Safety Warning and Localization for Lithium-Ion Batteries Inside the Pack by Laser Signals Under Thermal Runaway Conditions

Abstract

Safety issues arising from thermal runaway (TR) pose a significant obstacle to practical applications of lithium-ion batteries (LIBs). The energy storage system comprises numerous batteries arranged closely together. Failure to promptly locate the faulty battery for handling can easily escalate into a serious incident. This paper proposes a method for warning and locating TR of LIBs in pack. The vaporized electrolyte (VE) ejected from the faulty battery will obstruct and reflect the laser beam. Analyzing the phase change of the reflected laser signal enables both warning and positioning. Firstly, an investigation was conducted on the blocking ability of VE for lasers of different wavelengths. The comparison revealed that the 685 nm laser with a longer wavelength exhibits better warning effects. Subsequently, in a real battery pack, a commercial 100 Ah lithium iron phosphate battery was subjected to overcharging, and the laser module was employed for warning and localization of the TR of the battery. The results indicate that the laser signal can detect the faulty battery and achieve accurate positioning as soon as the safety valve opens. At this point, there is an average interval of 133 s before reaching the peak temperature on the battery surface, allowing for timely power cutoff to prevent further escalation of the incident. This study provides a novel approach for safety warning and localization in lithium battery energy storage stations and electric vehicles.

Keywords: Lithium-ion battery, thermal runaway, safety warning, fault location, laser signal