双希夫碱对AB_3型储氢合金的表面改性研究

Surface Modification of AB_3-type Hydrogen Storage Alloy by Double Schiff Base

目的提高Ni/MH二次电池中AB3型储氢合金负极的充放电性能与动力学性能。方法合成一种双希夫碱作为表面改性剂,添加到AB3型储氢合金La0.73Ce0.18Mg0.09Ni3.20Al0.21Mn0.10Co0.60中,进行表面处理,考察添加不同含量的双希夫碱对合金充放电性能及动力学性能的影响。结果紫外与红外图谱显示,合成了目标双希夫碱。合金添加双希夫碱后,合金的相结构基本没有发生变化。表面处理后的合金与未改性合金相比,最大放电容量从375.3 m Ah/g增加至376.4 m Ah/g,相对变化不大,50次充放电循环后的放电容量保持率从62.6%提高到81.1%(AB3/5%双希夫碱电极)。经过表面处理后的合金电极,腐蚀电位Ec从-0.902 V增至-0.853 V,交换电流密度I0从53.8 m A/g增至142.5 m A/g,极限电流密度IL从511.6 m A/g增至872.8 m A/g,交流阻抗图显示电极与电解液间的电荷转移阻抗减小。结论添加了双希夫碱的合金,循环稳定性、腐蚀电位等综合电化学性能有了较大改善。合金添加双希夫碱后,对强碱电解液的抗腐蚀能力有所增强,这是一种行之有效的合金表面处理方法。

Objective To improve the charge-discharge and kinetic properties of AB3-type hydrogen storage alloy electrode of Ni/MH rechargeable batteries. Methods A kind of double Schiff base was synthesized. AB3-type hydrogen storage alloy La0. 73 Ce0. 18 Mg0. 09 Ni3. 20 Al0. 21 Mn0. 10 Co0. 60 was modified by using double Schiff base as a modifier, and the effect of adding different＆amp;nbsp;amount of double Schiff base on the charge-discharge and kinetic properties of the treated alloy were systematically investigated. Results The UV spectrogram and the infrared spectrogram showed that the target double Schiff base was synthesized. After surface treatment, the phase structure was not changed. The maximum discharge capacity increased from 375. 3 mAh/g to 376. 4 mAh/g, which was not a big change. After 50 cycles, the cycle stability of the alloy electrodes was improved from the original 62. 6% to 81. 1% （adding 5% double Schiff base）. Moreover, the corrosion potential Ec increased from -0. 902 V to -0. 853 V, the ex-change current density I0 increased from 53. 8 mA/g to 142. 5 mA/g, the limiting current density IL increased from the original 511. 6 mA/g to 872. 8 mA/g, and the electrochemical impedance spectra showed that the charge-transfer resistance between the al-loy surface and the electrolyte decreased. Conclusion The comprehensive electrochemical properties such as cycle stability and the corrosion potential were considerably improved after the addition of double Schiff base. The double Schiff enhanced the corrosion re-sistance of the alloy in the alkali electrolyte. So adding double Schiff base was a good way to improve the comprehensive electro-chemical properties of hydrogen storage alloy.