Expansion force and pressure sensing for mechanics-aware battery management in electric vehicles: from state estimation to early safety warning

Conventional battery management systems (BMSs) for electric vehicles rely primarily on voltage, current, and surface temperature, potentially overlooking mechanical signatures of degradation and incipient failure. This mini review examines expansion force and pressure sensing as complementary observables for mechanics-aware battery management. We first relate reversible swelling, irreversible deformation, gas generation, and casing response to electrochemical and thermal processes. Established effective-stiffness approximations are then integrated into a review-level framework linking free cell expansion to constrained force and distinguishing SOC-dependent reversible behavior, SOH-related baseline drift and hysteresis, gas-related anomalies, thermal effects, and viscoelastic relaxation. Published studies report SOC estimation errors of approximately 3% or lower using electrical–mechanical sensor fusion and SOH errors below 1.5% in representative datasets. Under specific abuse conditions, swelling and strain-rate measurements have provided thermal-runaway warning lead times ranging from hundreds to more than 1,000 s. Strain, optical-fiber, and ultrasonic sensing are also examined as benchmark technologies to highlight their complementary capabilities and limitations. Building on these findings, we outline a conceptual timescale-separated mechanics-residual framework that coordinates independent normal-force prediction, force-assisted SOC estimation, slow aging-related updates, and rapid anomaly detection. This proposed framework requires further experimental validation across cell formats, operating conditions, and mechanical constraints. Overall, force and pressure sensing offer promising complementary information for improving battery-state observability and early safety warning in next-generation BMSs.