Graphene-embedded LiMn0.8Fe0.2PO4 composites with promoted electrochemical performance for lithium ion batteries

Electron transfer and lithium ion diffusion rates are the key factors leading to sluggish electrochemical kinetics of LiMn_0.8Fe_0.2PO₄. In this work, we have successfully synthesized graphene-embedded LiMn_0.8Fe_0.2PO₄ composites via a facile graphene oxide assisted solvothermal route associated with carbonthermal treatment. The effect of graphene on the morphology, crystalline structure as well as electrochemical properties of LiMn_0.8Fe_0.2PO₄ is investigated. It can be found that the introducing graphene can reduce the particle size to form LiMn_0.8Fe_0.2PO₄ nanocrystals without destroying the crystalline structure of LiMn_0.8Fe_0.2PO₄. And the LiMn_0.8Fe_0.2PO₄ nanocrystals dispersed on the graphene sheets which were further cross-linked via the oxygen-containing groups of GO as cross-linking sites, resulting in that graphene sheets embedded in the LiMn_0.8Fe_0.2PO₄ composites. Benefiting from the LiMn_0.8Fe_0.2PO₄ nanocrystal and embedded graphene, the interconnected conducting network referred to electron and lithium ion transport pathways can be improved, resulting in enhanced electrochemical performance. The graphene embedded LiMn_0.8Fe_0.2PO₄ composite displays a high discharge capacity of 163.5, 149.2, 136.0, 120.6, 100.1 and 84.5 mA h g^-1 at various rate of 0.1C, 0.5C, 1C, 2C, 5C and 10C, respectively. Meanwhile, it still maintains a reversible capacity of around 120 mA h g^-1 after 100 cycles at a rate of 1C.