Meaning
Release of volatile chemical compounds from lithium ion cells under elevated thermal conditions is a critical safety consideration for energy storage systems. This phenomenon, known as high-temperature storage outgassing, occurs when electrolyte solvents decompose and generate carbon dioxide, carbon monoxide, or light hydrocarbons. The resulting internal pressure can deform the cell housing and compromise the hermetic seal.
Outgassing Mechanism
Heat accelerates the breakdown of the solid electrolyte interphase on the anode, causing chemical reactions that produce gas. During high-temperature storage outgassing, the accumulation of gaseous species is proportional to both the storage temperature and the state of charge of the battery. Cells stored at higher state of charge are more susceptible to this degradation because the electrode potentials are more aggressive.
Testing Protocol
Sourcing and quality control procedures require heating the cell to temperatures such as sixty or eighty degrees Celsius for a fixed period of several weeks. The test measures the onset and volume of high-temperature storage outgassing by tracking changes in the physical dimensions or internal pressure of the test cell. Any loss of electrolyte through venting during this test indicates a deficiency in the cell design or seal composition.
To gain qualification, the cell must display zero leakage and the expansion must remain within specified mechanical limits of the housing.
Battery Protection
Pack designers include pressure relief valves and absorbing materials to manage the released gases and prevent cascading failures. If high-temperature storage outgassing is not managed, the gas buildup can lead to cell rupture or the propagation of thermal runaway. These venting strategies are documented in safety logs to verify compliance with industrial standards.
