The rapid development of electric vehicles demands the development of high performance nickel metal hydride battery that is able to endure high temperature. The discharge properties of Ti 0.7 Zr 0.5 V 0.2 Mn 1.8- x Ni...The rapid development of electric vehicles demands the development of high performance nickel metal hydride battery that is able to endure high temperature. The discharge properties of Ti 0.7 Zr 0.5 V 0.2 Mn 1.8- x Ni x ( x =0.4, 0.8, 1.1, 1.4, 1.7)hydrogen storage alloys was investigated and its phase composition was analyzed using X ray diffraction. The results show that the cycling life was improved as the content of nickel increases. When x =0.4, 0.8, 1.1 and 1.4, the main phase is MgZn 2 type C14 Laves phase and the second one is cubic TiNi phase. When x =1.7, the Laves phase structure disappears. EDAS analysis shows that the increase of nickel content is effective in suppressing the dissolution of vanadium component in alloys. [展开更多
The effect of the hot-charging treatment on the performance of AB(2) and AB(5) hydrogen storage alloy electrodes was investigated. The result showed that the treatment can markedly improve the voltage plateau ratio (V...The effect of the hot-charging treatment on the performance of AB(2) and AB(5) hydrogen storage alloy electrodes was investigated. The result showed that the treatment can markedly improve the voltage plateau ratio (VPR), the high rate discharge ability (HRDA), the diffusion coefficient of hydrogen DH and the discharge capacity of the AB2 hydrogen storage alloy electrode. The SEM analysis showed that the hot-charging treatment brings about a Ni-rich surface due to the dissolution of Zr oxides. It is also very helpful for the improvement of the kinetic properties of AB2 hydrogen storage alloy electrode because the microcracking of the surface results in fresh surface. This can be the basic modification treatment for NiMH battery used in electric vehicles (EVs) in the future. But for AB(5) type alloys, the treatment has the disadvantage of impairing the comprehensive electrochemical properties, because the surface of the alloy may be corroded during the treatment. The mechanism of the surface modification of the electrode is also proposed.展开更多
A hydrogen storage electrode alloy La_ 0.7Mg_ 0.3Ni_ 2.98Co_ 0.52 was obtained by electromagnetism inductive melting of alloys such as La, Mg, Ni and Co. XRD analyses indicate that the microstructure of the prepared a...A hydrogen storage electrode alloy La_ 0.7Mg_ 0.3Ni_ 2.98Co_ 0.52 was obtained by electromagnetism inductive melting of alloys such as La, Mg, Ni and Co. XRD analyses indicate that the microstructure of the prepared alloy was composed of LaNi_5 phase as matrix and another unknown phase as secondary phase. In this experiment, the highest discharge capacity of alloy is 378 mAh·g -1 at 293 K, which is 20% higher than the discharge capacity of LaNi_5-type alloys. The alloy was activated after two cycles and the discharge potential is high and stable, and more than 90% of the discharge time is in a voltage higher than 1.2 V. However, the cycle stability is poor as practical application, to improve the cycle life of the alloy becomes the key factor. Moreover, the loose structure of the alloy is maybe one reason that makes the cycle stability capacity of the alloy decrease by SEM.展开更多
Hydrogen diffusion coefficients in MlNi 3.75 Co 0.65 Mn 0.4 Al 0.2 alloy electrode as a function of state of charge (SOC) or temperature were determined by chronoamperometry. It is found that hydrogen diffusion coeffi...Hydrogen diffusion coefficients in MlNi 3.75 Co 0.65 Mn 0.4 Al 0.2 alloy electrode as a function of state of charge (SOC) or temperature were determined by chronoamperometry. It is found that hydrogen diffusion coefficient decreases with the increase of SOC or the decrease of temperature. The activation energy for hydrogen diffusion in the alloy electrode with 50%SOC is evaluated to be 19.9?kJ/mol.展开更多
The microstructure and electrochemical characteristics of Ml(NiCoMnAl) 5 alloys prepared by both the melt spinning method and the conventional induction melting were investigated and compared. SEM and XRD studies sh...The microstructure and electrochemical characteristics of Ml(NiCoMnAl) 5 alloys prepared by both the melt spinning method and the conventional induction melting were investigated and compared. SEM and XRD studies show that the microstructure of melt spinning alloys is columnar structure. With increasing melt spinning rate, the crystal grains become finer and preferentially grow along (111)[111] direction. The melt spinning and cast alloys belong to CaCu 5 type hexagonal crystal structure. The electrochemical measurements show that the initial capacities of melt spinning alloy electrodes are all above 210 mAh·g -1 with good activation behavior, reaching their maximum capacities after two charge discharge cycles. The maximum capacity (294 mAh·g -1 ) of melt spinning (10 m·s -1 ) alloy electrodes is as the same as that of as cast alloy electrode, and stability of charge discharge cycles of all melt spinning alloy electrodes is better than that of the as cast alloy electrodes. When charged at 600 mA·g -1 , the capacity of melt spinning (10 m·s -1 ) alloy electrode could reach 65% of its maximum capacity about 45 min with high rate discharge capability; but with the cycle number increasing, the stability of its capacity is less than that electrodes of melt spinning rate.展开更多
La0.75Mg0.25Ni3.5–xCo0.2Alx （x=0–0.09） hydrogen storage alloys were prepared by induction melting and effect of Al substitution for Ni on phase constitution and electrochemical property was investigated.With the s...La0.75Mg0.25Ni3.5–xCo0.2Alx （x=0–0.09） hydrogen storage alloys were prepared by induction melting and effect of Al substitution for Ni on phase constitution and electrochemical property was investigated.With the substitution of Al for Ni,LaNi5 and LaNi2 phases occurred and （La,Mg）2（Ni,Co,Al）7 phase with hexagonal Ce2Ni7-type structure replaced （La,Mg）2（Ni,Co）7 phase.The cell volumes of LaNi5 and （La,Mg）2（Ni,Co,Al）7 main phases increased with increasing Al content.Some electrochemical properties and kinetic parameters of the alloys,including discharge capacity,high rate discharge ability （HRD）,loss angle （ψ）,exchange current density （I0） and limiting current density （IL）,decreased with increasing amount of substitution of Al for Ni.Substitution of Al for Ni could be favorable for positive shift in corrosion potential of the alloy electrode,and prolonged cyclic lifetime of La0.75Mg0.25Ni3.5–xCo0.2Alx （x=0–0.09） alloy electrodes.展开更多
Crystal structure and some dynamic performances of Zi0.25V0.34Dy0.01Cr0.1Ni0.3 hydrogen storage electrode alloy have been investigated by XRD, FESEM-EDS, TEM and EIS measurements. The result shows that the alloy is ma...Crystal structure and some dynamic performances of Zi0.25V0.34Dy0.01Cr0.1Ni0.3 hydrogen storage electrode alloy have been investigated by XRD, FESEM-EDS, TEM and EIS measurements. The result shows that the alloy is mainly composed of V-based solid solution phase with body-centered-cubic structure and mono-crystal Ni3Ti phase with hexagonal structure （Space grope： P63/ mmc）, and it was first observed as TiNi-based secondary phase. The higher charge transfer resistance, higher apparent activation energy and lower hydrogen diffusion coefficient are reasons for the poor electrochemical activity of the dehydriding kinetics of Ti- V-Cr-Ni hydride alloy.展开更多
文摘The rapid development of electric vehicles demands the development of high performance nickel metal hydride battery that is able to endure high temperature. The discharge properties of Ti 0.7 Zr 0.5 V 0.2 Mn 1.8- x Ni x ( x =0.4, 0.8, 1.1, 1.4, 1.7)hydrogen storage alloys was investigated and its phase composition was analyzed using X ray diffraction. The results show that the cycling life was improved as the content of nickel increases. When x =0.4, 0.8, 1.1 and 1.4, the main phase is MgZn 2 type C14 Laves phase and the second one is cubic TiNi phase. When x =1.7, the Laves phase structure disappears. EDAS analysis shows that the increase of nickel content is effective in suppressing the dissolution of vanadium component in alloys. [
文摘The effect of the hot-charging treatment on the performance of AB(2) and AB(5) hydrogen storage alloy electrodes was investigated. The result showed that the treatment can markedly improve the voltage plateau ratio (VPR), the high rate discharge ability (HRDA), the diffusion coefficient of hydrogen DH and the discharge capacity of the AB2 hydrogen storage alloy electrode. The SEM analysis showed that the hot-charging treatment brings about a Ni-rich surface due to the dissolution of Zr oxides. It is also very helpful for the improvement of the kinetic properties of AB2 hydrogen storage alloy electrode because the microcracking of the surface results in fresh surface. This can be the basic modification treatment for NiMH battery used in electric vehicles (EVs) in the future. But for AB(5) type alloys, the treatment has the disadvantage of impairing the comprehensive electrochemical properties, because the surface of the alloy may be corroded during the treatment. The mechanism of the surface modification of the electrode is also proposed.
文摘A hydrogen storage electrode alloy La_ 0.7Mg_ 0.3Ni_ 2.98Co_ 0.52 was obtained by electromagnetism inductive melting of alloys such as La, Mg, Ni and Co. XRD analyses indicate that the microstructure of the prepared alloy was composed of LaNi_5 phase as matrix and another unknown phase as secondary phase. In this experiment, the highest discharge capacity of alloy is 378 mAh·g -1 at 293 K, which is 20% higher than the discharge capacity of LaNi_5-type alloys. The alloy was activated after two cycles and the discharge potential is high and stable, and more than 90% of the discharge time is in a voltage higher than 1.2 V. However, the cycle stability is poor as practical application, to improve the cycle life of the alloy becomes the key factor. Moreover, the loose structure of the alloy is maybe one reason that makes the cycle stability capacity of the alloy decrease by SEM.
文摘Hydrogen diffusion coefficients in MlNi 3.75 Co 0.65 Mn 0.4 Al 0.2 alloy electrode as a function of state of charge (SOC) or temperature were determined by chronoamperometry. It is found that hydrogen diffusion coefficient decreases with the increase of SOC or the decrease of temperature. The activation energy for hydrogen diffusion in the alloy electrode with 50%SOC is evaluated to be 19.9?kJ/mol.
文摘The microstructure and electrochemical characteristics of Ml(NiCoMnAl) 5 alloys prepared by both the melt spinning method and the conventional induction melting were investigated and compared. SEM and XRD studies show that the microstructure of melt spinning alloys is columnar structure. With increasing melt spinning rate, the crystal grains become finer and preferentially grow along (111)[111] direction. The melt spinning and cast alloys belong to CaCu 5 type hexagonal crystal structure. The electrochemical measurements show that the initial capacities of melt spinning alloy electrodes are all above 210 mAh·g -1 with good activation behavior, reaching their maximum capacities after two charge discharge cycles. The maximum capacity (294 mAh·g -1 ) of melt spinning (10 m·s -1 ) alloy electrodes is as the same as that of as cast alloy electrode, and stability of charge discharge cycles of all melt spinning alloy electrodes is better than that of the as cast alloy electrodes. When charged at 600 mA·g -1 , the capacity of melt spinning (10 m·s -1 ) alloy electrode could reach 65% of its maximum capacity about 45 min with high rate discharge capability; but with the cycle number increasing, the stability of its capacity is less than that electrodes of melt spinning rate.
基金Project supported by National 863 Program of China (2007AA03Z227, 2007AA03Z230)Natural Science Foundation of Hebei Province (E2010000301)+1 种基金Natural Science Research Planned Project of Hebei University (2009-152)Undergraduate Science and Technology Innovation Project of Hebei University (2010060)
文摘La0.75Mg0.25Ni3.5–xCo0.2Alx （x=0–0.09） hydrogen storage alloys were prepared by induction melting and effect of Al substitution for Ni on phase constitution and electrochemical property was investigated.With the substitution of Al for Ni,LaNi5 and LaNi2 phases occurred and （La,Mg）2（Ni,Co,Al）7 phase with hexagonal Ce2Ni7-type structure replaced （La,Mg）2（Ni,Co）7 phase.The cell volumes of LaNi5 and （La,Mg）2（Ni,Co,Al）7 main phases increased with increasing Al content.Some electrochemical properties and kinetic parameters of the alloys,including discharge capacity,high rate discharge ability （HRD）,loss angle （ψ）,exchange current density （I0） and limiting current density （IL）,decreased with increasing amount of substitution of Al for Ni.Substitution of Al for Ni could be favorable for positive shift in corrosion potential of the alloy electrode,and prolonged cyclic lifetime of La0.75Mg0.25Ni3.5–xCo0.2Alx （x=0–0.09） alloy electrodes.
基金financially supported by the Doctoral Foundation of Yanshan University(No.B330)
文摘Crystal structure and some dynamic performances of Zi0.25V0.34Dy0.01Cr0.1Ni0.3 hydrogen storage electrode alloy have been investigated by XRD, FESEM-EDS, TEM and EIS measurements. The result shows that the alloy is mainly composed of V-based solid solution phase with body-centered-cubic structure and mono-crystal Ni3Ti phase with hexagonal structure （Space grope： P63/ mmc）, and it was first observed as TiNi-based secondary phase. The higher charge transfer resistance, higher apparent activation energy and lower hydrogen diffusion coefficient are reasons for the poor electrochemical activity of the dehydriding kinetics of Ti- V-Cr-Ni hydride alloy.
