Cell and interface design strategies for low-pressure operation of solid-state batteries

Solid-state batteries (SSBs) are promising next-generation energy-storage systems because of their potential for improved safety and high energy density. However, their practical implementation remains limited by the strong dependence of electrochemical performance on externally applied stack pressure. Although high stack pressure can improve solid–solid interfacial contact and suppress degradation, it also imposes mechanical, manufacturing, and system-level constraints that are incompatible with practical cell and module designs. This review focuses specifically on the low-pressure operation of lithium-metal-based SSBs—defined here as operation under stack pressures of ≤2 MPa—by first examining the electrochemo-mechanical failure modes caused by insufficient mechanical confinement, including cathode-side contact loss and transport heterogeneity, anode-side void formation and current localization, and filament-mediated short-circuiting. Recent cathode, anode, anode-less, and cell-level pressure management strategies are then summarized to clarify how contact retention, transport robustness, Li deposition regulation, and pressure homogenization can reduce the need for high external compression. Finally, future research directions are suggested, including standardized low-pressure benchmarking, operando chemo-mechanical diagnostics, and scalable cell architectures, emphasizing that low-pressure operability should be regarded as a primary design criterion for practical SSBs.