Monitoring of Li-ion cells with distributed fibre optic sensors

The in-operando monitoring of surface temperature and strain distribution in 5 Ah Li-ion A5 pouch cells is presented in this work. The measurement is performed through Rayleigh scattering based Distributed Fibre Optic Sensors (DFOS) during cycling at three different C-rates and three different ambient temperature. The sensors were bonded on the pouch cell surface, covering four regions along the shorter cell direction, and on both sides, for a total of eight regions per cell. The distributed temperature and strain gradients were recorded over time. This study aims to contribute to the definition of an effective procedure to real-time monitor temperature and strain gradients in a Li-ion pouch cell during cycling to early detect abnormal conditions that can be critical for the battery state of health and safety. The study also intends to demonstrate the feasibility of the use of these kind of sensors for this application, to be further used for internal in-situ and in-operando monitoring.