Mg_3MnNi_(2-x)Co_x(x=0～0.2)储氢合金的相结构及电化学性能研究

The studyon phase structure and electrochemical performance of Mg_3MnNi_(2-x)Co_x(x=0～0.2)hydrogen storage alloys

为了研究Mg3MnNi2储氢合金的电化学储氢性能,实验采用Co元素部分取代Mg3MnNi2合金中的Ni,用固相扩散法制备出Mg3MnNi2-xCox（x=0~0.2）系列合金,并分析其相结构,以及测试合金的电化学性能和动力学性能。结果表明：Co元素的添加并不改变合金的主相,Co替代Ni明显改善了合金的放电容量、循环稳定性以及动力学性能等,其中当Co的含量从0增加到0.2时,合金的最大放电容量达到最大值282.36mA·h/g,20次循环后容量保持率仍有74.7%,而且动力学性能也是最优,高倍率放电性能ηHRD从66.4%增长到73.3%。这主要是Co替代Ni能够降低生成氢化物的稳定性,提高合金的抗粉化能力,以及降低合金的极化电阻。

In order to study the electrochemical hydrogen storage characteristics of the Mg3MnNi2 alloy,the Mg3MnNi2-xCox（x=0~0.2）hydrogen storage alloys were synthesized by sinering method,in which Ni was partially substituted by Co in the alloys.The phase structure was analysed,and the electrochemical performance and dynamics performance were tested.The results show that the principal phase of alloys has not changed after the substituting Ni with Co.The substitution of Co for Ni clearly improves the discharge capacity,cycling stability,dynamics performance and so on.As Co content increase from 0to 0.2,the maximum discharge capacity（Cmax）of the alloy increases to 282.36mA·h/g,the retention capacity still has 68.4% after 20 times cycle.And the dynamics performance is optimal,the high-rate discharge ability increases from 66.4% to 73.3%.This is mainly due to the substitution of Co for Ni reduces the stability of the hydride,increases the anti-pulverization ability of alloys,and reduces the polarization resistance.