锂离子电池正极材料中微裂纹演化的原位透射电镜观察与力/电化学耦合行为研究

Lithium ion batteries (LIBs) are playing an important role in portable devices and electric vehicles. How to improve the performance of LIBs and prevent their degradation and failure is one of the interdisciplinary research hotspots for mechanics, chemistry, and materials science. The formation of microcracks in cathode materials is an important factor causing the degradation and failure of LIBs. However, the mechanism for the nucleation and growth of microcracks in the cathode materials is still unclear due to lacking of systematically experimental investigation. In this proposal, we will pay major attention on the microcrack issue in layered transition metal oxide cathode materials. The research will focus on the nucleation and growth behaviors of microcracks, especially, on microcracking behaviors at the atomic level by using in situ transmission electron microscopy. The contributory factors for microcracking including composition, microstructure and surface stress will be fully investigated. In addition, numerical calculations and theoretical modeling combined mechanics and electrochemistry will be carried out to fully understand the degradation and failure mechanism induced by microcracks. The anticipated outcome will enrich the interdisciplinary knowledge across mechanics and electrochemistry and provide guidance to the design of layered transition metal oxide cathodes for long-life LIBs.

锂离子电池在便携式电子设备以及电动汽车等领域发挥着重要作用。如何提高锂离子电池性能，防止其失效和破坏是当前力学、化学、材料等学科交叉研究的重点和热点之一。锂离子电池正极材料中微裂纹是引发锂离子电池失效和破坏的重要因素，而目前正极材料中微裂纹产生的微观机理还不清晰，尚缺少深入系统的实验研究。本项目拟以层状过渡金属氧化物正极材料中裂纹问题为核心研究内容，以原位透射电子显微技术为主要实验手段，在原子尺度观察微裂纹的形核与长大，探讨充放电过程中化学成分、微结构及表面应力等因素对裂纹行为的影响。同时，结合力与电化学耦合下的数值模拟和理论模型，深入理解微裂纹引起的失效与破坏机制，对层状过渡金属氧化物正极材料的优化设计给予指导。

锂离子电池正极材料中微裂纹是引发锂离子电池失效和破坏的重要因素，因此对正极材料中微裂纹产生的微观机理的研究非常必要。按照计划书中所列，项目负责人及团队针对层状过渡金属氧化物正极材料的失效问题，通过透射电子显微镜表征技术对层状过渡金属氧化物正极材料失效前后微观结构的细致观察和深入分析，阐明了在充放电过程中其微裂纹产生机理，提出了通过表面改性和体内掺杂的结构设计方案，有效的维持了层状过渡金属氧化物正极材料在循环使用中的结构稳定性，提高了其循环寿命。本项目已完成项目计划书中的研究目标，执行期间在Nano Letter、Advanced Functional Materials和Nano Energy等期刊上发表SCI论文15篇，培养了1名博士和3名硕士研究生。