Decoupling of thermal and mechanical load with fiber optic sensors for in-situ battery monitoring

This work introduces a novel approach for in-situ monitoring of temperature, strain and electrode half-cell potentials within lithium-ion battery cells using distributed fiber-optic sensing based on Optical Frequency Domain Reflectometry combined with a Reference electrode. By embedding two co-located optical fibers with different core dopants, the method enables the decoupling of thermal and mechanical effects through calibrated differences in temperature sensitivity. By using a conductive fiber coating as a Reference electrode the measurement of half-cell potentials is combined with the optical measurement. The fibers were successfully integrated into a functional LIB pouch cell and validated through controlled thermal testing. This technique enables fully embedded diagnostics, offering a significant advancement for real-time thermal management and safer fast-charging strategies in future battery systems.