Non-Invasive Smart Pressure Sensor for Early-Stage Thermal Runaway Warning for Cylindrical Batteries

Batteries have been widely applied in various fields due to the advantages such as high energy density, long service life and so on, whereas they are accompanied by frequent thermal runaway incidents and this is a worldwide challenge. However, non-invasive warning methods capable of providing early-stage alerts are missing, especially for non-planar sidewall pressure monitoring of cylindrical batteries. Here, a smart pressure sensor based on shape memory sensing composite is introduced, which enables conformal contact with cylindrical batteries and can continuously monitor the lateral pressure caused by volume expansion during charging-discharging. Moreover, the assembly process, designed based on COMSOL simulations, ensures conformal contact between the sensor and the test interface, effectively preventing uneven stress distribution during the assembly of the multi-layer structure. This smart sensor features impressive stability and recoverability, a broad pressure detection range (50-2340 kPa), excellent hysteresis error (1.17%), high linearity (R² = 0.99) and a maximum deviation of 1.56% over 20000 cycles. It can monitor radial pressure changes, achieving a warning time ratio of 80%, 84%, 86%, and 79% in thermal runaway tests on 18650, 21700 ternary lithium-ion batteries, 32700 LiFePO₄ battery and 18650 sodium-ion battery, respectively. Timely measures after warning can prevent thermal runaway.