Cathode chemomechanics controls Li metal solid-state battery performance under low stack pressures

Stresses resulting from electrode material chemomechanics are strongly coupled to solid electrolyte-electrode interface failures. Such failures are significant barriers to realization of practical Li metal solid-state batteries (SSBs). Significant research efforts have been devoted to control anode chemomechanical stress. Here we show positive electrode (cathode) chemomechanical stress is also critical at commercially relevant low (e.g., <1 MPa) stack pressures. Using a series of model textured positive electrodes we provide the experimental evidence of the role of positive electrode lattice strain anisotropy during charge/discharge on positive electrode chemomechanics. Our model systems reveal that positive electrode chemomechanics significantly alter Li metal plating and stripping behavior at low stack pressure. We utilize these learnings to build long cycle-life SSBs with practical areal capacity (5 mAh/cm2) operating under a 1 MPa stack pressure and at room temperature. Our findings highlight the importance of controlling positive electrode chemomechanics to realize low stack pressure SSBs. Solid-state batteries typically require high pressure to operate reliably. Here, the authors show that tuning cathode chemomechanics enables stable lithium metal battery cycling at room temperature and low pressure, eliminating the need for interlayers or elevated temperatures.