Energy Storage Science and Technology ›› 2023, Vol. 12 ›› Issue (8): 2370-2381.doi: 10.19799/j.cnki.2095-4239.2023.0177

• Energy Storage Materials and Devices • Previous Articles     Next Articles

Preparation and property evaluation of Nb-doped Na3V2O2PO42F hollow microspheres as cathode materials for sodium-ion batteries

Zinan ZHANG1,2(), Jian CHEN1()   

  1. 1.Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
    2.University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2023-03-27 Revised:2023-04-08 Online:2023-08-05 Published:2023-08-23
  • Contact: Jian CHEN E-mail:zinan@dicp.ac.cn;chenjian@dicp.ac.cn

Abstract:

Na3V2O2(PO4)2F(NVOPF) is a cathode material with potential application prospects in sodium-ion batteries. This is due to its suitably stable polyanion structure, high operating voltage, and high theoretical specific capacity. However, the intrinsic conductivity of the material is low, and it is prone to irregular agglomeration during the synthesis process, resulting in low actual specific capacity and unsatisfactory rate and cycling performances. Ion doping and micro/nanostructured materials have been found to benefit the intrinsic conductivity and stability of the material. This work, for the first time, reports the synthesis of Nb5+-doped NVOPF(NVNOPF, Na3V2-x Nb x O2(PO4)2F (0≤x≤0.15)) material with a hollow microspheric structure by the polyol-assisted hydrothermal method. The as-prepared NVOPF and NVNOPF materials were microspheres with sizes of 0.7-1.0 μm with hollow structures. The microspheres were found to be composed of nanoparticles of with sizes <100 nm. Nanoparticles shortened the diffusion distance between sodium ions, buffered the volume change caused by the intercalation/extraction of sodium ions, and improved the material cycling stability. Meanwhile, doping Nb5+ increased the lattice parameters of NVNOPF and enlarged the Na+ diffusion pathway. The solid-phase diffusion coefficient of Na+ in the material increased from 6.46×10-16 for Na3V2O2(PO4)2F to 3.52×10-15 cm2/s for Na3V1.90Nb0.10O2(PO4)2F. The discharge specific capacity of Na3V1.90Nb0.10O2(PO4)2F was 126.4 mAh/g (0.1 C rate) and 98.1 mAh/g (10 C rate). After 500 cycles of charge and discharge at the 10 C rate, the capacity retention was 95.2%, which is better than that of the undoped material (66.8%). The results showed that Nb-doped and hollow spherical micro-/nanostructures could effectively improve the electrochemical performance and cyclic stability of NVOPF.

Key words: cathode material for sodium ion battery, Na3V2O2(PO4)2F, polyol assisted hydrothermal method, hollow microspheres, niobium doping

CLC Number: