Search

Abstract: Co-precipitation method of SnCl2·2H2O and graphene oxide (GO) solution was performed to fleetly prepare graphene/SnO2 composite. The structure and composition of the nanocomposite were detected by means of XRD, SEM, TEM and FT-IR. The GO was reduced by bivalent tin ions to graphene nanosheet (GNS) via solution reaction and SnO2 nano-crystals with size of 4–6nm were homogeneously distributed on the matrix of GNS. It was found that the disorder degree of graphene in GNS/SnO2 composite prepared by the bivalent tin ion assisted reduction method was much lower than that of GNS obtained via pyrolysis reduction. The possible mechanism for this phenomenon was discussed in detail. The N2 adsorption tests showed an ink-bottle-like pore structure of GNS/SnO2 and the SnO2 nanoparticles were confined in the interlayer of GNS without agglomeration. These structural features were desirable and enabled GNS/SnO2 an excellent anode material in lithium ion battery. The electrochemical tests showed that the composite could deliver a reversible capacity of 775.3mAh/g and capacity retention of 98% after 50 cycles. [Copyright &y& Elsevier]

• Size-tunable SnS 2 /RGO make facile study the effect of particle size on Li/Na storage. • Ions diffusion coefficient, surface and diffusion capacitive contribution are studied. • Small-sized particle promotes charge/ion transfer and pseudocapacitor contribution. • Controllable dimension promotes fast kinetics for high rate materials. Controlling the particle sizes of electrode materials has long been recognized as an effective way to improve the cycle stability and rate property of both lithium-ion battery (LIB) and sodium-ion battery (SIB). In this paper, a simple one-step hydrothermal process for the preparation of composites with size-tunable tin disulfide on reduced graphene oxide (SnS 2 /RGO) is reported. These novel material allow to comprehensively study the effect of particle sizes on electrochemical properties for LIB and SIB anodes. The structure, morphology, phase compositions, and Li+/Na+ storage behaviors of three different SnS 2 /RGO composites obtained at heat-treatment times of 12, 24 and 48 h are characterized systematically. The electrochemical reaction kinetics is demonstrated by differential charge capacity plots and apparent ion diffusion coefficients. Surface capacitive and diffusion-controlled capacitive contributions to lithium/sodium ions storage are also compared. The results show that the small-sized nanoarchitecture can promote both the charge and ions transfer and thus improve the pseudocapacitor contribution. The reversible capacity maintains at 1211 mAh g−1 for LIB after 200 cycles and 841 mAh g−1 for SIB after 100 cycles, respectively, which is superior to most of the previous reports. This work is expected to provide a profound understanding of composite anodes with controllable dimensions and fast kinetics. The effect of SnS 2 nanoparticle size on the Li and Na storage characteristics of SnS 2 /RGO composite anodes are compared, it show that the decreased particle size promotes the pseudocapacitor contribution, as well as the reversed conversion reaction and structural stability. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Yolk-shell structured nano-Si@void@C can greatly improve the electrical conductivity and buffer the large volume change of silicon nanoparticles, whereas inter poor electrical connection between Si cores and carbon shells still limits the lithium storage performance. Besides, it usually requires complex synthesis conditions and expensive nano-level silicon sources. Herein, we succeed in making the large-size industrial silicon ( ca . 400–500 nm) to a yolk-shell structure with a controllable space buffer layer. Most importantly, an interconnected porous carbon network deriving from the thermal decomposition of carbon chains in silicon sources is formed within the carbon shell simultaneously, which can improve the electrical contact between Si cores and hollow carbon shells and prevent the active particles exposure to the electrolyte. With the help of static outer thin carbon shell, optimized inner void and the flexible electrically conductive carbon network, such yolk-shell structured Si@void@C submicron particles synthesizing by one-step carbon-coating procedure exhibit high initial coulomb efficiency of 62%, good rate performance, and excellent long cycling stability with 950.7 mAh g −1  at 100 mA g −1 after 100 cycles. The low consumption and stable synthesis method make it feasible for large-scale fabrication of the yolk-shell structured Si/C composites as commercial anodes for energy storage. [ABSTRACT FROM AUTHOR]

Exploring versatile strategies for microstructural evolution and surface modification are of fundamental importance in the development of advanced electrode materials. In this work, we report that electron-beam irradiation is a facile approach to perform surface modification for the ultrathin cross-stacked graphene aerogels loaded with SnO 2 quantum dots, resulting in a remarkable modulation on the lithium storage performance. It is found that the as-synthesized SnO 2 /graphene aerogels composites irradiated at 280 kGy exhibit excellent high reversible lithium storage capacity, good rate capability and cycling stability, which retains a discharge capacity of 703 mAh g −1 after 50 cycles at 0.1 C rate. Microstructure analysis indicates that the enhanced electrochemical properties are mainly attributed to the exfoliation of graphene nanosheets, the increase of amorphization, disorder, defects and the removal of partial oxygen-containing functional groups on the surface of graphene nanosheets. The strategy presented here demonstrates that the electron-beam irradiation is a potential strategy to improve the electrochemical performance of graphene-based metal oxides. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, graphene-modified Li3V2(PO4)3 composites have been developed as Li-ion battery cathode materials with high specific capacity and excellent cycling stability. The composites are prepared by spray–drying process using graphene oxide nanosheet and citric acid as carbon source. X-ray diffraction patterns demonstrate that the as-prepared samples are well crystallized with orderly monoclinic structures. SEM and TEM images reveal that the 3D network graphene and Li3V2(PO4)3 primary nanoparticles interlace with each other. The citric acid-derived amorphous carbon species interrupt the stacking of graphene sheets and minimize in-plane anisotropy of electronic migration within graphene layers, which would facilitate fast electron migration and Li+ diffusion throughout the micro-sized spherical secondary particles. The discharge capacity of the composite could respectively achieve 131.4 and 181.5mAhg−1 in the voltage range 3.0–4.3V and 3.0–4.8V at 0.1C discharge rate, which almost reach the theoretical capacity of the cathode material. Both of them nearly showed no capacity decay at 0.1C charging and discharging rate after long cycles. [Copyright &y& Elsevier]