Ionic-liquid-engineered, interfacial π–π-anchored, cobalt-dispersed, and N-, F-, B-doped carbon matrix as an oxygen electrocatalyst for advanced zinc–air batteries

Abstract

Zinc–air batteries (ZABs) are a potential category of energy storage devices that are typically driven by strong and effective catalysts at the oxygen-based cathode. Hence, highly active and robust non-noble metal-based electrocatalysts with binary active sites for stabilizing the various oxygen-based species formed during the battery cycling are major requisites for the global application of zinc–air batteries. Co–N–C is a promising alternative to noble metal-based oxygen electrocatalysts. Herein, we report an ionic liquid-driven synthesis of a Co–N–C based catalyst via self-doping of ternary heteroatoms (B, N, and F) using a simple one-pot pyrolysis method. The heteroatoms further synergized the performance of the Co–N–C, and the best-optimized catalyst, namely, CoILPh 700, was capable of delivering a positive ORR onset potential of 0.956 V with a limiting current density of 5.6 mA cm⁻² and an OER overpotential of 380 mV with enhanced stability, outperforming their corresponding benchmarks. A prototype zinc–air battery fabricated based on the CoILPh 700 electrocatalyst achieved a maximum peak power density and specific capacity of 228 mW cm⁻² and 815 mA h g⁻¹, respectively, with a cycling stability of more than 300 h at 5 mA cm⁻². The novelty of this work is that an interesting study was performed, wherein the battery was cycled at different increasing depths of charge–discharge time intervals to evaluate its real-time performance. Notably, the device was able to completely recharge even after 72 h of discharge, which was quite impressive. This study offers an approach to improve the endurance of advanced zinc–air batteries at higher depths of discharge via the sensible design of non-noble metal catalysts.