Formation of effective carbon composite structure for improving electrochemical performances of rhombohedral Li3V2(PO4)3 as both cathode and anode materials for lithium ion batteries

Alkali vanadium phosphates are promising electrode materials for next-generation ion batteries. However, the materials have inherent problems of low electronic conductivity due to phosphate group. We present here a method to overcome the issue of alkali vanadium phosphate by building effective carbon backbone in alkali vanadium phosphate and carbon composite. The carbon backbone not only provides pathways for an electron but also suppresses agglomeration of particles, resulting in efficient ion diffusion and electron transfer in the composite. We applied the method for developing rhombohedral Li3V2(PO4)3 material which is a different phase from the well-known monoclinic Li3V2(PO4)3. Detailed redox mechanisms and associated structural changes of the rhombohedral Li3V2(PO4)3 materials are investigated as both cathode and anode for lithiumion batteries to demonstrate the importance of the formation of efficient carbon composite materials of phosphate-based electrode materials.