A Brand-New Hybrid Structure with Advantageous Electron State for Ultrahigh Energy Density Asymmetric Supercapacitors

Abstract

Rational design and preparation for improving surface chemical properties and electron structure of transition metal oxides to enhance their energy storage capacity are highly desired. Herein, a brand-new organic–inorganic hybrid structure (NH2-MIL-125/ZnMn2O4) consisting of a metal–organic framework and polynary transition metal oxide was synthesized successfully and further modified by Ag decoration engineering. In detail, the hybrid structure can provide abundant dual metal reactive sites (Zn and Mn), and based on the Ag decorating, the electron structure of the hybrid structure presents an advantageous state, which means high chemical activity for electrochemical redox reactions. Benefiting from the above and additional outstanding advantages of good electrical conductivity, complex valence states, high specific surface area (SSA), and well-developed micro-morphology, the targeted sample shows an extraordinary energy density of 204.31 Wh kg–1 at power density of 3.15 kW kg–1, which is advanced among related electrode materials. In addition, density functional theory (DFT) calculations confirm the pseudocapacitance improvement mechanism by Ag decorating. In summary, this work can not only provides some new thoughts for the design and preparation of electrode materials but also encourages more profound modification paths in the area of electron structure and reaction mechanism.