| Ni/MH battery has been widely applied as a rechargeable and high capacity battery. 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 plays an important role on the enhancement of Ni/MH battery's whole performance.In this paper, the optimum process parameters to synthesizeα-Ni(OH)2 by high energy ball milling were decided by orthogonal experiment. The optimum process parameters were as follows, the molar ratio of the nickel salt and aluminum salt was 10:2, the molar ratio of Ni(NO3)2 and NiSO4 was 1:2, the time of ball milling was 2 hour, the speed of ball milling was 300 r/min。The tap density of the sample reached 1.67g/cm3. The sample was hexagonal crystal structure, and its lattice parameters a=0.3073nm,c=0.7861nm. Its discharge capacity reached 308.2 mA·h·g-1 at 0.1C charge-discharge rate, furthermore, it showed good large current discharge performance. Its discharge capacity could maintain 85% and 72.7% at 0.5C and 1C charge-discharge rate.The optimum process parameters to synthesizeα-Ni(OH)2 by micro-emulsion system were also decided by orthogonal experiment. The optimum process parameters were as follows, molar concentration of NaOH used for titration was 1mol/L, the reaction temperature was 60℃, the reaction PH was 12, the time of the reaction was 2.5 hour. The sample was hexagonal crystal structure, and its lattice parameters a=0.3023nm ,c=0.7826nm. The samples were spherical, and its diameter was about 7um by SEM. The results of Cyclic Voltammetry (CV) indicate that the sample had good reversibility and poor oxygen evolution potential. The difference value of the redox peaks was only 0.14V, and the difference value of the oxygen evolution peak and oxidation peak was 71mV. Its discharge capacity reached 309.5 mA·h·g-1 at 0.1C charge-discharge rate. The nestedαandβNi(OH)2 was synthesized usingβ-Ni(OH)2 as crystal seed in this method whose discharge capacity reached 298 mA·h·g-1, and whose two pairs of redox peaks was 0.115V and 0.213V separately.The studies of constant current charge-discharge and electrochemical impedance spectroscopy (EIS) test showed that it could improve the electric conductivity of electrode material and reduce the internal resistance of electrode reaction by adding some waste Ni-MH batteries cathode material to new Ni(OH)2. It can realize recycling of the waste Ni-MH batteries cathode material simply. The discharge capacity reached maximum when the doping content is 20%, which was 202.8mA·h·g-1. |
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