Strategies toward addressing challenges of all-solid-state Li metal batteries based on quantitative interpretation of the electrochemo-mechanical correlation

For all-solid-state Li metal batteries, mechanical stress induced by Li deposition/dissolution causes severe challenges, including performance compromises between cell capacity, cell polarization and cycling stability, and safety hazards caused by Li dendrite growth. This work aims to address these challenges based on electrochemo-mechanical measurements and quantitative interpretation. A high-precision analytical expression of the induced stress is first elucidated and validated by experiment. Also, a critical stress is found to exist in the batteries. When the real stress induced by Li deposition is beyond this critical stress, mechanical damage with void formation is created near the Li|electrolyte interface. By combining the analytical expression of the induced stress with findings of the critical stress, the batteries can be precisely designed and operated to manipulate the stress just below the critical value; therefore, good cycling stability is achieved without sacrificing the cell capacity and polarization. Moreover, although the stress-created void itself has little effect on the battery electrochemical performance, it induces Li dendrite formation/growth, thus triggering the safety hazards. Consequently, the stress-derived signature corresponding to the void formation is extracted and demonstrated to be effective as an on-line early-warning strategy without interrupting the battery operation for forecasting the safety hazards.