Study on solid solubility of Mg in Pr3−xMgxNi9 and electrochemical properties of PuNi3-type single-phase RE–Mg–Ni (RE=La, Pr, Nd) hydrogen storage alloys

• Published in: Electrochimica acta Vol. 173; pp. 200 - 208
• Main Authors: Zhang, Lu, Du, Wenkai, Han, Shumin, Li, Yuan, Yang, Shuqin, Zhao, Yumeng, Wu, Cong, Mu, Hanzhou
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 10.08.2015
• Subjects: Electrochemical Property; Ni/MH secondary battery; Phase transformation; Pr2MgNi9; Solid solubility; Phase transformation; Electrochemical Property; Ni/MH secondary battery; Solid solubility; Pr2MgNi9
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2015.05.049

•PuNi3-type single phase La2MgNi9, Pr2MgNi9 and Nd2MgNi9 alloys were obtained.•Mg enters into Pr2 sites of PuNi3 and reaches the maximum solid solubility to 1.0.•Phase transformation occurs to raise the phase with more [A2B4] as increasing Mg.•Pr2MgNi9 alloy exhibits preferable cycling stability and HRD. In this paper, via adjusting Mg content in Pr3−xMgxNi9 (x=0.45−1.2) alloys, a PuNi3-type single-phase Pr2MgNi9 alloy was obtained by powder-sintering method. The solid solubility of Mg in PuNi3-type phase and phase transformation of Pr3−xMgxNi9 (x=0.45−1.2) alloys at 1173K sintering temperature, as well as hydrogen storage properties of single-phase RE2MgNi9 (RE=La, Pr, Nd) alloys were subsequently studied. We found that when x increased from 0.45 to 1.0, entrance of Mg into Pr2 sites of PuNi3-type phase resulted in a phase transformation from Gd2Co7-type to PuNi3-type, reaching the maximum solid solubility at x=1.0 with a PuNi3-type single phase at 1173K. As x further increased to 1.2, an MgCu4Sn-type secondary phase formed. That was the phase transformation occurs to increase the super-stacking phase possessing more [A2B4] slabs with increase of Mg content. Electrochemical results showed that single-phase alloy had good discharge capacity and superior cycling stability. Comparing with PuNi3-type single-phase La2MgNi9 and Nd2MgNi9 alloys, PuNi3-type single-phase Pr2MgNi9 alloy also exhibited preferable cycling stability and high rate dischargeability (HRD), which were 86.3% (at 100 cycles) and 56.7% (at a current density of 1500mAg−1), respectively.