LAUSR

Sodium-ion batteries have been regarded as promising candidate to lithium-ion batteries due to the abundance of sodium resource and cost-effectiveness. NVPF 1+2x polyanionic material, has shown superior electrochemical performances for advanced SIBs due to its high working voltage. Electrolyte composition, which plays an indispensable and critical role in determining cycle stability and electrode/electrolyte interfacial properties, are of great significance to possess good compatibility with electrode materials, especially NVPF1+2x. Here, different electrolyte systems, including commonly used 1.0 M NaPF6/diglyme (NP-005), 1.0 M NaPF6 /propylene carbonate (PC)/5.0% fluoroethylene carbonate (FEC) (NP-009), 1.0 M NaClO4 /ethylene carbonate-dimethyl carbonate (EC-DMC) =1: 1 Vol%/5.0% FEC (NC-019) and 1.0 M NaClO4 /PC (NC-013), are systematically investigated and compared for NVPF1+2x cathode. NVPF1+2x  with NP-009 shows a more superior cycle stability and rate capability at 1 C~10 C (1 C=130 mA g -1 ) than that of NC-019 and NC-013 while NVPF1+2x  with NP-005 shows the best high-rate capability at 20 C~50 C.  It demonstrates that NVPF1+2x  with NP-005 exhibits a thin, efficient and NaF-rich CEI layer with less polarization, smaller interfacial resistance and faster Na+ diffusion than that of NC-019 and NC-013 since they suffered from a thick, over-grown CEI layer due to the consecutive decomposition of FEC, NaClO4 and/or linear DMC. This work provides new insights for the battery community to gain more comprehensive understanding about the interfacial chemistry.