基于离子液体纳米微粒保护的钴酸锂电池电化学稳定机制的研究

Lithium cobalt oxide (LCO) battery has received intensive attentions because of its high energy density and reliable safety. However, its cathode material is expensive and cannot be fully activated, thus the utilization of active materials is low. Aim to develop a lithium battery with both high energy density and cost-effectiveness, firstly, we propose to create ionic liquid-nanoparticles (nano-IL) with tunable structure, physical and chemical properties. Then, the nano-IL is integrated with LCO particles to develop high voltage LCO cathode materials with enhanced capacity, which enables both high energy density and cost-effectiveness. This project mainly focuses on exploring the interacting relationship between LCO particles and nano-IL and the corresponding micromechanism. Furthermore, to enhance the ion transport property and ionic conductivity, two ion transfer pathways between the LCO and the ions are built to improve the ion transfer. One is direct ion transfer pathway based on covalent bonding between the ionic liquid anion and lithium cation, while the other one is mediated ion transfer pathway based on ion solvation structure. Based on this work, the performance of LCO battery under the protection of nano-IL at high voltages can be improved. Our work can provide a potential platform for developing cost-effective and high energy lithium-ion batteries.

钴酸锂（LCO）电池因其能量密度高、安全性能好，近年来备受关注；但其正极材料昂贵且不能完全被活化，因此活性物质利用率低。本项目针对锂电池能量密度与成本难以兼具的问题，首先，构建结构、物化性能可调的离子液体纳米微粒（nano-IL）保护层，进而将保护层与LCO颗粒相整合构建在高电压下能稳定循环的LCO正极材料，使其释放更多能量，从而实现低成本的高能量密度锂电池。本项目将重点针对nano-IL保护层与LCO颗粒相互作用关系及微观机制进行研究。并在此基础上，从nano-IL与LCO颗粒界面的离子传递入手，通过在两者之间构建直接或间接的离子传递途径，从而强化离子传输和导电率，最终实现基于nano-IL保护的LCO电池在高电压下循环性能最优化的目的。该项目的研究结果将为构建具有成本优势的高能量密度锂电池提供一个技术平台和理论支持。

钴酸锂（LCO）电池因其能量密度高、导电性好、安全性能好，近年来备受关注。然而实际应用中，易损的正极表面在深度脱锂状态下出现的副反应严重、氧、钴损失和结构退化等问题，严重限制了其使用寿命。因此，针对上述问题，本项目通过构筑保护层和设计高压稳定的电解液体系两大方面对其进行深入研究。通过冷冻透射电镜、X射线光电子能谱等表征手段针对保护层与LCO颗粒相互作用关系及微观机制进行研究，并在此基础上，从保护层与LCO颗粒界面的离子传递入手，通过在两者之间构建直接或间接的离子传递途径，从而强化离子传输和导电率，提高LCO电池在高电压下的循环稳定性。本项目所设计的石墨/LAF-LCO电池在70次循环后，在材料水平上提供了600 Wh kg−1的高比能量密度，为LCO电池的工业化作出了重要贡献，受到同行的广泛关注，在国际上产生了重要影响。