氮掺杂碳/锡基纳米自修复材料的构建与电化学储能性能研究

Li-ion batteries and sodium-ion batteries are the key energy storage devices for powering new-energy cars and storage of green and renewable energies, while the performances of them are heavily dependent on the composition and structure of the electrode materials. Tin and its oxides, sulfides and phosphides exhibit high specific capacity for Li-ion and Na-ion storage with the advantages of low cost, safety and environmental benign, and are considered as promising anode materials for applications in next generation of high-energy batteries. However, tin-based materials suffer from large volume change during electrochemical cycling, leading to rapid capacity fade, bad cyclability and rate capability. To address these issues, this project is aiming to create stain-resistant and self-healable nitrogen-doped carbon/tin-based porous nanocomposites for applications in LIBs and SIBs. The proposed nanocomposites have two distinct advantages: (1) The nitrogen-doped nanocarbons and self-healable conducting polymer can provide multiple protections such as immobilizing the active materials, buffering the volume variation, and suppressing the pulverization/cracking of the electrode materials to enhance their stability and cyclability . (2) The tin-based nanocrystals are incorporated or encapsulated into the nitrogen-doped carbon framework to create a porous conducting network, which is favorable for transportation of charges and enhancement of rate capability. The electrochemical performance of the Sn-based anode materials would be improved significantly through optimization of the structure and exploration of new synthetic methods. Meanwhile, the electrode process kinetics are investigated by combining the electrochemical measurements and theoretical calculations to disclose the relationship of composition-microstructure-electrochemical performance of the composites, and to further provide theoretical support for the development of LIBs and SIBs with high performance.

锂离子电池和钠离子电池是重要的储能供电装置，其性能依赖于电极材料。锡及其氧化物、硫化物和磷化物的理论储锂/钠比容量高、操作安全、环境友好，可望成为下一代高能电池负极材料。但是，它们在电化学循环过程中体积变化大、容量衰减快、稳定性和倍率性能差。为了解决这些问题，本项目拟构建能够抗应变的氮掺杂碳/锡基纳米自修复材料，发展高性能锂离子电池和钠离子电池负极材料。该复合材料具有两大优势：（1）氮掺杂的多孔纳米碳和自修复导电性聚合物能够固定活性物质、缓冲体积变化、抑制电极粉化，增强电极稳定性；（2）锡基纳米晶嵌入氮掺杂碳骨架构成多孔导电网络，有利于促进电子传导和离子扩散，提高倍率性能。通过优化材料结构设计，探索制备复合材料的新工艺，大幅提高锡基负极材料的电化学性能。同时，将电化学性能测试和理论计算相结合研究电极过程动力学，揭示材料的组成-结构-性能关系，为发展高能二次电池提供理论依据和技术支撑。

提高锂离子电池的能量密度、功率密度和循环寿命是当前锂离子电池发展的热点。锡基负极材料通过合金化/去合金化反应储锂，比容量是石墨材料的2倍以上，引起了广泛关注。但是，锡基负极材料在充放电循环过程中体积变化大，易粉化脱落，导致电极结构不稳定、电池的循环稳定性和倍率性能差。为解决这一重大难题，本项目设计合成了SnO2/氮、硫掺杂石墨烯复合材料，SnSx (x =1,2)/氮、硫掺杂纳米碳复合材料，SnO2/B,N,F掺杂石墨烯复合材料，SnO2@SnSx (x =1,2)/氮、硫掺杂纳米碳复合材料，Fe、Mo氧化物/氮掺杂纳米碳复合材料，杂原子掺杂的纳米碳材料等6个系列23种多孔复合材料，对其组成、结构、电化学储锂/催化性能进行了全面表征。实验发现，这些复合材料的储锂性能得到有效改善，比容量、循环稳定性和倍率性能明显优于单体材料，这主要归因于其独特的结构优势。一方面，氮掺杂的多孔纳米碳能够有效抑制锡基材料的过度生长和团聚，锚定活性物质、缓冲体积变化、抑制电极粉化，增强电极结构稳定性，提高电池的循环寿命。另一方面，嵌入掺杂碳骨架的锡基纳米晶电化学反应活性明显增强，且多孔掺杂碳导电网络有利于电子传导和离子扩散，提升电池的倍率性能。本项目将电化学性能测试和理论计算相结合研究电极过程动力学，揭示了材料的组成-结构-性能关系，为发展高能二次电池提供理论依据和技术支撑。