Metal–organic framework-derived selenium-doped manganese oxide@carbon composite for durable aqueous zinc-ion batteries

Abstract

Manganese (Mn)-based materials, owing to their high theoretical capacity, low cost, environmental benignity, and multiple accessible valence states, are attractive cathode candidates for aqueous zinc-ion batteries (AZIBs). However, their practical application is often hindered by intrinsically sluggish electron transport, slow Zn²⁺ diffusion kinetics, and structural instability associated with Jahn–Teller distortion during cycling. Herein, we reported a heterostructured manganese selenide/manganese oxide@carbon (MnSe/MnO@C) composite derived from metal-organic frameworks (MOFs) via a simple thermolysis of Mn MOFs under an inert atmosphere, followed by selenization. The carbonization of Mn MOFs generates a carbonaceous framework favorable for charge transport, while the formation of the heterostructured MnSe/MnO@C introduces abundant heterointerfaces and electrochemically active sites. These structural features are consistent with the reduced charge-transfer resistance and enhanced reaction kinetics observed for the MnSe/MnO@C electrode. Furthermore, when used as the cathode material for AZIBs, the MnSe/MnO@C electrode revealed superior specific capacity and improved cyclability, exhibiting 225 mA h g⁻¹ at 0.5 A g⁻¹ after 500 charge-discharge cycles. Surprisingly, the electrode could achieve a reversible specific capacity of 191 mA h g⁻¹ at 2 A g⁻¹. The ex-situ characterization indicates a mixed Zn²⁺/H⁺ co-storage mechanism accompanied by reversible structural evolution without causing significant morphological damage. This study provides insights into the synthesis of MnSe/MnO@C, electrochemical activation, and remarkable AZIB performances, which leads to a better understanding of its potential applications.