多孔碳/磷化铁优化匹配构筑高比能锂离子电容器

Combining the high energy feature of lithium-ion batteries and high power density of supercapaciors, lithium-ion capacitor, as one of novel electrical energy storage devices, exhibits wide applications in future. However, the capacity and kinetics imbalance between capacitor-type cathode and the lithium-ion battery-type anode, which leads to low energy density and short cycling life, greatly restricts its development. Herein, porous carbon will be utilized as cathode material. By introducing nitrogen and sulfur species into carbon matrix, the specific capacity of cathode will be enhanced due to the presence of pseudocapacitance and its physical adsoprion-desorption rate will slow down. Owing to its high theoretical capacity, low intercalation potential, high safety, cheapness and availability, iron phosphide will be selected as anode material. Aiming to bridge the gap between cathode and anode, the kinetics of iron phosphide will be accelerated by surface sulfur doping, carbon coating and designing hollow nanostructure. The high-energy lithium-ion capacitor device will be constructed through optimal matching of cathode and anode. The structure-activity relationship between the composition, morphology and microstructure of the electrode materials and their electrochemical performance will be demonstrated. The synergistic effect among different components in the electrode materials and their corresponding lithium storage mechanism will be also investigated. Finally, the theoretical guidance and practical basis for the development and application of electrode materials for high-energy lithium-ion capacitor will be provided.

锂离子电容器作为一种兼具锂离子电池的高能量密度与超级电容器高功率密度特性的新型储能器件，应用前景广阔。但是由于电容型正级材料与电池型负极材料的比容量和动力学匹配性较差，导致锂离子电容器能量密度低且循环寿命差，极大限制了其发展。本项目拟采用多孔碳为正极材料，通过氮/硫共掺杂，引入赝电容提高比容量的同时，减慢正极物理吸附/脱附速率；以理论储锂容量高、嵌锂电位低、安全性高且廉价易得的磷化铁为负极材料，通过表面硫掺杂、碳包覆和设计中空纳米结构，提升负极动力学特性，旨在缩小锂离子电容器正、负极动力学差距，实现两者的平衡与匹配，进而构筑高比能锂离子电容器。研究电极材料的组成、形貌、微观结构与锂离子电容器电化学特性之间的构效关系，探究电极材料各组分间协同效应和储锂机理，为高比能锂离子电容器电极材料的开发与应用提供理论指导和实践基础。

混合超级电容器在碳中和背景下有着巨大的应用前景，然而受制于正极材料反应动力学迟缓、负极材料容量低以及正、负极材料动力学不匹配，导致难以实现其比功率和比能量的协同提升。本项目围绕上述问题，通过异质原子掺杂和构建纳米核壳结构等纳米工程技术，对组成混合超级电容的多孔炭基负极材料和磷化铁基正极材料的组分、形貌和结构进行设计与调控，实现了正、负极材料比容量和动力学性能的平衡与匹配，揭示了混合超级电容器电化学性能与电极材料的组成、形貌和微结构之间的构效关系，阐明了核壳结构中各组分间的协同效应和微观储能机理，取得了以下研究成果：（1）开发了基于柠檬酸铜的化学活化法制备高比表面积、适宜石墨化度和高杂原子含量的生物质基层次孔炭材料的普适性方法，揭示了铜盐活化法的活化机理，探明了多孔炭材料表面杂原子对电化学性能的影响规律，该炭材料在电流密度为0.5和100 A g-1下，分别提供了401.6和165.6 F g-1的比容量；（2）通过形貌调控、阳离子掺杂和构建核壳异质结构等策略，研发了一系列具有独特形貌和核壳结构的铁基磷化物纳米复合材料，较好解决了铁基磷化物电极材料比表面积小、活性位点少、结构稳定性差和反应动力学迟缓等关键问题，实现了镍铁磷化物@镍钴硫化物复合纳米片阵列的高比容量（1 A g-1下874.4 C g-1）和优良倍率性能（20 A g-1下76.1%电容保持率）；（3）基于正、负极材料的优化匹配，成功构筑了高比能（87.9 Wh kg-1）和长循环寿命（一万次循环后85.2%电容量保持率）的水系混合超级电容器器件，为开发高性能混合储能器件提供了技术基础和科学依据。