Cobalt-free nickel–metal hydride battery for industrial applications

► The development of RE0.9Mg0.1Ni3.9Al0.2 alloy (alloy#1) electrode. ► Good high-rate discharge using alloy#1 as negative electrode. ► Effective self-discharge suppression using alloy#1 as negative electrode. ► Adequate cycling durability using carbon-coated Ni(OH)2 as positive electrode. ► Good high-rate characteristics in a large-sized Co-free Ni–MH battery. A cobalt-free (Co-free) RE0.9Mg0.1Ni3.9Al0.2 alloy (RE: rare earth) was prepared for use in a nickel–metal hydride (Ni–MH) battery. The use of the alloy as the negative electrode of the Ni–MH battery effectively improved the high-rate discharge and suppressed the self-discharge compared to the conventional AB5-type alloy. Moreover, carbon-coated Ni(OH)2 has been developed to produce a Co-free Ni–MH battery. This material exhibits a capacity retention comparable to that of the conventional CoOOH-coated Ni(OH)2. A 205Ah Co-free Ni–MH battery cell was constructed using the Co-free materials, and this cell exhibited a good high-rate discharge performance.