Potassium-doped copper oxide nanoparticles synthesized by a solvothermal method as an anode material for high-performance lithium ion secondary battery

A simple and efficient approach was developed to synthesize CuO nanoparticles with improved electrochemical performance. Potassium (K+)-doped CuO nanoparticles were synthesized by a simple and cost-effective solvothermal method followed by annealing at 500 °C for 5 h under air atmosphere. For comparison, an undoped CuO sample was also synthesized under the same conditions. X-ray diffraction analysis demonstrates that the K+ ion doping caused no change in the phase structure, and highly crystalline KxCu1−xO1−δ (x = 0.10) powder without any impurity was obtained. As an anode material for a lithium ion battery, the K+-doped CuO nanoparticle electrode exhibited better capacity retention with a reversible capacity of over 354.6 mA h g−1 for up to 30 cycles at 0.1 C, as well as a high charge capacity of 162.3 mA h g−1 at a high current rate of 3.2 C, in comparison to an undoped CuO electrode (275.9 mA h g−1 at 0.1 C and 68.9 mA h g−1 at 3.2 C). The high rate capability and better cycleability of the doped electrode can be attributed to the influence of the K+ ion nanostructure on the increased electronic conductivity, diffusion efficiency, and kinetic properties of CuO during the lithiation and delithiation process.