基于动力锂离子电池负极材料内嵌碳纳米管的金属氧化物空心复合微球的构筑及储锂性能

Metal oxide is one of promising anode materials for power lithium ion batteries due to its advantages of high theoretical specific capacity and better safety. Solving the problems resulted from poor electronic conductivity and volume effect is a key to promote its development as anode material for lithium ion batteries. Therefore, in this project, fully taking advantage of both carbon nanotubes, with unique structure, high strength, flexibility and excellent electronic conductivity, and metal oxide with high specific capacity, a hollow microsphere structure of network-like carbon cubes interconnecting with metal oxides will be synthesized by soft template method and the function of Oswald effect. This structure, with rich electronic transport channels and pores, will own the complementary advantages of two components and make synergies effectively between them so that the anode materials for lithium-ion battery, with high specific energy, high specific power and excellent cycle stability, can be obtained. The reaction procedure and structural evolution rules for the hollow composite microspheres in the process of preparation will be studied, and the approach of effectively adjusting hollow structure and the distribution of carbon nanotubes will be investigated. Furthermore，Electrochemical properties of hollow microspheres as anode materials for lithium-ion batteries will be researched. The transport mechanism of electrons and Li+ ions and the formation and stabilization mechanism of solid electrolyte film in the process of charge and discharge will be investigated. The key factors to make lithium ion batteries show excellent comprehensive lithium storage performances will be analyzed. They will lay a solid theoretical foundation for further study of power lithium-ion battery anode materials.

金属氧化物因具有理论比容量高、安全性好等优点，被作为当前极具吸引力的动力锂离子电池负极材料之一，有效地解决其导电性差和体积效应所导致的问题是推动其作为锂离子电池负极材料发展的关键。本项目充分利用碳纳米管独特的结构、高强高韧和高导电及氧化物高比容量的优势，采用软模板法并结合Owald熟化效应作用制备网络状碳纳米管与金属氧化物三维互联的中空微球，形成具有丰富电子通道和多孔的稳定复合体系，以实现两组份之间的优势互补和协同效应，获得高比能、高比功率及优异循环稳定性的动力型锂离子电池负极材料。考察氧化物复合中空微球形成的反应过程和结构演变规律，寻求碳纳米管分布状态及中空结构的有效调控方法。研究复合微球的电化学性能，探索其充放电时的电子、离子输运机制及SEI膜的形成和稳定机制，分析使其具有优异的综合储锂特性的关键因素，为锂离子电池负极材料的进一步深入研究奠定坚实的理论基础。

针对过渡金属化合物作为锂/钠离子电池负极材料充放电过程中具有导电性差和体积效应的问题，本项目设计和构筑碳纳米管（CNTs）基复合微结构材料，并研究影响储锂/钠电池负极材料电化学性能的关健因素，有效提高其综合电化学性能。（1）通过酸化处理对碳纳米管适度功能化的基础上，采用超声辅助沉淀法并结合热处理技术，可控得到了CNTs均匀内嵌的过渡金属氧化物（NiO,Co3O4,CuO）多孔微结构。探明了微结构演变规律，草酸作沉淀剂，热处理气氛是得到多孔微结构的关键工艺，沉淀过程中超声辅助是CNTs均匀分散在微结构中的保障。（2）以CNTs内嵌的过渡金属氧化物微球为原料，发展了分别采用水热法和高温硫化法可控得到CNTs内嵌的四硫化三钴和二硫化三镍微球的新技术。（3）发展了采用喷雾法制备多孔过渡金属氧化物微球的新技术。（4）探明了基于转换反应充放电机制的过渡金属氧/硫化合物作为锂/钠离子电池负极材料电化学性能的关键性影响因素。微球结构是提高首次库仑效率的有效途径，微球结构中的多级孔分布及SEI膜的稳定性是解决体积效应问题、获得优异循环性能的保障。均匀内嵌的CNTs可以大幅提高倍率性能。Co3O4/CNTs具有高达85%的首次库仑效率，1C下循环200次容量为627mAh/g,容量保持率79.4%，在5C下是0.1C比容量的68.9%。（5）采用液相或固相碳源，设计和合成了高度石墨化的掺氮多孔碳结构，实现对孔结构、氮种类和含氮量的调控；采用电化学法处理可控得到含氧丰富并具有较强导电性的还原氧化石墨烯膜，这为新型过渡金属化合物、合金类、硫正极等具有导电性差、体积效应严重的储锂/钠/钾负极材料的改性奠定了物质基础。（6）可控得到掺氮的定向碳纳米管，对其纯化、活化处理后渗硫，利用物理限域效应和键合作用，有效地改善了其循环性能。为进一步提高基于转换反应充放电机制的锂/钠离子电池负极材料的循环性能提供了新思路。