3D Macroporous Graphene Frameworks for Supercapacitors with High Energy and Power Densities

TLDR

Electrodes for high‑power, high‑energy storage must provide well‑defined pathways for efficient ionic and electronic transport. The study aims to build high‑performance supercapacitors by constructing a three‑dimensional macroporous structure of chemically modified graphene. The authors fabricated embossed‑CMG films using polystyrene colloidal particles as a sacrificial template and further deposited a thin MnO₂ layer to boost capacitance. The MnO₂/e‑CMG composite electrodes deliver a specific capacitance of 389 F/g at 1 A/g, retain 97.7 % at 35 A/g, and when paired asymmetrically with e‑CMG, achieve a full‑cell energy density of 44 Wh/kg, power density of 25 kW/kg, and excellent cycle life.

Abstract

In order to develop energy storage devices with high power and energy densities, electrodes should hold well-defined pathways for efficient ionic and electronic transport. Herein, we demonstrate high-performance supercapacitors by building a three-dimensional (3D) macroporous structure that consists of chemically modified graphene (CMG). These 3D macroporous electrodes, namely, embossed-CMG (e-CMG) films, were fabricated by using polystyrene colloidal particles as a sacrificial template. Furthermore, for further capacitance boost, a thin layer of MnO(2) was additionally deposited onto e-CMG. The porous graphene structure with a large surface area facilitates fast ionic transport within the electrode while preserving decent electronic conductivity and thus endows MnO(2)/e-CMG composite electrodes with excellent electrochemical properties such as a specific capacitance of 389 F/g at 1 A/g and 97.7% capacitance retention upon a current increase to 35 A/g. Moreover, when the MnO(2)/e-CMG composite electrode was asymmetrically assembled with an e-CMG electrode, the assembled full cell shows remarkable cell performance: energy density of 44 Wh/kg, power density of 25 kW/kg, and excellent cycle life.