聚苯胺/二硫化锡/石墨烯插层化合物结构调控及储锂机理研究

Tin disulfide layer material is a promising anode material because of its high lithium-ion storage capacity. However, the applications of SnS2 are held back by their low initial coulombic efficiency since the irreversible formation of Li2S during the first lithium insertion/de-insertion process. Besides, their cycliablities are usually poor because there is a critical problem of large volume change and electrode pulverization for tin-based anodes. In this proposal, exchange reactions is utilized to incorporate the polyaniline in the lithiated tin disulfide based a topotactic mechanism, then the amine functionalized graphene is restacked on the surface via electrostatic self-assembly. By this method, polyaniline/tin disulfide/graphene intercalation compounds were designed and synthesized. In this proposed structure, the increased interlayer spacing is more capable of buffering volume change during the charging/discharging process compared to bulk materials. In addition, ultrathin tin disulfide nanosheets bonds covalently to the high electrical conductivity polyaniline and graphene, which would enable the reversible transformation of LixSnS2 (0<x≤2) and Li2S. This proposal will clarify the associations between the micro-structure and electrochemical properties, and analyze the mechanism of lithium-ion diffusion, insertion and extraction in the suggested polyaniline/tin disulfide/graphene intercalation compounds.

二硫化锡层状化合物是具有较高储锂容量的锂离子电池负极材料。但二硫化锡首次储锂生成的硫化锂（Li2S）不可逆产生较大的不可逆容量，首次库伦效率偏低；且二硫化锡脱嵌锂时较大的体积变化造成结构的破坏，导致循环性能下降。本项目针对以上关键问题，根据剥离重堆积法和拓扑转化机制，以电化学活性聚苯胺材料为插层剂，通过与功能化石墨烯重堆积，设计了聚苯胺/二硫化锡/石墨烯插层复合材料。该结构具有较大的层间距膨胀，能够更好的缓冲脱嵌锂导致的晶格破坏；同时极细的二硫化锡纳米薄片与高导电的聚苯胺和石墨烯共价结合，能促使二硫化锡与锂离子首次形成LixSnS2（0<x≤2）和Li2S的反应能够可逆进行，从而针对性解决Li2S不可逆的问题。本项目将研究聚苯胺/二硫化锡/石墨烯插层复合材料合成的组分比例、形貌尺寸控制，并重点研究Li2S的可逆性机理及锂离子在此插层复合材料中插入、析出、储存机理。

二硫化锡作为一种高容量的材料，广泛应用于锂离子电池的负极，但其在进行充放电循环过程中会发生大于自身两倍的体积膨胀，导致其在循环过程中从集流体上脱落，降低其储锂性能。首先，我们先通过简单氧化剥层制备薄层的膨胀石墨，再通过一步水热法将二硫化锡（SnS2）六方相晶片均匀的生长在薄层石墨上，成功制备了高比容量和优异循环稳定性的膨胀石墨负载二硫化锡（SnS2/EG）的复合材料，并将其与纯相SnS2进行了电性能对比。测试结果表明，SnS2/EG复合材料在电流密度为100 mAg-1经过100次的循环后仍能达到655 mA h g-1，展示出较大的可逆容量，优异的循环性能和良好的导电性。随后，在此基础上，利用所制备六方晶相SnS2，氧化聚合制备二硫化锡@聚苯胺（SnS2@PANI）前驱体，再通过一锅水热法制备双层包覆结构的锡氧硫化合物@聚苯胺@还原石墨烯（SnOxSy@PANI@rGO）。此材料在电流密度为100 mAg-1经过100次的循环后仍能达到745.3 mA h g-1的可逆循环容量。这表明SnOxSy@PANI@rGO复合材料具有大的可逆容量，优异的循环性能和良好的导电性，其中导电聚苯胺和还原氧化石墨烯片层对SnS2电化学性能有着重要的影响。第三部分中，通过简单水热合成法成功制备了N,S共掺石墨烯包裹二硫化锡的复合材料（SnS2@NSG），并用相同的水热条件制备了SnS2@G，SnS2，进行了电性能对比。结果表明，SnS2@NSG复合材料具有大的可逆容量，优异的循环性能和良好的导电性，在电流密度为 0.1 A g-1下经过200次的循环后仍保持853 mAh/g的可逆循环容量。