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Fan Y.,Henan Polytechnic University | Liu B.,Henan Polytechnic University | Zhang B.,Henan Polytechnic University | Ji L.,Inner Mongolia Rare Earth Ovonic Metal Hydride Co. | Zhang Z.,Henan Polytechnic University
Journal of Rare Earths | Year: 2012

Phase structure and electrochemical characteristics of Co-free La 0.7Ce0.3(Ni3.65Cu0.75Mn 0.35Al0.15(Fe0.43B0.57) 0.10)x (0.90≤x≤1.10) alloys were investigated. When x was 0.90, the alloy was composed of LaNi5, La3Ni 13B2 and Ce2Ni7 phases. The Ce 2Ni7 phase disappeared, and the abundant of La 3Ni13B2 phase decreased when x increased to 0.95. When x was 1.00 or higher the alloys consisted of LaNi5 phase. The lattice parameter a and the cell volume V of the LaNi5 phase decreased, and the c/a ratio of the LaNi5 phase increased with x value increasing. Maximum discharge capacity of the alloy electrodes first increased and then decreased with x value increasing from 0.90 to 1.10, and the highest value was obtained when x was 1.00. High-rate dischargeability at the discharge current density of 1200 mA/g increased from 50.7% (x= 0.90) to 64.1% (x=1.10). Both the charge-transfer reaction at the electrode/electrolyte interface and the hydrogen diffusion in the alloy were responsible for the high-rate dischargeability. Cycling capacity retention rate at 100th cycle (S100) gradually increased from 77.3% (x= 0.90) to 84.6% (x=1.10), which resulted from the increase in Ni content and the c/a ratio of the LaNi5 phase with x value increasing. © 2012 The Chinese Society of Rare Earths.


Peng X.,Henan Polytechnic University | Liu B.,Henan Polytechnic University | Fan Y.,Henan Polytechnic University | Ji L.,Inner Mongolia Rare Earth Ovonic Metal Hydride Co. | And 2 more authors.
Electrochimica Acta | Year: 2013

Microstructures and electrochemical characteristics of La 0.7Ce0.3Ni4.2Mn0.9-xCu 0.37(V0.81Fe0.19)x hydrogen storage alloys were investigated. X-ray diffraction and scanning electron microscope results indicate that La0.7Ce0.3Ni4.2Mn 0.9Cu0.37 alloy is single LaNi5 phase, and the alloys containing V0.81Fe0.19 consist of LaNi5 matrix phase and V-Mn-Ni secondary phase, and the abundance of secondary phase increases with increasing x value. The activation property of the alloy electrodes is improved by increasing V0.81Fe0.19 content. Maximum discharge capacity of the alloy electrodes changes a little with increasing x value. HRD1200 first increases from 60.4% (x = 0) to 70.8% (x = 0.10), and then decreases to 56.6% (x = 0.20). Cycling stability decreases with increasing x from 0 to 0.20. The adequate substitution of Mn by V0.81Fe0.19 can improve overall electrochemical performances of Co-free high-Mn AB5 alloy. © 2013 Elsevier Ltd. © 2013 Elsevier Ltd. All rights reserved.


Peng X.,Henan Polytechnic University | Liu B.,Henan Polytechnic University | Fan Y.,Henan Polytechnic University | Zhu X.,Inner Mongolia Rare Earth Ovonic Metal Hydride Co. | And 2 more authors.
Journal of Power Sources | Year: 2013

Microstructures and electrochemical characteristics of La 0.7Ce0.3Ni4.2Mn0.9-xCu 0.37(Fe0.43B0.57)x (x = 0-0.20) hydrogen storage alloys are investigated. X-ray diffraction and backscattered electron results indicate that the pristine alloy is single LaNi5 phase while the alloys containing Fe0.43B0.57 consist of LaNi5 matrix phase and La3Ni13B2 secondary phase. The relative abundance of La3Ni13B 2 phase increases with the increase in x value. The a and V of LaNi5 phase increase with increasing x value. Activation property of the alloy electrodes is improved by substituting Mn with Fe0.43B 0.57. Maximum discharge capacity of the alloy electrodes monotonically decreases from 323.3 mAh g-1 (x = 0) to 311.3 mAh g-1 (x = 0.20). Cycling capacity retention rate at the 100th cycle decreases from 79.3% (x = 0) to 68.2% (x = 0.20) with increasing x value, which is ascribed to the degradation of corrosion resistance. High-rate dischargeability of the alloy electrodes first increases with increasing x from 0 to 0.10, and then decreases until x increases to 0.20. It demonstrates that the substitution of Mn with Fe0.43B0.57 is an effective approach to improve the overall electrochemical performances of the Co-free high-Mn alloy electrodes. © 2013 Elsevier B.V.All rights reserved.


Liu J.,Yanshan University | Han S.,Yanshan University | Li Y.,Yanshan University | Yang S.,Yanshan University | And 3 more authors.
Journal of Alloys and Compounds | Year: 2013

In this paper, the phase transformation and electrochemical characteristics of the as-cast and annealed La0.75Mg0.25Nix (x = 3.0, 3.3, 3.5, 3.8) alloys were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), pressure composition isotherm (PCI) and electrochemical measurements. The as-cast alloys were composed of LaNi 5, (La,Mg)2Ni7 and (La,Mg)Ni3 phases. Phase transformation of LaNi5 and (La,Mg)Ni3 phases into (La,Mg)2Ni7 phase occurred during annealing treatment, leading to the increase of the (La,Mg)2Ni7 phase and decrease or even depletion of the LaNi5 and (La,Mg)Ni3 phases. The two plateaus observed in P-C isotherms of the as-cast alloys tended to become single and the plateau pressure dropped after the phase transformation by annealing. Electrochemical study showed that for the alloy electrodes with and without annealing treatment, the maximum discharge capacity and HRD initially increased then decreased with × increasing from 3.0 to 3.8. The transformation of the LaNi5 and (La,Mg)Ni3 phases into (La,Mg)2Ni7 phase favored the maximum discharge capacity and cycling stability but suppressed the activation as well as HRD of the La0.75Mg0.25Nix (x = 3.0, 3.3, 3.5, 3.8) alloy electrodes. The annealing treatment significantly improved the cycling stability of the alloy electrodes by alleviating the pulverization and oxidation degree of the electrode alloys. © 2012 Elsevier Ltd. All rights reserved.


Liu B.,Henan Polytechnic University | Peng X.,Henan Polytechnic University | Fan Y.,Henan Polytechnic University | Ji L.,Inner Mongolia Rare Earth Ovonic Metal Hydride Co. | And 2 more authors.
International Journal of Electrochemical Science | Year: 2012

Microstructures and electrochemical characteristics of LaNi3.55Co0.2-xMn0.35Al0.15Cu0.75(V0.81Fe0.19)x hydrogen storage alloys were investigated. X-ray diffraction and Backscatter electron results indicate that LaNi3.55Co0.2Mn0.35Al0.15Cu0.75 alloy is single LaNi5 phase, and the alloys containing V0.81Fe0.19 consist of LaNi5 phase, Ni-rich second phase and La-rich segregation, and the abundant of secondary phase increases with increasing x value. The activation property of the alloy electrodes is improved by increasing V0.81Fe0.19 content. Maximum discharge capacity of the alloy electrodes first increases from 325.9 mAh/g (x = 0) to 330.3 mAh/g (x = 0.05), and then decreases to 301.3 mAh/g (x = 0.20). HRD1200 first increases from 43.3% (x = 0) to 58.5% (x = 0.05), and then decreases to 47.4% (x = 0.20). Cycling stability decreases with increasing x from 0 to 0.20. The adequate substitution of Co by VFe can improve the electrochemical performances and reduce the raw cost of alloy electrode. © 2012 by ESG.

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