辐射环境下锂电池电极材料的多变量耦合本构关系与ESM实验表征

Lithium-ion batteries have become the third generation of strategic energy storage device in space areas. However, because of the severe space environments, the electrode materials of lithium-ion batteries may suffer from various radiation effects for a long period of time, ranging from various radiation particles to rays. In addition, the combined effects of radiation and multi-fields environments have led to serious recession of electrochemical performances in electrode materials. Although there are a large number of investigations on the chemo-mechanical models of electrode materials at home and abroad, the failure mechanism of electrode materials under the extreme environment is not clear, so it’s urgent to build a theory model which could depict the evolution law of electrode materials under radiation and multi-fields coupling. Based on this, the application project, considering from the perspective of large deformation elastic-plastic constitutive theory, will combine diffusion dynamics with radiation damage and consider the co-effect of the force field, chemical field, electric field and radiation field etc.. We shall strive to build a coupled -multivariable constitutive relation of electrode materials in radiation environments, and then the numerical solution of constitutive relation will be obtained by finite element numerical simulations. Finally, with the aid of ESM experimental characterization method, we could explore the microstructure evolution laws under different physical conditions for electrode materials, quantify the relationship between various physical quantities and macro performances, optimize key parameters and obtain the reasonable constitutive relation. This project may provide the experimental and theoretical basis to evaluate the safety, reliability and in-orbit life of lithium-ion batteries in space environments.

锂电池已成为极具战略应用前景的第三代空间用储能器件，然而由于空间环境恶劣，锂电池电极材料长期遭受各种辐射粒子和射线的考验，辐射及多场耦合作用导致电化学性能严重衰退。虽然国内外对电极材料在力-化耦合方面的研究较多，但在辐射等极端环境下的多场耦合失效机理还不清楚，亟需一个能够刻画辐射环境下电极材料多场耦合演变规律的理论模型。基于此，本申请项目从大变形弹塑性本构理论出发，结合扩散动力学与辐射损伤，考虑力场、化学场及辐射损伤等物理量，力求构建辐射环境下电极材料的多变量耦合本构关系，进而通过有限元计算得到本构关系的数值解。最后，借助ESM实验表征方法，探究不同物理量条件下电极材料的微观结构演化规律，量化各物理量与宏观性能之间的关系，同时对本构关系进行实验研究，优化关键参数，得到合理的本构关系。本项目研究成果力争为评价锂离子电池在辐射环境中的安全性、可靠性和在轨寿命提供实验与理论依据。

锂离子电池作为一种绿色高效、无污染的储能装置，具有高电压平台、高能量密度和循环寿命长等优点，在航空航天、卫星等空间领域显现了良好的应用前景。但是空间锂离子电池的工作环境实际涵盖了电场、化学场、力场、辐射场等多物理场耦合，一方面，在电场和化学场作用下，锂离子在高容量电极间嵌入和脱出导致严重的体积变形甚至破坏，造成其电化学性能衰退；另一方面，辐射场作用的多变量耦合失效问题更为复杂，严重制约锂离子电池在空天领域的应用。因此，要从根源上认识和解决这一关键科学问题，探究其失效机理是刻不容缓的。为了解决辐射环境下高容量锂离子电池电极材料锂化耦合的力学及电化学失效问题，本项目通过辐照实验、电化学性能测试及表征，结合理论分析和有限元模拟，建立金属电极的辐射-电化学耦合塑性模型、基于两相锂化的电极材料辐射-电化学耦合本构关系以及不同辐照剂量下的电极材料电化学失效理论模型，旨在分析不同辐射条件下电极材料锂化过程中的微观结构及应力演化，辐射对锂离子电池电极材料电化学性能的影响。本项目的主要研究工作包括：(1) 建立了高容量电极材料两相锂化过程的应力演化解析模型，通过一个S函数描述两相锂化的一维浓度分布，基于弹塑性解析模型求解锂化应力，深入分析了球形颗粒锂化变形过程中浓度场和应力场的动态演化。(2) 进行了不同辐照剂量，不同电荷状态及温度下交叉工况的对比实验。发现，随SOC增加，弹性模量的降低，屈服应力降低；随辐照剂量的增加，出现辐照硬化；屈服应力随辐照温度的升高而减小。(3) 建立了辐射条件下锂离子电池电极材料电化学失效模型，通过有限元模拟，分析辐射剂量对电极材料电化学性能的影响。