The intercalation cathode materials of heterostructure MnS/MnO with dual ions defect embedded in N-doped carbon fibers for aqueous zinc ion batteries

Abstract

Manganese-based materials are often used as cathode materials for aqueous zinc ion batteries (AZIBs), which have the advantages of high theoretical capacity, low cost, low toxicity and various valence states. However, the inherent poor conductivity, sluggish zinc ion diffusion kinetics and terrible rate performance limit their practical application. Herein, MnS/MnO@NCF composite was synthesized by a simple electrospinning method. The N-doped carbon fibers (abbreviated as NCF) is produced during the carbonization process of PVP, which greatly improves the electronic conductivity of materials, and the formation of heterostructure MnS/MnO create abundant heterointerfaces with plentiful reaction active sites, which further improve the surface reaction kinetics. Meanwhile, an in-situ electrochemical approach inducing dual ions defect of Mn-defect and S-defect is used to unlock the electrochemical activity of MnS/MnO@NCF through the initial charge process for the first time, which can convert terrible electrochemical characteristic of MnS/MnO@NCF towards Zn2+ and H+ into high electrochemically active cathode for AZIBs. Finally, it exhibits a considerable capacity and superior cycleability with the specific discharge capacity of 151 mAh g−1 even after 400 cycles when used as the cathode material for AZIBs. Remarkably, it can even achieve a reversible capacity as high as 128.7 mAh g−1 at current density of 2 A g−1. Ex situ characterizations reveal the main co-insertion/extraction mechanism for H+ and Zn2+ without structural collapse, and the vacancy formation energies and the diffusion energy barrier of Zn2+calculated by density functional theory further explain the excellent rate performance and the energy storage mechanism of the MnS/MnO@NCF material.