高容量锂离子电池负极集流体泡沫铜的环境疲劳行为、损伤机理及寿命模型

In high capacity lithium ion battery, great volume variation of anode based on Si, Ge or Sn during the process of charge/discharge decreases cell performance significantly. Copper foam as the anode current corrector can favorablely buffer the volume variation compared with common copper foil. However, environmental fatigue damage is unavoidable for copper foam in the service process. In this regard, the project will investigate the environmental fatigue behavior of copper foam with three-dimensional network structure under the interaction of cycle loading, electrolyte and polarization potential. Combined with the analysis of internal stress, microstructure evolution and electrochemical characteristics, the plastic strain accumulation, strain evolution and microcrack initiation and propagation process under cyclic loading will be clarified, the electrochemical -mechanical interaction mechanism will be analyzed, the environmental fatigue damage mechanism of copper foam will be discovered. Based on the relationship between microstructure evolution and properties diversification, an environmental fatigue life model which reflects the pore structure characteristics, environment effect, loading factor will be established. This project will provide a scientific basis for the design of collector copper foam material and will supply an experimental support for its application in the anode of lithium ion battery. It also has important meaning to enrich the fatigue theoretical system of porous metal materials.

高容量锂离子电池新型Si、Ge、Sn基负极材料在充放电过程中产生巨大体积变化，致使电池循环性能下降，是制约其发展的瓶颈；以泡沫铜替代铜箔作为负极集流体能起到良好的缓冲作用，但在服役过程中易产生疲劳损伤。本项目以三维网状结构泡沫铜为研究对象，研究在循环应力、电解液、极化电位多因素交互作用下的环境疲劳行为；通过材料内部应力状态、微结构演变及电化学特性分析，阐明循环载荷下塑性应变累积及应变带演化规律和孔棱裂纹萌生与扩展过程，明晰电化学-力学交互作用机制，揭示泡沫铜的环境疲劳损伤机理；研究微观结构演化与材料性能变化之间形性演变关联，建立反映多孔结构特征、环境效应、载荷因素的环境疲劳寿命模型。为集流体泡沫铜材料的设计及在锂离子电池负极中的应用提供科学依据，同时对丰富多孔金属材料的疲劳理论体系具有重要意义。

高容量锂离子电池负极材料在充放电过程中产生巨大体积变化，导致电池循环性能下降，是制约其发展的瓶颈；以泡沫铜替代铜箔作为负极集流体能起到良好的缓冲作用，但缺乏服役过程中疲劳行为及机理的认识。本项目以三维网状结构泡沫铜为研究对象，通过实验研究，结合数值模拟和微观分析，对泡沫铜多孔结构特征与内部应力状态、单调压缩与循环疲劳特性、压缩应力下腐蚀电化学行为、电解液及极化电位作用下的环境疲劳机理与寿命进行了系统深入研究。通过多孔结构表征和几何分析方法，发展了一种新的基于十四面体胞体的泡沫金属比表面积计算方法；通过基于密度泛函理论的第一性原理计算和电化学测试分析，发现电解液中六氟磷酸锂分解产物氢氟酸是造成泡沫铜腐蚀的主要原因，揭示了应力作用下泡沫铜腐蚀的微观机制；研究了应变率、孔隙率、孔径对泡沫铜单调压缩变形的影响，探究了压缩过程中材料的吸能能力与变形机制；系统研究了开孔泡沫铜在空气、电解液及电位作用下的疲劳行为，发现疲劳变形主要集中在材料的中心区域，在循环加载初期变形区域会与加载方向垂直或者呈现出一定的倾斜角；分析了泡沫铜在压缩疲劳载荷下多孔体内部应力状态及应变带演化规律，阐明了电解液中循环载荷下孔棱微裂纹萌生与扩展过程，揭示了电解液中电位作用下泡沫铜疲劳损伤微观机理；构建了泡沫铜整体疲劳寿命与单胞棱柱裂纹扩展速率的关联，建立了泡沫铜在极化电位作用下的环境疲劳寿命模型。为集流体泡沫铜材料的设计及在锂离子电池负极中的应用提供科学依据。