Optimizing the electrochemical performance of annealed Zn-doped Ni (HO)2 as a cathode for Zn-Ni ion battery in aqueous KOH electrolyte solution
摘要
In this paper, electrochemical performance of Zn-Ni battery was enhanced by improving the quality of Ni (OH)2 cathode material. This improvement was achieved using (i) doping with Zn atoms, (ii) post growth annealing of Zn doped Ni (OH)2 nanoparticles at different temperatures and (iii) alloy the Zn doped Ni (OH)2 nanoparticles with carbon nanotubes. The electrode materials used in this study were synthesized by hydrothermal technique and were annealed at 200 –500 °C. A paste of 80 mg Zn doped Ni (OH)2 and 10 mg CNTs was used on the treated Ni foam along with 10 mg NMP and PVDF binder to fabricate a cathode electrode. Hydrothermally synthesized nanoparticles were tested by XRD and Raman spectroscopy to verify the structure before forming the paste. A good Ni (OH)2 structure was evident for samples annealed at 200 and 300 °C and further annealing resulted in the NiO based secondary phases. Cyclic voltammetry (CV) was used to investigate the electrochemical performance of as grown and annealed Zn doped Ni(OH)2 electrode measured at 10 mVs− 1 vs. Ag/AgCl in 3 M aqueous solution of KOH. An optimized specific capacity of 321.92 mAhg− 1 was achieved for a specific electrode which consisted of annealed Zn doped Ni (OH)2 at 300 °C. Electrochemical impedance spectroscopy (EIS) distinguish the high frequency semicircle and low frequency warburg type diffusion tail. The smaller semicircle for samples annealed at 200 °C and 300 °C confirm the improvement in charge transfer and better electrochemical performance over 200 cycles.