Controllable structure transitions of Mn₃O₄ nanomaterials and their effects on electrochemical properties

Mn₃O₄ with purposely tuned different morphologies, crystal structures and sizes is synthesized using a hydrothermal method with varying processing temperatures, together with the help of a surfactant. Systematic investigations, both by experimental and computational studies, into these Mn₃O₄ nanomaterials were conducted in order to find the most suitable morphology and a compatible electrolyte for energy storage applications. The Mn₃O₄ nanofibers with a tunnel size of 1.83 Å in the crystal structure show much higher volumetric capacitance (188 F cm^-3 at a scan rate of 1 mV s^-1 of cyclic voltammetry test) than two other morphologies/crystal structures, when using 1 M LiCl aq. as the electrolyte. It is demonstrated in this work that crystal morphology and particle size play important roles in determining the capacitance of an electrode material. In addition, the detailed structures, especially the atomic arrangements within the crystalline structure, are crucial in order to choose the most suitable electrolyte.