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Abstract: In order to improve the electrochemical cycle stability of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, a trace of Cr was added in the alloy and La2Mg(Ni0.85Co0.15)9Cr x (x =0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of Cr addition on the microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The obtained results show that Cr addition engenders an inappreciable influence on the phase composition of the as-cast and quenched alloys, but it changes the phase abundance of the alloys significant. The Cr addition markedly enhances the cycle stability of the as-cast and quenched alloys, but it decreases the discharge capacity. When Cr content increased from 0 to 0.4, the discharge capacity of the as-cast alloy decreased from 396.3 to 355.6mAh/g, and the cycle life prolonged from 72 to 97 cycles. For the as-quenched (30m/s) alloys, the discharge capacity reduced from 364.2 to 334.2mAh/g, and the cycle life extended from 100 to 131 cycles. [Copyright &y& Elsevier]

Abstract: The nanocrystalline and amorphous Mg2Ni-type alloys with nominal compositions of Mg2Ni1−xMnx (x = 0, 0.1, 0.2, 0.3, 0.4) were synthesized by melt spinning technique. The structures of the as-cast and spun alloys were characterized by XRD, SEM and HRTEM. The hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage performances were tested by an automatic galvanostatic system. The results show that the as-spun (x = 0) alloy holds a typical nanocrystalline structure, whereas the as-spun (x = 0.4) alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni facilitates the glass formation in the Mg2Ni-type alloy. The hydrogen absorption capacity of the alloys first increases then decreases with rising Mn content, but the hydrogen desorption capacity of the alloys grows with increasing Mn content. Furthermore, the substitution of Mn for Ni significantly improves the electrochemical hydrogen storage performances of the alloys, involving both the discharge capacity and the electrochemical cycle stability. With an increase in the amount of Mn from 0 to 0.4, the discharge capacity of as-spun (30 m/s) alloy grows from 116.7 to 311.5 mAh/g, and its capacity retaining rate at 20th charging and discharging cycle rises from 36.7 to 78.7%. [ABSTRACT FROM AUTHOR]

Abstract: The La–Mg–Ni system PuNi3-type La0.5Ce0.2Mg0.3Co0.4Ni2.6−x Mn x (x =0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and quenching. Ni in the alloy was partially substituted by Mn in order to improve the electrochemical characteristics of the alloys. The effects of the substitution of Mn for Ni and rapid quenching on the structures and electrochemical characteristics of the alloys were investigated in detail. The results obtained by XRD, SEM and TEM show that the alloys have multiphase structures which are composed of two major phases (La, Mg)Ni3 and LaNi5 as well as a residual phase LaNi. The substitution of Mn for Ni leads to an obvious increase of the LaNi5 phase and an decrease of the (La, Mg)Ni3 in the alloys. The electrochemical measurements indicate that the discharge capacities of the as-cast and quenched alloys first increase and then decrease with growing Mn content. The substitution of Mn for Ni clearly improves the high rate discharge abilities (HRDs) and the activation capabilities of the as-cast and quenched alloys, but it slightly impairs the cycle stabilities of the alloys. The rapid quenching significantly improves the cycle stabilities of the alloys, and the discharge capacities and HRDs of the alloys have the maximum values with the variety of the quenching rate. [Copyright &y& Elsevier]

Abstract: In order to improve the cycle stability of the La–Mg–Ni system PuNi3-type hydrogen storage electrode alloys, Ni in the alloy was partially substituted by Fe. The La0.7Mg0.3Co0.45Ni2.55−x Fe x (x =0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of the substitution of Fe for Ni on the structures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The results of the electrochemical measurement indicate that the substitution of Fe for Ni obviously decreases the discharge capacity, high rate discharge capability (HRD) and discharge potential of the as-cast and quenched alloys, but it significantly improves their cycle stabilities, and its positive impact on the cycle life of as-quenched alloy is much more significant than on that of the as-cast one. The microstructure of the alloys analyzed by XRD, SEM and TEM show that the as-cast and quenched alloys have a multiphase structure which is composed of two major phases (La, Mg)Ni3 and LaNi5 as well as a residual phase LaNi2. The substitution of Fe for Ni helps the formation of a like amorphous structure in the as-quenched alloy. With the increase of Fe content, the grain sizes of the as-quenched alloys significantly reduce, and the lattice constants and cell volumes of the alloys obviously increase. [Copyright &y& Elsevier]

Abstract: The La0.75Mg0.25Ni2.5Co x (x =0, 0.2, 0.4, 0.6, 0.8, 1.0) hydrogen storage alloys were prepared by vacuum medium-frequency induction furnace under the argon atmosphere. The microstructures and electrochemical performances of the alloys were analyzed and measured. The effects of Co addition on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results by X-ray diffractometer (XRD) showed that alloys were composed of the (La,Mg)Ni3, the LaNi5, LaNi2 and the La2Ni7 phases. With the increase of Co content x, the LaNi2 phase decreases, the (La,Mg)Ni3, the La2Ni7 and the LaNi5 phases increase. The results by the electrochemical measurements indicated that the maximum discharge capacity of the alloys is enhanced and activation performance is improved with the incremental change of Co content. The alloy (x =1.0) has a maximum discharge capacity of 388.7mAh/g. The addition of Co raises the high rate discharge capacity of the alloys. The cycle stability of the alloys first increases and then decreases with the growth of Co content. When Co content is 0.4, the capacity retention rate (S 100) of the alloy reaches a maximum volume of 76.9%. [Copyright &y& Elsevier]

Abstract: In order to investigate the influences of the stoichiometric ratios of B/A (A: gross A-site elements, B: gross B-site elements) and the substitution of Co for Ni on the structure and the electrochemical performances of the -type electrode alloys, the La–Mg–Ni–Co system (, Co; , 0.2, 0.4, 0.6, 0.8, 1.0) alloys were prepared by induction melting in a helium atmosphere. The structures and electrochemical performances of the alloys were systemically measured. The obtained results show that the structures and electrochemical performances of the alloys are closely relevant to the M content. All the alloys exhibit a multiphase structure, including , and phases, and the major phase in the alloys changes from to with the variety of M content. The electrochemical performances of the alloys, involving the discharge capacity, the high rate discharge (HRD) ability, the activation capability and the discharge potential characteristics, significantly improve with increasing M content. When M content increases from 0 to 1.0, the discharge capacity rises from 177.7 to 343.62 mAh/g for the alloy , and from 177.7 to 388.7mAh/g for the alloy . The cycle stability of the alloy first mounts up then declines with growing M content. The substitution of Co for Ni significantly ameliorates the electrochemical performances. For a fixed M content , the substitution of Co for Ni enhances the discharge capacity from 343.62 to 388.7mAh/g, and the capacity retention ratio after 100 charging–discharging cycles from 51.45% to 61.1%. [Copyright &y& Elsevier]

Abstract: The effects of the substitution of Mn for Ni on the structures and electrochemical characteristics of the as-cast and quenched (, 0.1, 0.2, 0.3, 0.4) alloys were studied systematically. The results obtained by XRD, SEM and TEM indicate that the as-cast and quenched alloys mainly consist of two major phases the and and a residual phase LaNi. With increasing Mn content in the alloys, the abundance of the phase decreases and that of the phase increases and both the lattice parameters and the cell volumes of major phases and increase. The as-quenched alloys display a nanocrystalline structure, and the grain sizes of the alloys are in a range of 20–30nm. The results by the electrochemical measurements indicate that the discharge capacities of the as-cast and quenched alloys first increase and then decrease with the variety of Mn content and obtain the maximum values for a Mn content of . The substitution of Mn for Ni clearly improves the high rate discharge abilities (HRDs) and the activation capabilities of the as-cast and quenched alloys, but it slightly impairs the cycle stabilities of the as-cast and quenched alloys. [Copyright &y& Elsevier]

Abstract: A new La–Mg–Ni system (PuNi3-type) La0.7Mg0.3Co0.45Ni2.55−x M x (M=Cu, Al, Mn; x =0, 0.1, 0.2, 0.3, 0.4) electrode alloys were prepared by casting and rapid quenching. The effects of element substitution and rapid quenching on the microstructures and electrochemical performances of the alloys were investigated. The results obtained by XRD, SEM and TEM show that the alloys have a multiphase structure, including the (La, Mg)Ni3, the LaNi5 and the LaNi2 phases. The substitution of Cu for Ni promotes the formation of an amorphous phase in the as-quenched alloy, and a reversal result produced by the substitution of Al for Ni. The electrochemical measurement indicates that the element substitution decreases the discharge capacity of the alloys, whereas it obviously improved the cycle stability of the alloys. The positive influence of three kinds of substitution elements on the cycle life of the alloys is in the sequence Al>Cu>Mn, and the negative influence on the discharge capacity in the sequence Al>Mn>Cu. [Copyright &y& Elsevier]

Abstract: In order to improve the cycle stability of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, Ni in the alloy was partially substituted by Al, and La0.7Mg0.3Ni2.55−x Co0.45Al x (x =0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of substituting Ni with Al on the microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The results obtained by XRD show that the as-cast and quenched alloys have a multiphase structure, including the (La, Mg)Ni3, the LaNi5 and the LaNi2 phases. The substitution of Al for Ni increases the amount of the LaNi2 phase in the as-cast alloys, but it has an inappreciable influence on the abundance of the LaNi2 phase in the as-quenched alloy. The results obtained by SEM and TEM indicate that the substitution of Al for Ni leads to the grains of the as-quenched alloys coarsen and restrain an amorphous phase formed in the as-quenched alloys. The results of the electrochemical measurement indicate that the capacities of the as-cast and quenched alloys monotonously decrease and their cycle stabilities significantly increase with the increase of Al content. When the amount of substitution Al for Ni increased from 0 to 0.4, the cycle life of the as-cast alloys increased from 72 to 132 cycles, and that of the as-quenched (20ms−1) alloys from 86 to 134 cycles. [Copyright &y& Elsevier]

Abstract: A trace of Cr was added in La–Mg–Ni based (PuNi3-type) electrode alloy and rapid quenching technique was used in order to improve its cycle stability. The electrode alloys La2Mg(Ni0.85Co0.15)9Cr x (x =0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and rapid quenching, and the effects of Cr addition on the microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The results obtained by XRD, SEM and TEM show that the as-cast and quenched alloys have a multiphase structure, including two main phases of (La, Mg)Ni3 and LaNi5, a residual phase of LaNi2. The Cr addition has an inappreciable influence on the phase compositions of the alloys, whereas it changes the phase abundance of the alloys. The results obtained by the electrochemical measurement indicate that the Cr addition obviously enhances the cycle stability of the as-cast and quenched alloys and leads to a different extent decrease of the discharge capacity of the alloys. When the amount of Cr addition changes incrementally from 0 to 0.4, the discharge capacity of the as-cast alloy decreases from 396.5 to 355.6mAh/g, and the cycle life increases from 72 to 97 cycles. For the as-quenched (30m/s) alloys, the discharge capacity decreases from 364.6 to 334.2mAh/g, and the cycle life increases from 100 to 131 cycles. The Cr addition improves the discharge voltage characteristic and activation capability of the as-cast alloys, but it slightly decreases the activation capability of the as-quenched alloys. [Copyright &y& Elsevier]

Abstract: In order to improve the cycle stability of the La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, Ni in the alloy was partly substituted by Cu. Hydrogen storage alloys La0.7Mg0.3Ni2.55−x Co0.45Cu x (x =0, 0.1, 0.2, 0.3, 0.4) were prepared by casting and rapid quenching. The effects of substituting Ni with Cu and the quenching rate on the microstructures and the cycle stability of the as-cast and quenched alloys were investigated in detail. The results obtained by X-ray diffraction show that the as-cast and quenched alloys have a multiphase structure, including the (La, Mg)Ni3 phase, the LaNi5 phase and the LaNi2 phase, and the amount of the LaNi2 phase increased with the increase of the Cu content. The substitution and rapid quenching have an inappreciable influence on the phase compositions of the alloys, but both obviously changed the phase abundances of the alloys. The results derived by transmission electron microscopy confirm that the substitution of Cu for Ni is favourable for the formation of an amorphous phase in the as-quenched alloys. The results obtained by the electrochemical measurement indicate that substituting Ni with Cu improved the cycle stability. When the Cu content increases from 0 to 0.4, the cycle lives of the as-cast and rapidly solidified alloys increased from 72 cycles to 88 cycles and from 100 cycles to 122 cycles, respectively. [Copyright &y& Elsevier]

Abstract: In order to improve the cycle stability of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, Ni in the alloy was partly substituted by Al, and La0.7Mg0.3Ni2.55−x Co0.45Al x (x =0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of substituting Ni with Al and rapid quenching on the microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The results obtained by XRD show that the as-cast and quenched alloys have a multiphase structure, including the (La, Mg)Ni3 phase, the LaNi5 phase and the LaNi2 phase. The substitution of Al for Ni increases the amount of the LaNi2 phase in the as-cast alloys, but it has an inappreciable influence on the abundance of the LaNi2 phase in the as-quenched alloy. The results obtained by the electrochemical measurement indicate that the capacities of the as-cast and quenched alloys monotonously decrease and their cycle stabilities significantly increase with the increase of Al content. Rapid quenching leads to the decrease of the capacity and an obvious improvement of the cycle stability of the alloys. [Copyright &y& Elsevier]

Abstract: La–Mg–Ni system (PuNi3-type) La0.7Mg0.3Ni2.55−x Co0.45Cu x (x =0, 0.2, 0.4) hydrogen storage electrode alloys were prepared by casting and rapid quenching. The effects of substituting Ni with Cu and rapid quenching on microstructures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The microstructures of the as-cast and quenched alloys were systematically determined by XRD, SEM and TEM. The obtained results show that the as-cast and quenched alloys are composed of the (La, Mg)Ni3 phase and the LaNi5 phase as well as the LaNi2 phase. The substitution and the rapid quenching do not have a large influence on the phase compositions of the alloys, but both changed the phase abundances of the alloys obviously. The results obtained by the electrochemical measurement indicate that the substitution decreased the discharge capacities of the as-cast and quenched alloys, whereas it improved the cycle stability and discharge voltage characteristic of the as-cast and quenched alloys. The rapid quenching significantly enhanced the cycle stability of the alloys, but it notably decreased the discharge capacity of the alloys. [Copyright &y& Elsevier]

Abstract: In order to improve the electrochemical performances of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, a trace of boron was added in La2Mg(Ni0.85Co0.15)9 and rapid quenching techniques were used. La2Mg(Ni0.85Co0.15)9 B x (x =0, 0.05, 0.1, 0.15, 0.2) hydrogen storage alloys were prepared by casting and rapid quenching. The microstructures and electrochemical performances of the as-cast and quenched alloys were determined and measured. The effects of the boron content and the quenching rate on the microstructures and electrochemical performances of the alloys were investigated in detail. The obtained results show that the as-cast and quenched alloys are composed of the (La, Mg)Ni3 phase (PuNi3 structure), the LaNi5 phase and the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloys containing boron. The Ni2B phase in the alloys containing boron nearly disappears after rapid quenching and the relative amount of each phase in the alloys changes with the variety of the quenching rate. The addition of boron obviously enhances the cycle stability of the as-cast and quenched alloys. The effects of boron content on the capacities of the as-cast and quenched alloys are different. The capacities of the as-cast alloys monotonously decrease with the increase of boron content, whereas the capacities of the as-quenched alloys have a maximum value with the change of boron content. The as-cast and quenched alloys have an excellent activation performance. [Copyright &y& Elsevier]

Abstract: The rare-earth-based AB5-type Mm(NiMnSiAl)4.3Co0.6−x Fe x (x =0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) hydrogen storage alloys were prepared by casting and rapid quenching. The microstructures of the as-cast and quenched alloys were analysed by XRD, SEM and TEM, and electrochemical cycle stabilities of the alloys were measured. The effects of substituting Co with Fe on microstructures and cycle stabilities of the as-cast and quenched alloys were investigated in detail. The obtained results show that the effects of substituting Co with Fe on the phase structures of the as-cast and quenched alloys are imperceptible, but its effects on cycle stabilities of the alloys are notable. Substituting Co with Fe improves slightly the cycle stabilities of the as-cast alloys, but it can significantly enhance the cycle lives of the as-quenched alloys, which is mainly attributed to the grain refinement of the alloys caused by substituting Co with Fe. [Copyright &y& Elsevier]

Abstract: The PuNi3-type La2Mg (Ni0.85Co0.15)9M x (M=B, Cr, Ti; x =0, 0.1) hydrogen storage electrode alloys were prepared by casting and rapid quenching. The electrochemical cycle stabilities and microstructures of the as-cast and quenched alloys were measured and determined. The effects of B, Cr, Ti and rapid quenching on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results show that the as-cast alloys are composed of the (La, Mg)Ni3 phase (PuNi3-type) and the LaNi5 phase as well as a small amount of the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloy containing boron, and the Ni2B phase in the alloy nearly disappears after rapid quenching. The relative amount of each phase in the alloys changes with varying quenching rate. The addition of B, Cr enhances the cycle stabilities of the alloys, whereas the addition of Ti reduces the cycle stabilities of the alloys. Rapid quenching increases the cycle stabilities of the alloys, the cycle stabilities of the alloys increase monotonously with the increase of the quenching rate. [Copyright &y& Elsevier]

Abstract: In order to improve the electrochemical cycle stability of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, a trace of Cr was added and rapid quenching techniques were employed. The electrochemical performances and microstructures of the as-cast and -quenched alloys were determined and measured. The effects of Cr content and quenching rate on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results show that the as-cast and -quenched alloys are composed of the (La, Mg)Ni3 phase (PuNi3-type structure) and the LaNi5 phase as well as the LaNi2 phase. The amount of the LaNi2 phase increases with the increase of Cr content. The addition of Cr enhances the cycle stability of the as-cast and -quenched alloys, but decreases the discharge capacities of the alloys. The cycle lives of the alloys increase with the increase of the quenching rate. The as-cast and -quenched alloys have an excellent activation performance. [Copyright &y& Elsevier]

Abstract: The microstructures of the rare-earth-based AB5-type Mm(NiMnSiAl)4.3Co0.6-xFex (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) hydrogen storage alloys were analysed by XRD, SEM and TEM, and electrochemical characteristics of the as-cast and quenched alloys were measured. The effects of substituting Co with Fe on microstructures and electrochemical characteristics of the as-cast and quenched alloys were investigated in detail. The obtained results show that the effects of substituting Co with Fe on the phase structures of the as-cast and quenched alloys are imperceptible, but its effects on electrochemical characteristics of the alloys are notable. The discharge capacities decrease, but the cycle lives of the alloys were improved with the increase of the amount of Fe substitution. Especially, substituting Co with Fe can significantly enhance the cycle lives of the as-quenched alloys, which is mainly attributed to the grain refinement caused by substituting Co with Fe. [Copyright &y& Elsevier]

Abstract: In order to enhance the electrochemical capacity of the Co-free AB5-type electrode alloy, Mm in the alloys was substituted with La and Co-free LaxMm1-x(NiMnSiAlFe)4.9 (x = 0, 0.45, 0.75, 1.0) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of the substituting Mm with La on the electrochemical performances of the as-cast and quenched alloys were investigated in detail. The obtained results show that substituting Mm with La can enhance markedly the capacities of the as-cast and quenched alloys. When the amount of substituting Mm with La, x increased from 0 to 1.0, the maximum capacity of the as-cast alloys at 0.2C rate increased from 273.45 to 304.47mAhg-1, and the capacity retaining rate (Rh) increased from 59.16 to 59.86%. The capacity of the as-quenched alloys with a quenching rate of 10ms-1 increased from 236.83 to 300.31mAhg-1, and the capacity retaining rate (Rh) decreased from 78.69 to 62.29%. The substituting Mm with La had an insignificant effect on the activation capabilities of the as-cast and quenched alloys. [Copyright &y& Elsevier]

In order to improve the electrochemical performance of rare-earth-based AB5-type electrode alloy, the AB5-type Mm(NiMnSiAl)4.3Co0.6-xFex (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) electrode alloys were quenched by melt-spinning. The phase structures and microstructure morphologies of the as-cast and quenched alloys were analyzed by XRD, SEM and TEM. The effects of the rapid quenching on the microstructures and electrochemical performances of the alloys were investigated in detail. The obtained results show that the as-quenched alloys have an excellent activation performance and can be completely activated through two to five charge–discharge cycles. The effect of the rapid quenching on the capacities of the alloys with Fe content x ≤ 0.2 is minor, and the capacities and high rate discharge abilities of the alloys with Fe content x > 0.2 decrease significantly with the increase of quenching rate. The cycle lives of the alloys increase greatly with the increase of the quenching rate. [Copyright &y& Elsevier]

The rare-earth Mg-based La2Mg(Ni0.85Co0.15)9Bx (x=0–0.2) hydrogen storage electrode alloys were prepared by casting and rapid quenching. The microstructures and electrochemical performances of the as-cast and quenched alloys were determined and measured systematically. The effects of boron content and quenching rate on the microstructures and electrochemical properties of the alloys were investigated in detail. The obtained results show that the as-cast and quenched alloys are composed of the (La, Mg)Ni3 phase (PuNi3-type structure), the LaNi5 phase as well as of the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast alloys containing boron, and when the quenching rate is larger than 15 m/s, the Ni2B phase in the alloys nearly disappears. The relative amount of each phase in the alloys depends on the composition of the alloys and the quenching rate. The addition of boron enhances the cycle stability of the as-cast and quenching alloys, but decreases the discharge capacity of the alloys. The capacity of the alloys without boron monotonously decreases with increasing quenching rate, but for the alloys containing boron, the capacities have a maximum value when varying the quenching rate. The cycle lives of the as-quenched alloys increase with increasing quenching rate. The as-cast and quenched alloys have an excellent activation performance. [Copyright &y& Elsevier]