Flexible self-supported bi-metal electrode as a highly stable carbon- and binder-free cathode for large-scale solid-state zinc-air batteries

Abstract

Flexible (Ni, Co)3O4 nanosheets are grown on the surface of a Ni-foam by a facile electrodeposition coupled electrochemical oxidation process. The as-synthesized (Ni, Co)3O4 nanosheets are self-supported and can be directly used as the oxygen electrode without an addition of carbon or binder. As expect, the physical measurements and density functional theory (DFT) calculation reveal that Ni doping decreases Co3O4 surface activity towards the O, OH, OOH species, thus reducing the OER and ORR over-potentials. As a result, the (Ni, Co)3O4@Ni-foam electrode exhibits an unprecedented performance with a lower potential gap (⊗E: 0.57 V) than Pt/C+IrO2. This nanosheet can be readily applied as an electrode for Zn-air battery with a large area up to 24 cm2. The improved performance of this large-area electrode includes: a small charge-discharge voltage drop (0.56 V) and super stability with a high voltage efficiency of 69 % across all cycles.