Limiting Internal Short-Circuit Damage by Electrode Partition for Impact-Tolerant Li-Ion Batteries

We report on a unique safety mechanism introduced to the Li-ion battery design to mitigate the effects of a mechanical impact event by limiting the current moving through resulting internal shorts, thereby preventing thermal runaway. “Slitted” electrodes and current collectors would electrically isolate the impacted parts of the electrodes before puncturing the separator. Batteries with such “slitted” electrodes were shown to perform normally prior to the mechanical impact. A proof-of-concept experiment showed that the battery with modified electrodes survived significant mechanical deformation without any change in the open-circuit voltage of the battery. It is interesting to note that, after the impact event, the modified battery was still viable with a reversible capacity of about 93% of that before the indentation test, while the standard battery was no longer functional. Mechanical abuse of Li-ion batteries (LIBs), through events such as automobile accidents, can lead to complete failure. Our research represents a promising new manufacturing method that will enable portions of LIBs to remain functional once damaged sections have ceased to function. Our approach for mitigating the severity of internal electrical shorts in LIBs involves using electrodes designed to break upon impact into electrically isolated parts before the separator is punctured and an internal electric short occurs. The electric current passing through the internal short will be reduced, preventing the onset of exothermic reactions and thermal runaway. The new design introduces slits to the electrode that adds minimal cost and does not require significant changes in roll-to-roll production, making this approach scalable. While more research is needed to optimize the slit patterns for various scenarios, this work opens a new avenue for incorporating inherent safety features into battery designs. In this study we report on a new design concept for Li-ion battery electrodes to mitigate mechanical impact without catastrophic failure for the battery. The concept is based on introducing breakable electrodes that, upon impact, isolate the damaged part from the rest of the electrode to limit the current going through any short circuit. We used patterns of slits to realize the breakable electrodes, which in principle add little cost and can be produced by the roll-to-roll process.