摘要
力学性质是材料的本质属性之一,随着锂离子电池应用于电动汽车、智能电网领域,活性材料的力学特性开始受到关注。动力电池、储能电池的循环寿命需要达到几千次,活性材料晶胞亦经历几千次规律的膨胀、收缩,材料颗粒的力学劣化成为必须面对的新挑战。本文以团队的研究结果为主,总结了锂电池层状正极材料力学劣化机制和改善措施。首先,讨论了正极材料的力学研究基础,明确正极材料符合弹性形变,可以使用胡克方程分析;其次,回顾了正极材料力学劣化行为符合“损伤-断裂”模型,应力产生缺陷,逐渐积累直至断裂,电解液会沿着裂缝扩散至电池内部发生副反应,造成循环跳水;最后,总结了抑制材料力学劣化的主要策略,重点介绍了降低晶胞形变和表面构筑刚性层,降低晶胞变化是通过减小材料应变降低颗粒应力,表面构筑刚性层是阻挡电解液扩散至开裂的体相,这些策略都显著提高了材料的循环寿命。总的来说,电极材料的力学劣化是无法避免的,但可以通过合适的改善措施,延迟、减缓力学劣化的影响。
Since lithium ion batteries gradually entered the market for electric vehicles and smart grids,mechanics,as one of the intrinsic characteristics of materials,has attracted an increasing amount of interest from the entire community.The current challenge in power batteries and energy-storage batteries is mechanics-induced deterioration,which is required to operate for thousands of cycles,and correspondingly active particles experiencing thousands of periods of periodic inflation and shrinkage.Based on our research results,we will discuss the mechanism of mechanics-induced degradation for layer-structured cathodes and possible solutions.First,we’ll go through the fundamentals of mechanics investigation.During cycling,the crystalline deformation of active materials is classified as the elastic deformation,and internal stress can be estimated using the Hookean Equation.Then,we return to the“damagefracture”model of mechanical-induced degradation.Internal stress in the model would generate more and more defects,finally leading to fractures where electrolytes permeate the bulk and react,causing the cyclic stability to drop.Finally,we describe effective solutions for mitigating the influence of particles’mechanics-induced degradation,with a focus on reducing lattice variation and constructing robust surface layers.The ablation of lattice change reduces particle stress by removing the stain,whereas the surface tough shell layer prevents electrolyte permeating into the fractured bulk.In general,the mechanics-induced degradation of active materials is unavoidable,although its influence can be delayed or lessened with the appropriate strategies.
作者
任重民
王斌
陈帅帅
李华
陈珍莲
王德宇
REN Zhongmin;WANG Bin;CHEN Shuaishuai;LI Hua;CHEN Zhenlian;WANG Deyu(Key Laboratory of Optoelectronic Chemical Materials and Devices,Academy of Optoelectronic Materials and Technologies,Jianghan University,Wuhan 430056,Hubei,China)
出处
《储能科学与技术》
CAS
CSCD
北大核心
2022年第3期948-956,共9页
Energy Storage Science and Technology
基金
国家自然科学基金项目(22179052)
湖北省自然科学基金项目(2021CFB544)。
关键词
力学劣化
损伤-断裂模型
颗粒开裂
层状正极材料
锂离子电池
mechanics-induced degradation
damage-fracture model
particle cracking
layerstructured cathodes
lithium ion batteries
