Effect of Scandium on the Structure and Electrochemical Properties of La1-xScxNi3.5 Alloy Electrodes
Effect of Scandium on the Structure and Electrochemical Properties of La1-xScxNi3.5 Alloy Electrodes
复制标题
钪对La1-xScxNi3.5合金电极结构和电化学性能的影响
DOI：
10.20964/2018.01.56
复制
发表时间：
2018
影响因子：
1.5
通讯作者：
Bian He
中科院分区：
文献类型：
--
作者：
Gao Zhijie;Zhang Bo;Bian He
采用电弧炉法制备了La-Sc-Ni基A2B7型储氢合金La1-xScxNi3.5（x = 0.0~1.0），并在1173 K下于密封不锈钢管中保温一周。XRD和SEMEDS结果表明，该合金主要由LaNi5、La2Ni7和少量LaNi相组成。当添加适量Sc时(x=0.3~0.5)，(La,Sc)2Ni7相增加，LaNi5和LaNi相减少。此外，Sc含量的进一步增加导致Sc2Ni7相的出现。热力学分析表明，La-Mg-Ni-H2体系的La0.7Sc0.3Ni3.5-H2的焓变更接近-7.5 kcal mol -1，而其平衡吸/解吸氢压力平台仍高于La-Mg-Ni体系，这表明含Sc合金的相规则与含镁合金不同。与纯La2Ni7合金相比，添加适量的Sc含量（x=0.3~0.5），最大放电容量增加，循环稳定性提高。特别是当x=0.5时，循环稳定性（S100）高达92.6%，明显优于A2B7型和AB5型储氢合金。我们希望我们的实验结果能够通过调整超晶格结构来开发新型La-Sc-Ni基储氢合金。
La-Sc-Ni based A2B7-type hydrogen storage alloys La1-xScxNi3.5 (x = 0.0~1.0) is prepared by an arc furnace method and maintained for a week in a sealed stainless steel tube at 1173 K. XRD and SEMEDS results show that the alloys are mainly consisted of LaNi5, La2Ni7 and minor LaNi phases. Under appropriate amount of Sc addition (x = 0.3~0.5), the (La, Sc)2Ni7 phase increases whereas the LaNi5 and LaNi phases decreases. Moreover, the further increase of Sc content results in appearance of Sc2Ni7 phase. The thermodynamic analyses show that the enthalpy change of La0.7Sc0.3Ni3.5-H2 is more close to -7.5 kcal mol -1 for the La-Mg-Ni-H2 system while the equilibrium absorption/desorption hydrogen pressure plateau of that is still higher than La-Mg-Ni systems, which indicate that the phase rule of Sc-containing alloy is different from Mg-containing alloy. Compared to pure La2Ni7 alloy, the maximum discharge capacity increases and the cycle stability improves by adding the right amount of Sc content (x = 0.3~0.5). Especially when x = 0.5, the cycle stability (S100) is up to 92.6% which is obviously superior to A2B7-type and AB5 type hydrogen storage alloys. We hope that our experimental results can develop the novel La-Sc-Ni-based hydrogen storage alloys by tuning their superlattice structures.