Research on Safety Warning Characteristics of Battery Based on Temperature and Force Coupling Signals

Abstract

As the core power source for electric vehicles, renewable energy grid connected systems, and portable electronic devices, the safety of lithium-ion batteries are crucial. Compared with single parameter warning, multi parameter warning can significantly improve the reliability of the warning system. This research focuses on the commonly used lithium iron phosphate (LFP) batteries in energy storage and explores the coupling relationship between temperature and force parameters in experiments where overheating leads to thermal runaway (TR). It has found that as the states of charge (SOC) of the battery increases, the venting time of the battery first increases and then decreases, while the trend of TR time is opposite. The increase in battery surface temperature and the decrease in battery capacity can shorten the time for venting and TR. In addition, the temperature change at the positive electrode ear position is most sensitive. The times when the first maximum value is selected and returns to 0, as well as the time when the force change rate first reaches 19.6N/s, are used as warning thresholds. The relationship between the warning time before valve opening and SOC can be accurate fit by cubic polynomial y=0.00355x3-0.8872x2+62.72x-728 and y=-0.00107x3+0.149x2-7.013x+307, respectively. However, for the triggering TR conditions of low temperature heating, the force change rate is more commonly used as a warning threshold for valve opening and TR than the temperature change rate. The research results of this article can provide strong scientific basis and technical support for the design and operation of battery early warning systems, and promote the development of electrochemical energy storage safety technology.

Keywords: Lithium ion battery, Thermal runaway, Temperature, Force, Early warning