Towards rational mechanical design of inorganic solid electrolytes for all-solid-state lithium ion batteries

All-solid-state lithium ion batteries are being actively considered as promising candidates for next-generation energy storage applications. Compared with conventional lithium ion batteries using organic liquid electrolytes, all-solid-state lithium ion batteries using inorganic solid electrolytes demonstrate various distinct advantages, such as better safety without flammable explosion, more eco-friendliness without volatilization, higher stability without liquid leakage, wider cell voltage window and higher energy density. Extensive efforts have been focused on material, chemistry and electrochemistry of new solid electrolytes to enhance the capacity and long-term stability of all-solid-state lithium ion batteries. However, mechanical properties of solid electrolytes and multi-scale modeling of all-solid-state lithium ion batteries are less discussed. As a matter of fact, mechanical properties of solid electrolytes play a significant role in suppressing the growth of lithium dendrites, reducing electrode-electrolyte interfacial resistances and avoiding the propagation of fractures or cracks. In this review effort, we will discuss the mechanical properties, i.e. bulk, Young's and shear modulus, hardness, fracture toughness and elastic anisotropy of solid electrolytes, density functional theory modeling of elasticity, engineering discussions on interfacial resistances between solid electrolytes and electrodes, and electrochemical-mechanical modeling of all-solid-state lithium ion batteries. It is hoped that this review will contribute to the rational mechanical design of solid electrolytes and further the development of advanced all-solid-state lithium ion batteries for energy storage.