This study explores manganese acetate hydrate solutions for energy storage, revealing notable thermal behaviors, unique transport properties, and effective performance in two-electrode supercapacitors. Manganese acetate emerges as a stable, green electrolyte, showcasing the potential for sustainable energy storage applications.

Abstract

While there have been numerous studies on the use of manganese acetate for electrode manufacture, scarce reports exist on the utility of manganese acetate electrolytes for energy storage applications. This study provides a comprehensive understanding of the thermal, volumetric, and transport properties of manganese acetate hydrate solutions and highlights their potential for use in energy storage applications. Noteworthy thermal behaviours, phase transitions, and strong interactions between manganese cations, acetate anions, and water molecules are observed. Transport properties reveal salt concentration‘s impact (0.4–3.9 mol L⁻¹) on viscosity and conductivity, with higher concentrations (>2.5 mol L⁻¹) indicating increased interaction. The non-Arrhenius behaviour in conductivity is elucidated using the Vogel-Fulcher-Tammann model, accentuating the unique properties of these solutions compared to other aqueous electrolytes due to the role of acetate ligands. The formulated two-electrode symmetric supercapacitors exhibit pseudocapacitive behaviour, reversible redox reactions (Mn²⁺/Mn³⁺), and salt concentration-dependent specific capacitance. Manganese acetate as an electrolyte leads to reversible manganese dioxide deposition, with its concentration affecting redox reactions and capacitance. Molecular simulations support the observed electrochemical performance, emphasizing the Mn²⁺-acetate complexation. Long-term cycling experiments demonstrate stability over 2000 cycles, with a stable specific capacitance of 130 F g⁻¹ and a gradual coulombic efficiency decrease (~97 %). The results of this work underscore the potential of manganese acetate hydrate solutions as a stable, effective and green electrolyte for energy storage applications.