Overcoming Cell Fixture Challenges in High-Pressure Operation of Solid-State Batteries

Solid-state batteries (SSBs) have long been regarded as the next-generation battery technology, offering improved performance and energy density compared with state-of-the-art lithium-ion batteries. While many challenges in SSB development have been addressed, the high operating pressures required for promising sulfide-based SSBs remain a major drawback. To better understand pressure-dependent effects, precise and accurate high-pressure cell testing fixtures for large-format batteries are essential. This work introduces a spring-loaded, uniaxial cell fixture for large-format pouch cells and a robust procedure to ensure accurate control of the operating pressure without the need for costly sensors. Finite-element analysis is combined with direct fixture deflection measurement to implement a deflection-based pressure-setting strategy. The approach is benchmarked against torque- and screw-angle-based methods and validated using digital pressure-mapping sensors. Across the design operating range of 10–30 MPa, the fixture achieves a mean absolute percentage error below 3% of the cell pressure with high repeatability and pressure homogeneity over the active area. This work provides design requirements, calibration and validation procedures, and practical guidelines, enabling affordable, reproducible high-pressure studies and facilitating the transfer of this methodology to other cell formats and pressure targets.