Fiber Optic Based Thermal and Strain Sensing of Lithium-Ion Batteries at the Individual Cell Level

A few safety challenges with lithium-ion batteries, stemming mostly from errors in assembly or from faulty electronics managing them, have created visibility and public concern. The ability to monitor all individual cells within large operational batteries containing many series/parallel cells, respectively, is challenging, and there is growing demand to identify new, non-invasive sensing technologies. Elevated temperatures, induced by either normal or abnormal operation, is a leading cause of failure. With traditional thermal sensing technology, it’s feasible to monitor a few spots within a large battery, introducing a high probability that elevated temperatures will not be measured by the managment system(s) intended to protect them. When abnormal conditions occur, a cell’s case expands and contracts in a measureable way. Detection of an abnormal stress/strain signature is another diagnostic that has great potential. The present study demonstrates the ability of an Optical Distributed Sensor Interrogator (ODiSI) to measure the surface temperature and case deformation of 18650 cells under normal and abnormal conditions, respectively. Multiple experiments have been performed to demonstrate the abilities of the ODiSI to measure temperature and stress/strain changes, respectively, and they show that the results are unique and repeatable making this a promising technique for monitoring lithium-ion cells.