| The requirements of batteries are asked more higher with Hybrid Electric Vehicle are more popular.As the one of the negative electrode materials of Ni-MH battery,TiFe-based alloys have been noticed by the high discharge capacity(512 mAh·g-1)and low-cost minerals,et al.However,the discharge capacity of TiFe-based alloys are barely satisfactory in the alkaline electrolyte.On the basis of electrochemical performance of TiFe-based hydrogen storage alloys are studied by researchers from all over the world.In this paper,the electrochemical performance of Ti1.1-xFe0.6Ni0.3Zr0.1Mn0.2Prx(x=0?0.08)+10 wt.%Ni were researched,including discharge capacity,discharge voltage characteristics,high rate discharge performance,open circuit potential,charge transfer impedance Rct,limit current density IL,hydrogen diffusion coefficient D,by the method of substituting Pr for Ti and adding Ni ball milling,systematically.Ti1.1-xFe0.6Ni0.3Zr0.1Mn0.2Prx(x=0?0.08)alloys are prepared by vacuum induction melting,and then 10 wt.%Ni are added before ball milling them.The phase composition and microstructure are analyzed by XRD,SEM and EDS.Some conclusions can be obtained,there are TiFe phase,NiTi2 phase and FeZr2 phase in as-cast Ti1.1-xFe0.6Ni0.3Zr0.1Mn0.2Prx(x=0?0.08)alloys,only TiFe phase is existed in as-milled Ti1.04Fe0.6Ni0.3Zr0.1Mn0.2Pr0.06 alloys,TiFe phase and FeNi phase are existed in as-milled Ti1.04Fe0.6Ni0.3Zr0.1Mn0.2Pr0.06+10 wt.%Ni powders alloys.As the milling time is prolonged,alloys particles are smaller.The discharge capacity of the as-cast Ti1.1-xFe0.6Ni0.3Zr0.1Mn0.2Prx(x=0?0.08)alloys is climbed up and then decline with the increase of Pr substitution,the value of them are 74.4,81.7,82.5,89 and 84 mAh·g-1,respectively.Discharge performance has been enhanced,the discharge median voltage is increased from 1.195 V to 1.240 V.The high rate discharge capability decrease at first and then increase and decrease again.The corrosion resistance of alloys is decreased with the increases of Pr substitution.The high-rate discharge capacity is better than others when the replacement amount of Pr is 0.06.According to the tested result of the charge transfer impedance Rct,the limit density IL,hydrogen diffusion coefficient D and variation trend of high-rate discharge capacity,the kinetic research indicates that the increase of the charge transfer rate the diffusion velocity of hydrogen in bulk are the main reason.The discharge capacity of Ti1.04Fe0.6Ni0.3Zr0.1Mn0.2Pr0.06 alloy is improved greatly with the ball milling time is prolonged,the discharge capacity of the ball milling 20 h can get 195.9 mAh·g-1.At the same time,the corrosion resistance of alloys is decreased.According to the tested result of the charge transfer impedance Rct,the limit density IL,the hydrogen diffusion coefficient D and variation trend of high-rate discharge capacity,the prolongation of balling milling time had a significant impact for hydrogen diffusion capacity inside of the alloys which is main reason for high-rate discharge capacity.The dynamic performance and electrochemical properties are better than others when ball milling time is 20 h of the alloys.The electrochemical performances of as-milled Ti1.04Fe0.6Ni0.3Zr0.1Mn0.2Pr0.06+10 wt.%Ni alloys are tested and it shown that discharge capacity is reduced slowly,maximum discharge capacity is 234.2 mAh·g-1 at 5 h.The capacity retention rate are improved when the as-milled alloys added 10 wt.%Ni.In addtion,the corrosion resistance of the alloys is decreased with ball milling time is prolonged.According to the analysed result of the charge transfer impedance Rct,the limit density IL,hydrogen diffusion coefficient D and variation trend of high-rate discharge capacity,the prolongation of balling milling time had a significant impact for hydrogen diffusion capacity inside of the alloys which is main reason for high-rate discharge capacity. |
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