基于气体分析的锂离子电池热失控早期预警研究进展

Li-ion batteries are widely used in electric vehicles, portable electronic devices, and distributed energy storage systems due to their high energy density, long cycle life, low self-discharge rate, and eco-friendly. However, there are still potential safety hazards. It may lead to failure or even fire and explosion accidents when cells are subjected to stress and abuse from mechanical, electrical, and thermal perspectives, posing a significant threat to the overall safety of a variety of battery systems. Therefore, studies on the thermal runaway and safety warning of Li-ion batteries have aroused great concern. On the premise of passing the battery manufacturer’s safety tests, a lot of methods for monitoring and detecting thermal runaway events have been developed to enhance the safety and robustness of Li-ion batteries in various application scenarios. Among these, the gas-based thermal runaway early warning mechanism has improved in reliability, accuracy, and response speed compared with the traditional electrical and thermal signals. Firstly, this paper summarizes the chemical reactions and their onset temperatures during the thermal runaway of Li-ion batteries, as well as the gases released. The decomposition of the solid electrolyte interphase membrane, the reactions between the active materials, and the decomposition of the electrolyte, especially the intercalated lithium with solvents, can release large amounts of combustible gases including H₂, CO, CO₂, and hydrocarbons. Flammable gases and solvent vapors are a potential fire hazard when mixed with oxygen. However, Li-ion batteries in various states may exhibit different characteristics of thermal runaway gas production. Thus, the effects and laws of the triggering method, cathode material, cell type, state of charge, and state of health on the components, content, and total amount of gas produced during thermal runaway were comprehensively compared and analyzed. Then the current status of research on the temperature-pressure evolution characteristics during thermal runaway of Li-ion batteries is reviewed from experimental and simulation perspectives, respectively, and the conclusions and limitations of existing studies are summarized. Experimental studies of Li-ion battery eruptions are generally conducted based on sealed chambers, and the output parameters are usually cell temperature, the pressure inside the pressure tank, and gas production components. But these studies are difficult to determine the gas temperature. Therefore, some researchers have simulated gas generation, pressure buildup, gas emission, and combustion processes based on gas production kinetic models. Finally, the current early warning schemes based on gas composition and internal pressure are summarized, and the shortcomings of existing research and potential research directions are discussed to further enhance the safety and robustness of Li-ion battery systems. Early warning methods based on gases (such as H₂, CO, electrolyte vapor, etc.) can provide effective early warning for thermal runaway of Li-ion batteries. However, the early warning techniques of a single sensor may not meet the detection requirements of practical engineering applications. The fusion mechanism based on the co-monitoring of multiple parameters may be more effective and comprehensive for the identification of Li-ion battery faults. Monitoring the thermal runaway processes with gas sensors has proven to be a more effective method than with voltage or with temperature sensors. In addition, the development of new portable gas sensors, such as the MEMS micro-optical gas sensors, the photoacoustic spectrometers, and the infrared spectrometers, may be beneficial in generating accurate early warning signals for applications involving Li-ion batteries with a potential thermal runaway problem.