Chromium doping into NASICON-structured Na3V2(PO4)3 cathode for high-power Na-ion batteries

Abstract

Na3V2(PO4)3 (NVP) is characterized by a robust 3D structural framework and a high operating potential; these properties have enabled it to be widely studied as a stable and high-energy density cathode material for sodium-ion batteries (SIBs). In the present study, we designed a Na3V1.6Cr0.4(PO4)3/C ([email protected]) cathode by implanting Cr into the crystal structure of NVP and simultaneously coating the surface of NVP with carbon for realizing high power density SIBs. The substitution of Cr to vanadium in the NVP structure significantly enhanced the structural stability of the electrode while the uniform and thin carbon layer improved the electrical conductivity. Interestingly, the [email protected] cathode showed high electrochemical activities with multiple V3+/4+/5+ redox reactions triggered by Cr3+ substitution in a wide voltage range (2.5–4.1 V). Consequently, the [email protected] cathode delivered excellent cycling stability over 500 cycles even at 15C-rate and power capability up to 70 C-rate. Results from the in-situ X-ray diffraction and ex-situ X-ray absorption near edge structure studies were combined to verify the detailed mechanism of the enhanced sodium storage in the [email protected] cathode.