The Study Of Preparation And Modification Of Electrode Material Ni(OH)₂

Ni/MH battery as a rechargeable and high capacity battery has been wide application. As Ni/MH battery's positive electrode, the nickel electrode is one of Ni/MH battery's key parts. The improvement on the performance of the nickel electrode becomes a kind of valid approach of the enhancement of Ni/MH battery's whole performance.In this thesis, the Ni(OH)2 is prepared by micro-emulsion method. The TEM photos show that the Ni(OH)2 grains are elipsoidal and are easy to reunite, with the grain sizes of 20～30nm. XRD spectra reveals that the Ni(OH)2 is still hexagonal β– Ni(OH)2 and has the crystal fault.The influence of different preparing technologies on the performance of nickel electrodes is studied by cyclic voltammetry(CV). Experimental results indicate that the factors affecting the performance of nickel hydroxide are pH, temperature, synthesizing stirring rate, synthesizing stirring time.The influence of the process parameters on the granularity of nickel hydroxide is discussed. These optimized process parameters change the structure of Ni(OH)2 and improve the charge-discharge performance of the nickel electrode. The reversibility of nickel electrodes is increased.A variety of nickel electrodes containing Ca are prepared by different doping means . The effects of different Ca-doping means and contents on properties of the nickel electrode are studied. The measurement results of XRD, AC impedance,cyclic voltammetry and constant current charge and discharge indicate that the Ni(OH)2 with Ca-doping prepared by micro-emulsion method is still hexagonal β-Ni(OH)2. However, its crystallite size is small. Ret and RΩ of electrochemical system are decreased. The reversibility of nickel electrode and the oxygen evolution potential are increased. To a certian extent,the Ca-doping improves the eletrochemical performance of nickel electrode. In particular,when doping 1% Ca before Ni(OH)2 synthesis, the properties of the nickel electrode are best.The effects of different Zn-doping means (coprecipitating with Zn(OH)2, coating with Zn(OH)2, mechanically mixing with Zn powder) and different Zn-doping concents on the structures and the properties of nickel hydroxide are studied. The measurement results of XRD, AC impedance,cyclic voltammetry and constant current charge and discharge indicate that the Ni(OH)2 with Zn-doping prepared by micro-emulsion method is still hexagonal β-Ni(OH)2. It is demonstrated that the addition of Zinc can increase the fault of crystal, improve the transport ability of electron and H+ in electrode material, so the reversibility of nickel hydroxide electrode and the oxygen evolution potential are increased and RΩ is also decreased, then the discharge capacity of Ni(OH)2 is enhanced. When coprecipitating with Zn(OH)2, the performance of nickel hydroxide electrode is best.