Progress on carbon for electrochemical capacitors

Abstract

Electrochemical capacitors bridge the energy gap between conventional dielectric capacitors and batteries. The energy storage mechanism relies on purely physical electrical double‐layer charging (EDL) and the faradaic process involving fast electrochemical redox reactions. These processes are strongly influenced by the surface area, porosity, electrical conductivity of the electrode materials, and the operating potential window of the electrolyte used. Carbonaceous materials play enormous roles in delivering outstanding electrochemical performance in electrochemical supercapacitors (ESCs) due to attractive material features suitable for high charge storage and release. However, due to the purely EDL‐based charge storage mechanism in only carbon‐based ESCs, the achievable energy density is low and hardly meets the high energy density demanding applications. Therefore, various carbon structures such as activated carbon, carbon nanotubes, graphene, and so on are designed and integrated with other hetero atoms or combined with transition metal oxides and polymer components to induce the pseudo‐capacitive contributions via the electrochemical faradaic reaction. Thus, promoting the electrochemical performance of ESC based on the hybrid/composite material attributed to synergistic capacitances from EDLC and pseudocapacitance. Therefore, this review overviews the general perspective of the ESCs based on nanocarbons with various forms trending the progressive research contributions in developing high‐performance ESCs.

High Mass‐Loading Biomass‐Based Porous Carbon Electrodes for Supercapacitors: Review and Perspectives

“…Representative heteroatoms include nitrogen (N), sulfur (S), phosphorus (P), boron (B), and fluorine (F), as shown in Figure 16b-f. [187,188] Doping can be divided into two ways: external doping and self-doping. External doping is the process of introducing heteroatoms into biomass carbon by using dopants such as thiourea, urea, phosphoric acid, amine, melamine, and boric acid, etc.…”

Natural polymers as sustainable precursors for scalable production of N/SOx doped carbon material enabling high‐performance supercapacitors

“…[1][2][3][4][5] Intrinsic SCs follow the electrochemical double layer (EDL) mechanism, in which the design and composition of the electrode are crucial in determining the performance of the SCs. [6][7][8][9] For EDLCs' electrodes, durable carbonaceous materials have become star candidates with their cost-effectiveness, stable chemical properties, elevated conductivity, and controllable porous architecture. [10][11][12][13] However, the carbon materials inherit relatively less theoretical specific capacitance (550 Fg À1 ) due to low packing density and hydrophobicity.…”

“…In the era of miniaturized electronics, flexible supercapacitors (SCs) with high power output and ultrafast charge and discharge rates have attained substantial consideration because they have the potential to bridge the gap between batteries and capacitors 1–5 . Intrinsic SCs follow the electrochemical double layer (EDL) mechanism, in which the design and composition of the electrode are crucial in determining the performance of the SCs 6–9 . For EDLCs' electrodes, durable carbonaceous materials have become star candidates with their cost‐effectiveness, stable chemical properties, elevated conductivity, and controllable porous architecture 10–13 .…”

All‐in‐one Biomass‐Based Flexible Supercapacitors with High Rate Performance and High Energy Density

“…[1][2][3] Their electrochemical performance mainly depends on three key components including electrodes, separator, and electrolyte. [4,5] Thus far, traditional SCs usually use metal oxides, [6] carbon materials [7] or conductive polymers [8] as electrode materials, commercial glass fiber (GF) [9] or polyolefin-based membrane (PL) [10] as the separator, and liquid-based solutions (e.g., aqueous/organic solutions, [11,12] and ionic liquids [13] ) as electrolyte. This configuration presents three main drawbacks: The toxic metal-oxides/polymers-based electrodes and corrosive liquid-based electrolytes used in commercial SCs have some safety and environmental concerns, [14][15][16][17] this is especially the case for the next-generation SCs for wearable and scalable electronics.…”