New advanced cathode material: LiMnPO4 encapsulated with LiFePO4

Coating the members of the olivine family LiMPO4 with conductive carbon is difficult, excepted in the case MFe. To overcome this difficulty, we found possible to coat LiMnPO4 with a thin layer of LiFePO4 to take benefit of the catalytic reaction of Fe with C, so that a 3 nm-thick layer of carbon can be deposited at the surface of this composite. We find that the electrochemical properties of the carbon-coated LiFePO4–LiMnPO4 composite are improved with respect to the carbon-coated LiMn2/3Fe1/3PO4 solid solution with comparable Fe/Mn ratio. Therefore, the use of a LiFePO4 as a buffer layer between the high-density cathode element (like LiMnPO4) and the carbon layer opens a new route to improve the performance of the olivine family as the active element of the cathode for Li-ion batteries.

► Composite made of LiMnPO4 as the core region, covered with a layer of LiFePO4.
► Thin carbon layer on top surface of LiFePO4- LiMnPO4 has been synthesized.
► The electrochemical performance is improved with respect to the Li(Mn,Fe)PO4 solid solutions with the same Fe/Mn ratio.