Effects of carbon coating on the temperature-dependent electrochemical properties of Li3V2(PO4)3

Carbon coated and carbon free Li3V2(PO4)3 cathode materials were prepared by carbothermal reduction and H2 reduction methods, respectively. The carbon free material had a grain size about 1 μm whereas the carbon coated material was less than 100 nm. The surface carbon layer enhanced the electronic conductivity of Li3V2(PO4)3 by five orders of magnitude. In addition, the surface carbon layer also prevented the formation of SEI film, decreased the charge transfer resistance and increased the chemical diffusion coefficient of Li+ ions. All of these advantages improved the electrochemical performance of Li3V2(PO4)3. As most of intercalation materials, the low temperature performance of Li3V2(PO4)3 was poorer than that at room temperature. This was attributed to the electrochemical sluggish kinetics which caused higher charge transfer resistance and smaller chemical diffusion coefficient. The carbon coating technique was effective to eliminate these sluggish kinetics, and then improved the low temperature performance of Li3V2(PO4)3.

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