Adjusting the Coordination Environment of Mn Enhances Supercapacitor Performance of MnO2

Abstract The electrochemical properties of transition metal oxides strongly depend on the coordination environment of metal atoms. Nevertheless, the relationship between the coordination environment of metal atoms and electrochemical performance of metal oxides is unclear, while the strategy of adjusting the coordination environment of metal atoms is rare. Herein, the engineering of the coordination environment of Mn atoms in manganese dioxides (MnO 2 ) by using a triethanolamine (TEA) complex‐induced method is reported. The detailed experimental characterizations and density functional theory calculations show that the optimized Mn coordination environment with oxygen deficiency and more corner‐shared Mn–Mn shells results in apparent electron dislocation and forms an effective built‐in electrical field. As a result, the obtained MnO 2 ‐TEA sample exhibits a high conductivity and an excellent ion diffusion capacity, with a remarkable specific capacitance of 417.5 F g −1 at 1 A g −1 . At the power density of 450.0 W kg −1 , the fabricated asymmetric supercapacitor delivers the maximal energy density (57.4 Wh kg −1 ). This work not only provides an effective strategy of adjusting the coordination environment of metal atoms in metal oxides, but also presents a deeper understanding of the electronic structure dependent electrochemical performance of electrode materials.