Enhanced electrochemical performance of LiMnPO4 by Li+-conductive Li3VO4 surface coatings

By a simple wet ball-milling method, Li3VO4-coated LiMnPO4 samples were prepared successfully for the first time. The thin Li3VO4 coating layer with a three-dimensional Li+-ion transport path and high mobility of Li+-ion strongly adhered to the LiMnPO4 material reduces Mn dissolution and increases the Li+ flux through the surface of the LiMnPO4 itself by preventing formation of phases on the surface that would normally block Li+ as well as Li+-ion permeation into the surface of the LiMnPO4 electrode and therefore improve the rate capability as well as the cycling stability of LiMnPO4 materials. The electrochemical testing shows that the 5% Li3VO4-coated LiMnPO4 sample shows a clear voltage plateau in the charge curves and a much higher reversible capacity at different discharge rates compared with the pristine LiMnPO4. EIS results also show that the surface charge transfer resistance and Warburg impedance of the Li3VO4-coated LiMnPO4 samples significantly decreased. The surface charge transfer resistance and Warburg impedance for the pristine LiMnPO4 are 955.1 Ω and 400.3 Ω, respectively. While, for the 5% Li3VO4-coated LiMnPO4, the value are only 400.2 Ω and 283.6 Ω, respectively. The surface charge transfer resistance decreases more than half. All of the improved performance will be favorable for application of the LiMnPO4 in high-power lithium ion batteries.

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