Synthesis of a leaf-like copper oxalate and copper oxide as binder-free anodes for lithium ion batteries

초록

Among the various transition metal oxides, copper oxide (CuO) has been considered as one of the most promising negative materials due to its high theoretical capacity (674 mAh g-1), low cost and chemical stability. In particular, since the copper foil is widely used as a current collector for the negative electrode of lithium ion batteries, CuO active materials directly grown on copper foil can be useful for the preparation of binder-free electrode. Because binder-free electrode can avoid the usage of polymeric binders and conductive additives, further increase in the energy density in the electrode can be expected. In this study, we studied on the binder-free leaf-like nanostructured CuO electrode on a Cu current collector, which was synthesized via a wet chemical reaction; The leaf-like structure was originally generated as a form of copper oxalate hydrate, which was converted to copper oxide by post-heat treatment. We found that copper-nickel alloy foil is more promising substrate for producing the homogeneous CuO leaf-like nanostructure strongly adhesive to the substrate, compared to that from the pure Cu substrate. The condition of preparation was optimized with adjusting immersing time, temperature, and molar concentration of reactants. The as-prepared nanosturucture was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analysis. Electrochemical performance was measured in 2032- type-coin-cell with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analysis. We found that cycle performance was fairly stable during 200 cycles at the current density of 420 mA g-1.