In order to improve the cycle stability of La-Mg-Ni-Co type alloy electrode, rapid quenching technology was employed. The effects of rapid quenching on the microstructure and cycle stability of the alloy were investig...In order to improve the cycle stability of La-Mg-Ni-Co type alloy electrode, rapid quenching technology was employed. The effects of rapid quenching on the microstructure and cycle stability of the alloy were investigated. The obtained results show that the La2Mg(Ni0.85Co0.15)9M0.1 (M=B, Cr) alloy electrodes are composed of (La, Mg)Ni3 phase, LaNi5 phase and a small amount of the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast MB alloy, and the Ni2B phase in the alloy nearly disappears after rapid quenching. Rapid quenching technology can slightly improve the cycling life of the alloy. When the quenching rate increases from 0 m·s-1 (As-cast is defined as quenching rate of 0 m·s-1) to 30 m·s-1, the cycle lives of the MB, MCr alloys enhance from 86 and 87 cycles to 106 and 119 cycles, respectively. On the other hand, the average capacity decay rates of the MB, MCr alloys decrease from 1.7172 and 1.7178 mAh·g-1·cycle-1 to 1.5751 and 1.3060 mAh·g-1·cycle-1 after 86 charge-discharges cycling, respectively.展开更多
The mechanism of the improvement of the cycling stability of the La-Mg-Ni-Co based hydrogen storage alloy electrode was systematically investigated. The results show that the cell volume expansion upon hydrogenation i...The mechanism of the improvement of the cycling stability of the La-Mg-Ni-Co based hydrogen storage alloy electrode was systematically investigated. The results show that the cell volume expansion upon hydrogenation is obviously decreased after the partial substitution of Al for Ni. Therefore a decrease in the pulverization of the alloy particles is obtained, which leads to the decrease of the contact area of the fresh alloy surface with alkaline electrolyte and the increase of the charge/discharge efficiency. Moreover, the occurrence of Al in the alloy can create a dense Al oxide film on the surface of the alloy during charge/discharge cycling. This dense oxide film can prevent further oxidation of the active components in the alloy, which is believed to be the most important factor responsible for the improvement of the cycling stability of the La-Mg-Ni-Mn-Co-Al type alloy electrodes.展开更多
The mechanism of the improvement of the cycling stability of the La-Mg-Ni-Co based hydrogen storage alloy electrode was systematically investigated. The results show that the cell volume expansion upon hydrogenation i...The mechanism of the improvement of the cycling stability of the La-Mg-Ni-Co based hydrogen storage alloy electrode was systematically investigated. The results show that the cell volume expansion upon hydrogenation is obviously decreased after the partial substitution of Al for Ni. Therefore a decrease in the pulverization of the alloy particles is obtained, which leads to the decrease of the contact area of the fresh alloy surface with alkaline electrolyte and the increase of the charge/discharge efficiency. Moreover, the occurrence of Al in the alloy can create a dense Al oxide film on the surface of the alloy during charge/discharge cycling. This dense oxide film can prevent further oxidation of the active components in the alloy, which is believed to be the most important factor responsible for the improvement of the cycling stability of the La-Mg-Ni-Mn-Co-Al type alloy electrodes.展开更多
In order to investigate the influences of the stoichiometric ratio of B/A (A: gross A-site elements, B: gross B-site elements) and the substitution of Co for Ni on the structures and electrochemical performances of th...In order to investigate the influences of the stoichiometric ratio of B/A (A: gross A-site elements, B: gross B-site elements) and the substitution of Co for Ni on the structures and electrochemical performances of the AB3.5-4.1-type electrode alloys, the La-Mg-Ni-Co system La0.75Mg0.25Ni3.5Mx (M=Ni, Co; x= 0, 0.2, 0.4, 0.6) alloys were prepared by induction melting in a helium atmosphere. The structures and electrochemical performances of the alloys were systemically measured. The results show that the structures and electrochemical performances of the alloys are closely relevant to the B/A ratio. All the alloys exhibit a multiphase structure, including two major phases, (La, Mg)2Ni7 and LaNi5, and a residual phase LaNi2, and with rising ratio B/A, the (La,Mg)2Ni7 phase decreases and the LaNi5 phase increases significantly. When ratio B/A=3.7, the alloys obtain the maximum discharge capacities. The high rate discharge(HRD) capability of the alloy (M=Ni) monotonously rises with growing B/A ratio, but that of the alloy (M=Co) first mounts up then declines. The cycle stability of the alloy (M=Co) monotonously increases with rising B/A ratio, but it first decreases slightly then increases for the alloy (M=Ni). The discharge potential of the alloy (M=Ni) declines with increasing B/A ratio (x>0.2), but for the alloy (M=Co), the result is contrary. The substitution of Co for Ni significantly ameliorates the electrochemical performances. For a fixed ratio B/A=3.7, the Co substitution enhances the discharge capacity from 365.7 to 401.8 mA·h/g, the capacity retention ratio (S100) after 100 charging-discharging cycles from 50.32% to 53.26% and the HRD from 88.65% to 90.69%.展开更多
In order to improve the cyclic stability of La-Mg-Ni system （Ce2Ni7-type） alloy electrode, small amount of Co was added in La0.75Mg0.25Ni3.5 alloy. The effect of Co on electrochemical performance and microstructure ...In order to improve the cyclic stability of La-Mg-Ni system （Ce2Ni7-type） alloy electrode, small amount of Co was added in La0.75Mg0.25Ni3.5 alloy. The effect of Co on electrochemical performance and microstructure of the alloys were investigated in detail. XRD results showed that the alloys had multiphase structure composed of （La, Mg）2Ni7, LaNi5 and small amount of LaNi2 phases. The discharge capacity of the alloys first increased and then decreased with increasing Co content. At a discharge current density of 900 mA/g, the HRD of the alloy electrodes increased from 81.3% （x=0） to 89.2 % （x=0.2）, and then reduced to 87.8 % （x=0.6）. After 60 charge/discharge cycles, the capacity retention rate of the alloys enhanced from 52.67% to 61.32%, and the capacity decay rate of the alloys decreased from 2.60 to 2.05 mAh/g per cycle with increasing Co content. The obtained results by XPS and XRD showed that the fundamental reasons for the capacity decay of the La-Mg-Ni system （Ce2Ni7-type） alloy electrodes were corrosion and oxidation as well as passivation of Mg and Lain alkaline solution.展开更多
基金This work was financially supported by National Natural Science Foundations of China (No.50131040)Key Technologies R & D Program of Inner Mongolia (No.20050205)College Scientific Research Project of Inner Mongolia (No.NJ05064).
文摘In order to improve the cycle stability of La-Mg-Ni-Co type alloy electrode, rapid quenching technology was employed. The effects of rapid quenching on the microstructure and cycle stability of the alloy were investigated. The obtained results show that the La2Mg(Ni0.85Co0.15)9M0.1 (M=B, Cr) alloy electrodes are composed of (La, Mg)Ni3 phase, LaNi5 phase and a small amount of the LaNi2 phase. A trace of the Ni2B phase exists in the as-cast MB alloy, and the Ni2B phase in the alloy nearly disappears after rapid quenching. Rapid quenching technology can slightly improve the cycling life of the alloy. When the quenching rate increases from 0 m·s-1 (As-cast is defined as quenching rate of 0 m·s-1) to 30 m·s-1, the cycle lives of the MB, MCr alloys enhance from 86 and 87 cycles to 106 and 119 cycles, respectively. On the other hand, the average capacity decay rates of the MB, MCr alloys decrease from 1.7172 and 1.7178 mAh·g-1·cycle-1 to 1.5751 and 1.3060 mAh·g-1·cycle-1 after 86 charge-discharges cycling, respectively.
基金Project (50131040) supported by the National Natural Science Foundation of China
文摘The mechanism of the improvement of the cycling stability of the La-Mg-Ni-Co based hydrogen storage alloy electrode was systematically investigated. The results show that the cell volume expansion upon hydrogenation is obviously decreased after the partial substitution of Al for Ni. Therefore a decrease in the pulverization of the alloy particles is obtained, which leads to the decrease of the contact area of the fresh alloy surface with alkaline electrolyte and the increase of the charge/discharge efficiency. Moreover, the occurrence of Al in the alloy can create a dense Al oxide film on the surface of the alloy during charge/discharge cycling. This dense oxide film can prevent further oxidation of the active components in the alloy, which is believed to be the most important factor responsible for the improvement of the cycling stability of the La-Mg-Ni-Mn-Co-Al type alloy electrodes.
基金Project (50131040) supported by the National Natural Science Foundation of China
文摘The mechanism of the improvement of the cycling stability of the La-Mg-Ni-Co based hydrogen storage alloy electrode was systematically investigated. The results show that the cell volume expansion upon hydrogenation is obviously decreased after the partial substitution of Al for Ni. Therefore a decrease in the pulverization of the alloy particles is obtained, which leads to the decrease of the contact area of the fresh alloy surface with alkaline electrolyte and the increase of the charge/discharge efficiency. Moreover, the occurrence of Al in the alloy can create a dense Al oxide film on the surface of the alloy during charge/discharge cycling. This dense oxide film can prevent further oxidation of the active components in the alloy, which is believed to be the most important factor responsible for the improvement of the cycling stability of the La-Mg-Ni-Mn-Co-Al type alloy electrodes.
基金Project(2006AA05Z132) supported by High-tech Research and Development Program of ChinaProject(50642033) supported by the National Natural Science Foundation of China+1 种基金Project(200711020703) supported by the Natural Science Foundation of Inner Mongolia, ChinaProject (20050205) supported by Science and Technology Planned Project of Inner Mongolia, China
文摘In order to investigate the influences of the stoichiometric ratio of B/A (A: gross A-site elements, B: gross B-site elements) and the substitution of Co for Ni on the structures and electrochemical performances of the AB3.5-4.1-type electrode alloys, the La-Mg-Ni-Co system La0.75Mg0.25Ni3.5Mx (M=Ni, Co; x= 0, 0.2, 0.4, 0.6) alloys were prepared by induction melting in a helium atmosphere. The structures and electrochemical performances of the alloys were systemically measured. The results show that the structures and electrochemical performances of the alloys are closely relevant to the B/A ratio. All the alloys exhibit a multiphase structure, including two major phases, (La, Mg)2Ni7 and LaNi5, and a residual phase LaNi2, and with rising ratio B/A, the (La,Mg)2Ni7 phase decreases and the LaNi5 phase increases significantly. When ratio B/A=3.7, the alloys obtain the maximum discharge capacities. The high rate discharge(HRD) capability of the alloy (M=Ni) monotonously rises with growing B/A ratio, but that of the alloy (M=Co) first mounts up then declines. The cycle stability of the alloy (M=Co) monotonously increases with rising B/A ratio, but it first decreases slightly then increases for the alloy (M=Ni). The discharge potential of the alloy (M=Ni) declines with increasing B/A ratio (x>0.2), but for the alloy (M=Co), the result is contrary. The substitution of Co for Ni significantly ameliorates the electrochemical performances. For a fixed ratio B/A=3.7, the Co substitution enhances the discharge capacity from 365.7 to 401.8 mA·h/g, the capacity retention ratio (S100) after 100 charging-discharging cycles from 50.32% to 53.26% and the HRD from 88.65% to 90.69%.
基金the National Natural Science Foundation of China (50701011)Natural Science Foundation of Inner Mongolia, China (200711020703)Science and Technology Planned Project of Inner Mongolia, China (20050205)
文摘In order to improve the cyclic stability of La-Mg-Ni system （Ce2Ni7-type） alloy electrode, small amount of Co was added in La0.75Mg0.25Ni3.5 alloy. The effect of Co on electrochemical performance and microstructure of the alloys were investigated in detail. XRD results showed that the alloys had multiphase structure composed of （La, Mg）2Ni7, LaNi5 and small amount of LaNi2 phases. The discharge capacity of the alloys first increased and then decreased with increasing Co content. At a discharge current density of 900 mA/g, the HRD of the alloy electrodes increased from 81.3% （x=0） to 89.2 % （x=0.2）, and then reduced to 87.8 % （x=0.6）. After 60 charge/discharge cycles, the capacity retention rate of the alloys enhanced from 52.67% to 61.32%, and the capacity decay rate of the alloys decreased from 2.60 to 2.05 mAh/g per cycle with increasing Co content. The obtained results by XPS and XRD showed that the fundamental reasons for the capacity decay of the La-Mg-Ni system （Ce2Ni7-type） alloy electrodes were corrosion and oxidation as well as passivation of Mg and Lain alkaline solution.
基金the National Natural Science Foundation of China(51071054,50861003)the Natural Science Foundation of Guangxi(2010GXNSFD013004)+2 种基金the Foundation of Key Laboratory of National Education Ministry for Nonferrous Metals and Materials Processing Technology(GXKFJ09-15)the Guangxi University Program for Science and Technology Research(XBZ110379)the Innovation Team Project of Guangxi University
基金The PhD Fund Project of Lanzhou University of Technology (BS01200904)Open Foundation of Key Laboratory of the Ministry of Education of Non-ferrous Metal Alloys and Processes (EKL09002)
