Synergistic action of highly-active porous carbon-based bifunctional electrocatalysts and neutral electrolyte: endowing zinc–air batteries with ultra-long cycle stability

Abstract

Sluggish kinetics of oxygen electrocatalysis reactions on the cathode and the strong corrosion of strong alkaline electrolyte seriously affect the cycle life of zinc–air batteries (ZABs). In order to solve the above problem, uniform porous carbon-based highly active bifunctional electrocatalysts together with neutral electrolyte were used to improve the cycle stability of ZABs. Herein, a honeycomb N/S co-doped Co₉S₈ nanoparticle material loaded with a porous carbon skeleton (N/SdCF-OIM/Co₉S₈) as a cathode bifunctional electrocatalyst was designed successfully by using a Co-MOF with a macroporous molecular framework structure as a precursor and introducing SiO₂ spheres as a hard template. The results showed that the designed N/SdCF-OIM/Co₉S₈ exhibits excellent bifunctional electrocatalytic activity (ΔE = 0.77 V) in an alkaline electrolyte. Subsequently, it was further applied to liquid ZABs, and the liquid ZABs based on N/SdCF-OIM/Co₉S₈ showed excellent electrochemical properties in alkaline electrolyte: long charge and discharge cycle stability (170 h/510 cycles), high power density (181 mW cm⁻²) and large specific capacity (803 mA h g⁻¹). In order to further improve the cycle stability of the ZABs based on N/SdCF-OIM/Co₉S₈, neutral electrolyte was used instead of alkaline electrolyte. The results show that the cycle stability of ZABs based on N/SdCF-OIM/Co₉S₈ in neutral electrolyte is greatly improved (1000 h/3000 cycles). This work provides an effective way to prepare ZABs with ultra-long cycle stability.