Phase relations and electrochemical research for vanadium-based compounds in Li2O–V2O3–P2O5 system

Abstract Vanadium-based oxides/phosphates (such as V2O5, Li3V2(PO4)3) are one class of the most important electrode materials for secondary batteries. Herein, phase equilibriums in the Li2O–V2O3–P2O5 ternary system have been studied by means of X-ray powder diffraction to explore new compounds for lithium ion batteries (LIBs). The Li2O–V2O3–P2O5 system can be characterized by the existence of 15 three-phase regions. For the Li2O–V2O3 binary system, it is found that Li3VO4 with high valence vanadium of +5 can stably exist in this system even in the presence of reducing atmosphere during sintering process. Based on this result, the in-situ carbon coated Li3VO4 sample has been synthesized successfully and it shows excellent rate ability and good cycling stability as anode for LIBs. The phase diagram determined in this paper can provide more information about the phase relation of Li2O–V2O3–P2O5 ternary system and serve as a guide for the future investigation of lithium vanadium-based phosphates in this system.