系统地研究了Al含量对富Ce储氢合金MmNi4-xCo0.7Mn0.3Alx(x=0,0.1,0.2,0.3)电极综合电化学性能,尤其是对低温和高倍率性能的影响.在常温下,储氢合金电极放电容量和循环性能均随着Al含量的增加而增加,而高倍率放电性能严重下降.-20℃时,放电容量仍随着Al含量的增加而增加,但在-40℃下放电容量随之严重衰退.电化学动力学结果表明,常温下高Al合金高倍率性能的降低主要是由于电极表面电荷转移过程的恶化;低温-40 ℃下,Al同时降低了合金电极的表面电催化活性以及体相H扩散能力,严重恶化电极过程动力学,从而导致了高Al合金极低的容量及电压输出.考虑到各电极的综合电化学性能,MmNi3.8Co0.7Mn0Al0.2为最佳的成分配比.%Effects of Al content on the comprehensive electrochemical performance of Ce-rich MmNi4-xCo0.7Mn0.3Alx (x=0,0.1,0.2,0.3) hydrogen storage alloys,particularly the low-temperature and high-rate capacity have been systematically investigated.At room temperature,both the discharge capacity and cycling stability of the electrode increase with the Al content increases,but the high-rate dischargeability seriously deteriorates.The discharge capacity still increases with the increase of Al content at-20 ℃,but gradually deteriorates when the temperature drops down to-40 ℃.Electrochemical kinetics results demonstrate that the high-rate capacity recession of the high-Al alloy at room temperature is contributed to the deterioration of the charge-transfer process.When the temperature drops down to-40 ℃,Al deteriorates both the surface catalytic ability and the bulk hydrogen diffusion ability,leading to the severe drop of discharge capacity and potential of the high-Al alloy.Based on the comprehensive electrochemical properties of the electrodes,the optimal composition of MmNi4-xCo0.7Mn0.3Alx is obtained when x=0.2.
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