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

We propose and experimentally demonstrate a noncontact optical thermometric study based on fluorescence intensity ratio (FIR) of nonthermally coupled levels (NTCLs) for real-time temperature detection of lithium batteries. The no-core Er3+/Yb3+ co-doped TeO2–Al2 O3–WO3–BaF2 + Er2O3 + Yb2O3 (TWA) optical fiber was prepared using the traditional melt-quenching method, and influence of the Al2O3 concentration on the fiber luminescence was investigated in detail. Meanwhile, temperature demodulation by means of thermally coupled level (TCL)-based FIR was juxtaposed for comparison. It was found that the sensor’s sensitivity was enhanced at least ten times utilizing the NTCL-based FIR method, and at an Al2O3 concentration of 4 mol%, the sensor demonstrated the best sensing performance, which was $434.3\times 10^{-{4}}$ K−1 in the temperature range of 258–371 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 FIR 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.