Chemo-Mechanical Challenges in Solid-State Batteries

Solid-state electrolytes (SSEs) can transmit stress and strain at interfaces, making solid-state batteries susceptible to chemo-mechanical degradation during electrochemical cycling. Most Li/SSE interfaces are chemically unstable and evolve to form an interphase layer with different structure and properties. Understanding these chemo-mechanical phenomena requires the use of advanced in situ and operando characterization techniques and correlated modeling. The development of high-performance solid-state batteries will require control over the evolution and reactivity of interfaces. Solid-state batteries (SSBs) could exhibit improved safety and energy density compared with traditional lithium-ion systems, but fundamental challenges exist in integrating solid-state electrolytes with electrode materials. In particular, the (electro)chemical evolution of electrode materials and interfaces can often be linked to mechanical degradation due to the all-solid nature of these systems. This review presents recent progress in understanding the coupling between chemistry and mechanics in solid-state batteries, with a focus on three important phenomena: (i) lithium filament growth through solid-state electrolytes, (ii) structural and mechanical evolution at chemically unstable interfaces, and (iii) chemo-mechanical effects within solid-state composite electrodes. Building on recent progress, overcoming chemo-mechanical challenges in solid-state batteries will require new in situ characterization methods and efforts to control evolution of interfaces. Solid-state batteries (SSBs) could exhibit improved safety and energy density compared with traditional lithium-ion systems, but fundamental challenges exist in integrating solid-state electrolytes with electrode materials. In particular, the (electro)chemical evolution of electrode materials and interfaces can often be linked to mechanical degradation due to the all-solid nature of these systems. This review presents recent progress in understanding the coupling between chemistry and mechanics in solid-state batteries, with a focus on three important phenomena: (i) lithium filament growth through solid-state electrolytes, (ii) structural and mechanical evolution at chemically unstable interfaces, and (iii) chemo-mechanical effects within solid-state composite electrodes. Building on recent progress, overcoming chemo-mechanical challenges in solid-state batteries will require new in situ characterization methods and efforts to control evolution of interfaces. the interplay between chemistry and mechanics. In batteries, chemo-mechanics typically manifests as reactions (chemical or electrochemical) driving a mechanical response in a material, such as an electrode particle expanding during the insertion of Li. Conversely, chemo-mechanics can also involve mechanical forces driving chemical changes, such as altering the chemical potential of a system. a mixture consisting of an active electrode material and a solid-state electrolyte (typically as particles). Additives such as conductive carbon can be included to enhance transport properties within the composite. the current density at which lithium metal first penetrates through a solid-state electrolyte in an electrochemical cell, causing a short-circuit. At current densities below this value, cells can be stably cycled without short-circuiting. a phase or mixture of phases that forms at the interface between an electrolyte material and an electrode material in a battery due to chemical or electrochemical reactions. a phase that is both an ionic and electronic conductor. In solid-state electrolytes, the formation of MIECs within the electrolyte is detrimental due to the inability of MIECs to passivate against electrochemical reduction. a solid material with high ionic conductivity (typically greater than 10–4 S cm–1 at room temperature) and low electronic conductivity (typically less than 10–8 S cm–1) that allows for ion transport between the anode and cathode in an electrochemical cell.