钾离子电池高石墨化度炭一体化电极的设计与构筑

As an anode material for Potassium-ion batteries, highly graphitic carbon (HGC) is the optimal choice for practical application. However, the large interlayer expansion during K+ intercalation/de-intercalation will cause structural degradation and accordingly poor cycle performance. Therefore， the poor potassium storage performance of HGC is a key issue to be solved for realizing the application of Potassium-ion batteries. For improving the potassium storage cyclability of HGC, this research program focuses on controlling micro structure of HGC and designing novel electrode. Optimization of carbon crystal size and design porous structure are introduced to accommodate volume change during potassium storage and thus improving cyclability. Furthermore, MXene nanosheets is used as an advanced structural forming agent to fabricate HGC/MXene all-integrated electrodes. In HGC/MXene all-integrated electrode, the MXene skeleton with good flexibility and high conductivity could further accommodate volume change during potassium storage to improve cyclability and ensure fast electron/ion conduction. The influence of carbon crystal size, porous structure and the interaction between MXene nanosheets and HGC in all-integrated electrode on potassium storage performance are investigated for clarifying the structure-activity relationship and the energy storage mechanism. This research program will promote the development and understanding for structural design and energy storage application of new carbon materials with high performance and its all-integrated electrodes.

高石墨化度炭（HGC）是钾离子电池实际应用时负极材料的较佳选择，而储钾高达60%的层间增幅会使HGC发生严重的结构退化并引发循环性能的衰减，故HGC较差的储钾循环性能成为钾离子电池应用亟待解决的关键问题。为提高HGC储钾时的循环性能，本项目着眼于HGC微观结构的调控设计和新型电极的构筑，提出调控晶粒尺寸以缓解储钾时碳层的膨胀和设计能缓冲体积膨胀的多孔结构来提升HGC的储钾性能，并使用MXene作为先进结构成型剂构建HGC/MXene一体化电极，利用MXene在电极内部形成的柔性骨架和导电网络以进一步缓解HGC的体积膨胀并确保电子/离子的稳定传导，获得具有优异储钾性能的炭基一体化电极，实现从储钾材料到电极的综合调控。本项目拟研究晶粒尺寸、多孔结构以及一体化电极内MXene对HGC储钾性能的影响，分析构效关系，揭示储能机制，为新型高性能炭材料及其一体化电极的结构设计与储能应用提供理论依据。

高石墨化度炭是钾离子电池实际应用时负极材料的较佳选择，而储钾高达60%的层间增幅会使其发生严重的结构退化并引发循环性能的衰减，故高石墨化度炭较差的储钾循环性能成为钾离子电池应用亟待解决的关键问题。为提高储钾时的循环性能，本项目使用多种方法设计并制备了具有不同晶粒尺寸、石墨化度的炭材料（高石墨化度炭与多孔炭），采用多种表征方法对其结构和组分进行解析，通过电化学测试详细研究了其电化学行为与性能，明确了材料/电极结构与电化学储钾性能之间的关系。在此基础上进一步使用MXene纳米片作为多功能电极骨架构建了MXene/炭材料电极，详细研究了制备方法中的实验参数对电极结构与性能的影响。研究结果表明MXene 作为电极骨架构具有优异的电子传导和钾离子传导性能，使用MXene作为电极的多功能骨架可以有效提升材料的电化学储钾性能。进一步地，通过同步/原位XRD详细表征了所制备的材料/电极的电化学储钾机理，明确了相转变机理，深入揭示了相关储能机制，阐明了相关材料/电极的储钾机理。通多DFT理论计算在材料微观尺度下深入解析了其对活性离子吸附和扩散的影响机制，揭示了异质界面对电化学性能提升的原因。使用所制备的材料/电极作为储钾负极、多孔炭作为正极、不可燃有机电解液为高安全电解液构建了具有高安全性能的钾离子电容器，研究了正、负极材料及有机电解液对钾离子电容器性能的协同影响机制，使用MXene/石墨纳米片负极构建的钾离子电容器的能量密度和功率密度可达113.1Wh/kg与12.2kW/kg，所制备的超薄壁介孔炭负极构建的钾离子电容器的能量/功率密度进一步提升至120.2Wh/kg与16.7kW/kg。本项目的研究结果为新型高性能储钾负极材料及储能应用提供较好的理论依据与研究基础。