Research Progress on Graphene Composite Electrode Materials for Supercapacitors

Abstract

Supercapacitors: Key Background and Recent Developments in Graphene-Based Electrode Design Supercapacitors are a really important building block for fast-charging systems and flexible electronics, because they have higher power densities and can keep working through many more charge-discharge cycles than other options. But their natural energy density is lower than what you get from regular batteries, and this is a big problem that holds the industry back right now. Two-dimensional (2D) graphene makes a great conductive base material for composite electrodes. Even so, using it on its own is really hard, because its nanosheets have a natural thermodynamic tendency to stick back together in a way that can't be reversed. This review breaks down the recent changes and new directions that graphene-based composite electrodes have taken over the last few years. We start by talking about the basic ways energy gets stored at the interface between materials, plus what shape and structure the material needs to have to work well in high-speed devices. After that, we pulled out three really important changes people have made to the structure of these electrodes: first, making one-dimensional (1D) microfiber topological networks to cut down on ohmic and charge-transfer resistance；second, adding local built-in electric fields at heterojunction interfaces to make Faradaic reactions happen faster；and third, creating multi-electron redox reactions by locking multivalent transition metal oxides in place in-situ across wide potential windows. We also talk about how 3D graphene networks can be scaled up to work in thermoelectric-coupled phase-change composites, as one way to build systems for organizational safety management. At the end, we point out where future work should go: things like atomic-scale covalent optimization, making large volumes at low cost with additive manufacturing, and figuring out how multiphysics dynamic failure mechanisms work in these materials.