Operando monitoring of strain field distribution in lithium battery anode via ultra-high spatial resolution optical frequency domain reflectometer

The cycling performance of lithium-ion batteries is closely related to the expansion effect of anode materials during charge and discharge processes. Studying the mechanical field evolution of anode materials is crucial for evaluating battery per-formance. Here, we propose a phase-sensitive ultra-high spatial resolution optical frequency domain reflectometry tech-nique, in which the test fiber is embedded into the anode of a lithium-ion battery to monitor the mechanical evolution of the anode material during cycling. We investigated the strain evolution of the anode material under different loading levels and used this method to infer the morphological changes of the material. Furthermore, combining this with battery capacity in-formation provides a new approach for assessing the performance of lithium-ion batteries.