多孔碳/过渡金属磷化物纳米复合纤维的制备及电化学储能特性研究

The dynamic mismatch between positive and negative electrode of the lithium ion hybrid capacitor will lead to the poor rate capability and low cycle life of the device. Combining the distinct characteristics of transition metal phosphide, including high capacitance and low voltage plateau with the unique nanoweb structure of electrospun nanofibers and the advantage of carbon coating, this project will to fabricate porous carbon/transition metal phosphides nanocomposite fibers with excellent lithium insertion/extraction kinetics as electrode materials, to make up the difference in the energy storage dynamic between positive and negative electrode. The relation between the synthesize process, microstructure and the electrochemical performance, especially, the influence of the chemical composition, microstructure on the dynamic properties of the nanocomposite electrode will be investigated. Based on the analysis change of the chemical composition and microstructure for electrode materials during the charge-discharge process, the structure-function relation between electrochemical behavior of electrode materials and its microstructure will be revealled. In virture of theoretical computation, the mechanism of migration/diffsuion of Li+ ion, transmission of electronic and energy stroage will be illuminated, to further clarify the influence mechanism of the dynamic mismatch between positive and negative electrode on the performance of lithium ion hybrid capacitor. Through the research of this project, the lithium ion hybrid capacitor high power density and enenrgy density can be obatined. The research result of this project can provide theoretical basis for the development and exploration new electrode materials for energy storage.

本项目针对目前制约锂离子混合电容器应用所存在的正负极动力学不匹配的关键科学问题，利用过渡金属磷化物高容量和低嵌/脱锂电位的鲜明特点、结合电纺纳米纤维独特的纳米网毡结构和碳包覆的优点，通过材料的结构设计和可控制备，合成多孔结构的碳/过渡金属磷化物纳米复合纤维作为电极，开发具有良好嵌/脱锂动力学特性的储锂电极材料；研究材料的制备工艺与材料结构、性能之间的关系，深入研究该纳米复合电极材料的化学组成、微观结构与其动力学特性之间的关系，分析复合电极材料在充放电过程中的化学组成与结构的变化，结合理论计算探究该纳米复合电极材料中锂离子扩散迁移、电子传输及储能机制，阐明该纳米复合电极的化学组成、结构与性能之间的关系，实现高性能锂离子电容器负极材料的设计合成，进而揭示正负极动力学的匹配对锂离子混合电容器性能的影响机制，最终组装出兼具高能量密度和功率密度的锂离子混合电容器，为新型电化学储能材料的开发提供借鉴。

本项目以静电纺丝技术为主要合成手段，设计制备了几种过渡金属磷化物多孔纳米纤维材料，包括多孔道结构的钒掺杂磷化钴纳米纤维、磷化钴/羟基氧化铁异质纳米纤维、钌/镍共掺杂磷化钴多孔纳米纤维。利用多孔纳米纤维其独特的纳米网毡结构增加活性位点数量和改善传质特性，通过掺杂或构筑异质结构调控材料的电子结构，优化其与反应中间体的吸附能力，增强体征活性，达到协同改善催化活性的目的。通过对纳米纤维催化剂析氢/析氧活性的系统考察，建立了材料的制备工艺与材料结构、性能之间的关系，深入分析了材料在催化过程中组成和结构的演变规律，并结合理论计算研究了材料的化学组成对催化剂电子结构和反应中间体吸附能力的影响，明确活性中心，揭示活性增强机制，阐明磷化物多孔纳米纤维的化学组成、结构与性能之间的关系。本项目设计合成了几种可用作析氢/析氧催化剂的过渡金属磷化物多孔纳米纤维，圆满完成了研究目标。本项目的研究成果对发展磷化物纳米材钌制备技术、深入认识析氢/析氧反应机理以及开发高效的析氢/析氧催化剂提供了理论和实验基础。