Implantable flexible temperature sensor for in-operando sensing of Lithium-ion batteries

The safety concerns play a key role in promoting the application of lithium-ion battery (LIB) in electric vehicles, renewable energy storage and consumer electronics. Thermal runaway is one of the primary risks of LIB. Operando monitoring LIB's temperature is expected to provide essential signal for the early warning of thermal runaway. In this study, a flexible temperature sensor with robustness to the internal environment of LIB cell is presented. By using ultra-violent laser micromachining and transfer-printing technique, the corrosion-resistant Molybdenum thin film is patterned and integrated with polyimide (PI) film to serve as the temperature sensitive layer. The encapsulation of Molybdenum layer enabled by the hot-pressing process further improves the reliability of the sensor in LIB cell. The stability of the sensor in the LIB cell is experimentally verified with the neglectable change of resistance when the sensor is immersed in the electrolyte for 48 hours. The ability of the proposed sensor to monitor the internal temperature of LIB is also demonstrated by implanting the sensor in a pouch cell and measuring the temperature in the charge-discharge cycles.