锂离子电池硅碳负极材料变形实时原位表征及失效机理研究

Lithium-ion batteries (LIBs) have the advantages of high energy density, high power, low self-discharge rate and no memory effect. They have become one of the important pillars of national energy development strategies. The deformation failure and layered fracture of silicon-carbon composite anode materials have become an important bottleneck in the development of LIBs with higher capacity and longer life. The developments of in-situ experimental measurement techniques and equipment of electrode deformation in LIBs play an important role in studying the mechanical behaviors of silicon-carbon anodes and enhancing the performance of LIBs. On the basis of our previous works, we will further develop an in-situ measurement technique and system of deformation failure of silicon-carbon anodes of LIBs based on digital image correlation, and prepare the semi-battery of silicon-carbon anode materials and special speckle materials resistant to chemical reaction, and then perform in-situ characterizations of deformation failure of silicon-carbon anodes under different operating temperatures and charge-discharge cycling. We further propose the thermo-chemo-mechanical coupling constitutive model of multilayer silicon-carbon anode materials, and establish the relationship between the deformed fracture failure of silicon-carbon anodes and performance degradation of LIBs. Finally, we will systematically analyze the deformation, stress evolution and failure mechanisms of multilayer structure silicon-carbon anode materials under thermo-chemical coupling conditions. The results can provide the related important guidance for the safety, reliability and durability capabilities of new LIBs.

锂离子电池具有高能量密度、高功率、低自放电率、无记忆效应等优点，已成为国家能源发展战略的重要支柱之一。硅碳负极材料变形失效和分层断裂已成为发展更高容量、更长寿命锂离子电池的重要瓶颈。发展不同原理的电极变形实时原位实验技术和实验装备是研究硅碳负极材料力学行为和提升锂离子电池性能的重要途径。在项目组的工作基础上，本申请项目拟进一步发展基于数字图像相关方法的锂离子电池硅碳负极变形失效的实时原位表征技术和实验系统；制备硅碳负极材料和耐化学反应的特殊散斑材料，在不同工作温度和充放电条件下实现硅碳负极变形失效实时原位表征；完善多层结构硅碳负极材料热-化-力多场本构模型，建立硅碳负极变形断裂失效与锂离子电池性能退化的关联，系统分析热-化多场耦合作用下硅碳负极材料变形、应力演变及失效机理，为新型锂离子电池安全性、可靠性和耐用性提供重要实验依据。

随着锂电池在移动通讯和电子电器等领域的广泛运用，锂电池的安全事故也频频爆光。发展合适的试验测试技术原位表征锂离子电池电极材料失效过程具有重要的科学意义。项目组首先设计和研制了一套用于充放电环境下电池电极活性层材料热力化耦合变形的原位表征测试系统，具体包括不与电解液发生反应的特殊散斑材料、特殊定制的透明充放电装置、定制的高倍光学镜头等，在国内率先实现采用数字图像散斑技术，应用于电池电极材料的热力化失效机理分析；考虑充放电次数、锂离子浓度等影响，建立了双层和三层的活性层+集流体结构的热力化本构方程，并预测了充放电过程中，电流大小、活性层厚度、掺杂材料质量分数对活性层材料应变场-应力场演变的影响；同时发展了基于拉伸剪滞模型的活性层断裂强度测试方法，先后测试了硅碳负极材料、LiNi0.5Mn0.3Co0.2O2电极材料、V2O5电极材料的力学强度参数；结合上述试验测试和理论预测结果，可以有效地预测在实际应用中，主流的几种锂离子电池材料性能衰减情况。全部完成了研究内容，达到了预期目标，其研究成果对于优化电极活性层材料成分、配比，固化工艺参数和服役性能预测具有重要意义。项目组顺利完成了相关研究任务，取得了预期研究成果，发表10篇SCI，培养2名研究生。