Abstract:

With the increase of new energy vehicles in the market and battery energy density， thermal runaway events gradually increase. Battery safety issues become particularly important， whereas leakage is one of the key factors inducing battery thermal runaway. In this paper， the influence of leakage on electrical performance and safety is studied by simulating leakage at the cells and modules. At the same time， based on experimental data and remote vehicle data， the characteristics of the leaked battery are extracted and the warning logic is established to achieve online monitoring of the leakage warning. For cells test， a comparative analysis is conducted on the test data of leaking and normal battery cells under cyclic and static states. It is found that compared with normal cells， leaking cells show mass reduction， thickness increase， capacity fade， DC internal resistance increase and dismantling characterization abnormity， which proves that leakage has certain impact on the electrical performance and safety. For module test， characteristics of the thickness and DC internal resistance changes from the parallel units with different leakage degrees are studied. It proves that the thickness and DC internal resistance increase with the increase of leakage degrees， which also augments the potential safety risk of the battery. For vehicle level big data， the pressure difference characteristics of the leaked battery during the starting and ending stages of charge are identified to establish warning and identification logic and conduct online monitoring.

Key words: lithium-ion battery, leakage, electrical performance, safety, early warning