More advanced, practical characterization techniques and developmental tools are essential to improve performance and safety of Li-ion batteries. While conventional tools have significantly improved understanding of reaction mechanisms related to battery safety, they have been limited to customized test cell configurations that require special facilities and expensive equipment. As a practical solution for in-situ monitoring of realistic battery cells, we have embedded fiber optic sensors within Li-ion pouch cells to monitor the internal electrode strain and temperature during cycling. Here we report on direct monitoring of strain evolution from 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 FBG sensors to be used as diagnostic tools in the development of new battery materials and structures.
Bae, C.; Manandhar, A.; Kiesel, P.; Raghavan, A. Optical Fiber Bragg Grating (FBG) sensor as a method to monitor strain evolution of electrodes in lithium-ion batteries. Energy technology. 3/1/2016