Rheological phase reaction method synthesis and characterizations of xLiMn0.5Fe0.5PO4-yLi3V2(PO4)3/C composites as cathode materials for lithium ion batteries

A series of xLiMn(0.5)Fe(0.5)PO(4)-yLi(3)V(2)(PO4)(3)/C (x:y = 4:1, 3:1, 2:1, 1:1, 1:2, and 1:3) composite cathode materials for lithium-ion batteries are successfully prepared by the rheological phase reaction method. The structures, morphologies, and electrochemical properties of these composite materials are studied. The results indicate that xLiMn(0.5)Fe(0.5)PO(4)-yLi(3)V(2)(PO4)(3)/C composites are composed of LiMn0.5Fe0.5PO4 and Li3V2(PO4)(3) phases and mutual doping exists. The initial discharge capacities, initial Coulombic efficiencies, and capacity retentions of composites increase but then decline with the increase of Li3V2(PO4)(3) content. All the composites show higher capacity retentions than LiMn0.5Fe0.5PO4/C and Li3V2(PO4)(3)/C single phases except LMFP-3LVP/C. The composite material of x:y = 1:1 exhibits remarkably superior electrochemical performance than the single phases and other composites both in discharge capacity and cycle performance, delivering the initial discharge capacity of 148.2 mA h/g (2.0-4.5 V) and 170.1 mA h/g (2.0-4.8 V) at 0.1 C. And the corresponding capacity retentions are 98.0 and 90.4% after 100 cycles, respectively.