Long‐Term Stability Evaluation of Optical Fiber Sensors Immersed in LiPF6 Electrolyte

Stability tests on silica optical fiber sensors (fiber Bragg gratings) within the lithium–ion battery (LiB) electrolyte are conducted, revealing their robustness over 24 months, only subject to variations in ambient temperature. Recurrent chemical analyses based on scanning electron microscopy and energy‐dispersive X‐ray spectroscopy characterizations demonstrate the formation of deposits (LiPF 6 crystals) from electrolyte decomposition in the fiber surfaces over time. However, no silica material degradation is observed. The performance and accuracy of the optical fiber sensors are tested before and after aging, revealing an insignificant variation in their thermal sensitivity, with values within the measurement error. This research demonstrates the durability and the potential of this advanced sensing technology in the field of LiB monitoring, making a substantial contribution to the domain of sustainable energy solutions. It offers invaluable insights for enhancing LiB safety, reliability, and overall performance, ultimately advancing the integration of LiBs within our evolving sustainable energy landscape.