| MH/Ni battery is the preference of prismatic batteries in the near future and medium-term and its performance need to be improved stilly. The performance of Ni-MH battery mainly depends on the capability of hydrogen storage alloy electrode. In order to improve the performances of hydrogen storage alloy electrode and MH/Ni battery, the performance improvements of hydrogen storage alloy electrode by low-temperature sintering of alloy electrode, Co3O4used as additive, pretreatment of AB5-type hydrogen storage alloy powders and the improvement of adhesive and conductive agent were investigated. By using the above results, the prismatic traction batteries with the capacities of6Ah and40Ah for HEVs which had excellent performances were prepared. The materials and electrodes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy with energy dispersive X-ray detector (TEM-EDX), inductively coupled plasma-atomic emission spectroscopy (ICP), Fourier transform infrared spectroscopy (FTIR) and BET method, et al. The electrodes or batteries were studied by electrochemical measurement methods such as:cyclic voltammogram (CV), linear polarization, anodic polarization, potential step method and electrochemical impedance spectroscopy (EIS). The charge/discharge performances of electrodes and batteries were measured by galvanostatic charge-discharge. The performances of electrodes and batteries were significantly improved and the influencing mechanisms were investigated.The kinetic properties of MH electrode were improved significantly by being sintered for1h at300℃. Compared with the untreated one, the polarization resistance (Rp), contact resistances(Rpp) and charge-transfer resistance (Rct) of sintered electrode decreased significantly, while the exchange current density(I0), hydrogen diffusion coefficient (D) and limiting current density (IL) of sintered electrode increased apparently. The high-rate discharge performance and cycle lifetime of sintered electrode were improved effectively. The capacity of sintered electrode at the discharge current density of1500mA·g-1was53.0mAh·g-1and27.95%more than that of the untreated one, and the value of HRD was14.87%more than that of the untreated one. The discharge voltage plateau at different discharge current density was higher and more horizontal for the sintered electrode. The decrease speed of capacity of sintered electrode was obviously slower than that of untreated one during cycling. These results should be due to the densification of electrode, the elimination or decrease of micro-stress and lattice distortion of alloy powders and the formation of micro-cracks on alloy powder surfaces.The proper amounts of Co3O4as additive in practical MH electrode was acquired by the investigation of effects of different contents of Co3O4additive on MH electrode. AA size cylindrical Ni-MH battery (with the rated capacity of1500mAh) was prepared from the electrode with proper amounts of Co3O4as additive. The performance measurement results proved that proper amounts of Co3O4can effectively improve the high-rate discharge ability, overcharge endurance capability, high-and-low temperature performance and cycle lifetime, and decrease the internal resistance, inner pressure and temperature-rising during the charge process of the battery. The influencing mechanism of Co3O4on the performance of MH electrode and MH/Ni battery was investigated via to the analysis of materials, electrodes and battery by some test methods. The effects of Co3O4on the performances of MH electrode and MH/Ni battery should be attributed to good electrochemical catalytic activity and capacitance performance, extended capability of hydrogen storage and low conductivity of Co3O4and the existing of conversion reaction of Co3O4-Co(OH)2-Co, and that Co3O4can restrain the oxidation of electrode alloys, increase gas consumption ability and the electro-reduction of oxygen among side-reactions.The electrocatalytic activity, diffusion rate of hydrogen, surface electric conductivity and oxidation resistance of alloy powders were significantly enhanced due to the removal of oxide film, the enriched Ni and Co metal layers on the alloy surface (the contents of Ni and Co on the alloy surface treated in NaOH and KOH solutions are92.91at%and90.68at%, and are26.62%,24.39%higher than that of untreated alloy, respectively) and the increase of specific surface area, and the slope of hydriding and dehydriding plateau of alloy powders was decreased by using new alkaline-treatment method. Hence, the activation, high-rate charge/discharge performance, high-and-low temperature performance, charging/discharging voltage plateau and cycle lifetime of MH electrode were improved effectively.The charge efficiency, high-rate discharge capability, discharge voltage plateau and low-temperature performance of MH electrode for HEV6Ah prismatic traction battery were enhanced by the improvement of adhesive and conductive agent. The prepared6Ah prismatic traction battery for HEV had good high-rate charge/discharge performance, high-and-low temperature performance and long cycle lifetime. The discharge efficiency of80%of SOC at45C was81.8%and the voltage was0.9797V when the battery was discharged for0.1S. The specific power was1422W/Kg. The discharge efficiency of80%of SOC at3C at-20℃was83.73%. The cycle lifetime at3C of SOC of80%was4424. The test results from testing institution proved that the prepared6Ah prismatic traction battery for HEV had international advanced performance. The test results from testing institution proved the performances of40Ah prismatic traction battery for HEV accorded with national standard, and the high-rate discharge ability, high-and-low temperature performance, charge retention, cycle lifetime and storage performance were significantly superior to national standard.
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