Pr替代Ti对TiFe系储氢合金微观结构和电化学性能的影响

Effect of Pr substitution of Ti on microstructure and electrochemical properties of TiFe based hydrogen storage alloy

采用感应熔炼法制备Ti_(1.1-x)Pr_(x)Fe_(0.6)Ni_(0.3)Mn_(0.2)(x=0, 0.04, 0.06, 0.08)合金,通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、蓝电电池测试等手段对合金的显微组织结构和电化学性能进行分析。XRD结果表明:合金基体相为TiFe,以及少量的ZrMn2第二相,添加Pr未改变合金相组成,但使合金的晶胞体积随Pr含量的增加而增大。SEM分析结果表明:大部分Pr在晶界处偏聚成团,基体为固溶Ni的TiFe相,同时基体表面偏聚大量ZrMn2相。电化学性能测试结果表明:该系列合金经过3次活化就可达到最大放电比容量,活化性能较好,Pr元素替代后合金电极的最大放电比容量提高到54.1 mAh·g^(-1);高倍率测试表明,该合金的高倍率放电性能较差,Pr元素替代后也未能提高高倍率性能;循环寿命测试表明,x=0.08时合金电极循环50次的容量保持率高达90.42%,说明Pr元素替代对合金的循环性能有较大提升。

Ti_(1.1-x)Pr_(x)Fe_(0.6)Ni_(0.3)Mn_(0.2)(x=0, 0.04, 0.06, 0.08) alloy was prepared by induction melting method, which was tested by X-ray diffractometer(XRD), scanning electron microscope(SEM), and LAND battery test system. And other methods to analyze the microstructure and electrochemical properties of the alloy. XRD results showed that the matrix phase of the alloy was TiFe and a small amount of the second phase of ZrMn2. The addition of Pr did not change the composition of the alloy phase, but the alloy cell volume increased with the increase of Pr content. SEM analysis showed that most of Pr was segregated into agglomerates at grain boundaries, the matrix phase was TiFe phase of solid solution Ni, and a large amount of ZrMn2 phase was segregated on the surface of the matrix. Electrochemical performance test results showed that this series of alloys could reach the maximum discharge specific capacity after 3 activations, and the activation performance was good. After Pr element substitution, the maximum discharge specific capacity of the alloy electrode increased to 54.1 mAh·g^(-1). High rate tests showed that the high-rate discharge performance of the alloy was poor, and the high-rate performance had not been improved after the Pr element substitution. The cycle life test showed that the capacity retention rate of the alloy electrode for 50 cycles at x=0.08 was as high as 90.42%, indicating Pr element substitution had greatly improved the cycling performance of the alloy.