Nonflammable Cocktail Electrolyte for Stable Li||SPAN Batteries

Abstract Lithium‐sulfurized polyacrylonitrile (Li||SPAN) batteries call for electrolytes that are simultaneously compatible with both the SPAN cathode and Li metal anode, and the nonflammable and low‐cost nature is also a plus. Whereas, the typical used ether (incompatible with SPAN and flammable), carbonate (incompatible with Li and flammable), or even the recently meticulously f ormulated ones fail to meet all the requirements. Here, a cocktail strategy is proposed to design the electrolyte for Li||SPAN battery. Just like a cocktail consists of multiple components, sulfolane is used as the nonflammable main solvent, fluorine‐contained lithium bis(trifluoromethane sulfonyl)imide salt and fluoroethylene carbonate additive to construct a stable electrode interface, lithium nitrate for anion‐coordinated solvation structure, triethyl phosphate to strengthen the flame resistance, and 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether as a non‐solvating diluent to modulate viscosity. Being used in Li||SPAN cells, the as‐formulated electrolyte enables the formation of robust electrolyte interface on both SPAN cathode and Li anode, even at a low salt concertation of 0.45 m , and enables Li||SPAN cell an exceptional cycling stability with 91.3% capacity retention over 500 cycles and high flame resistance.