Study on Gas-Generating Property of Lithium-Ion Batteries

Abstract

A main cause of fires and explosions in lithium-ion batteries is the generation of combustible gases by them, and when a large number of batteries are densely packed, like in an Energy Storage System, there is a high risk of thermal runaway and fire propagation. Currently, many studies are being conducted worldwide to predict and prevent the generation of combustible gases, and thermal runaway in lithium-ion batteries, but they are still in progress. Therefore, in this study, we analyzed the gases generated before and after thermal runaway in lithium ion batteries, to prepare a basis for reducing the risk of thermal runaway. We aimed to establish the basis for prevention by early detection in the event of thermal runaway, by understanding the type and characteristics of the generated gases. For the experiment, lithium ion batteries were classified in terms of appearance (cylindrical, prismatic, pouch type), and cathode materials (NCM, NCA, LFP). The gases generated was measured against time. An FT-IR analyzer was used for gas measurement, and a separate hydrogen sensor was installed in the chamber to analyze changes in the types of gas, and measure the mass of the lithium ion battery over time. In the experiment, CO2 and CO were generated the most during thermal runaway in all lithium-ion batteries. Thereafter, CO2 increased, and CO decreased in the prismatic and pouch types, and both CO2 and CO increased in the cylindrical type. HF (a toxic gas), and H2 having a wide explosive range, were also generated, and the concentrations of these gases were inversely proportional to each other.