Enhancing Lithium‐ion Battery Safety with a Multilayer Integrated Sensor for Synchronous Thermal‐Mechanical Monitoring

ABSTRACT Real‐time, colocated monitoring of thermal and mechanical signals is essential for accurate state estimation, early fault diagnosis, and safety management of lithium‐ion batteries. However, existing strategies often suffer from spatial asynchrony between temperature and pressure sensors and inter‐signal crosstalk, which undermines diagnostic fidelity. Here, we report a compact, flexible multilayer temperature‐pressure sensor (MTPS) enabling synchronous, colocated, and high‐fidelity dual‐parameter monitoring on cell surfaces. The vertically co‐laminated architecture integrates a high‐sensitivity temperature‐sensing unit with a wide‐range pressure‐sensing unit. The temperature sensor achieves a TCR of −0.6% °C −1 with fast response/recovery of 1.4/1.9s, and the hierarchical microstructure pressure sensor covers 0–1000 kPa with a low detection limit for 0.001 N. A hardware‐implemented compensation model quantitatively decouples thermal‐mechanical interference, further improving signal fidelity. Operando deployment of the MTPS accurately tracks signature signals associated with failure modes such as lithium plating under cooling, thermally aggravated side reactions under heating, and irreversible damage under compression, providing highly reliable evidence for early fault warning and elucidation of failure evolution mechanisms. At the system level, the MTPS distinguishes cell‐to‐cell inconsistencies in series/parallel packs and detects underbody scraping in a vehicle demonstration. This integrated non‐intrusive platform provides a practical pathway for real‐time, precise, and intelligent battery safety monitoring.