Study on microstructure and electrochemical performance of La sub(0.7)Mg sub(0.3)(Ni sub(0.9)Co sub(0.1)) sub(x) hydrogen storage alloys

Hydrogen storage alloys La sub(0.7)Mg sub(0.3)(Ni sub(0.9)Co sub(0.1)) sub(x) (x = 3.0, 3.1, 3.3, 3.4, 3.5, 3.7 and 3.8) were prepared by inductive melting followed by annealing treatment at 1173 K for 6 h. The effects of the stoichiometry (x) on the structural and electrochemical characteristics of...

Full description

Saved in:
Bibliographic Details
Published in:Journal of power sources 2008-12, Vol.185 (2), p.1519-1523
Main Authors: Cheng, L F, Wang, R B, Pu, Z H, Li, Z L, He, D N, Xia, B J
Format: Article
Language:English
Subjects:
Alloys
Annealing
ANNEALING PROCESSES
CURRENT DENSITY
DENSITY
Diffraction
Discharge
HYDROGEN
Hydrogen storage
INTERMETALLIC COMPOUNDS
MICA
MICROSTRUCTURES
MORPHOLOGY
STOICHIOMETRY
STORAGE
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Hydrogen storage alloys La sub(0.7)Mg sub(0.3)(Ni sub(0.9)Co sub(0.1)) sub(x) (x = 3.0, 3.1, 3.3, 3.4, 3.5, 3.7 and 3.8) were prepared by inductive melting followed by annealing treatment at 1173 K for 6 h. The effects of the stoichiometry (x) on the structural and electrochemical characteristics of the alloys were investigated systematically. X-ray diffraction (XRD), optical morphology and energy dispersive spectrometry (EDS) analyses showed that these alloys have a multiphase structure which consists of a (La, Mg)Ni sub(3) phase with the PuNi sub(3)-type rhombohedral structure, a LaNi sub(5) phase with the CaCu sub(5)-type hexagonal structure and a (La, Mg) sub(2)Ni sub(7) phase with the Ce sub(2)Ni sub(7)-type hexagonal structure. The main phase of the alloys with x = 3.0 and 3.1 is (La, Mg)Ni sub(3) phase (PuNi sub(3)-type structure), the main phase of the alloys with x = 3.3, 3.4 and 3.5 is (La, Mg) sub(2)Ni sub(7) phase (Ce sub(2)Ni sub(7)-type structure), and the main phase of the alloys with x = 3.7 and 3.8 is LaNi sub(5) phase (CaCu sub(5)-type structure). Moreover, the lattice parameters of the (La, Mg)Ni sub(3) phase, (La, Mg) sub(2)Ni sub(7) phase and LaNi sub(5) phase decrease monotonously with the increase of the value x. The electrochemical analysis shows that the maximum discharge capacity increases from 356.6 mA h g[super]-1 (x = 3.0) to 392.1 mA h g[super]-1 (x = 3.5) and then decreases to 344.1 mA h g[super]-1 (x = 3.8), and the alloys exhibit good cycling stability. As the discharge current density is 3000 mA g[super]-1, the high-rate dischargeability (HRD) increases from 30.1% (x = 3.0) to 56.1% (x = 3.8). The low temperature dischargeability (LTD) increases from 24.3% (x = 3.0) to 58.96% (x = 3.7) and then decreases to 48.1% (x = 3.8).
ISSN:0378-7753
DOI:10.1016/j.jpowsour.2008.08.005