Chemo-Mechanics of Silicon Anodes via Operando Acoustic Transmission in Solid-State Batteries

Silicon (Si) anodes paired with solid electrolytes have recently risen as a promising energy storage solution for energy-dense Li batteries. However, Si lithiation and delithiation can exacerbate electrochemical degradation due to its high mechanical dynamics, especially against a solid electrolyte. In this work, we utilize operando acoustic transmission to probe the chemo-mechanical dynamics of Si. Acoustic transmission utilizes ultrasound propagation to nondestructively monitor the electrode’s chemo-mechanics. The speed of sound through a material is proportional to its Young’s modulus and inversely proportional to density. We show that in an all-solid-state system with a sulfide solid electrolyte, the mechanical dynamics of Si electrodes and its distinct phasing are monitorable through acoustic time of flight. We combine operando acoustics with ex-situ techniques such as SEM and XPS to gain physical insight into the fundamental electrode mechanics. We demonstrate that acoustics time-of-flight transmission is a useful tool in probing electrode dynamics that give further insight into the degradation modes of next-generation anode materials.