Core-shell-structured Li3V2(PO4)3-LiVOPO4 nanocomposites cathode for high-rate and long-life lithium-ion batteries

Abstract

A facile strategy has been developed to construct unique core-shell-structured Li2.7V2.1(PO4)3 nanocomposites with a Li3V2(PO4)3 core and LiVOPO4 shell by using nonstoichiometric design and high-energy ball milling (HEBM) treatment. The HEBM treatment supplies enough energy to drive the excess V atoms to the surface to form a V-enriched shell. Such kind of cathode can deliver a high reversible capacity of 131.5 mA h g-1 at 0.5C, which is close to the theoretical capacity (133 mA h g-1 in 3.0-4.3 V). Even at 20C, it still delivers an excellent discharge capacity of 116.3 mA h g-1, and a remarkable capacity of 111.0 mA h g-1 after 1000 cycles, corresponding to an ultra-small capacity-loss of 0.0046% per cycle. The significantly improved high-rate electrochemical performance can be attributed to the active shell of LiVOPO4, which not only efficiently facilitates the electron and Li+ ion transport during cycling processes, but also accommodates more Li+ ions to effectively compensate the capacity loss of the core.