Zn-doping Effects of Na-rich Na3+xV2-xZnx(PO4)3/C cathodes for Na-Ion Batteries: Lattice distortion induced by doping site and enhanced electrochemical performance

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) nanopartides 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. (C) 2022 Elsevier Inc. All rights reserved.

Automated summary

This study addresses the low conductivity issue of the sodium ion battery cathode by employing transitional metal cation doping and carbon frame design. A stable and firm skeleton structure is achieved through the anchoring effect of external hard carbon layers and the pillar effect of Zn2+, leading to improved rate performance and long cycle life.