通过溶液水解反应在氧化石墨烯表面引入氧化锡(SnO2)纳米颗粒,再经过自组装作用形成具有三维结构的氧化锡/石墨烯水凝胶(SnO2-GH)负极材料.其中三维多孔的石墨烯水凝胶为碳质缓冲基体,SnO2纳米颗粒为活性物质,其颗粒尺寸为2-3 nm,均匀分布在石墨烯层上,担载量可以达到54％ (w,质量分数).直接将该材料用作锂离子电池负极时,在5000 mA· g-1的大电流密度下循环60次容量稳定在500 mAh·g-1,电流减小到50 mA· g-1循环80次后容量仍高达865 mAh·g-1.这些优异的循环稳定性和大电流充放电性能主要得益于三维石墨烯水凝胶的疏松、多孔结构和良好的导电性.石墨烯水凝胶能够提高电极比表面积,保证电解液对电极的浸润程度;内部空隙能够为锂离子的传输提供快速通道,缩短离子传输距离和时间.同时丰富的内部空间能够有效避免SnO2纳米颗粒团聚,缓冲SnO2巨大体积膨胀,维持电极结构的稳定性,是一种非常适于大电流充放电的锂离子电池负极材料.%With the widespread use of mobile electronic devices and increasing demand for electric energy storage in the transportation and energy sectors,lithium-ion batteries (LIBs) have become a major research and development focus in recent years.The current generation of LIBs use graphite as the anode material,which has a theoretical capacity of 372 mAh ·g-1.Tin-based materials are considered promising anode materials for next-generation LIBs because of their favorable working voltage and unsurpassed theoretical specific capacity.However,overcoming the rapid storage capacity degradation of tin caused by its large volumetric changes (＞ 200％) during cycling remains a major challenge to the successful implementation of such materials.In this paper,SnO2 nanoparticles with a diameter of 2-3 nm were used as active materials in LIB anodes and a three dimensional (3D) graphene hydrogel (GH) was used as a buffer to decrease the volumetric change.Typically,SnCl,aqueous solution (18 mL,6.4 mmol· L-1) and graphene oxide (GO) suspension (0.5％ (w,mass fraction),2 mL) were mixed together via sonication.NaOH aqueous solution (11.4 mmol· L-1,40 mL) was slowly added and then the mixture was stirred for 2 h to obtain a stable suspension.Vitamin C (VC,80 mg) was then added as a reductant.The mixture was kept at 80 ℃ for 24 h to reduce and self-assemble.The resulting black block was washed repeatedly with distilled deionized water and freeze-dried to obtain SnO2-GH.In this composite,GH provides large specific surface area for efficient loading (54％ (w)) and uniform distribution of nanoparticles.SnO2-GH delivered a capacity of 500 mAh·g-1 at 5000 mA·g-1 and 865 mAh·g-1 at 50 mA·g-1 after rate cycling.This outstanding electrochemical performance is attributed to the 3D structure of GH,which provides large internal space to accommodate volumetric changes,an electrically conducting structural porous network,a large amount of lithium-ion diffusion channels,fast electron transport kinetics,and excellent penetration of electrolyte solution.This study demonstrates that 3D GH is a potential carbon matrix for LIBs.
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