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Investigation of alloy structure shows that La_ 2-x Mg_xNi_7(x=0.3～0.8) alloys are mainly composed of Ce_2Ni_7-type, Gd_2Co_7-type and PuNi_3-type phase. The influence of Mg content in alloys on the phase structure is great, resulting in a linear decrease of the unit cell parameters of main phases and increase of hydrogen absorption/desorption plateau as Mg content increases. Electrochemical measurements show that as the Mg content increases, the discharge capacity of alloy electrodes first increases and then decreases. The cyclic stability presents a deteriorative trend, La_ 1.4 Mg_ 0.6 Ni_7 alloy electrode exhibits the maximum electrochemical discharge capacity (378 mAh·g~ -1 ), and the La_ 1.6 Mg_ 0.4 Ni_7 alloy electrode shows the best cyclic stability (S_ 270 =81%). The high rate dischargeability increases with the increase of Mg content. When the Mg content (x) is lower than 0.5, the rate-determining step of the electrode reaction is the diffusion of hydrogen in bulk. When the Mg content (x) is higher than 0.5, the control progress of the electrode reaction is converted to charge-transfer on the alloy surface.
The influence of Mg content in alloys on the phase structure is very large. The influence of Mg content on the phase structure of La_2-x Mg_xNi_7 (x = 0.3-0.8) alloys is mainly composed of Ce_2Ni_7-type, Gd_2Co_7-type and PuNi_3- resulting in a linear decrease of the unit cell parameters of main phases and increase of hydrogen absorption / desorption plateau as Mg content increases, the discharge capacity of alloy electrodes first increases and then decreases. The cyclic stability presents a deteriorative trend, La_1.4Mg_0.6Ni_7 alloy electrode exhibits the maximum electrochemical discharge capacity (378 mAh · g ~ -1), and the La_1.6Mg_0.4 Ni_7 alloy electrode shows the best cyclic stability (S_201 = 81%). . The high rate dischargeability increases with the increase of Mg content. When the Mg content (x) is lower than 0.5, the rate-determining step of the electrode reaction is the diffusion of hydrogen in bulk. Mg content (x) is higher than 0.5, the control progress of the electrode reaction is converted to charge-transfer on the alloy surface.