Electrochimica Acta, Vol.218, 325-334, 2016
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 planeplane 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 degrees 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. (C) 2016 Published by Elsevier Ltd.