Oxygen Vacancies Enhance H⁺ Diffusion Kinetics for a Flexible and Lightweight Aqueous Zinc/Manganese Monoxide Battery

Abstract

Manganese monoxide (MnO) currently has attracted increasing attention in aqueous zinc metal batteries (AZMBs) due to the high theoretical capacity, satisfactory output voltage, and low price. However, the development of a MnO cathode is still plagued by the low specific capacity arising from the sluggish reaction kinetics and rapid capacity decay induced by structural collapse. Herein, the oxygen-defect-rich MnO1–x integrated with a carbon nanofiber (MnO1–x@CNF) membrane is designed based on a facile electrospinning technique. In situ X-ray diffraction and ex situ X-ray photoelectronic spectroscopy results confirm the proton-dominated insertion electrochemistry during cycling. The theoretical calculation results revealed that the introduction of oxygen vacancies could effectively decrease the H+ diffusion energy barrier and thus promote H+ diffusion. In addition, CNFs could provide flexible and lightweight electron transport networks to ensure rapid electrode reaction kinetics. Consequently, the as-prepared MnO1–x@CNF cathode delivers a high specific capacity of 264 mAh g–1 at 0.1 A g–1 and an outstanding capacity retention after 2500 cycles at 2 A g–1. The high flexibility and light weight of the MnO1–x@CNF membrane may aid in future high-performance cathodes for wearable AZMBs.