Concentration-gradient LiMn0.8Fe0.2PO4 cathode material for high performance lithium ion battery

•Concentration-gradient LiMn0.8Fe0.2PO4 is constructed through solvothermal method.•The Mn dissolution of concentration cathode material is suppressed.•The rate capability of this concentration material is improved.•The cycle stability is improved, especially at elevated temperature.

It is a great challenge to combine good cycling performance with high rate capability for LiMn1–xMxPO4 cathode materials owing to the Mn dissolution upon cycling and its low electronic/ionic conductivity. Here, we report a novel concentration-gradient structure of LiMn0.8Fe0.2PO4 material constructed by solvothermal treatment. This material shows a linear increase of Mn concentration from the edge to the particle centre, but the inverse trend for Fe concentration, which leads to the formation of Mn-rich phase in bulk and Fe-rich phase at surface. The Fe-rich phase effectively suppresses the corrosion from the electrolyte that minimizes the Mn dissolution and also improves the electronic/ionic conductivity of the surface that decreases the cathode/electrolyte interface resistance. Consequently, this concentration-gradient material achieves superior capacity retention with 98% after 50 cycles at 1 °C even at elevated temperature, and also exhibits an excellent rate capability with the reversible capacity of 130 mA h g−1 at 5 °C rate. These results suggest that the concentration-gradient LiMn0.8Fe0.2PO4 is an ideal type of cathode material for high performance Lithium ion batteries.

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