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

ABSTRACT 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.