Stabilizing SPAN in Non-flammable Acetonitrile Electrolytes for Long-Life Graphite||SPAN Batteries.

Sulfurized polyacrylonitrile (SPAN) presents an opportunity to replace elemental sulfur as a "shuttle-free" cathode for secondary Li-S batteries, which can be an ideal choice for stationary energy storage due to its abundance, low cost, and sustainability. The electrolyte options for the state-of-the-art SPAN batteries have been limited to the flammable carbonate and ether ones, which raises safety concerns. Here, we explored the use of a non-flammable acetonitrile (AN) electrolyte for SPAN battery for the first time and identified the irreversible cleavage of C-S bonds of SPAN as the main reason for the failure of SPAN in AN electrolyte. Fortunately, by introducing 10 wt% fluoroethylene carbonate into the AN electrolyte, the bond cleavage in SPAN is suppressed and a stable cathode electrolyte interface is formed, both contributing to stabilizing the structure of SPAN during electrochemical process. Consequently, we achieved a stable cycling for 900 cycles in Li||SPAN cells. Moreover, by pairing with a pre-lithiated graphite (pGr) anode, the newly formulated electrolyte enables extended cycle life for 1500 cycles with a capacity retention of 91% and superb safety in pGr||SPAN full cell. The present exploitation broadens the electrolyte choices of SPAN-based batteries and paves the way for future applications for these batteries.