The Effects Of Carbon Nanotubes On The Hydrogen Storage Performance Of The Alloy Electrode For Ni-MH Batteries

This paper has studied the effects of adding appropriate amount of carbon nanotubes (CNTs) in the Ni-MH hydride batteries'negative electrodes,and through preparing composite CNTs electrodes, two-electrode system, three-electrode system,AA type Ni-MH batteries, SC Ni-MH batteris to research their electrochemical properties,internal resistance, capacity, performance and high rate discharge cycle life and other properties. And we found that adding appropriate amount of carbon nanotubes in the nickel-metal hydride batteries'negative electrodes can enhance the integrated performance of Ni-MH batteries,especially the large current performance and discharge cycle life.Using a three-electrode system of composite carbon nanotube electrodes to study the CV performance and impedance performance in different sweep,different cycles,different amount of carbon nanotubes,the experiment sweep were lmV/s,3mV/s,5mV/s,a composite of carbon nanotubes-added volume of 5%,3%,0.8%. We research the electrochemical properties of the working electrodes under different condition by cyclic voltammetry and AC impedance test.It's found that with the increase in scanning speed, the property of elctrodes'reversible getting worse. All the electrodes need a activation process, but pure hydrogen storage alloy CV curve area is smaller than that with CNTs adding. That is to say with the addition of carbon nanotube would get a high capacity.when the addition increase the oxidation-peak and reduction-peak will be larger, their CV curve area also will be large. The very peak of the current width of composite electrodes has increased significantly, showing a better CV characteristics. The CNTs content is 0.8% get a minimum impedance, and which with none CNTs and with too much CNTs(3% and 5%) resistance are very large.Prepared CNTs/LaNi₅ composite electrodes of 0.2%, 0.5%, 0.7%, 0.8%, 0.9%, 1% and 3% CNTs content each, and made two-electrode system, test the charge and discharge propertiy by BS9300 system. We found that the electrodes with CNTs adding showed a better properties than those with none, especially under the large current conditions. When the discharge current is 1000 mA, the capacity of pure hydrogen-electrodes is only 99.92 mAh, the discharge termination voltage for 1.03 V.And with 0.8% CNTs, capacity of the carbon nanotube composite electrodes reached 124.9 mAh, the termination voltage discharge for 1.11 V.AA-type Ni-MH batterys were pepared to discuss the charge and discharge property, capacity and performance of internal resistance. Experiments showed that the CNTs content in the negative of 0.5% and 1.0% the battery has a higher capacity and better discharge curve. When CNTs content is 0.5% and 1.0%,respectively, the capacity is 2341.22 mAh and 2299.67 mAh, discharge voltage platform for 1.291 V and 1.206 V. But when is 3.0%, the deterioration of its discharge capacity is reduced, only the capacity 1936 mAh, so too much CNTs adding is not better.When the weight ratio of the MWNTs in the compound electrode of SC Ni-mh batteries was 0.8%, the overall performance of the battery was the best, which with a highest capacity of 3369mAh, 2C (6000mA) cycle capacity of 600 remained after the 3280 mAh (97% DOD ( Discharge depth)) above, 5 C (15000mA) cycle capacity of 180, there are still 2850 mAh (89.1% DOD) above.