Molten salt synthesis of high quality 2D δ‑MnO2 nanosheets for advanced aqueous Zn/MnO2 batteries

Abstract

Rechargeable zinc-ion batteries (ZIBs) have garnered the attention of numerous researchers due to their environmentally friendly features, high safety, and abundance of raw materials. In this study, we present a zinc-manganese oxide (defined as Zn/NaMnO) battery system that employs the layered monocrystalline hexagonal phase, δ-MnO2, as the cathode, synthesized via the molten salt-assisted method. Our findings demonstrate that the ultra-thin δ-phase monocrystalline structure augments the active sites of electrochemical reaction, enhances surface interface interactions, and facilitates H+ diffusion kinetics, thus promoting high-rate performance. The Zn/NaMnO battery exhibits impressive capacity (335 mA h g−1 at 0.5 C) and ultra-long cycling stability at high current density (4000 stable cycles at 20 C with 90 % capacity retention). This work provides a novel methodology for the development of rechargeable ZIBs systems with excellent performance and mass production potential.