Thermal runaway monitoring in lithium-ion batteries via advanced optical fiber sensor

Operando monitoring of complex physical and chemical activities inside commercial cells during thermal runaway is critical to understanding thermal runaway mechanism and making early warning for cell safety. However, most of existing sensors cannot survive during such extremely hazard thermal runaway process. To address this, a compact-in-size and multi-functional optical fiber sensor capable of being inserted in commercial cells and continuously decoding internal temperature and pressure effects over cell thermal runaway is demonstrated. A stable and reproducible correlation between the cell thermal runaway and the optical response has been observed and quantified, in which two internal pressure peaks corresponds to safety venting and initiation of thermal runaway were found.