Ratiometric fluorescence optical fiber enabling operando temperature monitoring in pouch-type battery.

Thermal characteristics are essential for improving the performance and monitoring the status of Li-ion batteries (LIB). However, it is a challenge to design efficient and facile sensing materials for the detection of in-situ temperature of a working LIB. Herein, we develop a ratiometric fluorescence optical fiber and perform real-time temperature monitoring with a measurement accuracy of 0.12 °C, and the feasibility based on this polymer optical fiber composed of NaLaTi 2 O 6 :Yb/Er phosphors is verified in a pouch-type battery. During the charging and discharging cycles, the in-situ temperature is instantaneously converyed, revealing the internal situation of LIB. We further dwell on the thermal characteristics in constant current (CC) / constant voltage (CV) charging and CC discharging processes at different C-rates and the battery failure when operated at low temperature (0 °C). This work demonstrates an innovative strategy for operando solitary temperature monitoring conducted by ratiometric fluorescence optical fiber. This article is protected by copyright. All rights reserved.