A model of large volumetric capacitance in graphene supercapacitors based on ion clustering

TL;DR

This paper presents a theoretical model explaining the high volumetric capacitance in graphene-based supercapacitors through ion clustering and nonlinear screening effects, aligning with experimental observations.

Contribution

It introduces a novel model linking ion intercalation and nonlinear screening to explain large volumetric capacitance in graphene supercapacitors.

Findings

Large volumetric capacitance explained by ion clustering

Nonlinear screening by graphene electrons enhances charge storage

Model aligns with experimental capacitance values > 100 F/cm^3

Abstract

Electric double layer supercapacitors are promising devices for high-power energy storage based on the reversible absorption of ions into porous, conducting electrodes. Graphene is a particularly good candidate for the electrode material in supercapacitors due to its high conductivity and large surface area. In this paper we consider supercapacitor electrodes made from a stack of graphene sheets with randomly-inserted "spacer" molecules. We show that the large volumetric capacitances C > 100 F/cm^3 observed experimentally can be understood as a result of collective intercalation of ions into the graphene stack and the accompanying nonlinear screening by graphene electrons that renormalizes the charge of the ion clusters.