Co8S9/CoO–NiS2/NiO Dual-Heterostructured Nanosheet Arrays as Efficient Cathode Materials for Rechargeable Hybrid Zinc Batteries

Hybrid zinc batteries (HZBs) can deliver high cell voltage and high capacity by combining the Faradaic redox reactions of transition metals and the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the cell level. However, their performance is still far from satisfactory owing to the limited electrochemical activities of cathode materials. Herein, a cathode material of Co8S9/CoO–NiS2/NiO dual-heterostructured nanosheet arrays is developed based on a partial sulfidation strategy for rechargeable HZBs. The synergistic effect of transitional metal sulfide/oxide through the formation of sophisticated heterostructures not only enhanced conductivity and exposed more active sites but also significantly improved the intrinsic activities for Faradaic reaction and catalytic ORR/OER. This cathode material endowed the battery with outstanding cycling stability continued for 9000 cycles (over 2734 h) with a flat and high discharge voltage plateau of 1.67 V at 10 mA cm–2 and excellent rate capability at a discharge current density of up to 40 mA cm–2 in KOH electrolyte. Moreover, a superior discharge areal capacity of 3.90 mA h cm–2 is achieved at 10 mA cm–2 without increasing the loading amount of electrochemically active materials. This work offers a promising strategy of partial sulfidation for the development of cathode materials for realizing conceptual breakthroughs of HZBs with high voltage, cycling stability, rate capability, and areal capacity.