A unique polymer-inorganic cathode-electrolyte-interphase (CEI) boosts high-performance Na3V2(PO4)(2)F-3 batteries in ether electrolytes

The practical utilization of ether electrolytes has long been restricted due to the concern on its electrochemical oxidation stability. Recently, it has been demonstrated that ethers are compatible with a series of polyanionic cathodes for sodium batteries. However, the specific cathode-electrolyte interface is still poorly understood. In this work, via the use of highly complementary surface and interfacial characterization techniques, we identify that the use of an 1 M NaPF6-diglyme solution allows the formation of a unique polymer-inorganic cathode-electrolyte-interphase (CEI) on high-voltage Na3V2(PO4)(2)F-3 polyanionic cathodes, contributing to excellent cyclability (capacity retention of 96.2% after 300 cycles at 0.5C, 1C = 128 mAh g(-1)) and outstanding rate capability (124, 120 and 112 mAh g(-1), at 5C, 10C and 20C, respectively). The peculiar interfacial chemistry disclosed here may open up new opportunities for building high performance sodium batteries.