强限域、高电导硫化硒复合材料的构筑、储锂/钠性能和机制

The development of high performance and low cost secondary battery energy storage materials has attracted wide attention. Selenium sulfide (SexSy) is a novel electrode material, whose capacity decays rapidly because of low electronic conductivity, polysulfides and polyselenides dissolution, and large volume variations during repeating charge/discharge process. A novel hollow structure composed of metal nanoparticles embedded in SiO2 matrix and porous carbon shell is designed as host to fill SexSy electrode materials. The porous carbon, the surface modification of carbon, and the metal nanoparticles can improve the conductivity of SexSy. The polar SiO2 forms strong chemical bonds with polysulfides and polyselenides. The nonpolar porous carbon can bind polysulfides and polyselenides via physical adsorption. The synergetic effect of SiO2 and carbon can bind polysulfides and polyselenides in the cathode material effectively. The reserved void space between SexSy core and SiO2@carbon shell accommodates the volume expansion. The effects of core size, shell thickness, carbon surface modification, and filling amount on the electrochemical performance of composites will be studied systematically. The structure-active relationship between composition, microstructure, and lithium/sodium ion storage will be figured out. The lithium/sodium ion storage mechanism is investigated. The implement of this project will advance the development of novel SexSy secondary battery electrode material, which has important academic significance and application value.

开发高性能、低成本的二次电池储能材料一直是能源领域的研究热点。针对硫化硒(SexSy)电极材料导电性低、活性组分易溶出和储能过程中由于嵌锂/钠而产生的体积膨胀问题，本项目拟构筑金属纳米颗粒均匀镶嵌的二氧化硅和多孔碳空心结构作为载体填充活性客体SexSy。通过多孔碳及其表面改性、金属纳米颗粒镶嵌的方法增强其导电性；利用二氧化硅和多孔碳对多硫、多硒化物的化学和物理吸附协同作用，增强对活性组分的限域效应，有效抑制穿梭效应；通过控制SexSy的填充量，在空心结构中预留一定孔容缓解材料的体积膨胀。重点研究空心球的尺寸、壳层厚度、碳材料的表面改性和填充率等参数对复合物电化学性能的影响，获得电化学性能良好的SexSy复合物；建立材料的组成、微观结构和锂/钠离子存储性能之间的构效关系，揭示其储锂/钠机制，为发展新型高性能电池奠定科学基础。本项目的开展具有重要的学术意义和应用价值。

开发新型高能量密度、低成本且环境友好的新型锂离子电池是纳米技术和能源技术亟需解决的前沿科学问题。针对SeS2电极材料导电率低、穿梭效应和体积变化大，导致电池的循环稳定性较差这些问题，本项目设计合成了金属纳米颗粒修饰的二氧化硅和多孔碳双壳层结构空心球，用以提高电池的循环性能和倍率性能。我们成功制备了多孔碳@镍纳米颗粒均匀分布的二氧化硅空心球，并在其中填充了SeS2。此外，我们还合成了一系列碳和硅酸盐微纳分级构复合物，这些材料表现出良好的储锂性能。例如，我们合成了碳包覆的硅酸锌纳米棒束，该复合物在0.2 A g−1电流密度下循环50圈之后，容量高达644 mAh g−1，在电流密度为2 A g−1是循环1000圈之后，容量依然保持在427 mAh g−1。