Phase structure and cycling stability of A2B7 superlattice La0.60Sm0.15Mg0.25Ni3.4 metal hydride alloy. (21st January 2016)

• Record Type: Journal Article
• Authors: Zhang, Lu; Ding, Yanqiao; Zhao, Yumeng; Du, Wenkai; Li, Yuan; Yang, Shuqin; Han, Shumin
• Is Part Of: International journal of hydrogen energy. Volume 41:Number 3(2016)
• Page Start: 1791
• Page End: 1800
• Publication Date: 2016-01-21
• Subjects: Nickel metal hydride battery -- La–Mg–Ni-based alloy -- Samarium -- Phase structure -- Cycling stability; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2015.12.049
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: Improvement in cycling stability is a key issue for La–Mg–Ni-based alloys to be widely applied as anode electrode materials of nickel metal hydride batteries. In this paper, we report the phase structure and melioration of cycling stability of a Sm-containing A2 B7 -type La–Mg–Ni-based alloy. Sm element promotes the Gd2 Co7 -type phase formation with increasing annealing period, which the Ce5 Co19 -, CaCu5 - and MgCu4 Sn-type phases in as-cast La0.60 Sm0.15 Mg0.25 Ni3.4 alloy are successively eliminated as the annealing time increases from 6 to 24 h at 950 °C and forms a single A2 B7 -type alloy with coexistence of 73.2 wt.% Gd2 Co7 - and 26.8 wt.% Ce2 Ni7 -type phases. The single A2 B7 -type La0.60 Sm0.15 Mg0.25 Ni3.4 alloy is superior in discharge capacity (382 mAh g −1 ) and high rate dischargeability (40% at a 1500 mA g −1 discharge current density). Especially, the cycling stability of the alloy is enhanced to 87.7% at the 100th cycle. The improved cycling stability of the single A2 B7 -type alloy is mainly attributed to its slower growth of inner strain during charging/discharging, which improves anti-pulverization/amorphization ability, and drops oxidation degree of the alloy. Therefore, Sm is a positive element in improvement of the cycling stability property of the La–Mg–Ni-based alloys. Highlights: Single A2 B7 -type Sm-containing La0.60 Sm0.15 Mg0.25 Ni3.4 alloy was obtained. Sm element promotes formation of Gd2 Co7 -type phase, reaching 73.2 wt.%. Single A2 B7 -type alloy shows superior HRD 1500, achieving 40%. Cycling stability of single A2 B7 -type alloy is enhanced to 87.7% at 100th cycle. Slower inner strain growth during cycling of single alloy ascribes to improved S 100 .