of transfer electrons, A the electrode are, C the concentration, Dδ the chemical diffusion coefficient of Na, and v is the scanning rate. The peak of anodic current in CV curves was chosen for linear fit (Figure 4c). Considering the ultrasmall size of Sb nanodots, it should take only very short times to accomplish sodium storage. In addition, the porous 2D carbon nanosheets buffer the volume change of Sb-NDsCNs and prevent Sb nanodots from aggregating hence keep integrity of the overall electrode structure on cycling. Figure 4d shows the typical SEM images of the Sb-NDsCNs electrode after 100 cycles. The morphology of inter-connected sheets is still preserved after cycling. The SEM mapping images reveal that Sb nanodots are uniformly embedded into the carbon sheets after cycling although the carbon nanosheets are covered by SEI films (Figure S10). Electrochemical impedance spectra of the Sb-NDsCNs electrodes were tested before and after cycling. As shown in Figure 5a, both Nyquist plots of the Sb-NDsCNs electrodes display a depressed semicircle associated with the charge-transfer process in the high frequency region and an oblique line corresponding to mass diffusion process. The charge-transfer resistance of the SbNDsCNs electrode after 20 cycles is slightly less than that before cycling, indicating excellent kinetics of Sb-NDsCNs electrodes. Figure 5b displays SEM image of the Sb-NDsCNs electrodes with high magnification after 100 cycles. No big aggregated Sb clusters were observed on the nanosheets after cycling, indicating that the carbon nanosheets can prevent Sb nanodots from agglomerating on cycling. 4. Conclusion In conclusion, we have developed a “top-down” strategy to synthesize inter-connected 2D carbon nanosheets embedding 0D Sb nanodots. This strategy is facile and convenient, with the

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potential to be used for other relevant materials. Such combination of multi-dimensional and multi-scale nanostructures greatly improves the electron/ion transport kinetics for the electrode materials and ensures the integrity of the electrode structure on cycling. The Sb-NDsCNs electrode materials show excellent electrochemical performance for sodium storage in terms of reversibility, rate capability and cycle life. The reversible capacity of Sb-NDsCNs does not perceptibly decay after 100 cycles at 0.1 A g-1, and it shows a capacity retention of 94 wt% compared to the second cycle after 100 cycles. This multi-dimensional and multi-scale structure design of Sb-NDsCNs provides a promising pathway for developing high performance nanoparticle-based electrode materials.

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Schematic 1. Combination styles of 0D active nanoparticles and 2D current-collectors.

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Figure 1. (a) Schematic of the “Top-down” synthesis strategy for Sb-NDsCNs using the bulk K3Sb3P2O14 as the source of Sb and the optical images of the exfoliated H3Sb3P2O14 solution (inset). (b) XRD pattern H3Sb3P2O14 compared to JPCD card no.00-040-0218 and (c) TEM image of H3Sb3P2O14 nanosheets.

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Figure 2. (a) XRD pattern, (b-d) SEM images, and (e, f) TEM images of Sb-NDsCNs. (g) Nitrogen adsorption/desorption isotherms of Sb-NDsCNs and (h) the corresponding pore size distribution. (i) Raman spectrum of Sb-NDsCNs.

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Figure 3. (a) The initial charge/discharge profiles of Sb-NDsCNs at 0.1 A g-1. (b) Cycling performance of Sb-NDsCNs and Sb@carbon at 0.1 A g-1. (c) Rate performance of SbNDsCNs at various current densities. (d) Rate comparison of Sb-NDsCNs and previously reported Sb/Carbon composites (the capacities are calculated based on the total mass of Sb and carbon). (e) Long-term cycling performance of Sb-NDsCNs at 0.3 A g-1.

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Figure 4. (a) The initial charge/discharge profiles of full battery with Sb-NDsCNs as anode and Na3V2(PO4)3@carbon as cathode as well as cycling performance (inset). (b) Cyclic voltammetry curves of Sb-NDsCNs at different scan rate. (c) The peak of anodic current as function as the scan rate (v1/2). (d) SEM image of the Sb-NDsCNs electrode after 100 cycles, showing that the inter-connected nanosheets are still preserved.

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Figure 5. (a) Electrochemical impedance spectroscopy of the Sb-NDsCNs electrodes before and after cycling. (b) SEM image of the Sb-NDsCNs electrodes with high magnification after 100 cycles.

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ACKNOWLEDGMENT This work was financially supported by the National Key R&D Program of China (No.2016YFB0100305), the Sofja Kovalevskaja award of the Alexander von Humboldt Foundation, the National Natural Science Foundation of China (No. 21373195, No. 51622210), the Fundamental Research Funds for the Central Universities (WK3430000004), the Collaborative Innovation Center of Suzhou Nano Science and Technology. C. Wu acknowledges financial support by ARC DECRA Grant (DE170101426). The authors would like to thank A. Fuchs for BET investigations, H. Hoier for XRD measurements, B. Fenk for SEM mapping test, A. Schulz for Raman test, and G. Zhao for EIS test. We are grateful to C. C. Chen for discussions.

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Table of Contents

Interconnected 2D carbon nanosheets embedding ultrasmall 0D Sb nanodots have been developed through a previously unexplored “top-down” strategy. Such combination of multidimensional and multi-scale nanostructures lead to excellent electron/ion transport kinetics and pronounced integrity of the electrode structure on cycling, providing a promising pathway for developing advanced electrode materials in terms of reversibility, rate capability and cycle life.

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