| The demand of the high-rate cylinder nickel metal-hydride batteries is growing in vehicles and high power applications, with the amount of 5 hundred millions annually. Some performances in Ni-MH can't meet the need of the electrical tools. So the development of high-rate nickel metal-hydride batteries with high performance is very important both in the scientific research and the market applications. The mainly contents in this paper are the preparation of Sub-C type Ni-MH power batteries. The aim, exploitation project and the conditions were all given. The performance aim requires the discharge time is longer than 5 minutes at 10C, the middle voltage is more than 1.0V. The discharge capacity is above 60% at 20A and 0℃. The life time of discharging at 10A and 2A alternately is over 200 cycles. Combined with development of the products, the research emphasis in this paper is focus on the studies of the high-rate discharging performance at different temperature.1. In the research of the discharge performance with high rate, the results of different effects including thickness of positive electrode, materials of hydrogen storage alloy, concentration of the electrolyte and separators. The effect of the electrode thickness to discharging at high rate is explained with kinetics and porous electrode law. It showed that the internal resistance decrease from 6.0m Ω to 4.9m Ω ,the middle voltage at 1C increase from 0.90V to 1.05V, discharging time increase from 5 min to 6 min with the lessen of the electrode thickness from 0.75mm to 0.55mm. So 0.55mm and 2.85 g/cm3 is selected. The test was demonstrated about the particle, content and XRD spectrum. The test results of Sub-C type showed that middle voltage is higher with 50 u m alloy particle, La-rich alloy has perfect performance at high rate, Ce-rich alloy is excellent at high rate and lower temperature, low Co alloy is good to decreasing middle voltage except the less recycle life. Experiments about the electrolyte showed that the performance is optimized with contents : KOH 78%, NaOH 20%, LiOH 2% and density 1.300 g/cm3. The FS2216 was selected as separator.2. In order to develop the performance of the batteries at high temperature, TiO2 ZnO Y2O3, Er2O3 was added to positive electrode material. Discharging capacity is above 94% with charging at 50℃. The feasible quantity is 3 wt% TiO2, 0.5 wt% Er203 through orthogonal experiment, When the batteries charge at 65℃ Through the high rate discharging test of the positive and the negative electrodes separately at 0 ℃,strong polarization occurs in the negative electrode. The voltage lag is feeble with the decreasing of the alloyparticle. Ce-rich alloy Mm Ni3.95Coo.50oMn0.40Al0.15 is excellent at high rate and lower temperature. According to the above results, using 50 m La-rich alloy MlNi4.0Co0.65Mn0.25Al0.10 and Ce-rich alloy Mm Ni3.9$Co0.50Mn0.40Al0.15 with the ratio of 1:1.5, the batteries have excellent performance even at lower temperature.3. Sub-C MH-Ni power batteries were prepared with excellent electrochemical performance based on the research of the high rate performance at different temperature. The change of temperature, impedance and weight loss was investigated in the process of recycle at high rate. It showed that the discharge time is 5.9min at 10C and the middle voltage is 1.05V. The discharging capacity is over 2500mAh at 20A under 0℃ The life of discharging at 10A and 2A alternately is 280 cycles. Together with the results of SEM both showed that the internal resistance is increased. We think increase of the internal resistance of battery is the main problem to the recycle life deteriorating at high rate, besides the influence of the materials. Decomposition occurred on positive and negative electrode at high rate current and the interspaces increased. The restrains of swelling and the increase of an oxygen overvoltage can improve the performance of recycle life. |
PDF Full Text Request