Needle penetration studies on automotive lithium-ion battery cells: Influence of resistance between can and positive terminal on thermal runaway

Thermal runaway (TR) can be initiated by the heat dissipated from an internal short circuit (ISC). In prismatic cells, a crucial type of ISC is located between the cell can on positive potential and the first anode layer. To enhance the safety, the potential of the can could be adjusted by increasing the ISC resistance, i.e., realizing a floating can, whereas a universal automotive prismatic cell has a can on potential in contrast. This work demonstrates that the floating can mitigates the ISC current and possibly prevents ISC from leading to TR using an advanced needle penetration test. Moreover, the ISC current was quantitatively measured, proving that there is no significant ISC current between floating can and outmost anode, while the ISC with can on potential can cause TR. To demonstrate that such difference originates only from the increased resistance, the equivalence in thermal behaviors between the two types of cans was analyzed by a heat-wait-seek test in an accelerating rate calorimeter. This work provides not only a guidance on designing a safer prismatic cell but also a prospect how the optimized needle penetration test can bring a deeper insight into the internal processes of Lithium-ion cells during mechanical abuse.