Preparation and electrochemical properties of Li3V2(PO4)3 glass-ceramic materials

Abstract

The monoclinic lithium vanadium phosphate (Li3V2(PO4)3, LVP) is a promising cathode material for lithium-ion batteries due to its high theoretical specific capacitance, high operating voltage, good ionic conductivity, and thermal stability. However, synthesizing the pure LVP phase requires complicated procedures, expensive equipment, and long processing times. Moreover, the pure LVP phase has poor electrical conductivity, limiting its electrochemical properties and application. This study investigated the effect of glass preparation methods (single-crucible and double-crucible) and carbon coating on the crystalline phase, surface morphology, electrical conductivity, and electrochemical properties. A highly crystalline pure LVP phase can be synthesized effectively through heat treatment of the glass powder produced using the double crucible method at 700°C under a 5% H2-95% Ar atmosphere for 2 h. Adding C6H12O6 as a carbon source could increase the reducing atmosphere, preventing the oxidation of V3+ to V4+ and inhibiting the formation of the LiVOPO4 phase. This is beneficial for the synthesis of the pure LVP phase.Furthermore, the formation of an amorphous, uniform carbon coating on the surface of the LVP inhibits grain growth and increases the specific surface area. The CR2032 coin cell made with the LVP added with 10 wt% C6H12O6 had the highest initial discharge specific capacitance of 159.07 mAh g-1, with a specific capacitance retention rate of 77.31% even after 50 cycles. These findings suggest that LVP powder prepared using the double crucible method with carbon coating has the potential as a high-performance cathode material for lithium-ion batteries.