In situ monitoring of internal temperature and hydrogen gas evolution in commercial lithium-ion batteries via flexible bifunctional sensors

Abstract

Lithium batteries (LIBs) in energy storage plants experience thermal runaway in severe cases due to inconsistent charging and discharging conditions. Traditional external parameter collection is insufficient for a battery management system to achieve a safe and comprehensive assessment. In this study, we propose a method for in-situ monitoring of the internal temperature and H₂ within batteries. This method is based on an ultrathin, flexible, bifunctional sensor, which can measure the resistance parameters induced by temperature and gas changes. We construct the temperature and gas sensors on flexible electrodes prepared through microelectronic printing technology. Polyimide films with flexible, breathable, and hydrophobic properties are prepared via electrospinning technology to encapsulate the sensors, which exhibit high thermal-response sensitivity of 0.036 °C⁻¹ and achieve an ultra-fast gas response/recovery time of 3 s/4.2 s. The results of long-term cycling experiments demonstrate that this thin-film sensor can efficiently monitor the internal temperature changes of batteries at different rates in real time, and it is capable of long term in-situ detection of H₂ under actual working conditions. Throughout the entire monitoring process, the influence of the sensor on battery performance is almost negligible. This method provides a new approach for the detectability of smart LIBs and early warning of thermal runaway, contributing to the intelligent management of LIBs.