Comparison among Constituent Phases in Superlattice Metal Hydride Alloys for Battery Applications

Kwo-Hsiung Young,Taihei Ouchi,Yu-Ling Lien,Jean Nei,John Koch

doi:10.3390/batteries3040034

Kwo-Hsiung Young, Taihei Ouchi + Show 3 more

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https://doi.org/10.3390/batteries3040034

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Journal: Batteries	Publication Date: Oct 31, 2017
Citations: 9	License type: CC BY 4.0

Affiliation: Wayne State University, Michigan State University

Abstract

The effects of seven constituent phases—CeNi3, NdNi3, Nd2Ni7, Pr2Ni7, Sm5Ni19, Nd5Co19, and CaCu5—on the gaseous phase and electrochemical characteristics of a superlattice metal hydride alloy made by induction melting with a composition of Sm14La5.7Mg4.0Ni73Al3.3 were studied through a series of annealing experiments. With an increase in annealing temperature, the abundance of non-superlattice CaCu5 phase first decreases and then increases, which is opposite to the phase abundance evolution of Nd2Ni7—the phase with the best electrochemical performance. The optimal annealing condition for the composition in this study is 920 °C for 5 h. Extensive correlation studies reveal that the A2B7 phase demonstrates higher gaseous phase hydrogen storage and electrochemical discharge capacities and better battery performance in high-rate dischargeability, charge retention, and cycle life. Moreover, the hexagonal stacking structure is found to be more favorable than the rhombohedral structure.

Highlights

Misch metal (Mm, a mixture of more than one rare earth element)-based superlattice metal hydride (MH) alloys are very important for today’s nickel/metal hydride (Ni/MH) batteries, because of their higher hydrogen storage (H-storage) capacity, better high-rate dischargeability (HRD) capability, superior low-temperature and charge retention performances, and improved cycle stability [1,2,3,4,5,6,7,8].The three main components in the superlattice alloy can be classified by chemical stoichiometry—or more precisely, the B/A ratio—and they are AB3, A2 B7, and A5 B19
Two common constituent elements used in the AB5 MH alloy, Mn and Co, are excluded in this study for better charge retention and cycle stability [1,73]
C15-based MH alloys behave differently in the EC environment, and we have reported the comparison containing the NdNi3, Pr2Ni7, and Nd5Co19 phases shares the same A2B4 stacking as the C15 previously [82] and concluded that the C14-predominated alloy is more suitable for high-capacity and structure

Summary

Introduction

Misch metal (Mm, a mixture of more than one rare earth element)-based superlattice metal hydride (MH) alloys are very important for today’s nickel/metal hydride (Ni/MH) batteries, because of their higher hydrogen storage (H-storage) capacity, better high-rate dischargeability (HRD) capability, superior low-temperature and charge retention performances, and improved cycle stability [1,2,3,4,5,6,7,8].The three main components in the superlattice alloy can be classified by chemical stoichiometry—or more precisely, the B/A ratio—and they are AB3 , A2 B7 , and A5 B19. Misch metal (Mm, a mixture of more than one rare earth element)-based superlattice metal hydride (MH) alloys are very important for today’s nickel/metal hydride (Ni/MH) batteries, because of their higher hydrogen storage (H-storage) capacity, better high-rate dischargeability (HRD) capability, superior low-temperature and charge retention performances, and improved cycle stability [1,2,3,4,5,6,7,8]. H-storage characteristics of the single rare earth element (RE)-based AB3 alloys [10,11,12] and soon shifted to the Mm-based A2 B7 chemistry for battery applications [13,14,15,16].

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