Biomass-Derived Carbon Materials for High-Performance Supercapacitors: Current Status and Perspective

Abstract

Supercapacitors are electrochemical energy storage systems that depend on high-surface-area electrodes and can play a dominant role in areas that require high power delivery or uptake. And of various electrodes, biomass-derived carbonaceous electrodes have recently shown impressive promise in high-performance supercapacitors because of their widespread availability, renewable nature and low-cost electricity storage. Based on this, this review will discuss the current status of biomass-derived carbon materials in supercapacitors and highlight current research with a specific emphasis on the influences of structure and elemental doping on the electrochemical performance of corresponding carbon electrodes. This review will also discuss the gap between laboratory achievements and practical utilization in terms of these biomass-derived carbon materials and outline practical strategies for future improvement.

Magnetic Fe2O3/biochar composite prepared in a molten salt medium for antibiotic removal in water

“…Currently, biochars have been developed via carbonizing the biomass and then used as electrode materials for energy storage and adsorbents for antibiotics (Rajendran et al 2019;Zhou et al 2021a). However, the adsorption capacities of unmodified biochars are usually quite low, and their shortcomings such as small particle size and low density are making them difficult to separate from the treated solution.…”

“Porous and Yet Dense” Electrodes for High‐Volumetric‐Performance Electrochemical Capacitors: Principles, Advances, and Challenges

“…[ 3 , 4 ] Electrochemical capacitors (ECs), also called supercapacitors, fill in the large gap of electrochemical energy storage systems/applications requiring fast‐charging capability, high power density, and extra‐long cycling life ( Figure 1 a ). [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ] Over the past three decades, ECs have been extensively developed to complement or even replace part of the functions played by LIBs in several practical fields, where, e.g., a high power density of above 10 kW kg −1 is required for a short time period (a few seconds). There has been a steady and continuing rise of the global EC market over recent years (Figure 1b ).…”

“…[ 8 , 10 , 25 , 26 , 27 , 28 ] Thus, an appropriate porous electrode made of carbon‐based materials with high ion‐accessible surface area, good electrical conductivity, and high chemical stability in electrolytes is crucial to realize a class of high‐performance EDLCs. [ 7 , 11 , 12 , 14 , 28 ] For PCs, because they store the charges via chemically fast and reversible Faradaic reactions at the surface/near‐surface of the transition metal oxides or conductive polymers‐based electrodes (e.g., RuO 2 , MnO 2 , polypyrrole, and polyaniline), advanced pseudocapacitive electrodes shall also possess an appropriate porous structure, which not only benefits the electrolyte penetrating into active materials, but also largely speeds up the ion transport across the entire surface. [ 19 , 20 , 21 , 22 , 23 , 25 , 26 , 27 , 29 ] Although the HCs offer an opportunity to take the advantage of the merits of both ECs and batteries, [ 19 , 24 , 30 ] the wide charge/capacity gap remaining between capacitive or pseudocapacitive electrode (low capacity) and battery‐type electrode (high capacity) is the main barrier for realizing an overall high‐performance HC (particularly the desired energy and power densities, and long cycle‐life).…”

“…More recently, tremendous research efforts have been devoted to improving the energy density of ECs by tuning the highly porous electrodes, in which the surface conditions and pore structures are designed to precisely couple with the fluid electrolytes, while at the same time optimizing the interfaces involved. [ 7 , 8 , 11 , 12 , 28 , 31 ] Broadening the working voltage window of ECs is another effective approach to increase their energy densities, where, e.g., it could be realized by employing an appropriate electrolyte chosen from ionic liquids (ILs) and organic electrolytes that allow for a large voltage window (up to 2.5–4.0 V) and the development of asymmetric ECs (≈1.8–2.6 V); similarly, an appropriately porous structure is also needed to match with these large size of electrolyte ions. [ 32 , 33 ]…”

“…Over the past few years, there has been a steady progress in improving the volumetric performance of EDLC, PC, and HC, by engineering “porous and yet dense” electrodes, especially those carbon‐based, and there are a few reviews published lately in the on‐going hot topic area. [ 7 , 8 , 10 , 11 , 14 , 15 ] For example, Yang et al have reviewed advances on the dense and yet porous electrode with superior volumetric performance from a pore‐engineering perspective. [ 8 ] Simon et al briefly summarized the then up‐to‐date advances in nanoporous carbon‐based electrodes.…”