An Er3+/Yb3+ Co-Doped Tellurite Fiber Temperature Sensor for Real-time Thermal Monitoring for Lithium Battery

We propose and experimentally demonstrate a non-contact optical thermometric study based on Fluorescence Intensity Ratio (FIR) of non-thermally coupled levels (NTCLs) for real-time temperature detection of lithium battery. The no-core Er ³⁺ /Yb ³⁺ co-doped TeO ₂ -Al ₂ O ₃ -WO ₃ -BaF ₂ +Er ₂ O ₃ +Yb ₂ O ₃ (TWA) optical fiber was prepared using the traditional melt-quenching method, and influence of the Al ₂ O ₃ concentration on the fiber luminescence was investigated in detail. Meanwhile, temperature demodulation by means of thermally coupled level (TCLs)-based FIR was juxtaposed for comparison. It was found that the sensor's sensitivity was enhanced at least 10 times utilizing the NTCLs-based FIR method, and at Al ₂ O ₃ concentration of 4 mol%, the sensor demonstrated the best sensing performance, which was 434.3×10 ^-4 K ^-1 in the temperature range of 258 to 371 K. In addition, this sensor had high temperature resolution and good repeatability, and its maximum measurement error during thermal monitoring of the charging/discharging process of an 18650-type lithium battery was only 0.7 K. To the best of our knowledge, this was the first report to use a temperature sensor based on fluorescence intensity ratio for real-time monitoring of 18650-type lithium batteries. The proposed sensor demonstrated excellent stability and repeatability, resistance to electromagnetic interference and corrosion, and the capability to avoid cross-sensitivity. It provides an effective and reliable measurement solution for long-distance and real-time temperature monitoring in new energy battery applications.