Temperature-dependence vanadium regulation for extreme fast charging LiFePO4 cathode materials with multilevel core-shell structure

Abstract

Lithium-ion batteries (LIBs) with LiFePO4 cathode are widely used in electric vehicles and energy storage systems owing to their cost-effectiveness and safety. However, this type of LIBs is limited by poor fast-charging capabilities owing to the inherent poor electronic conductivity and one-dimensional ionic pathways. Herein, we show that the approach of temperature-dependence vanadium (V) regulation can greatly improve the Li+ diffusion dynamics both in bulk and at interface, leading to the achievement of ultrafast charging/discharging capability of LiFePO4-based LIBs. The formation of V3+ doping induced Fe-site vacancy in bulk and Li3V2(PO4)3 phase at interface with high ionic conductivity can be achieved at the optimal conditions of 700°C and 0.10 V content. Additionally, this regulatory V effect endows the LiFe1-3/2xVxPO4 (LFVP) materials with a specific multilevel core-shell structure. Consequently, the optimal LFVP-0.10-700 sample delivers high specific capacities of 169.6 mAh g−1 at 0.1 C with an excellent capacity retention of 97.5 % after 200 cycles at 1 C, as well as ∼100 mAh g−1 at an ultrahigh rate of 50 C for 3500 cycles. These performances make LiFePO4 cathode possible for extreme fast charging LIBs.