Copper-Diphosphide Composites: A Key Factor Evaluation and Capacity Enhancement Route for High-Energy Lithium-Ion Storage

Carbon-modified phosphide-rich CuP2 anode is prepared by mechanical ball-milling technique for Li-ion batteries. HRTEM image demonstrates carbon is fully and homogeneously wrapped on the CuP2-core material. The bare and carbon-coated CuP2 deliver initial specific capacities of 1454 and 1416 mAh/g with Columbic efficiencies of 83 and 61% at 100 mA/g, respectively. Conversely, carbon-coated electrode exhibited cyclic stability superior to that of bare electrode. The CuP2/C lithiation capacity is 700 mAh/g over the 100 cycles at 100 mA/g. Furthermore, 1 wt % CNTs addition in CuP2/C slurry dramatically enhanced the Li storage and rate performance compared to the rest of the electrodes. The capacity nature is studied by cyclic voltammetry analysis, and the result of bare electrode is based on the diffusion process. Surprisingly, after carbon-modified electrode, the capacity contribution nature is observed as being surface control behavior. Hence, the enhancement of electrochemical performance is predicted by accelerating of kinetics, buffering of volume changes through carbon coating, improving catalytic effect, and controlling surface capacity behavior.