Multi-heteroatom doped carbon coated NaV(PO) derived from ionic liquids.

Multi-heteroatom (N, S and F) doped carbon coated NaV(PO) (labeled as NVP/C-ILs) derived from an ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM]TF2N) has been successfully fabricated. The as-prepared NaV(PO) particles are well dispersed and closely coated with a multi-heteroatom (N, S and F) doped carbon layer. As a cathode for sodium-ion batteries, the NVP/C-ILs electrode exhibits high reversible specific capacity (117.5 mA h g at 1C), superior rate performance (93.4 mA h g at 10C) and excellent cycling stability (∼95% capacity retention ratio at 10C over 1000 cycles). The impressive electrochemical performance of NVP/C-ILs can be attributed to effectively conductive networks for electrons and Na ions induced by a joint effect of N, S and F doping on carbon. The use of multi-heteroatom doped carbon coated NaV(PO) provides a facile and effective strategy for the fabrication of high performance electrode materials with low intrinsic electrical conductivity.