Fabrication,characterization and electrochemical behavior of <i>δ</i>-MnO₂ nanoflakes

Abstract

Two types of ultrathin-flaky δ-MnO2 electrode materials (denoted as δ-MnO2-A and δ-MnO2-B) were synthesized through the reduction of potassium permanganate with manganese acetate and ethanol separately.The crystalline structure,chemical component,microstructure and pore size distribution of these nano-materials were determined by XRD,XPS,SEM/TEM and BET analysis.The electrochemical test demonstrates two δ-MnO2 electrode materials own similar specific capacitance and rate capability.Comparing to δ-MnO2-A,however,electrode material δ-MnO2-B contains a higher potassium and manganese vacancy content,and the lamellar structure of δ-MnO2-B is more legible and stable,therefore it displays a much more superior cycling stability.In 0.5mol/L Na2SO4 electrolyte,the specific capacitance of δ-MnO2 reaches 227F·g-1(1mV·s-1) and the capacitance retention rate is achieved 87.6% after 5000 cycles at 100mV·s-1.

Keywords

• manganese dioxide
• lamellar nanoflake
• supercapacitor
• energy storage electrode material