Effects of Co3O4 as additive on the performance of metal hydride electrode and Ni–MH battery

In this paper, the performance of metal hydride electrodes prepared with different amounts of tricobalt tetraoxide (Co3O4) and AA size cylindrical Ni–MH battery with the capacity of 1500 mAh prepared with Co3O4 as negative additive has been investigated. The investigation reveals that the charge and discharge efficiency at 1400 mA g−1 at room temperature, and the discharge efficiency at 140 mA g−1 at −20 °C of metal hydride electrode are increased from 82.2% to 92.4%, from 55.1% to 84.7%, and from 30.2% to 68.8%, respectively, by adding proper amounts of Co3O4. Furthermore, it is also found that the high-rate and low-temperature discharge ability, overcharge endurance ability, cycle life, inner pressure of battery are greatly improved by adding Co3O4. These results can be attributed to the high electrocatalytic activity and extended hydride storage capability of Co3O4, the improvement of gas consumption ability and the restraining of oxidation of electrode alloys by adding Co3O4.

► The effects of Co3O4 on the performance of MH electrode and Ni/MH battery were investigated.
► The discharge efficiency of MH electrode at −20 °C increased from 22.54% to 68.82% by adding Co3O4.
► The discharge capacity of Ni/MH battery with Co3O4 as negative additive at −20 °C increased 46.9 mAh.
► The discharge capacity of Ni/MH battery with Co3O4 as negative additive at 50 °C increased 32.5 mAh.
► A new possible influencing mechanism was proposed.