Monitoring the Strain Evolution of Lithium‐Ion Battery Electrodes using an Optical Fiber Bragg Grating Sensor

More advanced characterization and developmental tools are essential to improve the performance and safety of Li‐ion batteries. Conventional tools have been limited to customized test cell configurations that require special facilities and expensive equipment. As a practical solution for the in situ monitoring of realistic battery cells, we have embedded fiber optic sensors within Li‐ion battery pouch cells to monitor the internal electrode strain and temperature during cycling. Here we report the direct monitoring of strain evolution using implanted fiber‐optic sensors within the individual electrodes in a Li‐ion battery. Reproducible peak shifting and splitting in the implanted fiber optic sensor originate from the accumulated longitudinal and transverse strains associated with the expansion or contraction of the anode electrode. These discoveries demonstrate the feasibility and utility of fiber Bragg grating (FBG) sensors to be used as diagnostic tools in the development of new battery materials and structures.