College of Sciences, NEU and EPM Laboratory Collaborated to Publish Important Research Achievements in Advanced Functional Materials

On May 1, Associate Professor Yu Song from the Department of Chemistry at the College of Sciences, NEU and Professor Weibin Cui from the EPM Laboratory published their collaborative research achievement in the field of aqueous zinc-ion batteries, titled "Hydrogenated Manganese Oxide Cathode for Stable Aqueous Zinc Ion Batteries," online in the TOP journal, Advanced Functional Materials in the field of materials science. The first author of the paper is Mengxue Li, a master’s student at grade of 2021 from the College of Sciences, and Associate Professor Yu Song and Professor Weibin Cui from EPM are co-corresponding authors. This work is another important achievement of the deep integration and innovation of science and engineering between the College of Sciences and the EPM Laboratory, contributing to the development of the Materials Science discipline of our university in aspect of chemistry.

Rechargeable aqueous zinc-ion batteries have great potential in large-scale energy storage applications. Among many positive electrode materials in aqueous zinc-ion batteries, manganese oxide has the advantages of large theoretical capacity, high discharge platform, low cost, and environmental friendliness, and has attracted much attention from the scientific community. Related studies have shown that the reaction between H⁺ and manganese oxide can lead to irreversible dissolution of manganese, which is the main reason for the performance degradation of manganese oxide materials. In order to improve the cycling stability of the manganese oxide electrode in zinc-ion batteries, Mn²⁺ electrolyte additives are usually used to ensure stable electrical energy output. However, during battery operation, the deposition/dissolution of Mn²⁺ additives also provides capacity, making it difficult to accurately evaluate the actual capacity contribution of electrodes and/or electrolytes. In addition, the amount of Mn²⁺ additives is closely related to battery performance, which is not applicable to zinc-ion battery systems under poor electrolyte conditions. Therefore, the development of stable zinc-manganese batteries without Mn²⁺ additives is of great research value.

Associate Professor Yu Song from the College of Sciences, NEU, in collaboration with Professor Weibin Cui from the EPM Laboratory, and others, used electrochemical methods to prepare hydroxylated layered manganese oxide materials (H-MnO₂) rich in Mn-OH components. As the positive electrode of aqueous zinc-ion batteries, H-MnO₂ shows good electrochemical stability in 3 M ZnSO₄ electrolyte (without manganese salt additives), with 5,000 consecutive cycles and a specific capacity maintenance rate of up to 95%. It is superior to other aqueous zinc-manganese batteries reported in the literature. The experimental results indicate that the hydroxylation strategy of manganese oxide can effectively inhibit the reaction between H⁺ and manganese oxide in the electrolyte, thereby inhibiting manganese dissolution and improving the cycling stability of the material. Theoretical calculation results show that the partial hydroxylation of MnO₂ weakens the interaction between H⁺ and the surface of manganese oxide, promotes the chemical adsorption of Zn²⁺, accelerates the diffusion process of Zn²⁺ on the material surface, and explains the evolution of charge storage mechanism after hydroxylation.

Aqueous batteries are expected to become reliable energy storage units for smart grids. Creating low-cost, high-safety, and long-life aqueous battery systems is a huge challenge facing the fields of materials and chemistry. This achievement proposes a novel concept of electrochemical hydroxylation, which changes the surface charge distribution of materials, regulates the interaction between charge carriers and electrode materials, and effectively improves the service life of aqueous zinc-manganese batteries. This study provides new ideas for designing stable aqueous zinc-manganese batteries and plays an important role in promoting the commercial application of aqueous zinc-manganese batteries.

The Analysis and Testing Center of NEU provides important assistance in the TEM image acquisition of this experiment.