Preparation of NaV 1− xAl xPO 4F cathode materials for application of sodium-ion battery

Abstract

The effects of Al doping on the electrochemical properties of NaVPO 4F as a cathode material for sodium-ion batteries were investigated. Al-doped NaV 1− x Al x PO 4F ( x=0, 0.02) samples were prepared by a simple high temperature solid-state reaction involving VPO 4 and NaF for the application of cathode material of sodium-ion batteries. The crystal structure and morphology of the material were studied by Flourier-infrared spectrometry(FT-IR), X-ray diffractometry(XRD) and scanning electron microscopy(SEM). The results show that NaV 1− x Al x PO 4F ( x=0, 0.02) has a typical monoclinic structure. The effects of Al doping on the performance of the cathode material were analyzed in terms of the crystal structure, charge-discharge curves and cycle performance. It is found that NaV 0.98Al 0.02PO 4F shows an improved cathodic behavior and discharge capacity retention compared with the undoped samples in the voltage range of 3.0–4.5 V. The electrodes prepared from NaV 0.98Al 0.02PO 4F deliver an initial discharge capacity of 80.4 mA·h/g and an initial coulombic efficiency of 89.2%, and the capacity retention is 85% after 30th cycle. Though the Al-doped samples have lower initial capacities, they show better cycle performance than Al-free samples.