Hierarchical structured LiMn0.5Fe0.5PO4 spheres synthesized by template-engaged reaction as cathodes for high power Li-ion batteries
Porous hierarchical LiMn0.5Fe0.5PO4 spheres were synthesized via a novel template-engaged method using pre-synthesized hollow spherical Li3PO4 as template and FeCl2·4H2O/MnCl2·4H2O as Fe2+/Mn2+ source. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the porous hierarchical spheres exhibit hollow structure and have a size distribution of 0.4-1 um consisting of aggregated approx. 50 nm nanoparticles. A mechanism of the reaction from Li3PO4 to LiMn0.5Fe0.5PO4 was proposed on the basis of the phase and morphology transformation of the intermediates. With the short Li+ diffusion path and porous structure, the carbon coated LiMn0.5Fe0.5PO4 spheres show high specific capacity and superior rate capability with the discharge capacities of 159.3 mA h g-1 at 0.1C and 80.6 mA h g-1 at 20C. The porous hierarchical spheres also exhibit an excellent cycling stability with about 90.7% of the initial value at 1C after 100 cycles.