Molar Volume Mismatch: A Malefactor for Irregular Metallic Electrodeposition in Solid Electrolytes

Regularizing metallic electrodeposition has been a long-standing challenge in energy storage. Leveraging mechanical stresses, solid ion conductors have been proposed to stabilize the evolving interface. Paradoxically softer electrodepositing metals are often found to form penetration fronts under the hypothesized stable conditions. We find that mechanical contributions to energy of the interacting species (i.e., metal and cation) relate to respective molar volumes. The stresses at the electrodepositing interface are correlated, and consequently, localized deposition is energetically favored for larger cationic molar volumes. Electrolyte stresses cause a stress-driven ionic flux away from compressed locations, which proves to be a stabilizing influence. Stability is found to be nonlinearly related to electrolyte stiffness. Material complexities such as interphases, interlayer, and grain boundaries are also examined to proffer guidelines for a stabilized growth.