Abstract
The main objective of this dissertation is to improve the electrochemical performances of ZnCo2O4 (ZCO) Li-ion anode material by nitrogen-doping and carbon deposition. As for nitrogen doping, two rapid methods, including hydrothermal to treat powder and atmospheric pressure plasma jet (APPJ) to modify the electrode, were used to dope nitrogen in the ZCO anode material. Via hydrothermal method, nitrogen was doped in the ZCO spinel lattice, while APPJ mainly activated and modified the electrode surface binding with the dangling bond. N-doped compounds were formed on the electrodes by hydrothermal and APP methods. The uniformity, chemical composition, and diffraction patterns were examined by electron probe microanalyzer (EPMA), X-ray photoelectron spectroscopy (XPS) and X-ray diffractometer (XRD). Nitrogen doping effectively improved electrochemical performance in cycling retention and the capacity at a current density of 1C. This study provides a rapid and inexpensive nitrogen doping processes to efficiently promote the electrochemical performance in ZCO anode. In addition, a special set-up of atmospheric pressure plasma jet generator was applied to deposit carbon on the electrode. Significant amounts of C(I) and C2 clusters were discovered using optical emission spectroscopy. After adding N2, the CN species appeared in the plasma, owing to C and N2 reaction during the plasma generation. The results from the field emission scanning electron microscope (FESEM) and X-ray photoelectron microscopy (XPS) reveal the change in surface morphology and chemical bonding by plasma treatment. After 20 times of Ar+N2 plasma treatment, a significant increment in cycling stability under 1000 mA/g was evident.