The best addition of graphene to LiMn0.7Fe0.3PO4/C cathode material synthesized by wet ball milling combined with spray drying method

LiMn_xFe_1-xPO₄ with high electronic conductivity is synthesized by a combination of wet ball milling, spray drying, carbon thermal reduction technology and using graphene oxide (denoted as GO) as the carbon additive. The effect of graphene content on morphology and structure of LiMn_0.7Fe_0.3PO₄/C cathode material is systematically investigated. The graphene-LiMn_0.7Fe_0.3PO₄ composite has ordered olivine structure and micro-spherical morphology assembles with nanosized primary particles. SEM and TEM images indicate that the particle size of LiMn_0.7Fe_0.3PO₄-G2 is about 800 nm in diameter. The initial discharge capacity of LiMn_0.7Fe_0.3PO₄-G2 nanoparticles is 153 mAh·g⁻¹. It shows that graphene oxide can restrict the growth of LiMn_0.7Fe_0.3PO₄ and improve the electrical conductivity. Through adding different amount of graphene, we get the best addition of graphene. The LiMn_0.7Fe_0.3PO₄-G2 sample has a core-shell structure, not only does the surface of nanoparticles have a homogeneous and complete carbon coating but also exhibits a microspherical morphology. What 's more the surface of microspheres is fully covered with GO sheets, which enhances electronic conductivity. All above mention factors lead to its excellent electrochemical performance at room temperature and low temperature.