Advances in the Application of Fiber Optic Sensors for High Spatial Resolution Monitoring of Lithium-Ion Batteries

With the development of electric vehicles and energy storage systems, lithium-ion batteries are widely used due to their high energy density and other advantages, but their capacity degradation and thermal runaway problems need to be solved. Traditional monitoring methods have limitations such as low precision and weak anti-interference, etc. Fiber optic sensors have become an emerging technology by virtue of their noninvasive, antielectromagnetic interference and high sensitivity characteristics, especially the high spatial resolution sensing technology that can accurately monitor the local characteristics of the battery microstructure and provide key data for analyzing the working mechanism of the battery. This paper reviews the principles and applications of three types of fiber-optic sensors: FBG sensors monitor temperature and strain through a wavelength shift and are suitable for single-point or quasi-distributed measurements inside the battery; plasma-based fiber-optic sensors utilize the surface plasmon resonance effect to achieve nanoscale sensitivity and track the ionic activities on the surface of the electrodes in real time; and FOEWS are suitable for the overall monitoring of electrolyte composition through the interaction of the bare core with the outside world. The fiber optic sensor based on abrupt wave interacts with the outside world through a bare fiber core, which is suitable for the overall monitoring of electrolyte composition. The differences in sensitivity, spatial resolution and stability among the three are compared, and the integration technology of embedded packaging and surface mounting is introduced. At the application level, FBG sensors have realized real-time monitoring of temperature and strain inside and outside the battery, and plasma and swift wave sensors show potential in monitoring lithium ion concentration and electrolyte aging. High spatial resolution technologies such as distributed fiber optic sensors and multifunctional integrated sensors can capture temperature gradients and phase transition processes inside the battery. Currently, fiber optic sensors face challenges such as technology adaptation, material stability and massive data processing. Future research will focus on improving the ability to analyze the internal structure of batteries, promoting multiphysical field data fusion and efficient feature extraction, and reducing costs to accelerate marketization. This review provides a systematic reference for the in-depth study of fiber optic sensors in lithium-ion battery monitoring.