Synchronous coupling of defects and a heteroatom-doped carbon constraint layer on cobalt sulfides toward boosted oxide electrolysis activities for highly energy-efficient micro-zinc–air batteries

Abstract

The sluggish kinetics of oxygen electrocatalysis reactions on cathodes significantly suppresses the energy efficiency of zinc–air batteries (ZABs). Herein, by coupling in situ generated CoS nanoparticles rich in cobalt vacancies (V_Co) with a dual-heteroatom-doped layered carbon framework, a hybrid Co-based catalyst (Co_1−xS@N/S–C) is designed and synthesized from Co-MOF precursor. Experimental analyses, together with density functional theory (DFT)-based calculations, demonstrate that the facilitated ion diffusion enabled by the introduced V_Co, together with the enhanced electron transport benefiting from the well-designed dual-heteroatom-doped laminated carbon framework, synergistically boost the bifunctional electrocatalytic activity of Co_1−xS@N/S–C (ΔE = 0.76 V), which is much superior to that of CoS@N/S–C without V_Co (ΔE = 0.89 V), CoS without V_Co (ΔE = 1.23 V), and the dual-heteroatom-doped laminated carbon framework. As expected, the further assembled ZAB employing Co_1−xS@N/S–C as the cathode electrocatalyst exhibits enhanced energy efficiency in terms of better cycling stability (510 cycles/170 hours) and a higher specific capacity (807 mA h g⁻¹). Finally, a flexible/stretched solid state micro-ZAB (F/SmZAB) with Co_1−xS@N/S–C as the cathode electrocatalyst and a wave-shaped GaIn-Ni-based liquid metal as the electronic circuit is further designed, which can display excellent electrical properties and long elongation. This work provides a new defect and structure coupling strategy for boosting the oxide electrolysis activities of Co-based catalysts. Furthermore, F/SmZAB represents a promising solution for a compatible micropower source in wearable microelectronics.