Preparation and electrochemical properties of Co3O4-coated layered manganese oxide by a novel coating method

摘要

Potassium type birnessite (K-bir) was synthesized by O2 oxidizing Mn2+ in aqueous solution of KOH. Co3O4-coated K-bir (Co-K-bir) was prepared by employing a novel coating method, in which the remaining OH? ions on the particle surface of the as-precipitated K-bir reacted with Co2+ ions in aqueous solution, forming CoOOH coverage; the coating layer of CoOOH was subsequently annealed at 300 °C to transform into Co3O4. All the K-bir and Co-K-birs were investigated by scanning electron microscopy, transmission electron microscopy, inductive coupled plasma–atomic emission spectroscopy, Brunauer–Emmett–Teller specific area, and laser particle size analyzing techniques. Their electrochemical properties were also studied by discharging–charging at constant current. The results show that the covering layers of Co3O4 are incompact, and their average thickness are about 0.65–0.78 μm. Compared to the as-prepared and the annealed K-bir, the Co3O4-coated samples have higher initial discharge capacities and show distinctly improved cycleability performance.