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Li2SnO3 anode material for rechargeable lithium ion batteries
Applied Surface Science 469 (2019) 253–261
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Full Length Article
Synthesis of graphene supported Li2SiO3/Li2SnO3 anode material for rechargeable lithium ion batteries ⁎
T
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Qiufen Wanga, , Shuai Yanga, Juan Miaob, , Yanlei Zhanga, Dafeng Zhanga, Yumei Chena, Zhi Lia a b
Henan Key Laboratory of Coal Green Conversion, College of Chemistry and Chemical Engineering, Henan Polytechnic University, Jiaozuo 454000, China Medical College, Henan Polytechnic University, Jiaozuo 454000, China
A R T I C LE I N FO
A B S T R A C T
Keywords: Lithium ion battery Li2SiO3 Li2SnO3 Graphene Anode material
Graphene supported Li2SiO3/Li2SnO3 (LSO-LSnO-GE) composite has been prepared through a hydrothermal method. The microstructure and electrochemical performance of LSO-LSnO-GE have been investigated by a variety of means. When used as an anode material for lithium ion battery, the initial specific discapacity of LSOLSnO-GE composite is 1016.5 mAh/g at the current density of 150 mA/g, and its specific capacity is 440.8 mAh/ g after 200 cycles. The improvement of lithium storage performance of LSO-LSnO-GE composite can be explained the synergistic effect of that LSnO, LSO and graphene. In addition, the LSO-LSnO-GE shows the initial discharge capacity of 263.1 mAh/g at the current density of 30 mA/g in LSO-LSnO-GE/LiMn2O4 full cell, which could indicate that LSO-LSnO-GE may be used as an anode material for lithium ion full cells.
1. Introduction Lithium ion battery as a rechargeable cell is widely used due to its advantage characterizes of environmental friendly, high density and lower self-discharge rate [1–3]. Anode and cathode materials are the important parts of lithium ion battery. Li2SnO3, as a kind of Sn-based materials, has been researched in many references as a potential anode material [4]. Its theoretical capacity is > 600 mAh/g, which is much higher than that of the commercial graphite [5]. However the large volume change of about 300% hinders its application in high energy lithium ion battery [6,7]. These materials, such as Li2SnO3/ppy/graphene [8], Li2SnO3/carbon and etc. [9] have been prepared to solve this problem. Si-based materials have been also paid much attention due to its high capacity [10,11]. But the large expansion-contraction volume occurs when Li+ is alloyed and de-alloyed. Thus compositing with carbon materials has been a wide modified method [12], such as Si/C [13] and SiO2/C [14] composites. As large volume change materials, the compositing of Si-based materials and Sn-based materials, such as Si/SnO2/C composite, has been roughly reported [15]. As a kind of Si based materials, the Li2SiO3 has been synthesized to enhance ion transport abilities for its well structure and well ion transport property [3,16–19]. Graphene, as a kind of the carbon-based nanomaterials, has been widely used in several fields due to its large specific surface area, good ion and electronic conductivities, such as bioimaging,
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photocatalysis, memory storage and logic circuits, etc. [20–22]. When used as an anode material in lithium ion battery, the merits can effectively improve the electrochemical performances of the composites [23,24]. In this article, we used Si-based material and graphene to modify Li2SnO3, and to improve its property. Thus graphene supported Li2SiO3/Li2SnO3 (LSO-LSnO-GE) composite has been synthesized through a hydrothermal method. The structure, morphology and electrochemical performance of LSO-LSnO-GE have been characterized and compared with Li2SiO3/Li2SnO3 (LSO-LSnO). 2. Materials and methods 2.1. Synthesis of electrode materials All the reagents were directly used without further purification. Graphite oxide (GO) was prepared by a modified Hummers’ method [17]. 2 g of NaNO3 was added into 110 ml of H2SO4 (98%) under the magnetic stirring. When the temperature was below 5 °C, 2 g of graphite flakes and 12 g of potassium permanganate were slowly added into it and stirred for 1.5 ∼ 2 h. The beaker was transferred to a thermostatic water bath at 35 °C and stirred for 2 ∼ 2.5 h. And 80 ml of demonized water was added into it at 85 °C. After that, 15 ml of H2O2 and 400 ml of demonized water were added in it. Finally, the solution was centrifuged several times until the pH of the solution was 5.0 ∼ 6.0. The GO
Corresponding authors. E-mail addresses: [email protected] (Q. Wang), [email protected] (J. Miao).
https://doi.org/10.1016/j.apsusc.2018.11.055 Received 9 July 2018; Received in revised form 28 September 2018; Accepted 6 November 2018 Available online 07 November 2018 0169-4332/ © 2018 Published by Elsevier B.V.
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the crystal of the Li2SiO3-Li2SnO3-GE compound was produced in the space of graphene and some bulks were attached on the surface of the graphene. The phase identifications of the as-synthesized samples are confirmed by XRD patterns, as shown in Fig. 2a. We can observe the main diffraction peaks of LSnO (0 0 2), (1 1 0), (− 1 1), (2 0 0), (0 0 4), (2 0 2), (1 3 3), (0 0 6), (0 6 0), (1 3 5) and (0 6 2) at 17.97°, 19.54°, 20.23°, 34.36°, 36.40°, 41.91°, 45.94°, 55.86°, 60.46°, 61.06° and 63.63°, which may agree with the standard patterns of Li2SnO3 (JCPDS 31-0761), indicating the as-synthesized LSnO with the monoclinic crystal structure. Moreover, a few diffraction peaks of SnO2 (1 1 0) and (2 1 1) at 26.61° and 51.78° can be observed because of the incomplete reaction between SnCl4·5H2O and LiOH, which may agree with the standard patterns of SnO2 (JCPDS 41-1445). When compositing with Si powder, the main diffraction peaks of the Li2SiO3 (2 0 0), (1 1 1), (0 2 0), (0 0 2) and (0 2 2) at 18.89°, 26.98°, 33.18°, 38.61° and 51.80° agree with the standard patterns of Li2SiO3 (JCPDS 29-0829) due to the reaction between Si and LiOH. In the curve of LSO-LSnO-GE, except the main diffraction peaks of Li2SiO3 and Li2SnO3, few diffraction peaks of Sn (JCPDS 04-0673) can be shown, which could be caused by the hydrolytic reaction of SnCl4·5H2O. To further investigate the surface structures and the binding natures of the elements, the XPS spectra of LSO-LSnO-GE have been provided in Fig. 2. The spectrum of Sn 3d (Fig. 2b) has two pesks at 485.48 eV and 493.88 eV, corresponding to Sn 3d5/2 and Sn 3d3/2, which represents the Sn mental and Sn4+ in Li2SnO3 [9]. The C1s spectrum in Fig. 2c displays several probably deconvolved peaks. The peaks fitted at 284.18 eV, 285.88 eV, 287.58 eV and 288.48 eV represent C]C, CeC, CeO and C]O bond in graphene [25]. The spectrum of Si 2p (Fig. 2d) shows the peaks at 100.88 eV, representing the existence of Si4+ [26]. The O 1s spectrum (Fig. 2e) in 530.28 eV represents the O2−, which can form the SneO band and SieO bands. The curve of Fig. 2f shows the existence of Li, Si, Sn, O and C elements, which could be accorded with the photoelectron spectroscopy of LSO-LSnO-GE. These can further verify the structures of LSO-LSnO-GE. The morphology of the material is an important factor for the electrochemical property. Fig. 3 shows the SEM image of the three samples. The Li2SnO3 (Fig. 3a) is a bulk structure with the diameter of 200–600 nm, which is made up of many small nanoparticles. When doped with Si powder, the LSO-LSnO (Fig. 3b) shows the porous bulk structure, which is also composed of many small nanoparticles. And the LSO-LSnO bulks are more irregular than that of Li2SnO3. The reason could be as follows. According to the formation of LSO-LSnO, the Si powder is doped in the first synthesis procedure of Li2SnO3, the Li2SiO3 and Li2SnO3 particles are synthesed at the same time, further form the structure of the porous and irregular bulks. In LSO-LSnO-GE sample (Fig. 3c), the porous and irregular LSO-LSnO bulks are attached on the surface of graphene nanosheets. Fig. 3d, e, f, g and h show the elemental mapping images of the inset in Fig. 3c. These clearly display the distributions of Li, Sn, C, Si and O, which demonstrates that LSO and LSnO particles are coated together. Fig. 4 shows the TEM images of LSO-LSnO and LSO-LSnO-GE. The TEM images are in agreement with as-presented SEM images. As shown in Fig. 4a, the LSO-LSnO sample is a bulk structure, which is composed of many small nanoparticles in the size range from 20 nm to 50 nm. In Fig. 4c, the irregular LSO-LSnO bulks are attached on the surface of graphene nanosheets. Fig. 4b and d exhibits the fringes with the spacing of 0.49 nm, 0.34 nm and 0.33 nm, assigned to the (0 0 2) plane of Li2SnO3, the (1 1 0) plane of SnO2 and the (1 1 1) plane of Li2SiO3, respectively. The lattice fringles of Fig. 4d are not clearer than that of Fig. 4b due to the addtion of GE. They indicate that the as-synthesized LSO-LSnO and LSO-LSnO-GE display good crystal structure.
concentration was 11.22 mg/ml. The LSO-LSnO-GE compound was synthesized through a hydrothermal method [9]. 25 ml of GO, 50 ml of alcohol, 0.3 g of Si powder and 3.02 g of LiOH·H2O were added in a 100 ml tafel reactor under the magnetic stirring. 0.25 g of polyethylene glycol (PEG), 3.501 g of SnCl4·5H2O were dissolved in several alcohol and water solution (4:1 in volume) and dropped in the solution above. The solution was stirred magnetically for 1 h and then reacted at 180 °C in the oven for 24 h. Finally, the solution was centrifuged several times and dried to obtain the precursor of LSO-LSnO-GE. The LSO-LSnO compound was prepared using a similar method above except that the GO solution was replaced by water, and the lastly gained solution was kept at 80 ml. Li2SnO3 (LSnO) was prepared by a similar method with LSO-LSnO-GE except that the GO solution and Si powder were not added. The three prepared precursors were all calcinated at 800 °C for 5 h in the atmosphere of Ar to obtain the products. 2.2. Materials characterization The samples were characterized by scanning electron microscopy (SEM, NoVaTM Nano 250, FEI Company), field emission transmission electron microcopy (FETEM, Tecnai G2 F20), X-ray diffraction analysis (XRD, Panalytical Holland) and X-ray photoelectron spectroscopy (XPS, Thermal Scientific England). The porous structure of the samples was analyzed by a Quantachrome Intruments Autosorb IQC at −196 °C and the original density functional theory (DFT) model and the surface area was calculated with the Brunauer-Emmett-Teller (BET) formalism. 2.3. Electrochemical measurements The battery was assembled in two electrode system using metal lithium as counter electrode and CR2032 cells as battery case. The working electrode was prepared as follows. Active material (80%), acetylene black (10%) and PVDF (10%) were dissolve in NMP and mixed to form slurry. The assembling of the battery was conducted in a glove box filled with argon. And the electrolyte used consists of 1 M LiPF6 dissolving in the solution of ethylene carbonate (EC)/diethyl carbonate (DEC) (1:1 in volume). The mass loading of the active material of the anode is 1.6 mg/cm2. In the case of Li-ion full cells, LiMn2O4 was chose as active material for cathode. LiMn2O4 was provided by Jiaozuo polyfluoro chemical co. Ltd. Similarly, the electrode was composed of 90 wt% active materials (LiMn2O4), acetylene black (5%) and PVDF (5%), and N-methyl pyrrolidone (NMP) was used as solvent. The mixture was spread on an Al foil and was used as cathode after drying. In this study, the specific capacity ratio of anode material (LSO-LSnO-GE) and cathode material (LiMn2O4) in the lithium-ion full cell is about 1: (2.5 ∼ 3.0). Cyclic voltammetry (CV) and electrical impedance spectra (EIS) were conducted at CHI660 electrochemical workstation (CH Instruments, USA). Charge and discharge properties were tested by charge and discharge analysis (CT2001, Wuhan Land charge and discharge analysis Lt, d). All these tests were conducted at 25 °C. 3. Results and discussion 3.1. Structural characterization of materials Fig. 1 illustrates the structure change of the samples from Li2SnO3 to LSO-LSnO-GE in the synthesis progress. The LSnO sample was prepared through a reaction of SnCl4·5H2O with a large density of LiOH solution, which is different from the reference before [4]. The Li2SnO3 is the structure of bulks which is composed of many uniform and regular nanoparticles. When doped with Si powder, the Si powder is doped in the first synthesis procedure of Li2SnO3, the Li2SiO3 and Li2SnO3 particles are synthesed at the same time. The Li2SiO3 and Li2SnO3 particles heap up in the structure of bulks. After further doped with graphene,
3.2. The electrochemical performances of materials The electrochemical performances of LSO, LSO-LSnO and LSO254
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Fig. 1. Synthesis procedure of LSnO, LSO-LSnO and LSO-LSnO-GE.
Fig. 2. The XRD curves of LSnO, LSO-LSnO and LSO-LSnO-GE (a); the XPS spectra of LSO-LSnO-GE: Sn (b), C (c) and Si (d), O (e) and the survey spectrum (f).
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Fig. 3. The SEM images of the three samples: LSnO (a), LSO-LSnO (b), LSO-LSnO-GE (c); the elemental mappings of LSO-LSnO-GE (d ∼ h).
decreases to 440.8 mAh/g after 200 cycles, while the capacities of LSOLSnO and LSnO decrease fastly. The initial discharge capacities and the retained capacities of LSO-LSnO-GE are higher than that of LSO-LSnO and LSnO due to the dopant of LSO and graphene. Firstly, according to the formation of LSO-LSnO-GE, LSnO and LSO are closed together and attached on the surface of graphene nanosheets. So, LSO-LSnO-GE composites have better interface bonding, which could provide interconnected Li+ diffusion channels and further shorten the diffusion distance of lithium ions. In addition, GE nanosheets possess more defects to facilitate ion and electron conductivity and further decrease
LSnO-GE composites have been studied in two-electrode cell. Fig. 5a shows the initial discharge and charge capacities of the three samples at the current density of 150 mA/g. The cell potential window is set between 0.01 V and 3.0 V vs. Li+/Li. From the curves we can observe that the LSO-LSnO-GE shows the highest discharge capacity of 1016.5 mAh/ g, while LSO-LSnO and LSnO show a lower capacity of 935 mAh/g and 860 mAh/g, respectively. Fig. 5b shows the cycling performance of the three samples at the current density of 150 mA/g. In the second cycle, the discharge capacity of LSO-LSnO-GE is 750 mAh/g and the coulombic efficiency is 73.6%. The capacity of LSO-LSnO-GE slowly 256
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Fig. 4. The TEM images of LSO-LSnO (a, b) and LSO-LSnO-GE (c, d).
the material (Fig. 6a). The structure of LSO-LSnO is partly remained, while some of particles become to large sphere after the charge and discharge progress, thus the doping of Si can improve the electrochemical performance of Li2SnO3 (Fig. 6b). When doped with graphene, the LSO-LSnO-GE composite can remain its raw structure (Fig. 6c). The large space of graphene can improve the structure of LSO-LSnO-GE, indicating that LSO-LSnO-GE composite has low polarization. And it can imply the well cycling performance of the LSO-LSnO-GE composite. To evaluate the diffusion of lithium ion and further explain the rate capabilities and cycling stabilities of LSO, LSO-LSnO and LSO-LSnO-GE, Fig. 6d shows the EIS curves of the three samples from 0.01 Hz to 100 kHz after 200 cycles. It can be shown that all curves are consisted of a semicircle at the high-middle frequency region and rough straight line at the low frequency region. The high frequency semicircle may be described as the charge transfer resistance among the electrode and electrolyte, and the sloping line is related to the lithium-ion diffusion process. It can be observed that the EIS spectra fitted roughly agree with that of the experiments, indicating that the equivalent circuit diagram is reasonable [17]. The charge and transfer resistances of LSO, LSO-LSnO and LSO-LSnO-GE composites are about 154.2 Ω, 111.5 Ω and 94 Ω, respectively. It demonstrates that the LSO-LSnO-GE has the smallest charge transfer resistance (Rct) among three composites. So, LSO-LSnOGE composite possesses well electrochemistry property. The BET specific surface areas and pore size distributions of LSO, LSO-LSnO and LSO-LSnO-GE were measured by the nitrogen adsorption/desorption method. Fig. 7a shows the nitrogen adsorption-desorption isotherm, and Fig. 7b is the pore diameter distribution of LSO, LSO-LSnO and LSO-LSnO-GE. Results show that the BET specific surface areas calculated of LSO, LSO-LSnO and LSO-LSnO-GE are 1.12 m2/g,
charge transfer resistance [14,27,28]. Table 1 shows the comparison of the initial discharge capacities and the retained capacities between LSO-LSnO-GE and the references. It could be shown that the initial discharge capacity and the retained capacity of LSO-LSnO-GE are higher than that of the related papers [17,29,30]. Fig. 5c shows the curves of the rate performances of the three samples at the current density from 150 mA/g to 300 mA/g, 750 mA/g and lastly turned to 150 mA/g again. The LSO-LSnO-GE displays well rate performance. The capacities of LSO-LSnO-GE are 652 mAh/g, 540.7 mAh/g and 363.3 mAh/g at the current density from 150 mA/g to 300 mA/g and 750 mA/g, respectively. When turned to at the current density of 150 mA/g, the capacity can still retain 552.7 mAh/g. Compared to the LSO-LSnO-GE sample, the capacities of LSO-LSnO and LSnO are 315.1 mAh/g, 197.8 mAh/g, 92.8 mAh/g and 157.8 mAh/g, 137 mAh/g, 73.8 mAh/g from 150 mA/g to 300 mA/g and 750 mA/g, respectively. The higher rate capacity of LSO-LSnO-GE is due to the cooperating effect of graphene and Li2SiO3 doped in the Li2SnO3 sample [5]. The composite of graphene can improve the transport property of lithium ion and electronic conduction property due to its well property. Moreover, the graphene sheets in LSO-LSnO-GE can act as a buffer matrix to provide the paths for the entrance of electrolyte in the lithiation and de-lithiation process [16].Thus the LSO-LSnO-GE composite can possess well rate performance. To explain the rate capabilities and cycling stabilities of LSO, LSOLSnO and LSO-LSnO-GE, we study the structure change before and after charge and discharge of LSO, LSO-LSnO and LSO-LSnO-GE composites by SEM, Fig. 6a, b and c show their SEM images after 200 cycles. After 200 cycles, the surface of the Li2SnO3 electrode shows big cracks and the pulverization of the electrode, which demonstrates the damage of 257
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2.98 m2/g and 7.42 m2/g, which could indicate that the BET specific surface area of LSO-LSnO-GE is relatively higher than that of LSO, LSOLSnO. In addition, the most of the pore diameter distributions of LSO, LSO-LSnO and LSO-LSnO-GE is < 5 nm, and the pore volume of LSOLSnO-GE is higher than that of LSO and LSO-LSnO due to the addition of graphene, which indicates that LSO-LSnO-GE possesses an increasing contact surface between electrolyte and electrode materials to improve its electrochemical performance. CV measurements are used to investigate possible electrochemical reactions of LSO-LSnO-GE electrode during the charge-discharge cycles. Fig. 8a shows the CV curves of the LSO-LSnO-GE sample at 5 cycles. The scanning rate was 0.2 mV s−1 between 0.0 V and 2.5 V. The stably anode and cathode peaks imply the well cycling performance of the material. The anode peaks at ∼0.63 V, ∼0.18 V and ∼0.33 V represent the side reaction with the electrolyte involved as well as the formation of solid electrolyte interphase (SEI) film, the lithiation of Li2SnO3, SnO2 and Li2SiO3, respectively [31]. The cathode peaks at ∼0.70 V and ∼0.29 V represent the delithiation process of LixSn and LixSi [17,31]. The weak redox peaks at 1.60 V and 1.95 V could be caused by the subsidiary redox reaction between Sn and Li2O [27]. To further investigate possible electrochemical reactions of LSO, LSO-LSnO and LSO-LSnO-GE electrodes during the charge-discharge cycles, their phase identifications are performed by the XRD. Fig. 8b shows the XRD patterns of LSO, LSO-LSnO and LSO-LSnO-GE electrodes after the 200th discharge-charge cycle. In the curve of LSO, there are many diffraction peaks of Sn and a small amount of SnO2, which may be ascribed to the de-alloying reaction of LixSn and the redox reaction between Sn and Li2O. In the curves of LSO-LSnO and LSO-LSnO-GE, except the diffraction peaks of Sn, SnO2 and Cu foil, there are a few diffraction peaks of Si (JCPDS 17-0901), which could be ascribed to delithiation process of LixSi. In addition, it could be observed that the diffraction peaks of Sn and SnO2 of LSO-LSnO-GE are roughly stronger than that of LSO-LSnO due to the addition of graphene. Thus, the possible electrochemical reactions of LSO-LSnO-GE could be written as [9,17]: Li2SnO3 + 4Li → 3Li2O + Sn Li2SiO3 + 4Li → 3Li2O + Si Sn + xLi ↔ LixSn (x ≤ 4.4) Si + xLi ↔ LixSi Sn + 2Li2O ↔ SnO2 + 4Li To discuss roughly the practicability of LSO-LSnO-GE used as the anode material for lithium-ion full cells. We employ LSO-LSnO-GE as the anode material and commercial LiMn2O4 as the cathode material to assemble a full cell. The theoretical specific capacity can be obtained according to the following equation [32]: C = 1/(1/CC + 1/CA) = CACC/(CC + CA)
Fig. 5. The initial charge and discharge curves of LSO, LSO-LSnO and LSOLSnO-GE (a); the cycling performance (b) and the rate capabilities of LTO, LSOLSnO and LSO-LSnO-GE (c). The potential window is set between 0.01 and 3.0 V vs. Li+/Li.
Where CA is the theoretical specific capacity of the anode material, CC is the theoretical specific capacity of the cathode material; C is the theoretical specific capacity of full cells. So the theoretical specific capacity is calculated to 100 mAh g−1 for LiMn2O4 /LSO-LSnO-GE full cell. Fig. 9 shows the charge and discharge curves, cycling performance of LSO-LSnO-GE/LiMn2O4 at the current density of 30 mA/g in full cell.
Table 1 The comparison of the initial discharge capacities and the retained capacitied between LSO-LSnO-GE and the references. Materials
The initial discharge capacity, mAh/g
The retained capacity, mAh/g
The current density, mA/g
Li2SiO3-GE [17] GE@ Li2SiO3/Li4Ti5O12 [29] Li2SnO3-GE [30] LSO-LSnO-GE (this work)
878.3 720.6 1552.3 1016.5
200n, 400 200n, 399.2 50n, 602.1 200n, 440.8
150 150 60 150
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Fig. 6. The SEM image of LSO (a), LSO-LSnO (b) and LSO-LSnO-GE (c) composites after 200 cycles; the EIS of LSO, LSO-LSnO and LSO-LSnO-GE after 200 cycles.
Fig. 8. The CV curves of LSO-LSnO-GE (a); the XRD patterns of LSO, LSO-LSnO and LSO-LSnO-GE electrodes after the 200th discharge-charge cycle (b).
Fig. 7. The nitrogen adsorption-desorption isotherm (a) and the pore diameter distribution (b) of LSO, LSO-LSnO and LSO-LSnO-GE. 259
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Fig. 9. The charge and discharge curves (a), cycling performance (b) of LSO-LSnO-GE/LiMn2O4 full cell at 30 mA/g and the application of full cell (c).
and Grant No. 162102310152 and the Key Science Research Program of High School of Henan province under Grant No. 16A480007.
In Fig. 9a, the LSO-LSnO-GE shows the initial discharge capacity of 263.1 mAh/g, and its initial coulombic efficiency is 81.1%, which is roughly higher than that of carbon in full cells [19]. This improvement could be explained as follows. Firstly, the theoretical specific capacity of LSO-LSnO-GE is > 600 mAh/g, which is higher than that of the commercial carbon [5]. Moreover, according to the formation of LSOLSnO-GE, LSnO and LSO are closed together and attached on the surface of graphene nanosheets because the effect of an electrostatic adherence takes place between Sn4+ and GE with a few negative charges. So, the structure can depress the electrochemical polarization (Fig. 6c), decrease charge transfer resistance (Fig. 6d), and further speed up the transmission of lithium ions [29,33]. After 50 cycles, its coulombic efficiency is 90.6%, and the discharge capacity retains 91.5 mAh/g (Fig. 9b). In addition, the light-emitting diode shows that the power is switched on in Fig. 9c, which further indicates the LSO-LSnO-GE can be used as the anode material for lithium-ion full cells.
References [1] J. Luo, C.-C. Fang, N.-L. Wu, High polarity poly (vinylidene difluoride) thin coating for dendrite-free and high performance lithium metal anodes, Adv. Energy Mater. 8 (2017) 2. [2] J.-M. Tarascon, M. Armand, Issues and challenges facing rechargeable lithium batteries, Nature 414 (2001) 359–367. [3] E. Zhao, X. Liu, H. Zhao, X. Xiao, Z. Hu, Ion conducting Li2SiO3-coated lithium-rich layered oxide exhibiting high rate capability and low polarization, Chem. Commun. 51 (2015) 9093–9096. [4] Q.F. Wang, Y. Huang, J. Miao, Y. Zhao, Y. Wang, Synthesis and properties of carbon-doped Li2SnO3 nanocomposite as cathode material for lithium-ion batteries, Mater. Lett. 71 (2012) 66–69. [5] Y. Zhao, Y. Huang, Q.F. Wang, X.Y. Wang, M. Zong, Carbon-doped Li2SnO3/graphene as ananode material for lithium-ionbatteries, Ceram. Int. 39 (2013) 1741–1747. [6] H.J. Wang, X.Y. Jiang, Y.Q. Chai, X. Yang, R. Yuan, Sandwich-like C@SnO2/Sn/ void@C hollow spheres as improved anode materials for lithium ion batteries, J. Power Sources 379 (2018) 191–196. [7] D.L. Jia, X. Li, J.G. Huang, A. Hierarchical, Nanofibrous, tin-oxide/Silicon composite derived from cellulose as a high-performance anode material for lithium-ion batteries, Chem. Select. 2 (2017) 5667–5676. [8] Y. Zhao, Y. Huang, Q.F. Wang, Graphene supportedpoly-pyrrole (PPY)/ Li2SnO3 ternary composites as anodematerialsforlithiumionbatteries, Ceram. Int. 39 (2013) 6861–6866. [9] Q.F. Wang, Y. Huang, J. Miao, Y. Wang, Y. Zhao, Hydrothermal derived Li2SnO3/C composite as negative electrode materials for lithium-ion batteries, Appl. Surf. Sci. 258 (2012) 6923–6929. [10] H.J. Tian, S.L. Zhang, H.J. Ying, Z. Meng, W.Q. Han, W. He, Scalable synthesis of Si/ C anode enhanced by FeSix nanoparticles from low-cost ferrosilicon for lithium-ion batteries, J. Power Sources 353 (2017) 270–276. [11] L.R. Shi, C.L. Pang, S.L. Chen, M.Z. Wang, K.X. Wang, Z.J. Tan, P. Gao, J.G. Ren, Y.Y. Huang, H.L. Peng, Vertical graphene growth on SiO microparticles for stable lithium ion battery anodes, Nano Lett. 17 (2017) 3681–3687. [12] K. Wang, Y. Huang, M. Yu, X.L. Qin, A facile route to synthesize hollow Si-Ni3Sn2 nanospheres@ reduced graphene oxide nanocomposites for high performance lithium-ion batteries, J. Alloys Compd. 698 (2017) 547–554. [13] Q.J. Zhao, Y.H. Huang, X.L. Hu, A Si/C nanocomposite anode by ball milling for highly reversible sodium storage, Electrochem. Commun. 70 (2016) 8–12. [14] L.H. Yin, M.B. Wu, Y.P. Li, Synthesis of SiO2 @ carbon-graphene hybrids as anode materials of lithium-ion batteries, New Carbon Mater. 32 (2017) 311–318.
4. Conclusions The LSO-LSnO-GE sample was synthesized through a hydro-thermal method. The LSO-LSnO bulks disperse on the surface and interval of the grphene. Li2SnO3 and graphene can efficiently ease the volume change of Li2SnO3 during cycling process and enhance the electrochemistry property. The initial specific discapacity of LSO-LSnO-GE composite is 1016.5 mAh/g at the current density of 150 mA/g, and its specific capacity is 440.8 mAh/g after 200 cycles. In addition, the LSO-LSnO-GE shows the initial discharge capacity of 263.1 mAh/g at the current density of 30 mA/g in LSO-LSnO-GE/LiMn2O4 full cell, which indicates that LSO-LSnO-GE may be used as the anode material for lithium-ion full cells. Acknowledgments This work was supported by the Key Science and Technology Research Program of Henan province under Grant No. 152102210106 260
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[24] S.Y. Li, W.H. Xie, L.L. Gu, Z.J. Liu, X.Y. Hou, B.L. Liu, Q. Wang, D.Y. He, Facilely scraping Si nanoparticles@reduced graphene oxide sheets onto nickel foam as binder-free electrodes for lithium ion batteries, Electrochim. Acta 193 (2016) 246–252. [25] G. Niu, G. Capellini, G. Lupina, Photodetection in hybrid single-Layer graphene/ fully coherent germanium island nanostructures selectively grown on silicon nanotip patterns, ACS Appl. Mater. Interfaces 8 (2016) 2017–2026. [26] P. Wu, X.L. Xu, Q.Y. Zhu, X.S. Zhu, Y.W. Tang, Y.M. Zhou, Self-assembled graphenewrapped SnO2 nanotubes nanohybrid as a high-performance anode material for lithium-ion batteries, J. Alloys Compd. 626 (2015) 234–238. [27] M. Shirotori, S. Nishimura, K. Ebitani, Fine-crystallized LDHs prepared with SiO2 spheres as highly active solid base catalysts, J. Mater. Chem. A 5 (2017) 6947–6957. [28] G.R. Hu, M.F. Zhang, L.L. Wu, Z.D. Peng, K. Du, Y.B. Cao, Enhanced electrochemical performance of LiNi0.5Co0.2Mn0.3O2 cathodes produced via nanoscale coating of Li+-conductive Li2SnO3, Electrochim. Acta 213 (2016) 547–556. [29] Q.F. Wang, S. Yang, J. Miao, M.W. Lu, T. Wen, J.F. Sun, Graphene supported Li2SiO3/Li4Ti5O12 nanocomposites with improved electrochemical performance as anode material for lithium-ion batteries, Appl. Surf. Sci. 403 (2017) 635–644. [30] Y. Zhao, Y. Huang, Q.F. Wang, X.Y. Wang, M. Zong, H.W. Wu, W. Zhang, Graphene supported Li2SnO3 as anode material for lithium-ion batteries, Electron. Mater. Lett. 9 (2013) 683–1386. [31] Y. Tian, Q.H. Tian, Z.X. Zhang, L. Yang, S. Hirano, Carbon-tin oxides@ titanium dioxide core-shell nanospheres for lithium ion battery anode electrodes with high rate cyclability, Mater. Lett. 155 (2015) 142–145. [32] U. Kasavajjula, C. Wang, A.J. Appleby, Nano-and bulk-silicon-based insertion anodes for lithium-ion secondary cells, J. Power Sources 163 (2007) 1003–1039. [33] J.A. Brant, D.M. Massi, N.A.W. Holzwarth, J.H. MacNeil, A.P. Douvalis, T. Bakas, Fast lithium ion conduction in Li2SnS3: Synthesis, physicochemical characterization, and electronic structure, Chem. Mater. 27 (2015) 189–196.
[15] Z.W. Zhou, Y.T. Liu, X.M. Xie, Constructing novel Si@SnO2 core-shell heterostructures by facile self-assembly of SnO2 nanowires on silicon hollow nanospheres for large, reversible lithium storage, ACS Appl. Mater. Interfaces 8 (2016) 7092–7100. [16] G.R. Hu, M.F. Zhang, L.L. Wu, Z.D. Peng, K. Du, Y.B. Cao, Effects of Li2SiO3 coating on the performance of LiNi0.5Co0.2Mn0.3O2 cathode material, J. Alloys Compd. 90 (2017) 6589–6597. [17] S. Yang, Q.F. Wang, J. Miao, J.Y. Zhang, D.F. Zhang, Y.M. Chen, H. Yang, Synthesis of graphene supported Li2SiO3 as a high performance anode material for lithium-ion batteries, Appl. Surf. Sci. 444 (2018) 522–529. [18] Y.L. Deng, J.R. Mou, H.L. Wu, N. Jiang, Q.J. Zheng, K.H. Lam, C.G. Xu, D.M. Lin, A superior Li2SiO3-composite LiNi0.5Mn1.5O4 cathode for high-voltage and high-performance lithium-ion batteries, Electrochem. Acta 235 (2017) 19–31. [19] S.M. Ma, S.H. Shen, X.G. Kong, T. Gao, X.J. Chen, C.J. Xiao, T.C. Lu, A new interatomic pair potential for the modeling of crystalline Li2SiO3, Mater. Design 118 (2017) 218–225. [20] Z.G. Zang, X.F. Zeng, M. Wang, W. Hua, C.R. Liu, X.S. Tang, Tunable photoluminescence of water-soluble AgInZnS-grapheneoxide (GO) nanocomposites and their application in-vivo bioimaging, Sensor. Actuat. B-Chem. 252 (2017) 1179–1186. [21] J. Wei, Z.G. Zang, Y. Zhang, M. Wang, J.H. Du, X.S. Tang, Enhanced performance of light-controlled conductive switching in hybrid cuprous oxide/reduced graphene oxide (Cu2O/rGO) nanocomposites, Opt. Lett. 42 (2017) 911–914. [22] H.J. Huang, J. Zhang, L. Jiang, Z.G. Zang, Preparation of cubic Cu2O nanoparticles wrapped by reduced graphene oxide for the efficient removal of rhodamine B, J. Alloys Compd. 718 (2017) 112–115. [23] R.Y. Li, Y.Y. Jiang, X.Y. Zhou, Z.J. Li, Z.G. Gu, G.L. Wang, J.K. Liu, Significantly enhanced eletrochemical performance of lithium titanate anode for lithium ion battery by the hybrid of nitrogen and sulfur co-doped graphene quantum dots, Electrochim. Acta 178 (2015) 303–311.
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Full Length Article
Synthesis of graphene supported Li2SiO3/Li2SnO3 anode material for rechargeable lithium ion batteries ⁎
T
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Qiufen Wanga, , Shuai Yanga, Juan Miaob, , Yanlei Zhanga, Dafeng Zhanga, Yumei Chena, Zhi Lia a b
Henan Key Laboratory of Coal Green Conversion, College of Chemistry and Chemical Engineering, Henan Polytechnic University, Jiaozuo 454000, China Medical College, Henan Polytechnic University, Jiaozuo 454000, China
A R T I C LE I N FO
A B S T R A C T
Keywords: Lithium ion battery Li2SiO3 Li2SnO3 Graphene Anode material
Graphene supported Li2SiO3/Li2SnO3 (LSO-LSnO-GE) composite has been prepared through a hydrothermal method. The microstructure and electrochemical performance of LSO-LSnO-GE have been investigated by a variety of means. When used as an anode material for lithium ion battery, the initial specific discapacity of LSOLSnO-GE composite is 1016.5 mAh/g at the current density of 150 mA/g, and its specific capacity is 440.8 mAh/ g after 200 cycles. The improvement of lithium storage performance of LSO-LSnO-GE composite can be explained the synergistic effect of that LSnO, LSO and graphene. In addition, the LSO-LSnO-GE shows the initial discharge capacity of 263.1 mAh/g at the current density of 30 mA/g in LSO-LSnO-GE/LiMn2O4 full cell, which could indicate that LSO-LSnO-GE may be used as an anode material for lithium ion full cells.
1. Introduction Lithium ion battery as a rechargeable cell is widely used due to its advantage characterizes of environmental friendly, high density and lower self-discharge rate [1–3]. Anode and cathode materials are the important parts of lithium ion battery. Li2SnO3, as a kind of Sn-based materials, has been researched in many references as a potential anode material [4]. Its theoretical capacity is > 600 mAh/g, which is much higher than that of the commercial graphite [5]. However the large volume change of about 300% hinders its application in high energy lithium ion battery [6,7]. These materials, such as Li2SnO3/ppy/graphene [8], Li2SnO3/carbon and etc. [9] have been prepared to solve this problem. Si-based materials have been also paid much attention due to its high capacity [10,11]. But the large expansion-contraction volume occurs when Li+ is alloyed and de-alloyed. Thus compositing with carbon materials has been a wide modified method [12], such as Si/C [13] and SiO2/C [14] composites. As large volume change materials, the compositing of Si-based materials and Sn-based materials, such as Si/SnO2/C composite, has been roughly reported [15]. As a kind of Si based materials, the Li2SiO3 has been synthesized to enhance ion transport abilities for its well structure and well ion transport property [3,16–19]. Graphene, as a kind of the carbon-based nanomaterials, has been widely used in several fields due to its large specific surface area, good ion and electronic conductivities, such as bioimaging,
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photocatalysis, memory storage and logic circuits, etc. [20–22]. When used as an anode material in lithium ion battery, the merits can effectively improve the electrochemical performances of the composites [23,24]. In this article, we used Si-based material and graphene to modify Li2SnO3, and to improve its property. Thus graphene supported Li2SiO3/Li2SnO3 (LSO-LSnO-GE) composite has been synthesized through a hydrothermal method. The structure, morphology and electrochemical performance of LSO-LSnO-GE have been characterized and compared with Li2SiO3/Li2SnO3 (LSO-LSnO). 2. Materials and methods 2.1. Synthesis of electrode materials All the reagents were directly used without further purification. Graphite oxide (GO) was prepared by a modified Hummers’ method [17]. 2 g of NaNO3 was added into 110 ml of H2SO4 (98%) under the magnetic stirring. When the temperature was below 5 °C, 2 g of graphite flakes and 12 g of potassium permanganate were slowly added into it and stirred for 1.5 ∼ 2 h. The beaker was transferred to a thermostatic water bath at 35 °C and stirred for 2 ∼ 2.5 h. And 80 ml of demonized water was added into it at 85 °C. After that, 15 ml of H2O2 and 400 ml of demonized water were added in it. Finally, the solution was centrifuged several times until the pH of the solution was 5.0 ∼ 6.0. The GO
Corresponding authors. E-mail addresses: [email protected] (Q. Wang), [email protected] (J. Miao).
https://doi.org/10.1016/j.apsusc.2018.11.055 Received 9 July 2018; Received in revised form 28 September 2018; Accepted 6 November 2018 Available online 07 November 2018 0169-4332/ © 2018 Published by Elsevier B.V.
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the crystal of the Li2SiO3-Li2SnO3-GE compound was produced in the space of graphene and some bulks were attached on the surface of the graphene. The phase identifications of the as-synthesized samples are confirmed by XRD patterns, as shown in Fig. 2a. We can observe the main diffraction peaks of LSnO (0 0 2), (1 1 0), (− 1 1), (2 0 0), (0 0 4), (2 0 2), (1 3 3), (0 0 6), (0 6 0), (1 3 5) and (0 6 2) at 17.97°, 19.54°, 20.23°, 34.36°, 36.40°, 41.91°, 45.94°, 55.86°, 60.46°, 61.06° and 63.63°, which may agree with the standard patterns of Li2SnO3 (JCPDS 31-0761), indicating the as-synthesized LSnO with the monoclinic crystal structure. Moreover, a few diffraction peaks of SnO2 (1 1 0) and (2 1 1) at 26.61° and 51.78° can be observed because of the incomplete reaction between SnCl4·5H2O and LiOH, which may agree with the standard patterns of SnO2 (JCPDS 41-1445). When compositing with Si powder, the main diffraction peaks of the Li2SiO3 (2 0 0), (1 1 1), (0 2 0), (0 0 2) and (0 2 2) at 18.89°, 26.98°, 33.18°, 38.61° and 51.80° agree with the standard patterns of Li2SiO3 (JCPDS 29-0829) due to the reaction between Si and LiOH. In the curve of LSO-LSnO-GE, except the main diffraction peaks of Li2SiO3 and Li2SnO3, few diffraction peaks of Sn (JCPDS 04-0673) can be shown, which could be caused by the hydrolytic reaction of SnCl4·5H2O. To further investigate the surface structures and the binding natures of the elements, the XPS spectra of LSO-LSnO-GE have been provided in Fig. 2. The spectrum of Sn 3d (Fig. 2b) has two pesks at 485.48 eV and 493.88 eV, corresponding to Sn 3d5/2 and Sn 3d3/2, which represents the Sn mental and Sn4+ in Li2SnO3 [9]. The C1s spectrum in Fig. 2c displays several probably deconvolved peaks. The peaks fitted at 284.18 eV, 285.88 eV, 287.58 eV and 288.48 eV represent C]C, CeC, CeO and C]O bond in graphene [25]. The spectrum of Si 2p (Fig. 2d) shows the peaks at 100.88 eV, representing the existence of Si4+ [26]. The O 1s spectrum (Fig. 2e) in 530.28 eV represents the O2−, which can form the SneO band and SieO bands. The curve of Fig. 2f shows the existence of Li, Si, Sn, O and C elements, which could be accorded with the photoelectron spectroscopy of LSO-LSnO-GE. These can further verify the structures of LSO-LSnO-GE. The morphology of the material is an important factor for the electrochemical property. Fig. 3 shows the SEM image of the three samples. The Li2SnO3 (Fig. 3a) is a bulk structure with the diameter of 200–600 nm, which is made up of many small nanoparticles. When doped with Si powder, the LSO-LSnO (Fig. 3b) shows the porous bulk structure, which is also composed of many small nanoparticles. And the LSO-LSnO bulks are more irregular than that of Li2SnO3. The reason could be as follows. According to the formation of LSO-LSnO, the Si powder is doped in the first synthesis procedure of Li2SnO3, the Li2SiO3 and Li2SnO3 particles are synthesed at the same time, further form the structure of the porous and irregular bulks. In LSO-LSnO-GE sample (Fig. 3c), the porous and irregular LSO-LSnO bulks are attached on the surface of graphene nanosheets. Fig. 3d, e, f, g and h show the elemental mapping images of the inset in Fig. 3c. These clearly display the distributions of Li, Sn, C, Si and O, which demonstrates that LSO and LSnO particles are coated together. Fig. 4 shows the TEM images of LSO-LSnO and LSO-LSnO-GE. The TEM images are in agreement with as-presented SEM images. As shown in Fig. 4a, the LSO-LSnO sample is a bulk structure, which is composed of many small nanoparticles in the size range from 20 nm to 50 nm. In Fig. 4c, the irregular LSO-LSnO bulks are attached on the surface of graphene nanosheets. Fig. 4b and d exhibits the fringes with the spacing of 0.49 nm, 0.34 nm and 0.33 nm, assigned to the (0 0 2) plane of Li2SnO3, the (1 1 0) plane of SnO2 and the (1 1 1) plane of Li2SiO3, respectively. The lattice fringles of Fig. 4d are not clearer than that of Fig. 4b due to the addtion of GE. They indicate that the as-synthesized LSO-LSnO and LSO-LSnO-GE display good crystal structure.
concentration was 11.22 mg/ml. The LSO-LSnO-GE compound was synthesized through a hydrothermal method [9]. 25 ml of GO, 50 ml of alcohol, 0.3 g of Si powder and 3.02 g of LiOH·H2O were added in a 100 ml tafel reactor under the magnetic stirring. 0.25 g of polyethylene glycol (PEG), 3.501 g of SnCl4·5H2O were dissolved in several alcohol and water solution (4:1 in volume) and dropped in the solution above. The solution was stirred magnetically for 1 h and then reacted at 180 °C in the oven for 24 h. Finally, the solution was centrifuged several times and dried to obtain the precursor of LSO-LSnO-GE. The LSO-LSnO compound was prepared using a similar method above except that the GO solution was replaced by water, and the lastly gained solution was kept at 80 ml. Li2SnO3 (LSnO) was prepared by a similar method with LSO-LSnO-GE except that the GO solution and Si powder were not added. The three prepared precursors were all calcinated at 800 °C for 5 h in the atmosphere of Ar to obtain the products. 2.2. Materials characterization The samples were characterized by scanning electron microscopy (SEM, NoVaTM Nano 250, FEI Company), field emission transmission electron microcopy (FETEM, Tecnai G2 F20), X-ray diffraction analysis (XRD, Panalytical Holland) and X-ray photoelectron spectroscopy (XPS, Thermal Scientific England). The porous structure of the samples was analyzed by a Quantachrome Intruments Autosorb IQC at −196 °C and the original density functional theory (DFT) model and the surface area was calculated with the Brunauer-Emmett-Teller (BET) formalism. 2.3. Electrochemical measurements The battery was assembled in two electrode system using metal lithium as counter electrode and CR2032 cells as battery case. The working electrode was prepared as follows. Active material (80%), acetylene black (10%) and PVDF (10%) were dissolve in NMP and mixed to form slurry. The assembling of the battery was conducted in a glove box filled with argon. And the electrolyte used consists of 1 M LiPF6 dissolving in the solution of ethylene carbonate (EC)/diethyl carbonate (DEC) (1:1 in volume). The mass loading of the active material of the anode is 1.6 mg/cm2. In the case of Li-ion full cells, LiMn2O4 was chose as active material for cathode. LiMn2O4 was provided by Jiaozuo polyfluoro chemical co. Ltd. Similarly, the electrode was composed of 90 wt% active materials (LiMn2O4), acetylene black (5%) and PVDF (5%), and N-methyl pyrrolidone (NMP) was used as solvent. The mixture was spread on an Al foil and was used as cathode after drying. In this study, the specific capacity ratio of anode material (LSO-LSnO-GE) and cathode material (LiMn2O4) in the lithium-ion full cell is about 1: (2.5 ∼ 3.0). Cyclic voltammetry (CV) and electrical impedance spectra (EIS) were conducted at CHI660 electrochemical workstation (CH Instruments, USA). Charge and discharge properties were tested by charge and discharge analysis (CT2001, Wuhan Land charge and discharge analysis Lt, d). All these tests were conducted at 25 °C. 3. Results and discussion 3.1. Structural characterization of materials Fig. 1 illustrates the structure change of the samples from Li2SnO3 to LSO-LSnO-GE in the synthesis progress. The LSnO sample was prepared through a reaction of SnCl4·5H2O with a large density of LiOH solution, which is different from the reference before [4]. The Li2SnO3 is the structure of bulks which is composed of many uniform and regular nanoparticles. When doped with Si powder, the Si powder is doped in the first synthesis procedure of Li2SnO3, the Li2SiO3 and Li2SnO3 particles are synthesed at the same time. The Li2SiO3 and Li2SnO3 particles heap up in the structure of bulks. After further doped with graphene,
3.2. The electrochemical performances of materials The electrochemical performances of LSO, LSO-LSnO and LSO254
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Fig. 1. Synthesis procedure of LSnO, LSO-LSnO and LSO-LSnO-GE.
Fig. 2. The XRD curves of LSnO, LSO-LSnO and LSO-LSnO-GE (a); the XPS spectra of LSO-LSnO-GE: Sn (b), C (c) and Si (d), O (e) and the survey spectrum (f).
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Fig. 3. The SEM images of the three samples: LSnO (a), LSO-LSnO (b), LSO-LSnO-GE (c); the elemental mappings of LSO-LSnO-GE (d ∼ h).
decreases to 440.8 mAh/g after 200 cycles, while the capacities of LSOLSnO and LSnO decrease fastly. The initial discharge capacities and the retained capacities of LSO-LSnO-GE are higher than that of LSO-LSnO and LSnO due to the dopant of LSO and graphene. Firstly, according to the formation of LSO-LSnO-GE, LSnO and LSO are closed together and attached on the surface of graphene nanosheets. So, LSO-LSnO-GE composites have better interface bonding, which could provide interconnected Li+ diffusion channels and further shorten the diffusion distance of lithium ions. In addition, GE nanosheets possess more defects to facilitate ion and electron conductivity and further decrease
LSnO-GE composites have been studied in two-electrode cell. Fig. 5a shows the initial discharge and charge capacities of the three samples at the current density of 150 mA/g. The cell potential window is set between 0.01 V and 3.0 V vs. Li+/Li. From the curves we can observe that the LSO-LSnO-GE shows the highest discharge capacity of 1016.5 mAh/ g, while LSO-LSnO and LSnO show a lower capacity of 935 mAh/g and 860 mAh/g, respectively. Fig. 5b shows the cycling performance of the three samples at the current density of 150 mA/g. In the second cycle, the discharge capacity of LSO-LSnO-GE is 750 mAh/g and the coulombic efficiency is 73.6%. The capacity of LSO-LSnO-GE slowly 256
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Fig. 4. The TEM images of LSO-LSnO (a, b) and LSO-LSnO-GE (c, d).
the material (Fig. 6a). The structure of LSO-LSnO is partly remained, while some of particles become to large sphere after the charge and discharge progress, thus the doping of Si can improve the electrochemical performance of Li2SnO3 (Fig. 6b). When doped with graphene, the LSO-LSnO-GE composite can remain its raw structure (Fig. 6c). The large space of graphene can improve the structure of LSO-LSnO-GE, indicating that LSO-LSnO-GE composite has low polarization. And it can imply the well cycling performance of the LSO-LSnO-GE composite. To evaluate the diffusion of lithium ion and further explain the rate capabilities and cycling stabilities of LSO, LSO-LSnO and LSO-LSnO-GE, Fig. 6d shows the EIS curves of the three samples from 0.01 Hz to 100 kHz after 200 cycles. It can be shown that all curves are consisted of a semicircle at the high-middle frequency region and rough straight line at the low frequency region. The high frequency semicircle may be described as the charge transfer resistance among the electrode and electrolyte, and the sloping line is related to the lithium-ion diffusion process. It can be observed that the EIS spectra fitted roughly agree with that of the experiments, indicating that the equivalent circuit diagram is reasonable [17]. The charge and transfer resistances of LSO, LSO-LSnO and LSO-LSnO-GE composites are about 154.2 Ω, 111.5 Ω and 94 Ω, respectively. It demonstrates that the LSO-LSnO-GE has the smallest charge transfer resistance (Rct) among three composites. So, LSO-LSnOGE composite possesses well electrochemistry property. The BET specific surface areas and pore size distributions of LSO, LSO-LSnO and LSO-LSnO-GE were measured by the nitrogen adsorption/desorption method. Fig. 7a shows the nitrogen adsorption-desorption isotherm, and Fig. 7b is the pore diameter distribution of LSO, LSO-LSnO and LSO-LSnO-GE. Results show that the BET specific surface areas calculated of LSO, LSO-LSnO and LSO-LSnO-GE are 1.12 m2/g,
charge transfer resistance [14,27,28]. Table 1 shows the comparison of the initial discharge capacities and the retained capacities between LSO-LSnO-GE and the references. It could be shown that the initial discharge capacity and the retained capacity of LSO-LSnO-GE are higher than that of the related papers [17,29,30]. Fig. 5c shows the curves of the rate performances of the three samples at the current density from 150 mA/g to 300 mA/g, 750 mA/g and lastly turned to 150 mA/g again. The LSO-LSnO-GE displays well rate performance. The capacities of LSO-LSnO-GE are 652 mAh/g, 540.7 mAh/g and 363.3 mAh/g at the current density from 150 mA/g to 300 mA/g and 750 mA/g, respectively. When turned to at the current density of 150 mA/g, the capacity can still retain 552.7 mAh/g. Compared to the LSO-LSnO-GE sample, the capacities of LSO-LSnO and LSnO are 315.1 mAh/g, 197.8 mAh/g, 92.8 mAh/g and 157.8 mAh/g, 137 mAh/g, 73.8 mAh/g from 150 mA/g to 300 mA/g and 750 mA/g, respectively. The higher rate capacity of LSO-LSnO-GE is due to the cooperating effect of graphene and Li2SiO3 doped in the Li2SnO3 sample [5]. The composite of graphene can improve the transport property of lithium ion and electronic conduction property due to its well property. Moreover, the graphene sheets in LSO-LSnO-GE can act as a buffer matrix to provide the paths for the entrance of electrolyte in the lithiation and de-lithiation process [16].Thus the LSO-LSnO-GE composite can possess well rate performance. To explain the rate capabilities and cycling stabilities of LSO, LSOLSnO and LSO-LSnO-GE, we study the structure change before and after charge and discharge of LSO, LSO-LSnO and LSO-LSnO-GE composites by SEM, Fig. 6a, b and c show their SEM images after 200 cycles. After 200 cycles, the surface of the Li2SnO3 electrode shows big cracks and the pulverization of the electrode, which demonstrates the damage of 257
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2.98 m2/g and 7.42 m2/g, which could indicate that the BET specific surface area of LSO-LSnO-GE is relatively higher than that of LSO, LSOLSnO. In addition, the most of the pore diameter distributions of LSO, LSO-LSnO and LSO-LSnO-GE is < 5 nm, and the pore volume of LSOLSnO-GE is higher than that of LSO and LSO-LSnO due to the addition of graphene, which indicates that LSO-LSnO-GE possesses an increasing contact surface between electrolyte and electrode materials to improve its electrochemical performance. CV measurements are used to investigate possible electrochemical reactions of LSO-LSnO-GE electrode during the charge-discharge cycles. Fig. 8a shows the CV curves of the LSO-LSnO-GE sample at 5 cycles. The scanning rate was 0.2 mV s−1 between 0.0 V and 2.5 V. The stably anode and cathode peaks imply the well cycling performance of the material. The anode peaks at ∼0.63 V, ∼0.18 V and ∼0.33 V represent the side reaction with the electrolyte involved as well as the formation of solid electrolyte interphase (SEI) film, the lithiation of Li2SnO3, SnO2 and Li2SiO3, respectively [31]. The cathode peaks at ∼0.70 V and ∼0.29 V represent the delithiation process of LixSn and LixSi [17,31]. The weak redox peaks at 1.60 V and 1.95 V could be caused by the subsidiary redox reaction between Sn and Li2O [27]. To further investigate possible electrochemical reactions of LSO, LSO-LSnO and LSO-LSnO-GE electrodes during the charge-discharge cycles, their phase identifications are performed by the XRD. Fig. 8b shows the XRD patterns of LSO, LSO-LSnO and LSO-LSnO-GE electrodes after the 200th discharge-charge cycle. In the curve of LSO, there are many diffraction peaks of Sn and a small amount of SnO2, which may be ascribed to the de-alloying reaction of LixSn and the redox reaction between Sn and Li2O. In the curves of LSO-LSnO and LSO-LSnO-GE, except the diffraction peaks of Sn, SnO2 and Cu foil, there are a few diffraction peaks of Si (JCPDS 17-0901), which could be ascribed to delithiation process of LixSi. In addition, it could be observed that the diffraction peaks of Sn and SnO2 of LSO-LSnO-GE are roughly stronger than that of LSO-LSnO due to the addition of graphene. Thus, the possible electrochemical reactions of LSO-LSnO-GE could be written as [9,17]: Li2SnO3 + 4Li → 3Li2O + Sn Li2SiO3 + 4Li → 3Li2O + Si Sn + xLi ↔ LixSn (x ≤ 4.4) Si + xLi ↔ LixSi Sn + 2Li2O ↔ SnO2 + 4Li To discuss roughly the practicability of LSO-LSnO-GE used as the anode material for lithium-ion full cells. We employ LSO-LSnO-GE as the anode material and commercial LiMn2O4 as the cathode material to assemble a full cell. The theoretical specific capacity can be obtained according to the following equation [32]: C = 1/(1/CC + 1/CA) = CACC/(CC + CA)
Fig. 5. The initial charge and discharge curves of LSO, LSO-LSnO and LSOLSnO-GE (a); the cycling performance (b) and the rate capabilities of LTO, LSOLSnO and LSO-LSnO-GE (c). The potential window is set between 0.01 and 3.0 V vs. Li+/Li.
Where CA is the theoretical specific capacity of the anode material, CC is the theoretical specific capacity of the cathode material; C is the theoretical specific capacity of full cells. So the theoretical specific capacity is calculated to 100 mAh g−1 for LiMn2O4 /LSO-LSnO-GE full cell. Fig. 9 shows the charge and discharge curves, cycling performance of LSO-LSnO-GE/LiMn2O4 at the current density of 30 mA/g in full cell.
Table 1 The comparison of the initial discharge capacities and the retained capacitied between LSO-LSnO-GE and the references. Materials
The initial discharge capacity, mAh/g
The retained capacity, mAh/g
The current density, mA/g
Li2SiO3-GE [17] GE@ Li2SiO3/Li4Ti5O12 [29] Li2SnO3-GE [30] LSO-LSnO-GE (this work)
878.3 720.6 1552.3 1016.5
200n, 400 200n, 399.2 50n, 602.1 200n, 440.8
150 150 60 150
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Fig. 6. The SEM image of LSO (a), LSO-LSnO (b) and LSO-LSnO-GE (c) composites after 200 cycles; the EIS of LSO, LSO-LSnO and LSO-LSnO-GE after 200 cycles.
Fig. 8. The CV curves of LSO-LSnO-GE (a); the XRD patterns of LSO, LSO-LSnO and LSO-LSnO-GE electrodes after the 200th discharge-charge cycle (b).
Fig. 7. The nitrogen adsorption-desorption isotherm (a) and the pore diameter distribution (b) of LSO, LSO-LSnO and LSO-LSnO-GE. 259
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Fig. 9. The charge and discharge curves (a), cycling performance (b) of LSO-LSnO-GE/LiMn2O4 full cell at 30 mA/g and the application of full cell (c).
and Grant No. 162102310152 and the Key Science Research Program of High School of Henan province under Grant No. 16A480007.
In Fig. 9a, the LSO-LSnO-GE shows the initial discharge capacity of 263.1 mAh/g, and its initial coulombic efficiency is 81.1%, which is roughly higher than that of carbon in full cells [19]. This improvement could be explained as follows. Firstly, the theoretical specific capacity of LSO-LSnO-GE is > 600 mAh/g, which is higher than that of the commercial carbon [5]. Moreover, according to the formation of LSOLSnO-GE, LSnO and LSO are closed together and attached on the surface of graphene nanosheets because the effect of an electrostatic adherence takes place between Sn4+ and GE with a few negative charges. So, the structure can depress the electrochemical polarization (Fig. 6c), decrease charge transfer resistance (Fig. 6d), and further speed up the transmission of lithium ions [29,33]. After 50 cycles, its coulombic efficiency is 90.6%, and the discharge capacity retains 91.5 mAh/g (Fig. 9b). In addition, the light-emitting diode shows that the power is switched on in Fig. 9c, which further indicates the LSO-LSnO-GE can be used as the anode material for lithium-ion full cells.
References [1] J. Luo, C.-C. Fang, N.-L. Wu, High polarity poly (vinylidene difluoride) thin coating for dendrite-free and high performance lithium metal anodes, Adv. Energy Mater. 8 (2017) 2. [2] J.-M. Tarascon, M. Armand, Issues and challenges facing rechargeable lithium batteries, Nature 414 (2001) 359–367. [3] E. Zhao, X. Liu, H. Zhao, X. Xiao, Z. Hu, Ion conducting Li2SiO3-coated lithium-rich layered oxide exhibiting high rate capability and low polarization, Chem. Commun. 51 (2015) 9093–9096. [4] Q.F. Wang, Y. Huang, J. Miao, Y. Zhao, Y. Wang, Synthesis and properties of carbon-doped Li2SnO3 nanocomposite as cathode material for lithium-ion batteries, Mater. Lett. 71 (2012) 66–69. [5] Y. Zhao, Y. Huang, Q.F. Wang, X.Y. Wang, M. Zong, Carbon-doped Li2SnO3/graphene as ananode material for lithium-ionbatteries, Ceram. Int. 39 (2013) 1741–1747. [6] H.J. Wang, X.Y. Jiang, Y.Q. Chai, X. Yang, R. Yuan, Sandwich-like C@SnO2/Sn/ void@C hollow spheres as improved anode materials for lithium ion batteries, J. Power Sources 379 (2018) 191–196. [7] D.L. Jia, X. Li, J.G. Huang, A. Hierarchical, Nanofibrous, tin-oxide/Silicon composite derived from cellulose as a high-performance anode material for lithium-ion batteries, Chem. Select. 2 (2017) 5667–5676. [8] Y. Zhao, Y. Huang, Q.F. Wang, Graphene supportedpoly-pyrrole (PPY)/ Li2SnO3 ternary composites as anodematerialsforlithiumionbatteries, Ceram. Int. 39 (2013) 6861–6866. [9] Q.F. Wang, Y. Huang, J. Miao, Y. Wang, Y. Zhao, Hydrothermal derived Li2SnO3/C composite as negative electrode materials for lithium-ion batteries, Appl. Surf. Sci. 258 (2012) 6923–6929. [10] H.J. Tian, S.L. Zhang, H.J. Ying, Z. Meng, W.Q. Han, W. He, Scalable synthesis of Si/ C anode enhanced by FeSix nanoparticles from low-cost ferrosilicon for lithium-ion batteries, J. Power Sources 353 (2017) 270–276. [11] L.R. Shi, C.L. Pang, S.L. Chen, M.Z. Wang, K.X. Wang, Z.J. Tan, P. Gao, J.G. Ren, Y.Y. Huang, H.L. Peng, Vertical graphene growth on SiO microparticles for stable lithium ion battery anodes, Nano Lett. 17 (2017) 3681–3687. [12] K. Wang, Y. Huang, M. Yu, X.L. Qin, A facile route to synthesize hollow Si-Ni3Sn2 nanospheres@ reduced graphene oxide nanocomposites for high performance lithium-ion batteries, J. Alloys Compd. 698 (2017) 547–554. [13] Q.J. Zhao, Y.H. Huang, X.L. Hu, A Si/C nanocomposite anode by ball milling for highly reversible sodium storage, Electrochem. Commun. 70 (2016) 8–12. [14] L.H. Yin, M.B. Wu, Y.P. Li, Synthesis of SiO2 @ carbon-graphene hybrids as anode materials of lithium-ion batteries, New Carbon Mater. 32 (2017) 311–318.
4. Conclusions The LSO-LSnO-GE sample was synthesized through a hydro-thermal method. The LSO-LSnO bulks disperse on the surface and interval of the grphene. Li2SnO3 and graphene can efficiently ease the volume change of Li2SnO3 during cycling process and enhance the electrochemistry property. The initial specific discapacity of LSO-LSnO-GE composite is 1016.5 mAh/g at the current density of 150 mA/g, and its specific capacity is 440.8 mAh/g after 200 cycles. In addition, the LSO-LSnO-GE shows the initial discharge capacity of 263.1 mAh/g at the current density of 30 mA/g in LSO-LSnO-GE/LiMn2O4 full cell, which indicates that LSO-LSnO-GE may be used as the anode material for lithium-ion full cells. Acknowledgments This work was supported by the Key Science and Technology Research Program of Henan province under Grant No. 152102210106 260
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Q. Wang et al.
[24] S.Y. Li, W.H. Xie, L.L. Gu, Z.J. Liu, X.Y. Hou, B.L. Liu, Q. Wang, D.Y. He, Facilely scraping Si nanoparticles@reduced graphene oxide sheets onto nickel foam as binder-free electrodes for lithium ion batteries, Electrochim. Acta 193 (2016) 246–252. [25] G. Niu, G. Capellini, G. Lupina, Photodetection in hybrid single-Layer graphene/ fully coherent germanium island nanostructures selectively grown on silicon nanotip patterns, ACS Appl. Mater. Interfaces 8 (2016) 2017–2026. [26] P. Wu, X.L. Xu, Q.Y. Zhu, X.S. Zhu, Y.W. Tang, Y.M. Zhou, Self-assembled graphenewrapped SnO2 nanotubes nanohybrid as a high-performance anode material for lithium-ion batteries, J. Alloys Compd. 626 (2015) 234–238. [27] M. Shirotori, S. Nishimura, K. Ebitani, Fine-crystallized LDHs prepared with SiO2 spheres as highly active solid base catalysts, J. Mater. Chem. A 5 (2017) 6947–6957. [28] G.R. Hu, M.F. Zhang, L.L. Wu, Z.D. Peng, K. Du, Y.B. Cao, Enhanced electrochemical performance of LiNi0.5Co0.2Mn0.3O2 cathodes produced via nanoscale coating of Li+-conductive Li2SnO3, Electrochim. Acta 213 (2016) 547–556. [29] Q.F. Wang, S. Yang, J. Miao, M.W. Lu, T. Wen, J.F. Sun, Graphene supported Li2SiO3/Li4Ti5O12 nanocomposites with improved electrochemical performance as anode material for lithium-ion batteries, Appl. Surf. Sci. 403 (2017) 635–644. [30] Y. Zhao, Y. Huang, Q.F. Wang, X.Y. Wang, M. Zong, H.W. Wu, W. Zhang, Graphene supported Li2SnO3 as anode material for lithium-ion batteries, Electron. Mater. Lett. 9 (2013) 683–1386. [31] Y. Tian, Q.H. Tian, Z.X. Zhang, L. Yang, S. Hirano, Carbon-tin oxides@ titanium dioxide core-shell nanospheres for lithium ion battery anode electrodes with high rate cyclability, Mater. Lett. 155 (2015) 142–145. [32] U. Kasavajjula, C. Wang, A.J. Appleby, Nano-and bulk-silicon-based insertion anodes for lithium-ion secondary cells, J. Power Sources 163 (2007) 1003–1039. [33] J.A. Brant, D.M. Massi, N.A.W. Holzwarth, J.H. MacNeil, A.P. Douvalis, T. Bakas, Fast lithium ion conduction in Li2SnS3: Synthesis, physicochemical characterization, and electronic structure, Chem. Mater. 27 (2015) 189–196.
[15] Z.W. Zhou, Y.T. Liu, X.M. Xie, Constructing novel Si@SnO2 core-shell heterostructures by facile self-assembly of SnO2 nanowires on silicon hollow nanospheres for large, reversible lithium storage, ACS Appl. Mater. Interfaces 8 (2016) 7092–7100. [16] G.R. Hu, M.F. Zhang, L.L. Wu, Z.D. Peng, K. Du, Y.B. Cao, Effects of Li2SiO3 coating on the performance of LiNi0.5Co0.2Mn0.3O2 cathode material, J. Alloys Compd. 90 (2017) 6589–6597. [17] S. Yang, Q.F. Wang, J. Miao, J.Y. Zhang, D.F. Zhang, Y.M. Chen, H. Yang, Synthesis of graphene supported Li2SiO3 as a high performance anode material for lithium-ion batteries, Appl. Surf. Sci. 444 (2018) 522–529. [18] Y.L. Deng, J.R. Mou, H.L. Wu, N. Jiang, Q.J. Zheng, K.H. Lam, C.G. Xu, D.M. Lin, A superior Li2SiO3-composite LiNi0.5Mn1.5O4 cathode for high-voltage and high-performance lithium-ion batteries, Electrochem. Acta 235 (2017) 19–31. [19] S.M. Ma, S.H. Shen, X.G. Kong, T. Gao, X.J. Chen, C.J. Xiao, T.C. Lu, A new interatomic pair potential for the modeling of crystalline Li2SiO3, Mater. Design 118 (2017) 218–225. [20] Z.G. Zang, X.F. Zeng, M. Wang, W. Hua, C.R. Liu, X.S. Tang, Tunable photoluminescence of water-soluble AgInZnS-grapheneoxide (GO) nanocomposites and their application in-vivo bioimaging, Sensor. Actuat. B-Chem. 252 (2017) 1179–1186. [21] J. Wei, Z.G. Zang, Y. Zhang, M. Wang, J.H. Du, X.S. Tang, Enhanced performance of light-controlled conductive switching in hybrid cuprous oxide/reduced graphene oxide (Cu2O/rGO) nanocomposites, Opt. Lett. 42 (2017) 911–914. [22] H.J. Huang, J. Zhang, L. Jiang, Z.G. Zang, Preparation of cubic Cu2O nanoparticles wrapped by reduced graphene oxide for the efficient removal of rhodamine B, J. Alloys Compd. 718 (2017) 112–115. [23] R.Y. Li, Y.Y. Jiang, X.Y. Zhou, Z.J. Li, Z.G. Gu, G.L. Wang, J.K. Liu, Significantly enhanced eletrochemical performance of lithium titanate anode for lithium ion battery by the hybrid of nitrogen and sulfur co-doped graphene quantum dots, Electrochim. Acta 178 (2015) 303–311.
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