Thermo-luminescent optical fibre sensor for Li-ion cell internal temperature monitoring

The internal temperature of a Li-ion battery is one of the critical parameters for monitoring cell performance, ageing and safety. The development of new sensor technologies to control the internal temperature of cells without compromising performance and safety remains a challenge. It is one of the objectives of the European INSTABAT project in the framework of the Battery2030+ initiative. The objective of this paper is to describe the development of a new optical fibre sensor based on a thermoluminescent material to monitor internal cell temperature. The development of the sensor, its thermal characterisation and its calibration are presented here. This sensor was inserted into a commercial Li-ion cell and its response during cycling at high charge and discharge rates (2C in charge and 4C in discharge) was investigated. The comparison between external and internal temperature measurements shows good agreement. These results demonstrate the ability of this type of sensor to monitor the internal temperature of a Li-ion battery without affecting its performance at high loading.