A Na3V2(PO4)3 cathode material for use in hybrid lithium ion batteries

Abstract

A NASICON-structure Na₃V₂(PO₄)₃ cathode material prepared by carbothermal reduction method is employed in a hybrid-ion battery with Li-involved electrolyte and anode. The ion-transportation mechanism is firstly investigated in this complicated system for an open three-dimensional framework Na₃V₂(PO₄)₃. Ion-exchange is greatly influenced by the standing time, for example, the 1 hour battery presents a specific capacity of 128 mA h g⁻¹ while the 24 hour battery exhibits a value of 148 mA h g⁻¹ with improved rate and cycling performances over existing literature reported Li-ion batteries. In the hybrid-ion system, an ion-exchange process likely takes place between the two Na(2) sites in the rhombohedral structure. NaLi₂V₂(PO₄)₃ could be produced by ion-transportation since the Na⁺ in the Na(1) site is stationary and the three Na(2) sites could be used to accommodate the incoming alkali ions; Li_xNa_yV₂(PO₄)₃ would come out when the vacant site in Na(2) was occupied depending on the applied voltage range. The reported methodology and power characteristics are greater than those previously reported.