Graphene encapsulated spherical hierarchical superstructures self-assembled by LiFe0.75Mn0.25PO4 nanoplates for high-performance Li-ion batteries

the electrochemical performance of LiFe0.75Mn0.25PO4 material is further enhanced via synergistic strategies including crystal orientation growth, microspherical self-assembly and graphene encapsulation. The crystal orientation growth of LiFe0.75Mn0.25PO4 with plate-like morphology not only reduces the Li-ion transport length, but also enlarges the (010) surface, and leads to the improvement of Li-ion diffusion. The self-assembled spherical hierarchical superstructures can effectively prevent the plane-plane stacks of LiFe0.75Mn0.25PO4 nanoplates during spontaneously aggregating, providing more (010) surface for Li+ insertion/extraction. The graphene encapsulation can build a 3D conductive network as well as stabilize the microspherical aggregations, resulting in superior electronic conductivity and stability. As a consequence of the synergistic effects, the as-obtained LiFe0.75Mn0.25PO4 sample exhibits excellent rate capability (141.1 mA h g−1 at 5 C, 126.5 mA h g−1 at 10 C, 107.7 mA h g−1 at 20 C) and outstanding cyclability (25 °C, 94.6% capacity retention after 500 cycles at 1 C). The synergistic strategy involving crystal orientation growth, microspherical self-assembly and graphene encapsulation provides a fascinating candidate to obtain superior olivine-type cathode materials with excellent rate capability and cycling stability, and holds the potential to be extended to the controlled preparation of other electrode materials.