Towards more realistic Li-ion battery safety tests based on Li-plating as internal cell error

Herein the development of a novel test procedure for lithium ion cells to trigger cell internal defects under more realistic conditions (ambient temperature/voltage) than procedures that are currently used as triggers for propagation tests (e.g. nail penetration, massive heating/overcharge) is reported. Therefore, lithium plating, a common phenomenon of aging but also appearance of misbalanced/inhomogeneous cell construction, occurring within graphite-based lithium-ion battery cells, was chosen to be induced systematically and reproducibly by electrochemical cycling within different lithium-ion cell chemistries as well as pouch cell types (commercial and self-made). Using plating as a trigger method on different kind of test cells, showed that the behavior of cells differed, such that it is possible to classify the cells into categories based on the outcome of the test (e.g., swelling, venting, thermal runaway). Interestingly, not the lithium plating and dendrite growth through the separator itself but its consequences, such as degradation reactions with increase in inner resistance caused safety critical behavior of the cells. The test procedure can be applied on an electrically connected cell within a battery system and therefore has great potential to be used alternatively as a trigger method for the propagation test.