Internal temperature monitoring in a lithium-ion battery using capillary-based optical fiber Fabry-Perot interferometer

This manuscript experimentally validates an optical fiber Fabry–Perot interferometer fabricated from a silica capillary and a UV-cured polymer for internal temperature monitoring in a coin-cell lithium-ion battery. Once the proposed interferometric fiber-optic sensor is fabricated, mounted on the anode, and then coin-cell packaged, its sensitivity increases by approximately 30×, reaching a maximum of 1.57 nm/°C. Afterwards, two C-rate battery conditions (C/and C/21) and their internal thermal effects were evaluated. Here, the evolution of the reflection interference spectrum and its thermal relation were analyzed using the Singular Value Decomposition (SVD) method. This technique can follow thermal rates of ∼0.20 °C h−1 (C/42) and ∼0.30 °C h−1 (C/21). In these thermal routes, consistent thermal jumps of 0.5 °C were observed throughout the time. The proposed CFPI provides a sensitive and reliable platform for internal temperature monitoring in lithium-ion batteries.