Synthesis of Mn2O3 microstructures and their energy storage ability studies

Graphical abstract: Mn2O3 powder with various microstructures was fabricated by pyrolysis of MnF2 precursors hydrothermally synthesized using Mn(CH3COO)2 and hydrofluoric acid in ethanol, water, and glycerol, respectively. Mn2O3 exhibited high discharge capacity for lithium battery anode materials, and showed acceptable capacitance for supercapacitor electrode and transformed into burserite in charge/discharge process. -- Highlights: • MnF2 precursor was hydrothermally synthesized and then pyrolyzed to α-Mn2O3 microstructures. • Spherical α-Mn2O3 exhibited excellent lithium storage capacity of 2899 mAh g−1 at first cycle and 265 mAh g−1 after 15 cycles. • As supercapacitor electrode materials, α-Mn2O3 was transformed into burserite in charge/discharge process. • Small particle facilitated the transformation of α-Mn2O3, and 202 F g−1 was obtained after many cycles of activation. -- Abstract: α-Mn2O3 microstructures, including spheres and polyhedrons, were fabricated through a two-step process: MnF2 precursor was first hydrothermally synthesized using manganese acetate and hydrofluoric acid in ethanol, and then pyrolyzed to α-Mn2O3 at 350 °C. α-Mn2O3 morphologies were controlled through MnF2 precursors by adjusting HF/Mn(CH3COO)2 molar ratio and solvents. Spherical α-Mn2O3 particles were formed when HF/Mn(CH3COO)2 molar ratio was 2:1, and polyhedral α-Mn2O3 particles were prepared and particle size increased when the molar ratio increased to 12:1. Solvent viscosity affected Mn2O3 morphologies and particle size. Irregular particles of α-Mn2O3 with larger size were formed as aqueous solvent was substituted for ethanol. Smaller particles of α-Mn2O3 were formed when glycerol was used instead. The discharge mechanism and cycling stability of α-Mn2O3 electrode materials were studied. Spherical α-Mn2O3 exhibited excellent lithium storage capacity of 2899 mAh g−1 at first cycle and 265 mAh g−1 after 15 cycles. The formation of LiAl alloy did much contribution to the discharge capacity of first cycle. As for supercapacitor electrode materials, α-Mn2O3 was transformed into burserite during charge/discharge process, and capacitance increased with the increase of surface area. The highest specific capacitance was 202 F g−1 and kept steady after 400 cycles. The as-prepared α-Mn2O3 with various microstructures might be applied as rechargeable electrode materials for lithium-ion battery and supercapacitor