Microstructure-tuned cobalt oxide electrodes for high-performance Zn–Co batteries

The insufficient utilization of active material results in the poor performance of Zn–Co batteries. In this work, by adjusting the key parameters in the synthesis process, the Co₃O₄ electrodes with different pore size distributions, morphologies, and loadings are fabricated. The effects of the tuned microstructures on three-electrode and battery systems are compared carefully. In this way, a heterogeneous porous nanowire structure with reasonable loading is constructed for the first time, which shows the optimal performance. Particularly, a Zn–Co battery with this electrode exhibits a high capacity of 230.0 mAh g⁻¹ with a utilization ratio of 51.6% and a decent energy density of 308.8 Wh kg⁻¹ based on the weight of Co₃O₄ and Zn plate. Besides, with an increase of the current densities from 0.5 to 10 A g⁻¹, the capacity drops from 230.0 to 144.0 mAh g⁻¹ with the capacity retention of only 62.6%. Moreover, the battery can operate 3000 cycles (up to 547 h) with a retention ratio of 66.8%, illustrating excellent stability. This work gives an ultrahigh-capacity Co₃O₄ electrode benefiting from the novel-designed structure, which dramatically improves the utilization level of the active materials, leading to high and stable battery performance.