Electrochemical hydrogen storage properties of non-stoichiometric La _0.7Mg_0.3-xCa_xNi_2.8Co_0.5 (x = 0-0.10) electrode alloys

The microstructure and electrochemical hydrogen storage characteristics of La_0.7Mg_0.3-xCa_xNi_2.8Co _0.5 (x = 0, 0.05 and 0.10) alloys prepared by arc-melting and subsequent powder sintering method are investigated. The electrochemical measurement results show that the cycle stability after 100 charge/discharge cycles first increases from 46.4% (x = 0) to 54.3% (x = 0.05), then decreases to 43.2% (x = 0.10), and the high rate dischargeability increases from 64.5% (x = 0) to 68.5% (x = 0.10) at the discharge current density of 1200 mA/g. The electrochemical impedance spectroscopy analysis indicates that the electrochemical kinetics of the alloy electrodes is improved by increasing Ca. The entire results exhibit that a suitable content of Ca (x = 0.05) can improve the overall electrochemical hydrogen storage characteristics of the alloys.