Asymmetric Supercapacitors Based on Graphene/MnO₂ and Activated Carbon Nanofiber Electrodes with High Power and Energy Density

TLDR

An asymmetric supercapacitor using graphene/MnO₂ as the positive electrode and activated carbon nanofibers as the negative electrode in neutral aqueous Na₂SO₄ electrolyte has been developed to achieve high energy density. The optimized asymmetric cell delivers a maximum energy density of 51.1 Wh kg⁻¹, retains 97 % of its specific capacitance after 1000 cycles, and outperforms comparable MnO₂//DWNT cells, demonstrating strong potential for high‑energy, high‑power practical energy storage.

Abstract

Abstract Asymmetric supercapacitor with high energy density has been developed successfully using graphene/MnO 2 composite as positive electrode and activated carbon nanofibers (ACN) as negative electrode in a neutral aqueous Na 2 SO 4 electrolyte. Due to the high capacitances and excellent rate performances of graphene/MnO 2 and ACN, as well as the synergistic effects of the two electrodes, such asymmetric cell exhibits superior electrochemical performances. An optimized asymmetric supercapacitor can be cycled reversibly in the voltage range of 0–1.8 V, and exhibits maximum energy density of 51.1 Wh kg −1 , which is much higher than that of MnO 2 //DWNT cell (29.1 Wh kg −1 ). Additionally, graphene/MnO 2 //ACN asymmetric supercapacitor exhibits excellent cycling durability, with 97% specific capacitance retained even after 1000 cycles. These encouraging results show great potential in developing energy storage devices with high energy and power densities for practical applications.