Cathode Nano-additives For Improving The Performance Of Mh / Ni Battery

In order to improving the performance of high-power Ni/MH batteries, nano-scale additives including CNTs and nano-scale CoO were added into the positive electrode of the batteries. The overall characteristics of Ni(OH)2/NiOOH electrode and Ni/MH batteries were investigated at different charge-discharge conditions at room temperature.Multi-walled carbon nanotubes were synthesized by chemical vapor deposition (CVD). Then the CNTs were purified by nitric acid and shortened by ball milling. The microstructure of carbon nanotubes was observed using transmission electron microscope (TEM).Nano-scale CoO was obtained by the decomposition of CoCO3, which synthesized by the liquid reaction. The grain-size of CoCO3 and CoO were measured by laser diffraction grain-size analysis. The microstructure of the samples was observed using transmission electron microscope (TEM).The electrochemical characteristics of the Ni(OH)2/NiOOH electrode were tested by DC-5 battery testing instrument. The results shows: the electrode with nano-scale CoO has best active properties. Nano-sacle CoO is apt to dissolve in the electrode homogeneously, and better conductive net of CoOOH come into being, thus contribute a lot to the procedure of the activation. The electrode with nano-scale CoO and CNTs shows higher discharge voltage and higher discharge capacity. Nano-scale additives can improve the specific capacity of the electrode, the volume specific capacity and the mass specific capacity of the electrode with nano-scale CoO are 784mAh/cm3 and 224mAh/g, respectively. That dates of the electrode with CNTs are 778mAh/cm3 and 223mAh/g.The improvement of overall characteristics of sealed MH/Ni batteries were investigated by BS-9365 rechargeable batteries and BS-GF internal-resistance testing instrument. The results shows: under high-rate discharge conditions, the batteries with CNTs added in the positive electrodes exhibited much better cycling stability, higher discharge voltage and high-rate capability. The increase in internal resistance of the batterieswith CNTs was lower than that of the batteries without CNTs during charge-discharge cycles. The addition of 0.5 wt.% CNTs was proved a desired amount to modify the batteries performance at the high discharge rates. Too much CNTs contributed no effect in the improvement of overall performance of the batteries.The batteries with nano-scale CoO shows better active properties, the addition of nano-scale CoO further the conductivity of the nickel electrode, thus lower the internal resistance of the batteries, higher discharge voltages are achieved accordingly. For the formation of the better conductive net of CoOOH, the effectivity of discharge rise, that contributes positive effect to the high rate capability of the batteries.