Multielectron-Reaction Stimulated Na3al0.1sn0.1v1.8(Po4)3@C Cathode for High-Energy Density and Long-Life Sodium Ion Batteries

Sodium vanadium phosphate (Na3V2(PO4)3, NVP), as a typical natrium superionic conductor (NASICON) phosphate has been extensively studied as cathode for sodium ion batteries (SIB) due to its 3D open frameworks favoring for Na+ diffusion migration. However, the energy density of NVP is mediocre, and the cycle life at high cycling rates needs urgently to be improved. Herein, we synthetize a novel multielectron-reaction, high energy density and long-life Na3Al0.1Sn0.1V1.8(PO4)3@C (NASVP@C-2) cathode for SIB. It releases a considerable capacity of 147.6 mAh g-1 at 1 C and exhibits an extremely low attenuation of 0.0028% per cycle after 18,000 cycles at 80 C. Electrochemical kinetics and ex-situ XPS analyses reveal that Sn doping effectively activates V4+/V5+ redox to achieve multielectron-reaction for sodium storage. Ex-situ XRD results discover that the Na+ diffuses along Na2-Na1-Na2 in NASVP@C-2, generating a special low volume variation of 1.07%. Theoretical calculations validate the favorable forbidden band and low Na+ diffusion energy barrier of NASVP@C-2. Our work provides a new route to obtain NVP cathodes with high energy density and long-cycle stability under high power density, which further accelerate the commercial application of SIB.