Electrolyte Leakage in Cylindrical Lithium-Ion Batteries Subjected to Temperature Cycling

In transportation and operation, lithium-ion batteries can be exposed to environments where the temperature exceeds 75 °C, compromising seal integrity and leading to electrolyte leakage and safety issues. Standards introduced by regulatory bodies require temperature testing, including temperature cycling tests. This study examines cylindrical battery electrolyte leakage due to temperature cycling between 25 °C and 80 °C through capacity tests, electrochemical impedance spectroscopy, computed tomography scans, and thermal analysis. Different thermal expansions among battery cap elements were identified as the cause of leakage. The thermal test parameters and requirements in the UN Manual of Tests and Criteria Section 38.3 were reviewed, revealing the 72 °C upper-temperature limit and the 24 h storage period after temperature cycling fail to effectively qualify lithium-ion batteries for real-world applications.