A high-performance Zn battery based on self-assembled nanostructured NiCo₂O₄ electrode

Abstract

Zn batteries are attractive for energy storage due to their low cost and intrinsic safety. However, the low utilization of active materials results in unsatisfied capacities. Herein, Zn batteries based on nanostructured NiCo2O4 electrodes are developed. Through hydrothermal reactions, porous NiCo2O4 nanosheets, nanowires, and nanoplates are fabricated, which are in-situ grown on the surface of nickel foam substrates, facilitating the electron transport and electrochemical reactions. In particular, the battery with the nanowire electrode exhibits the largest discharge capacity of 230.1 mAh g−1, which accounts for 68.7% of the theoretical capacity of NiCo2O4. Based on the weights of NiCo2O4 and consumed Zn, the energy density of the battery is 301.3 Wh kg−1, higher than most of the reported Zn batteries. At a high current density of 8 A g−1, the capacity is still 164.25 mAh g−1, with the retention of 71.38%, which illustrates the high rate performance. Moreover, after 1000 discharge-charge cycles, the capacity retention is 63.23%, which reveals remarkable cycling stability. The results show that the NiCo2O4 nanowire electrode is attractive for Zn batteries with high capacity, energy density, rate performance, and cycling stability.