Kinetics and electrochemical characteristics of Mg₂NiH₄-x wt.% MmNi_3.8Co_0.75Mn_0.4Al_0.2 (x聽=聽5, 10, 20, 40) composites for Ni-MH battery

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• 作者：Zhenggan Pu ; Yunfeng Zhu ; Jinyu Zhu ; Jianguang Yuan ; Jiguang Zhang ; Wei Chen ; Jiaojiao Fang ; Liquan Li
• 关键词：Hydrogen storage alloy electrode ; Mg-based alloy ; Mechanical milling ; Electrochemical characteristics ; Kinetics
• 刊名：International Journal of Hydrogen Energy
• 出版年：6 March, 2014
• 年：2014
• 卷：39
• 期：8
• 页码：3887-3894
• 全文大小：3060 K

文摘

The structure, kinetics and electrochemical characteristics of Mg₂NiH₄-x wt.% MmNi_3.8Co_0.75Mn_0.4Al_0.2 (x聽=聽5, 10, 20, 40) composites prepared by mechanical milling have been investigated in this paper. XRD results indicate that the as-milled Mg₂NiH₄ shows nanocrystalline or amorphous-like structure, and it does not react with MmNi_3.8Co_0.75Mn_0.4Al_0.2 during mechanical milling. As the amount of MmNi_3.8Co_0.75Mn_0.4Al_0.2 increases, the maximum discharge capacity decreases initially from 508聽mAh/g (x聽=聽5) to 440聽mAh/g (x聽=聽10) and then increases to 509聽mAh/g (x聽=聽40). Meanwhile, the capacity retention (R₁₀) increases from 12.8% (x聽=聽5) to 23.4% (x聽=聽40), and the corrosion potential of electrode (E_corr) increases from 鈭?.930聽V to 鈭?.884聽V (vs. Hg/HgO). Especially, the more MmNi_3.8Co_0.75Mn_0.4Al_0.2 content the composite contains, the higher high rate dischargeability (HRD) the electrode exhibits, which could be attributed to the catalytic reaction and reduction of the Mg₂NiH₄ grain size brought by MmNi_3.8Co_0.75Mn_0.4Al_0.2. The improvement in electrode kinetics has been depicted from the bulk hydrogen diffusion coefficient (D), the exchange current density (I₀) and the charge transfer resistance (R_ct) on the alloy surface.