Investigation of the Mechanical Properties of Porous Argyrodite Sulfide Electrolytes for All-Solid-State Batteries

Argyrodite sulfide (Li6PS5Cl) has been recognized as a promising solid electrolyte material for all-solid-state high-energy-density lithium ion batteries. However, the issue of Li dendrite penetration through Li6PS5Cl continues to be a challenge that limits its performance and wider applications. To understand dendrite growth that is mediated by fracture, measurement of the relevant mechanical properties, i.e., the elastic modulus and the fracture toughness of Li6PS5Cl, is necessary to develop quantitative predictive models of dendrite initiation and propagation and help develop strategies to toughen Li6PS5Cl. Here, an investigation to measure the Young’s modulus and fracture toughness of porous Li6PS5Cl material is reported; it makes use of a custom-built experimental setup. An analysis of the experimental data in conjunction with finite element simulations shows the Young’s modulus of porous Li6PS5Cl to be 4.7 ± 1.1 GPa and the fracture toughness to be 0.17±0.03MPam. These results characterize the bulk behavior of the material at a millimeter scale in contrast to the local surface properties at the micrometer scale through nanoindentation. Based on these values, for a pre-existing crack of size 1 μm, the corresponding critical overpotential and critical current density are estimated to be approximately 12 mV and 1 mA/cm2 respectively. The measurements reported here contribute to the body of knowledge on Li6PS5Cl toward the larger goal of enhancing the ability to predict Li dendrite initiation and propagation in it.硫银锗矿型硫化物（Argyrodite sulfide，Li₆PS₅Cl）已被公认为极具应用潜力的全固态高能量密度锂离子电池固体电解质材料。然而，锂枝晶穿透Li₆PS₅Cl的问题仍是制约其性能提升与规模化应用的核心挑战。为厘清由断裂介导的锂枝晶生长机制，亟需表征该材料的相关力学性能——即弹性模量（elastic modulus）与断裂韧性（fracture toughness），以建立锂枝晶形核与扩展的定量预测模型，并为开发Li₆PS₅Cl的增韧策略提供理论支撑。本研究报道了一套采用定制化实验装置表征多孔Li₆PS₅Cl材料杨氏模量（Young’s modulus）与断裂韧性的实验工作。结合有限元仿真（finite element simulations）对实验数据开展分析后，结果显示多孔Li₆PS₅Cl的杨氏模量为4.7 ± 1.1 GPa，断裂韧性为0.17 ± 0.03 MPa·m。相较于纳米压痕（nanoindentation）技术测得的微米级局部表面特性，本研究表征了毫米尺度下该材料的体相力学特性。基于上述测试结果，针对尺寸为1 μm的预制裂纹，估算得到对应的临界过电位与临界电流密度分别约为12 mV与1 mA/cm²。本研究测得的力学参数丰富了Li₆PS₅Cl的相关研究数据体系，为进一步提升该材料内部锂枝晶形核与扩展的预测能力这一核心目标奠定了重要基础。