In-situ mechanical evolution of lithium magnesium alloy anodes in Li-Ion batteries

As the demand for batteries with greater capacity increases, understanding their mechanics has become crucial for achieving stability. Specifically, metallic anodes, many of which have higher theoretical capacities than the conventional carbon-based anodes, often experience huge volume changes during electrochemical cycling, leading to significant mechanical stress generation within the material and often resulting in mechanical failure. These types of electrochemical-reaction-induced mechanical issues must be addressed for commercialization of metallic anodes. To this end, this study focuses on the interplay between mechanics and electrochemistry in lithium-magnesium alloy anodes, which are promising for future anodes of Li-based batteries due to their high theoretical capacity. We performed in-situ stress measurements using a multibeam optical stress sensor during electrochemical operation and characterized mechanical properties (elastic modulus and hardness) of various lithiated phases and compositions through nanoindentation. As a key consequence of this study, by correlating electrochemical reactions with the structural and mechanical behaviors in lithium-magnesium alloy anodes, we suggest a strategy called ‘ β-phase cycling ’, which involves operating solely within the Li-rich phase to avert phase transformations and correspondingly mitigate mechanical damage.