The Influence of Pressure on Structural Evolution of Lithium Alloy Materials

Stack pressure plays an important role in influencing electro-chemo-mechanical phenomena of electrodes in batteries and other energy conversion/storage devices. Despite progress in engineering strategies that aim to achieve durable device performance, the influence of mechanical stress on structural evolution and electrochemical behavior of electrodes is not well understood. Here, we investigate the effects of applied stack pressure on electrochemical alloying/dealloying of lithium alloy materials (Li-Al, Li-Sn, Li-In, and Li-Si) using both solid-state and liquid electrolytes. We elucidate the central role of stack pressure on morphological evolution and electrochemical reversibility of various alloy anodes in lithium batteries. The porosity evolution of electrodes during lithium dealloying under different stack pressures is found to be universally governed by the same scaling laws, with pressures at least 20% of the yield strength required to achieve ~80% relative density. With this information, we design a tailored alloy electrode structure with enhanced capacity and cycle life in solid-state batteries at stack pressure <2 MPa. These results provide insight into the phase transformation mechanism of electrode materials under mechanical confinements, and they have implications for developing high-capacity alloy electrodes for next-generation batteries.