Porous spherical LiFePO4·LiMnPO4·Li3V2(PO4)3@C@rGO composites as a high-rate and long-cycle cathode for lithium ion batteries

The porous spherical LiFePO₄·LiMnPO₄·Li₃V₂(PO₄)₃@C@rGO (Sample-G) composites are prepared via a spray drying process. The results show that the composites consist of orthorhombic olivine-type LiFe_0.5Mn_0.5PO₄ and monoclinic Li₃V₂(PO₄)₃, which are evenly distributed. In particular, nanoparticles are embedded in graphene nanosheets, which are interconnected and stacked to form a porous sphere structure with an interior three-dimensional conductive network, resulting in the huge improvement on electrochemical performance and structural stability. Due to the increased Li⁺ diffusion coefficient, the composite possesses 98.6 and 82.9 mAh g^?1 with capacities retention of 81.6% and 71.8% at 10 and 20C after 1000 cycles, respectively. The mutual cross-doping effect between LFP·LMP·LVP and a porous sphere structure with a 3D conductive network inside provides a practical method for improving the cycling and rate performance.