Effects of external stack and lateral pressures on Li dendrite growth by phase field modelling

Solid-state lithium metal batteries have garnered considerable interest as next-generation energy storage devices owing to higher energy density and safety. However, uneven deposition at the Li anode/solid electrolyte (SE) interface during charging induces the growth of Li dendrites, posing significant safety risks due to potential short circuits. The interface evolution is intrinsically coupled with mechanical contact between the Li anode and SE, where external pressure plays a critical role. In this paper, we develop a mechano-electrochemical bi-coupled phase-field model to simulate Li dendrite growth under various loading conditions, thereby elucidating and quantifying the impact of external pressure - including both stack and lateral pressures on Li dendrite growth. Our key findings include: 1) The lateral widening and vertical penetration of Li dendrites can be inhibited under lateral pressure and stack pressure, respectively. Notably, the length and width of the Li dendrites are considerably reduced when stack and lateral pressures are simultaneously applied. The direction of inhibition is closely associated with the regions/branches which maintain higher stress and smooth surface. 2) Larger external pressure decreases the Li dendrite area and enhances space utilization, due to the reduced overall reaction rate at the Li dendrite/SE interface. 3) The uniformity of electrochemical reaction at Li dendrite/SE interface is improved under equal large stack and lateral pressures. These insights provide essential guidance for pressure management strategies in battery design.