新型负泊松比结构负极材料应力与断裂失效机制研究

Alloy anode materials have been expected to improve the specific energy density of ithium-ion batteries due to high specific capacity. Unfortunately, these alloy anode materials experience large volume expansion and stress during lithiation process, resulting in pulverization and fracture, which is the bottleneck of its development in lithium-ion batteries. Herein, this project is mainly focus on adopting a stannum-based concave honeycomb structure which presents negative poisson's ratio effect. Based on the theory and experiment analysis, we investigate the deformation and the stress evolution during lithiation process for these anode structures in detail. And we establish the mechanical-chemical coupling model of negative poisson's ratio materials during lithiation, revealing the effect of novel negative poisson's ratio on stress evolution for anode materials. In addition, combined with the numerical simulation and experimental testing, this project will explore the mechanical properties and stress of the negative poisson's ratio structure anode materials during lithiation. Finally, introducing the fracture toughness parameter, we describe the intrinsic relationship between fracture toughness and negative Poisson's ratio during lithiation. The fracture failure criterion of concave honeycomb anode materials will be discussed, and the internal relationship among structrue-stress-lifetime is revealed for improving the anode materials broken pulverization phenomenon. Our project will provide experimental and theoretical basis for improving the application of anode with high capacity and long cycle life in lithium ion batteries.

合金负极材料因具有极高的比容量而有望大幅度提升锂离子电池能量密度。然而，充电过程因锂离子嵌入产生巨大的应力而造成负极材料的粉化和断裂失效是高比容量合金负极材料发展的瓶颈所在。本项目拟采用锡基凹蜂窝结构，使其呈现负泊松比特殊效应，采用理论和实验相结合的方法系统考察充电过程中此材料的结构及应力演化规律，建立负泊松比结构的力-化耦合数值模型，揭示负泊松比效应对负极材料中应力的作用机制。此外，结合数值模拟和实验测试，探索储锂过程中负泊松比结构应力及力学性能的变化规律。最后，引入断裂韧性参数，描述锂离子浓度作用下断裂韧性与负泊松比材料的内在关系，建立储锂过程此结构的断裂失效判据，阐明结构-应力-寿命三者之间的内在联系，进而最大程度改善合金负极材料破裂粉化现象，为研究与设计高比容量长循环负极材料在锂离子电池中的应用提供实验和理论依据。

合金负极材料因具有极高的比容量而有望大幅度提升锂离子电池能量密度。然而，充电过程因锂离子嵌入产生巨大的应力而造成负极材料的粉化和断裂失效是高比容量合金负极材料发展的瓶颈所在。本项目采用锡基凹蜂窝结构，使其呈现负泊松比特殊效应，通过计算和实验相结合的方法分析充放电过程中此材料的结构及应力演化规律，建立负泊松比结构的力-化耦合数值模型。此外，结合数值计算和实验分析，探索储锂过程中负泊松比结构应力及力学性能的变化规律。最后，通过有限元模拟，第一性原理计算应力模型构建，描述锂离子浓度作用下体系应力与负泊松比材料的内在关系，建立储锂过程此结构的失效判据。研究发现，在嵌锂过程中，结构负极斜肋会承受弯矩作用并发生弯曲变形，从而降低负极内部应力水平，增加约30.9％的锂化膨胀空间，并提升锂离子电池负极循环使用寿命。同时，结构优化设计可以减少约7.0％的过电势值和6.4％的电压降值，从而一定程度上解决负极即时电势与平衡电势之间不一致的问题有效提升负极使用寿命。阐明结构-应力-寿命三者之间的内在联系，进而最大程度改善合金负极材料破裂粉化现象，为研究与设计高比容量长循环负极材料在锂离子电池中的应用提供实验和理论依据。