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One Step Synthesis of Uniform SnO2 Electrode by UV Curing Technology toward Enhanced Lithium-Ion Storage Hang Wei, Zhonghong Xia, and Dingguo Xia ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b15820 • Publication Date (Web): 06 Feb 2017 Downloaded from http://pubs.acs.org on February 14, 2017

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ACS Applied Materials & Interfaces

One Step Synthesis of Uniform SnO2 Electrode by UV Curing Technology toward Enhanced LithiumIon Storage Hang Wei a, b, Zhonghong Xia b and Dingguo Xia b* a

College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021,

P.R. China. b

Key Lab of Theory and Technology for Advanced Batteries Materials, College of Engineering,

Peking University, Beijing 100871, P.R. China. KEYWORDS: UV curing technology, one step, SnO2 electrode, ultrafine nanoparticle, lithium ion battery

ABSTRACT: A uniform anode material composed of ultrasmall tin oxide (SnO2) nanoparticles with an excellent lithium-ion (Li-ion) storage performance is obtained for the first time through one step UV curing technology. The diameter of ~3 nm-sized SnO2 particles is uniformly dispersed in the styrylpyridinium (SbQ) polymer due to its photocrosslinking property. The insitu crosslinking of SbQ polymer not only assist synthesis of uniform ultrasmall SnO2, but act as a strong adhesion binder on SnO2 nanoparticles, thereby effectively accommodating the volume

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expansion of SnO2 anodes during cycling process. The uniform electrode exhibits substantially higher specific capacity and longer cycling stability compared with the SnO2 nanoparticles electrodes treated by traditional PVDF-mixing method. A stable specific capacity of 572.5 mA h g-1 of the SnO2 electrode derived from UV curing technology is obtained at a current density of 0.2 C (156.2 mA g-1) after 150 cycles. Even at high rate of 5 C (3905 mA g-1), the electrode still demonstrates specific capacity of 440.2 mA h g-1. Therefore, the scalable and low-cost synthetic approach described herein can readily be extended to other nanomaterials electrodes to improve their lithium-storage properties.

Introduction Lithium-ion batteries (LIBs) with superior performance are very attractive and important in satisfying the imminent rapid developments of portable electronic products and electrical vehicles1-4. However, the assembly of high energy/power density LIBs is still hindered by the prevailing commercial anode material, graphite, due to its low theoretical capacity (372 mAh g-1) and safety challenge5-6. Therefore, nanomaterials of transition metal oxides have been developed as choice of anode materials for LIBs with higher specific capacities than commercial graphite710

. Among various transition metal oxides, SnO2-based materials have garnered considerable

attention due to its high theoretical capacity (781 mAh g-1) and appropriate reaction potential11-14. Nevertheless, the exploration of SnO2 as an anode material is still hampered by low electrical conductivity and poor durability resulted from the severe agglomeration and pulverization of electrodes during the charge/discharge process11-15. Thus it remains a great challenge for


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synthesizing SnO2 electrode to obtain excellent electrochemical performances. In previous research, tremendous strategies are focused on such nanostructured materials as nanowire16, nanosheet17, nanotube18 and core-hollow structure19 proposed to configure the electrode and expected to achieve better Li-ion performance. Moreover, previous reports revealed that particle size is also a determining factor as to the cycling and rate performance of SnO2 anode, since the smaller SnO2 particle size is, the more strain relaxation is attained20-21. For example, Cho et al. claimed that the ~3 nm-sized SnO2 nanoparticles had a superior capacity and cycling stability compared with the~4 and ~8 nm-sized particles20. The experiments from Kovalenko et al. showed the 10 nm Sn/SnO2 nanocrystals had higher Li insertion/removal cycling stability in contrast to commercial 100−150 nm ones21. Although many approaches have been proposed for synthesis of novel SnO2 nanomaterials11-13,

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, most of their reaction steps are relatively

sophisticated; the binder poly(vinylidenedifluoride) (PVDF) used in the synthesis is expensive and the solvent N-methyl-2-pyrrolidone (NMP) is very toxic23. Moreover, considerable research has verified that due to the huge volume changes of some high-capacity anode particles, the PVDF binder with non-functionalized linear chain structure cannot afford sufficient binding to the resultant particles24,

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. Therefore, for the sake of operation simplicity and extensive

application of the Li-ion battery, one step synthesis of uniform SnO2 electrode with better electrochemical performance is highly needed and deserves to be studied. Polyvinyl alcohol (PVA) with pendent styrylpyridinium groups (SbQ), which is a synthetic polymer and a photocrosslinkable material, has been widely used due to its stability in water and high photosensitivity26, 27. The PVA-SbQ polymer can not only be used as template, substrate or coating layer for the nanomaterials which are reacted in the water, but also replace PVDF as the unique binder in Li-ion batteries. Moreover, the polar functional group of the PVA would show


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enhanced binding property with active materials via hydrogen bonding and/or covalent chemical bonds25. Herein, we demonstrate a simple and effective process to fabricate a uniform SnO2 electrode by using a one-step photocrossing method. The PVA-SbQ polymer acts as a dispersing substrate for the SnO2 nanoparticles as well as a binder for the whole electrode. This novel SnO2 anodes demonstrated superior specific capacities and rate performance compared with the SnO2 nanoparticles electrodes treated by traditional PVDF-mixing procedure. As such, the difficulties in the preparation of nanostructure materials can be tackled and the ultrafine SnO2 particles are in-situ dispersed uniformly in the PVA-SbQ polymer after hydrolysis and UV curing treatment, which renders the synthetic approach effective and environmentally friendly for the whole Li-ion battery industry. Experimental Materials Tin (IV) isopropoxide was obtained from Accelerating Scientific and Industrial Development thereby Serving Humanity and SbQ polymer (SBQ-W100) was from Denbishi Fine Chemical. Carbon nanotube (CNT) and all other used reagents were purchased from Sinopharm Chemical Reagent Beijing Co. Ltd and all chemical reagents were of analytical grade and were used as purchased without any further purification. Sample preparation SnO2-SbQ electrode (Wt% SnO2: CNT: SbQ = 75: 10: 15) was obtained by the one step UV curing process at a dark room. Firstly, the slurry composed of appropriate amount of Tin (IV) isopropoxide, CNT and SbQ polymer was prepared by stirring in water in 1 hour at room


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temperature. And after being coated on a copper foil, the slurry dried in 80 oC oven. Then the SnO2-SbQ electrode was obtained after UV irradiation with a high-pressure mercury lamp (365 nm, 15 mWcm-2) for 2 hours. The SnO2 ultrafine nanoparticles were prepared by the hydrolysis process of the Tin (IV) isopropoxide in water (1 hour at room temperature). After the filtration and drying in the oven, the obtained SnO2 nanopartices were mixed with CNT and polyvinylidene difluoride (PVDF in N-Methyl-2-pyrrolidone solution) with a weight ratio of 75:10:15. The slurry was coated on a copper foil and dried at 80°C which gain the SnO2-PVDF electrode. Characterization Powder XRD patterns and X-ray photoelectron Spectra (XPS) measurements were collected on a Bruker D8 Advance diffractometer using Cu Kα irradiation (λ = 1.5406 Å) and on an Axis Ultra system with monochromatic Al Kα X-rays (1486.6 eV) , respectively. Fourier transform infrared spectroscopy (FTIR) was performed with a VECTOR22 spectrometer. The composition and morphology of the nanocomposite were characterized by scanning electron microscopy (SEM, FEI NanoSEM 430) coupled with a BRUKER QUANTAX EDS spectrometer. Transmission electron microscopy (TEM) were characterized using a TECNAI-F20 microscope. Electrochemical measurements All the working electrode were dried at 100 oC in vacuum oven for 12 h. The electrochemical measurements were performed using 2032-type coin cells which were assembled in a glovebox under Ar atmosphere, lithium metal was used as the counter electrode. 1 M LiPF6 and 5% fluoroethylene carbonate (volume ratio) in ethylene carbonate/dimethyl carbonate/ diethyl carbonate (v/v/v=1:1:1) were used as the electrolyte. A glass fiber (GF/D) from Whatman were


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used as the separator. The charge-discharge tests were carried out using a Neware battery tester (Shenzhen, China) with galvanostatic under different current densities in the voltage range of 0.01-1.5 V at room temperature. Other electrochemical measurements were collected on an SP240 workstation (Bio-Logic Science Instruments, France). Results and discussion

Figure 1. Schematic of (a) photocrosslinking process of the SbQ polymer, the synthesis of (b) SnO2 nanoparticles and (c) SnO2-SbQ electrode. The scheme of PVA-SbQ cycloaddition reactions of which the mechanism have been systematically investigated by other reports28 is shown in Figure 1a. The reactions between SbQ pendant groups crosslink the PVA backbones, which makes it of high potential as a new binder. Moreover, Figure 1b shows the scheme of SnO2 formation. SnO2 nanoparticle was nucleated and prepared during the hydrolysis process of Tin alkoxides22, and the size of the obtained SnO2 nanoparticles is generally small but the particles aggregated because of the residual organic ligands. Importantly, the present study is the first report to use PVA-SbQ as both binder and


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dispersing substrate to prepare a uniform SnO2 electrode. The whole synthetic process is illustrated in Figure 1c. Tin isopropoxide acts as the Sn sources, CNT acts as the conductive agent and SbQ polymer acts as both binder as well as a dispersing substrate for the SnO2 nanoparticles. Through the simple and inexpensive one-step UV curing process, the SnO2-SbQ electrode can be easily obtained.

Figure 2. (a) XRD patterns of SnO2-SbQ powder and SnO2 nanoparticles, (b) FTIR spectrum of SbQ and SnO2-SbQ powder, (c) XPS spectra of SnO2-SbQ powder, and (d) XPS Sn3d spectrum. X-ray diffraction (XRD) patterns of the SnO2-SbQ powder (obtained by scraping off the electrode) and the obtained pure SnO2 nanoparticles are presented in Figure 2a. Both diffraction peaks could be readily well identified to SnO2 (JCPDS no. 41-1445), and no other byproduct diffraction peaks are detected20-22, 29. Calculated by the Scherrer equation29, the average diameter of the SnO2 in the SbQ polymer is ~ 3 nm, which is less than the directly obtained SnO2 nanoparticle (~5 nm), due to the viscosity and dispersant effect of SbQ polymer. The FTIR


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spectrum was further used to obtain the functional group information of the SbQ polymer and SnO2-SbQ electrode, with big difference between them are observed from Figure 2b. The spectra of SbQ polymer reflects the characteristic of the SbQ polymer after UV irradiation30. The two typical bands, 1642 cm-1 and 1712 cm-1 are assigned to C=C in a cinnamoyl group and the C=N existed in the SbQ group, respectively. The band located at 3349 cm-1 is attributable to the vibration of O-H and the band located at 2921 cm-1 and 2850 cm-1 are due to the stretching vibrations of C-CH2. The peaks at 1426 and 1375 cm-1 are attributed to the CH3 symmetric stretching behavior31. Though many character peaks of SnO2-SbQ powder are the same as the SbQ polymer, the main crystalline forms of SnO2 can be distinguished from the spectrum. The bands at around 539 and 1630 cm-1 are assigned to the Sn-O stretching vibration and the O-Sn-O bending vibration in SnO2, respectively32. Furthermore, the decrease of the peak at 1712 cm-1 indicates that the C=N band may be the active site of SnO2 growth due to its strong interaction of electrical attraction33. Considering the abundant –OH groups in the SbQ polymer, the intimate interactions between the binder and the SnO2 particles can be achieved, which has been previously proved by many studies25. The strong interaction is favorable for improving the electrode integrity even under a huge volume change during cycling. Additionally, the X-ray photoelectron spectroscopy (XPS) spectrum (Figure 2c) was also conducted to show that the SnO2-SbQ sample is composed of Sn, O, and C elements. As shown in the Sn 3d spectrum (Figure 2d), the two signals at 486.9 eV and 495.5 eV are assigned to Sn 3d5/2 and Sn 3d3/2, respectively, which demonstrates the characteristic of SnO234. In light of the smaller size of the SnO2 nanoparticle and the tight binding between the SnO2 nanoparticle and SbQ polymer, the better battery performance will be obtained and this SnO2-SbQ electrode has great potential for further development of the lithium-ion battery.


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Figure 3. SEM image of (a) SnO2-SbQ electrode without rolling, (b) layered image, and corresponding EDX maps of (c) carbon, d) oxygen, and (e) tin. (f) SEM image of SnO2-SbQ electrode after rolling. (g)TEM and (h) HRTEM image of SnO2-SbQ electrode. The scanning electron microscope (SEM) and transmission electron microscopy (TEM) images were used to investigate the microstructures and morphology of the surface of the SnO2SbQ electrode and SnO2-PVDF electrode. Figure 3 shows that the uniform structure of asprepared SnO2-SbQ electrode consists of nanoparticles which cross connection with each other


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due to the SbQ polymer. The nanoparticles of the SnO2 are finely encapsulated by the polymer framework and the surface of the composite is smooth. In particular, no individual SnO2 nanoparticle or agglomerate were observed in the SEM and TEM images. EDX elemental mapping (Figure 3b, 3c, 3d and 3e) further confirms the compositional uniformity of the SnO2SbQ electrodes. It is worth mentioning that the SnO2-SbQ electrode in Figure 3a is prepared without rolling for illustrating the uniformity, thus the electrode surface is not smooth enough. Nevertheless Figure 3f shows the surface morphology of SnO2-SbQ electrode after rolling, which displays the surface of the electrode become smooth and the nanomaterial binding tightly. In addition, ~ 3 nm sized SnO2 particles are observed from the TEM images (Figure 3g, 3h)， which is consistent with the calculated result of XRD pattern. Moreover, the microstructure of the SnO2-SbQ electrode which ultrafine SnO2 particles was uniformly confined by SbQ polymer was also revealed by the TEM images. Higher-magnification TEM image (Figure 3d) reveals that crystalline SnO2 particles are tightly bounded with the carbon nanotubes and the SbQ polymer. The lattice fringe corresponding to an interplanar distance of 0.338 nm and 0.179 nm can be ascribed to the (110) and (211) plane of SnO2, respectively11-13, 22, 34. Therefore, it is evident from the above researches that hydrolysis of the tin isopropoxide in SbQ aqueous solution followed by one step UV curing process resulted in the formation of uniform electrode of ultrafine SnO2 nanoparticles confined by the SbQ polymer.


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Figure 4. SEM (a, b), TEM (c), and HETEM (d) images of SnO2-PVDF electrode. SnO2-PVDF electrodes consist of a mixture of nanosized SnO2 particles and commercial PVDF binder used for comparing the electrochemical performance. Therefore, the electrodes are also investigated by the SEM and TEM technology. The micro-sized agglomerates are clearly observed from the SEM images (Figure 4a, and 4b). The TEM and HRTEM analysis (Figure 4c, and 4d) reveals that the composition of the agglomerates is ~5 nm SnO2 nanoparticles, which also maintains a good consistent result with the particle size derived from XRD pattern. From the above investigation, the big difference between the SnO2-SbQ electrode and SnO2-PVDF electrode is found to stem from the following aspects. First, the SbQ in the water plays an important dispersive role in the hydrolysis process of tin isopropoxide. Second, the PVDF can only act as the binder action in the whole electrode, and the SnO2 particles can hardly be redispersed in the electrode preparing process.


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In order to get insights into the electrochemistry of the two kinds of SnO2 electrodes, cyclic voltammetry (CV) analysis was evaluated in the 1.5–0.01 V voltage window. Figure 5a shows representative CV curves of the SnO2-SbQ electrode for the initial four cycles at a scan rate of 0.1 mV s-1. In the first cycle, the little peak at 0.8V corresponds to the formation of solid electrolyte interface (SEI) layers which is so tiny indicating fewer irreversible conversion reaction occurred in SnO2-SbQ electrode. Besides, a broad cathodic peak at 0.12 V is assigned to the reduction of SnO2 to metallic Sn (SnO2+4Li++ 4e−↔Sn+2Li2O) and the formation of nonstoichiometric LixSn alloys (Sn+xLi↔LixSn, 0≤x≤4.4). The anode peak discernible at 0.54 V is related to the dealloying of LixSn alloys to Sn. After three cycles, the cathodic peak appears at 0.22 V, and the corresponding anodic peak shifts to 0.48 V for SnO2-SbQ electrode, of which the potentials of peak-to-peak are lower with compared SnO2-PVDF electrode and some other reports11, 22. In addition, the CV curves of four cycles are almost similar, indicating the SnO2SbQ electrode might exhibit higher reversibility of the chemical reactions and faster Li-ion diffusion kinetics. On the other hand, the CV curves for the battery with SnO2-PVDF electrode (Figure 5b) exhibit two cathodic peaks at around 0.97 and 0.21 V vs Li/Li+ which are assigned to the formation of SEI and the transformation from SnO2 to LixSn alloys, respectively; the reduction peak around 0.55 V also reflects the dealloying of LixSn. However, for the SnO2PVDF electrode, the current peaks gradually vanish with the increasing number of CV cycles, which suggests that the electrochemical activity of the electrode is inhibited due to the SnO2 agglomerates.


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Figure 5. Cyclic voltammogram scans of (a) SnO2-SbQ electrode, and (b) SnO2-PVDF electrode. (Both of scan rate are 0.1 mV s-1).

Figure 6. (a) Galvanostatic cycling stability at 0.2C rate of SnO2-SbQ electrode and SnO2-PVDF electrode, (b) Voltage profile and (c) electrochemical rate performance of ordered SnO2-SbQ electrode, and (d) electrochemical impedance spectra of SnO2-SbQ electrode and SnO2-PVDF electrode.


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Typical charge/discharge profiles are used to evaluate the cycling performance of the SnO2SbQ electrode and SnO2-PVDF electrode tested at a current density of 0.2 C (156.2 mA g-1) with voltage 0.01−1.5 V (Figure 6a, and 6b). The initial discharge specific capacity of SnO2 is 1575.6 mAh g-1 with an initial columbic efficiency of 41%. The large irreversible discharge capacity at the initial cycle mainly results from the formation of the SEI film and the irreversible reduction of SnO2 to Sn during the discharging process. After initial 50 cycles, a stable capacity of 593.5 mA h g-1 is obtained for the SnO2-SbQ electrode, with the columbic efficiency increasing up to nearly 100%. The specific capacity values are calculated on the basis of the mass of the SnO2 particles. Even after 150 charge/discharge cycles, the SnO2-SbQ electrode still exhibits a reversible capacity of 572.5 mAh g-1, indicative of high accessibility for lithium intercalation and delithiated in the obtained electrodes. This high stability for SnO2-SbQ electrode can be explained by the following reasons. First, as far as we are aware, the required activation energy for lithiation and dealloying reactions diminishes as particle size decreases. In our experiment, the size of the SnO2 particles synthesized by the UV curing method is so small and uniformly distributed, which leads to the high reversible conversion storage. Second, the SbQ polymer, used as both binder and template, serves to suppress the aggregation of Sn nanoparticles during the discharge process, and the variation of stresses caused by charge/discharge process can be successfully inhibited at the same time due to the strong binding effect between SnO2 particle and SbQ polymer. As revealed in Figure 6b, two distinct long voltage plateaus also can be noticeable at around 0.2 and 0.5 V during the discharge-charge process, matching well with the above CV analysis. On the other hand, the cycling performance of the SnO2-SbQ electrode is markedly better than that of the SnO2-PVDF electrode. The SnO2-PVDF displays an initial and second discharge capacity of 1326 mAh g-1 and 471.7 mAh g-1 at current density of 0.2 C (156.2


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mA g-1), but it decays rapidly and just maintains 137.2 mAh g-1 after only 20 cycles, which is a clear indication of lower utilization of active materials in the SnO2-PVDF electrode. Moreover, the charge/discharge capacities versus cycle number were examined by increasing the current densities from 0.2 C (156.2 mA g-1) to 5 C (3905 mA g-1) shown in Fig. 6c, of which the SnO2-SbQ electrodes display excellent rate capability. At a charge-discharge rate of 0.2 C, a reversible capacity of 693 mAh g-1 was obtained. And then with the increasing of the current density, the discharge capacity decreases very slowly. The SnO2-SbQ electrode can still deliver 542.8 mAh g-1, 467.4 mAh g-1 and 440.2 mAh g-1 when the current density was increased to 1C, 3 C and 5 C, respectively. And the capacity of 552.6 mAh g-1 at 0.2 C was still recovered after 60 discharge-charge cycles at different rates, which demonstrates the superior electrochemical activities of SnO2-SbQ electrode due to its ingenious material structure and excellent structural stability. The critical factors of why SnO2-SbQ electrode exhibited higher rate performance and cycling stability than SnO2-PVDF electrodes was confirmed by using electrochemical impedance spectroscopy (EIS). The Nyquist plots of SnO2-SbQ electrode and SnO2-PVDF electrode are compared in Figure 6d. The single semicircle and sloping line are characteristic of charge transfer resistance (Rct) and solid-state diffusion (ZW) of Li ions, respectively. Thus, a much lower charge transfer resistance (Rct) of the SnO2-SbQ electrode than the SnO2-PVDF are unambiguously shown in EIS spectra16. This result indicates that the SnO2-SbQ electrode exhibits a higher electrical conductivity that results from the reduced particle size and the homogeneous dispersion. To get further discernment of the effect of the cycling process on different electrode and further validate the excellent performance of the SnO2-SbQ electrode, SEM analysis (Figure 7) of both SnO2-SbQ and SnO2-PVDF electrodes after cycling was performed. Figure 7a and 7b


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display the SEM images of the SnO2-PVDF anodes after 50 charge/discharge cycles. It is clear that structural integrity of the electrode is broken during the cycling process. The pulverization and cracks observed on the electrode arise as a result of the agglomeration of the SnO2 particles and the relatively weak interaction between the PVDF binder and the active materials. In contrast, the SnO2-SbQ electrode can retain an integrated structure without any pulverization or cracks (Figure 7c, and 7d). In order to provide more evidence to the process of the schematics, two amplifying SEM images were also provided in the supporting information. Figure S1 shows the cracks of the SnO2-PVDF electrode more clearly, and Figure S2 shows the whole integrated structure of the SnO2-SbQ electrode after 50 cycles. This is because of the strong dispersive effect of the SbQ polymer in the synthetic process as well as robust interaction between the SbQ and SnO2 particles which effectively inhibits the large volume variation in the whole cycling process.


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Figure 7. SEM images of SnO2-PVDF electrodes (a, b) and SnO2-SbQ electrodes (c, d) after 50 charge/discharge cycles, (e) proposed working mechanism of different binders for SnO2 anodes. The much enhanced electrochemical performance of SnO2-SbQ electrode compared to the SnO2-PVDF electrode could be attributed to the unique electrode structure. As mentioned above (Figure 7e), limited success of the anode has been achieved due to the fact that commercial PVDF binder is not able to restrain the particle agglomeration. In the case of using SbQ polymer as dual functional binder, uniform dispersion of ultrafine particles and the accommodation of huge volume change can be accomplished. In addition, this nature really can suppress the agglomeration into electrochemically inactive clusters and reduce charge transfer resistance at the same time. Considering that all these features are the prerequisite for the superior


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electrochemical performance, the SnO2-SbQ electrodes may be suitable as anode material for next generation Li-ion batteries, and this facile one-step UV-curving method may be a better way for the whole electrode fabrication.

Conclusions In summary, a uniform SnO2 electrode has been successfully fabricated through a facile UV curing process. This unique electrode composed of uniformly ultrafine SnO2 nanoparticles and SbQ polymer exhibited remarkable electrochemical performance which is much better than the SnO2-PVDF electrode. During the repeated charge/discharge procedure, the SbQ polymer not only acts as binder for the whole electrode, but also plays an important role of a buffer network because of its unique photocrosslinking trait. The remarkable electrochemical performance with stable specific capacity of 572.5 mA h g-1 at 0.2 C after 150 cycles and 440.2 mAh g-1 at 5 C suggest that this novel structure of SnO2 electrode could be a promising anode material for advanced lithium-ion batteries. Furthermore, considering its simplicity and low cost, this strategy, owing to its simplicity and low cost, may open up new route for the design of other electrochemical materials with extraordinary lithium-storage properties.

AUTHOR INFORMATION Corresponding Author *Email: [email protected] Author Contributions


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The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes The authors declare no competing financial interest. ACKNOWLEDGMENT This work is supported by the National Natural Science Foundation of China (11179001), the National High Technology Research and Development Program (No.2012AA052201) and Program of Higher-level Talents of Inner Mongolia University (21300-5165155). ASSOCIATED CONTENT Supporting Information Two amplifying SEM images of SnO2 electrodes after 50 cycles supplied as Supporting Information REFERENCES (1)

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Rechargeable Lithium-Ion Batteries. Chem. Soc. Rev. 2015, 44, 5926-5940. (3)

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One Step Synthesis of Uniform SnO2 Electrode by ... - ACS Publications

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