RESUMEN
To tackle the intrinsic inferior conductivity of the sodium ion batteries (SIBs) cathode Na3V2(PO4)3, transitional metal cation doping, and carbon frame design are employed for NASICON structural modification. Herein, a hard carbon skeleton Na3+xV2-xZnx(PO4)3 NASICON structure is proposed resorting to the combination of flimsy hard carbon slices coating and Zn2+ doping along with the introduction of spare Na+. The structural distortion caused by the insertion of Zn2+ and Na+ broadens the transfer channels and increases diffusion routes for Na+. At the same time, the anchoring effect for Na3+xV2-xZnx(PO4)3 nanoparticles brought by external hard carbon layers and pillar effect aroused by Zn2+ provide a stable and firm skeleton, which is conducive to structural stability and reversibility at high current density. Among various doping concentrations, Na3.03V1.97Zn0.03(PO4)3 performs a significantly enhanced rate performance with a reversible capacity up to 60 mAh·g-1 (40C) and ultra-long cycle life of 1000 cycles with a capacity retention of 92.6% at 5C.