C₃N₄ Preintercalation of α-MnO₂ Nanotubes with Expanded Interlayer Spacing for High-Performance Aqueous Zn-Ion Batteries

As a competitive and promising cathode material for aqueous zinc-ion batteries (AZIBs), manganese dioxide (MnO2) possesses essential characteristics of high theoretical capacity, sufficient reserves, and environmental friendliness. However, due to the inherent poor electrical conductivity, sluggish reaction dynamics, and collapsible structure, its further development is limited. In this paper, g-C3N4 is inserted into MnO2 through a hydrothermal strategy to obtain an advanced material (MCN) with a hollow nanotube structure, which can not only provide abundant active sites but also shorten the ion transfer pathways in electrochemical processes. The most significant aspects of the introduction of g-C3N4 are the increase of the conductivity and interlayer spacing of MnO2, which significantly accelerates the intercalation dynamics of Zn2+. The optimized MCN material demonstrates an outstanding specific capacity of 210 mAh g–1 at 0.5 A g–1 and eminent cycle stability, maintaining 85.9% of its capacity after 1000 cycles at 3.0 A g–1. Furthermore, the development of flexible quasi-solid ZIBs equipped with MCN represents a significant advancement in energy storage technology and exhibits exceptional Zn2+ storage properties, positioning them as promising candidates for future energy applications. The work provides feasible methods to achieve MnO2 cathode electrodes for aqueous Zn-ion batteries.