Research on operating mechanism and state of battery based on fiber Fabry-Pérot cavity

A compact sensor based on a fiber Bragg grating (FBG) and an open Fabry-Pérot (FP) cavity for measuring temperature and pressure changes inside the battery is proposed and demonstrated. In this work, the dual-parametric measurement mechanism is analyzed, and a dual-parametric simultaneous measurement structure with an FBG cascaded with an open FP cavity is designed and fabricated, where the open FP cavity is used for pressure measurements and the cascaded fiber Bragg grating to measure the temperature, and finally, the internal dynamic behavior of a lithium-ion battery during charging and discharging is explored. The experimental results show that the sensitivity of the sensor is 4.0745 nm/Mpa in the pressure range of 2.4 Mpa, the gas pressure and temperature change nonlinearly with the discharge of the battery, and the internal temperature of the 1500 mAH capacity monobloc battery discharged at 2 C is measured to be increased by 32.86 °C, the external surface is warmed up by 17 °C, and the pressure is increased by 0.136 MPa. The sensor can effectively, directly, and in real-time reflect the mechanism of gas and temperature changes inside the battery. It has potential application value in detecting small pressure changes caused by gas precipitation inside the battery can be used as an indicator for judging the health condition of the battery. The early gas evolution inside the battery is the most important basis for judging the operating state of the battery, and the change of temperature and pressure can directly and effectively reflect the state of gas evolution. A low cost, small size, high temperature resistance, corrosion resistance, all-fiber temperature and pressure measurement F-P cavity combined with FBG internal battery detection sensor is ingeniously proposed. Spectral contrast is guaranteed to be excellent and the optimal temperature characteristics is guaranteed to the maximum extent, successfully achieving in situ detection inside the battery. The changes of temperature and pressure inside the battery under different discharge rates are effectively detected, and the reaction rate of the battery is discussed in depth. The experimental results obtained reflect the desired response characteristics, and this type of sensor with high-performance characteristics lays a solid foundation for the accurate measurement of the internal state of the energy storage battery and the optimization of the battery design. • Aiming at the complex environment inside the lithium-ion battery, based on the fiber-optic FP cavity and FBG theory, a compact probe-type fiber-optic sensor for the simultaneous measurement of the internal temperature and pressure of lithium-ion batteries is designed and fabricated. • Analyzed in detail the internal pressure changes and internal/external temperature changes of 18650 batteries monitored by the fiber-optic sensor at different discharge rates, as well as the rates of change of pressure and temperature with time, and the thermal behavior and internal reaction mechanisms inside the cell are analyzed. • The fiber optic sensing scheme is used to achieve in-depth exploration and analytical understanding of the internal state information inside the lithium-ion battery.