New Insights into Mossy Li Induced Anode Degradation and Its Formation Mechanism in Li-S Batteries

Optimization of cathodes and cell configurations has dramatically improved current Li-S batteries; it is now necessary to rescrutinize failure in Li-S batteries from an anodic perspective. Here, we reveal another possible failure mechanism induced by mossy Li in long-lifespan Li-S batteries and present a factor that might influence the inhomogeneous growth of Li whiskers. The large volume expansion derived from the growth of mossy Li promoted the formation and densification of a crust layer comprising passive sediments, which blocked the charge transfer for the lithium underneath, leading to low lithium utilization and battery failure. Further research showed the growth of mossy Li is related to inhomogeneous stripping, which began at imperfections on the SEI and self-amplified into large irregular pits, from which delicate mossy Li whiskers sprouted preferentially because of the relatively stable environment within. These findings are anticipated to enhance the performance of Li-S batteries and facilitate the development of other lithium batteries.