  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.
