基于动态电化学应变的纳米尺度锂电池电极材料多场耦合研究

High performance Li-ion batteries are attractive for a wide range of applications, including consumer electronics, electric vehicles, and storage of sustainable energy. However, the electrodes of Li-ion batteries experience large strain and deformation due to Li-ion intercalation and extraction during charging and discharging, resulting in highly complicated couplings among electric, chemical, mechanical, thermal, and transport behaviors of electrode materials. Recent researches have revealed significant effects of stress and strain on the electrochemical performance of Li-ion batteries, yet there is no effective experimental technique to probe these coupling phenomena at the nanoscale. Newly developed electrochemical strain microscopy (ESM) is capable of probing electrochemical process with fine spatial resolution, though there still lacks reliable quantitative analysis and interpretation of ESM data, and it is also very challenging for in-situ characterizations. Motivated by these observations, we seek to develop novel quantitative dynamic electrochemical strain microscopy with high spatial resolution and sensitivity, in combination with micromechanical analysis and numerical simulations, complemented by synthesis of novel nanostructured oxides for electrode materials and conventional characterizations, to enable in-situ probing of the couplings among electric, chemical, mechanical, thermal, and transport behaviors in Li-ion batteries with high resolution and sensitivity. This will provide powerful tools for design, analysis, and optimization of high performance Li-ion batteries.

锂电池在消费电子产品、电动汽车及可再生能源的调控和存储中具有广泛的应用前景。然而在充放电过程中，锂离子在电极中嵌入和脱嵌，引起材料显著的体积形变，使其呈现复杂的电、化、力、热及输运等多场耦合关联。近几年，国内外的研究深入揭示了应力应变对锂电池电极材料电化学性能的影响，可是目前还缺乏有效的实验手段对电极材料在纳米尺度进行实时原位观测。新近发展的电化学应变原子力显微镜能够在纳米尺度表征电极材料的电、化、力多场耦合效应，但目前尚缺乏准确可靠的定量分析方法，实时原位观测也极具挑战性。基于此，本项目旨在发展新型动态电化学应变原子力显微方法，结合细观力学解析分析和数值模拟，并进行纳米结构电极材料制备及传统的材料表征和电化学测试。同时系统定量原位地研究锂电池电极材料在纳米尺度下的电、化、力、热及输运等多场耦合性能，测量其局部的电化学、热力学、机械及输运参数，为高性能锂离子电池的性能预测、设计优化和安全评估服务。

锂电池在充放电过程中，锂离子在电极中嵌入和脱嵌，引起材料显著的体积形变，使其呈现复杂的电、化、力、热及输运等多场耦合关联。基于电化学应变原子力显微技术在纳米尺度表征电极材料的多场耦合性能可以促进高性能锂离子电池的应用。本项目中实验方面采用熔融法、静电纺丝法、放电等离子烧结等方法制备了一系列不同成分和结构的锂硫电池复合正极材料、γ氧化铁/C复合纳米纤维用作锂钠离子电池负极以及不同电导率的固体电解质材料，在表征材料结构和形貌的同时，分析测试了材料的电化学性能，并解析了材料电化学性能提高的原因；发展了扫描热离子显微镜（STIM）探测材料在纳米尺度下局部热离子运动，排除了电信号所带来的静电力作用；发展了时序激励原子力显微方法（SE）提高了成像精度，并大大降低了形貌像对电化学性能测试的干扰。理论方面基于热力学和连续介质力学，建立了一套分析ESM响应的力-电-化学解耦方法。用于分析导电AFM探针下锂离子电池电极材料的力-电-化学多场耦合响应。在此基础上，通过电化学应变原子力显微方法，实现了锂离子电池电极材料的局部机械振动的准确测量。并对锂离子电池电极材料在纳米尺度下的电化学特性进行了深入的理论分析和探讨。研究工作可以促进锂电池的性能分析预测、优化设计和安全评估。相关研究工作已在Nano Energy、Journal of Power Sources、National Science Review、npj Quantum Materials等期刊发表SCI论文17篇，EI论文1篇，授权国家发明专利1项。