锂离子电池多孔电极理论的回顾与新思考

本文总结了Newman多孔电极理论的基本内容,提出若干改进思路. 提出基于离子-空穴耦合传输机制描述浓电解质中的离子输运过程,在此基础上引入离子-电子耦合转移反应的思想处理电极材料中的离子传输问题,并通过计算嵌锂材料的离子扩散系数验证其合理性. 总结了描述多孔电极多尺度结构的相关理论和技术,表明均质化方法和基于结构重建的介观模拟方法均能给出比较合理的有效输运参数,从而提高多孔电极理论模拟结果的准确性.

Porous-Electrode Theory of Lithium Ion Battery: Old Paradigm and New Challenge

A critical review on the porous electrode theory developed by Newman and his colleagues is presented. We propose several ideas for further development of this theory by analyzing its limitations. The classical Newman theory does not consider ion steric effect in describing ion transport in electrolyte solutions, which can be amended by a newly developed ion-vacancy coupled charge transfer model for ion transport in concentrated solutions. Ion transport in solid particles of active materials is essentially an ion-electron coupled transport process, and its rationality is verified by comparing the calculated and experimental diffusion coefficients of Li ⁺ ion in intercalation materials. The methods for describing multiscale structures of porous electrodes and the theories of porous structure reconstruction are summarized, and their applications in determining the effective transport parameters are presented and discussed. We would like to point out that further development remains necessary for porous electrode theory, especially with the emerging of new materials and systems to meet high energy and power density. A number of issues associated with/raised by high working current densities should be considered, for instances, nonlinear non-equilibrium mass transportation, overlapping of electrical double layer (EDL) and mass transport layer, the interfacial charge transfer kinetics, the fusion of phase and interface, the phase transformation of electrode materials in the process of charging and discharging, and the coupling among electrochemical, thermal and mechanical properties and processes. It is our consensus to build a universal theoretical framework that can contain electrochemistry, thermodynamics and mechanics in the electrochemical systems, with careful consideration of microscopic mechanisms for charge and mass transfer in different spatial and temporal domains.