High-Accuracy and Resolution Fluorescence Intensity Ratio Thermometer for Real-Time Temperature Monitoring in a Lithium-Ion Battery

Significant efforts have been invested toward the research of optical sensing materials, devices, and applications based on fluorescence intensity ratio (FIR) technology. However, there are many significant obstacles in the development of high-performance temperature sensors for practical applications. Herein, an all-fiber FIR thermometer was built and used for the real-time temperature monitoring of lithium-ion batteries (LIBs). Three orders of magnitude enhancement in upconversion luminescence in Er³⁺/Yb³⁺ codoped Y₂Mo₃O₁₂ phosphors were achieved via K⁺/Mg²⁺ ion codoping and used to construct a high-accuracy and resolution FIR thermometer for real-time temperature monitoring in LIBs. The temperature measurement accuracy and resolution are ±0.1 and 0.01 K, respectively. The thermal response time for a temperature difference of 100 K is 1.14 s. The as-built optical fiber sensing probe was implanted in the anode sheet of a 2000 mAh pouch LIB, and the internal temperature at different charging rates was determined. The maximum temperature rise was 25.30 K at a 5C charging rate. This work provides a new attempt from material design to device applications that is expected to lay the foundation for the practical utilization of ratiometric temperature sensors.