Enhancing Efficiency and Durability of Alkaline Zn‐Co/Air Hybrid Batteries with Self‐Reconstructed Co/Co₂P Heterojunctions

Abstract

Zn‐Co/air hybrid batteries showcase enhanced energy efficiency, power density, and stability compared to Zn‐air batteries. Nevertheless, it remains challenging to fabricate multi‐functional cathode materials with fast reaction kinetics. Herein the synthesis of a wheat‐like cathode composed of the “cereal‐grains” of densely arranged Co/Co2P heterostructures grown on the “central stems” of P/N codoped carbon nanofibers (denoted as Co/Co2P@PNCF) is presented. The biomimetic nanostructures not only offer abundant exposed active sites to maximize accessibility but also establish efficient multi‐channel networks for both electron transfer and O2/OH− diffusion. Furthermore, the active species of high‐valent Co, resulting from self‐reconstruction of the Co/Co2P heterojunction during the first cycle, create efficient Co2+ ↔ Co4+ redox pairs and provide additional charging‐discharging voltage plateaus. In situ Raman spectroscopy measurement combined with ex situ X‐ray diffraction evidence supports the reversible process of Co3+/4+Ox(OH)y ↔ KxCo2+/3+Oy, leading to improved efficiency and durability of the battery. As a result, Zn‐Co/air hybrid battery based on the Co/Co2P@PNCF exhibits a remarkable power density (321 mW cm−2), ultralong cycle stability (700 h), and a large energy efficiency (62% at 20 mA cm−2).