Activated Carbon Supercapacitor Research Articles

Boosting the Energy Density of Bowl-Like MnO2@Carbon Through Lithium-Intercalation in a High-Voltage Asymmetric Supercapacitor with "Water-In-Salt" Electrolyte.

Highly concentrated "'water-in-salt"' (WIS) electrolytes are promising for high-performance energy storage devices due to their wide electrochemical stability window. However, the energy storage mechanism of MnO2 in WIS electrolytes-based supercapacitors remains unclear. Herein, MnO2 nanoflowers are successfully grown on mesoporous bowl-like carbon (MBC) particles to generate MnO2/MBC composites, which not only increase electroactive sites and inhibit the pulverization of MnO2 particles during the fast charging/discharging processes, but also facilitate the electron transfer and ion diffusion within the whole electrode, resulting in significant enhancement of the electrochemical performance. An asymmetric supercapacitor, assembled with MnO2/MBC and activated carbon (AC) and using 21m LiTFSI solution as the WIS electrolyte, delivers an ultrahigh energy density of 70.2Whkg-1 at 700W kg-1, and still retains 24.8Whkg-1 when the power density is increased to 28kWkg-1. The ex situ XRD, Raman, and XPS measurements reveal that a reversible reaction of MnO2 + xLi+ + xe-↔LixMnO2 takes place during charging and discharging. Therefore, the asymmetric MnO2/MBC//AC supercapacitor with LiTFSI electrolyte is actually a lithium-ion hybrid supercapacitor, which can greatly boost the energy density of the assembled device and expand the voltage window.

Low metal content and hierarchically porous structure of “Fabaceae-Plants” derived activated carbon for high-performance supercapacitors

Plants with naturally ordered tissues and unique cell structures have become good precursors as activated carbon (AC) electrodes for supercapacitors. The various inherent plants derived ergastic substances induce numerous impurities in ACs, seriously impeding electrochemical performance. Aiming at elevating electrochemical activities, we herein, select suitable “Fabaceae-Plants” precursors via pre-leaching and carbonization-KOH activation for purer AC supercapacitor electrodes. The inherent parenchyma tissues and intrinsic low metal ion properties ensure “Fabaceae-Plants” derived ACs have large specific surface areas (SSA) (> 3000 m2 g−1) and low self-discharge rates. After ethanol reflux, most ergastic substances were removed, leading to a lower metal ion content that meets the standard procedure in Chinese GB/T 37386-2019 codes and higher mesopore volumes due to the better KOH activation effect. The mung bean sprouts-based activated carbon (AC) prepared by ethanol reflux exhibits higher capacitance (370 F g−1 at 0.5 A g−1), excellent rate performance (81.8 % from 0.5 to 50 A g−1), and an impressively low open circuit voltage attenuation rate (19.9 mV h−1). These characteristics are attributed to the synergistic effect of low metal ion impurities and higher mesopore volumes. Hence, the “Fabaceae-Plants” derived ACs are potential materials for clean energy storage and conversion systems, and the pre-leaching strategy may propose a strategy for high value-added utilization of biomass.

Multifunctional sulfur doping in cobalt-based materials for high-energy density supercapacitors

In this study, S-CCO@Co(OH)2 (‘CCO’ representing CuCo2O4/Cu2O; ‘S-’representing sulfur doping) was synthesized by hydrothermal method followed by electrodeposition. The multiple effects of S doping were studied by S doping and constructing 3D core–shell structure. S doping induced the reduction of Cu2+ and Co3+ to Cu+ and Co2+, respectively. Also, S partially replaces O and creates oxygen vacancies, which increases a number of active sites for the redox reaction enhancing the redox reaction activity. After the electrodeposition, S–Co bond is formed between the Co(OH)2 shell and the S-CCO core, which suggests a synergistic effect between S doping and core–shell structure. The formation of S–Co bond is conducive to electron and ion transport, thus improving electrochemical performance. After modification, the specific capacitance of S-CCO@Co(OH)2 is 4.28 times higher than CCO, up to 1730 Fg−1. Furthermore, the assembled S-CCO@Co(OH)2//activated carbon supercapacitor exhibits an energy density of 83.89 Whkg−1 at 848.81 Wkg−1 and a retention rate of 98.48% after 5000 charge and discharge cycles. Therefore, S doping and its mutual effect with the utilization of the core–shell structure considerably enhanced the electrochemical performance of the CCO-based electrodes, endowing its potential in further application.

Development of NiS@f-MWCNT nanocomposite-based high-performance supercapacitor coin cell prototype device

This work reports the fabrication of supercapacitor coin cell prototype devices using lab-made NiS@f-MWCNT, their in-depth physical and electrochemical characterization, and the design of Arduino-based set-up to power temperature sensor. A one-step hydrothermal technique was developed to rationally synthesize bare NiS and f-MWCNT decorated NiS nanocomposites (NiS@f-MWCNT) using CTAB as a surfactant. Loading of f-MWCNT into NiS resulted in an enhancement in electrochemical characteristics. The specific capacitance values are found to be 1400 Fg−1 and 1966 Fg−1 (at 1 Ag−1) for bare NiS and NiS@f-MWCNT, respectively. Further, an improvement in rate capability is also noticed in the case of the f-MWCNT loaded sample (78.0 %) vis-à-vis bare NiS (64.0 %). The as-prepared NiS and NiS@f-MWCNT were utilized as the positive electrode while activated carbon (AC) as a negative electrode to fabricate distinct asymmetric supercapacitor coin cells, namely NiS//AC and NiS@f-MWCNT//AC, respectively. The as-fabricated NiS@f-MWCNT//AC supercapacitors exhibited a high energy density of ∼74.1 Whkg−1 (vis-à-vis 58.0 Whkg−1 for NiS//AC) and power density of 1405.0 Wkg−1 (vis-à-vis 850.0 Wkg−1 for NiS//AC), respectively. In addition, four ASCs composed of NiS@f-MWCNT//AC were used in demonstrating the hands-on process for powering an Arduino-driven temperature sensor. The as-developed set-up was sensitive enough to record a minor temperature fluctuation with an accuracy of ±1 °C.

A self-supporting multi-component collaborative structure for enhancing interface electron transfer in hybrid supercapacitor

Multi-component synergistic effect is a feasible strategy to boost the capacity of electrode materials. Herein, carbon nanotubes (CNTs) film supporting NiCo phosphide (NiCoP) modified metal-organic framework (MOF) is reasonably synthesised as a self-supporting electrode for high-performance supercapacitors. Benefiting from the synergistic effect of the high conductivity of the CNT film substrate, the specific surface area of Cu-MOF (HKUST-1), and the high activity of NiCoP, the charge transfer and ionic diffusion among the electrode greatly improved. The as-prepared electrode displays a remarkably enhanced specific capacitance of 1154 F g−1. In addition, the as-assembled NiCoP/HKUST-1@CNTs//activated carbon supercapacitor possesses a considerable energy density of 58.2 W h kg−1 and satisfactory cyclic performance (retaining 80.6 % capacitance over 10,000 cycles). The synthesis approach of this study provides some reference for the controllable preparation of new high-capacity MOF-based electrode materials.

Wide-temperature activated carbon-based symmetric supercapacitors with impressive performance empowered by H3PO4 electrolyte

As a commercial electrode material, activated carbon (AC) has been widely used in electrochemical energy storage systems. However, the electrochemical performance of AC for supercapacitors has not been well developed due to the absence of an ideal electrolyte. In this paper, we report on the all-temperature impressive performance of AC‖AC symmetric supercapacitors with commercial loading level (>10 mg cm−2) empowered by H3PO4 electrolyte. The physicochemical properties of H3PO4 electrolytes with different weight ratios of H3PO4 to H2O have been characterized. The H3PO4 electrolyte with H3PO4/H2O weight ratio of 1 endows AC‖AC supercapacitors with enhanced performance at a wide temperature range of –45–55 °C, compared with the counterparts with H3PO4/H2O weight ratio being 0.5 and 2. The electrochemical performance of AC‖AC supercapacitors operating with the H3PO4 electrolyte (H3PO4/H2O = 1:1, w/w) is increased as the temperature increases from −45 to 55 °C. The impressive performance of AC‖AC supercapacitors operating with H3PO4/H2O weight ratio of 1 is attributed to the high conductivity and reduced water activity of the electrolyte, as confirmed by instrumental analysis and molecular dynamic simulations.

Neutral pH Na2SO4/glycerol/PVA polymer hydrogel electrolyte prepared at room temperature for activated carbon supercapacitors

Neutral pH Na2SO4/glycerol/PVA polymer hydrogel electrolyte prepared at room temperature for activated carbon supercapacitors

A novel P-doped Ni0.5Cu0.5Co2O4 sphere with a yolk-shell hollow structure for high-energy–density supercapacitor

P-doped multi-metal oxide is an effective method to improve its electrochemical energy storage performance. Herein, a novel P-doped ternary metal oxide (P-Ni0.5Cu0.5Co2O4) with a yolk-shell hollow structure is reasonably prepared and used as electrode material for supercapacitors. The as-prepared electrode has significantly improved conductivity and capacity, with a high specific capacitance of 1570.2F g−1 in a three-electrode system. Furthermore, the as-assembled P-Ni0.5Cu0.5Co2O4//activated carbon supercapacitor possesses an ultra-high energy density of 118.6 W h kg−1 and stable cyclic performance.

Cationic, electrostatic shielding, ion-sieving nanocellulose separators stabilize zinc metal anodes

A bio-based, electrostatic shielding, ion-sieving separator is proposed by surface amine functionalization of nanocellulose paper to stabilize Zn metal anode, for the first time. Such cationic nanocellulose separator exhibits uniformly and narrowly distributed nanopores with immobilized cationic groups, which yields a homogenous current distribution at the separator/electrode interfaces, inhibits SO42− migration, enhances the Zn2+ transference number to 0.73, and generates a zincophobic repulsion layer to eliminate the “tip effect”. Unlike pristine nanocellulose separator, the combination of ion-sieving nanofibrous network and immobilized electrostatic shielding functional groups lead to smoother and more compact Zn deposition/stripping behavior during repeated cycles. Hence, highly reversible Zn metal anodes and durable supercapacitors are realized: the symmetric Zn//Zn cells can last 180 h under a high current density of 20 mA cm−2 with a high capacity of 10 mAh cm−2, and the Zn//activated carbon supercapacitor shows a discharge capacity of 104.3 mA g−1 at 1 A g−1 with a capacity retention ratio of ∼ 80% after 2500 cycles. The surface charge engineering approach constitutes a practical separator modification strategy toward even Zn deposition and a promising route for the development of aqueous Zn-based energy storage devices with improved sustainability and enhanced cycling stability.

Special Section on 2D Materials for Electrochemical Energy Storage and Conversion

Electrochemical energy storage and conversion are currently one of the most critical challenges due to the increasing energy demand. Therefore, discovering novel materials to develop low-cost and more efficient energy storage technologies is urgently necessary. Among various novel materials, two-dimensional (2D) materials have attracted intensive research activities in multiple fields due to their fascinating physical and chemical properties. The 2D materials having a higher surface-to-volume ratio are beneficial to developing low-cost and large-scale energy storage systems for practical applications. There have been many promising concepts of 2D material-based real-life energy applications recently in batteries, supercapacitors, fuel cells, solar cells, thermoelectric, triboelectric generators, etc. Despite recent progress, significant efforts are still needed to investigate the fundamentals of 2D materials for electrochemical energy storage and conversion. Over the past few years, there has been substantial progress in modeling, theories, and experimental characterizations of 2D materials for energy storage and conversion. This timely Special Section issue addressed some recent advances in this critical area. We have selected eight papers covering a gamut of electrochemical-centric research in 2D materials for energy storage and conversion.In this issue, Qu et al. reported the electrochemical evaluation of helical carbon nanofibers (HCNFs) prepared by the ethanol flame method as anode materials of lithium-ion batteries. Their results show that HCNFs possess high reversible capacity, good rate performance, and excellent cycling stability. Farma et al. investigated a simple and cost-effective method to generate porous carbon activation from Palmae plant waste biomass, namely, areca leaf midrib (ALM). They showed that the electrochemical properties of activated carbon supercapacitor cells derived from ALM biomass have the highest specific capacitance value and scan rate in a two-electrode system. Arumugam et al. discussed a ternary composite made up of graphene oxide, polyaniline, and zinc oxide as an electrode material for supercapacitors with its structural and electrochemical properties. The ternary composite exhibited the highest specific capacitance. Metzger et al. focused on using graphene-coated proton exchange membrane (PEM) to reduce fuel crossover. They found that the adhesion of graphene on PEMs is insufficient for prolonging fuel cell operation, resulting in graphene delamination at high temperatures and higher fuel crossover values compared to lower temperature testing. Zaidi et al. reported the superior performance of graphene nanosheet (GNS) materials over Vulcan XC incorporated as a cathode catalyst in Li-O2 battery. The GNS catalysts demonstrated promising performance at higher current densities and with various organic electrolytes. Pandey et al. synthesized a mechanically stable, proton-conducting, and very cost-effective nanocomposite membrane using a simple and scalable phase-inversion approach. The synthesized proton-conducting nanocomposite membrane was demonstrated as a potential advanced functional solid electrolyte for possible application in proton exchange membrane fuel cells. Fauzi et al. reported the thermophysical properties of N,N-diethylethanolammonium chloride/ethylene glycol-DES (deep eutectic solvent) for the replacement of ionic liquid. They studied the physical properties of DES, which are thermal conductivity, viscosity, and surface tension. Finally, the review article by Zeng et al. provided an overview of the application of conductive diamond in electrocatalytic reduction and outlined the improvement of electrochemical properties by employing metal particles to modify the surface.We believe that this Special Section issue will be a valuable contribution to the energy storage and conversion literature and open new frontiers for researchers. The interdisciplinary field of 2D material-based energy storage is rapidly evolving. Our Special Section issue will motivate many researchers to implement novel techniques, such as artificial intelligence, digital twins, and automated advanced manufacturing, in this field and initiate new collaborations between experimentalists, theorists, and modelers. We would like to thank all contributors to this Special Section issue for submitting their latest high-impact work. Also, special thanks would go out to the invited reviewers for helping us further enhance the quality of the articles.

Construction of three-dimensional nickel-vanadium hydrotalcite with ball-flower architecture for screen-printed asymmetric supercapacitor

As a promising energy storage matter, two-dimensional (2D) layered double hydroxides (LDHs) suffer from a lower specific capacitance and poor retention. Morphology engineering is deemed to be an effective means. Herein, three-dimensional (3D) nickel-vanadium hydrotalcite (NiV-LDHs) with ball-flower structure are synthesized successfully via a facile dynamic-refluxing route, such a green strategy dispenses with template and high pressure, and generates a specific surface area as high as 61.6 m2/g. Then, the screen-printed inks with outstanding rheological performances are formulated and the resulting electrodes display superior hydrophilic performance. Benefitted from the 3D architecture and shear-flow process, the NiV-LDHs electrode can deliver an enhanced specific capacitance of 1069 F/g at 1 A/g with cycling stability of ∼68.0 % after 1500 cycles at 20 A/g, in contrast with that of NiV-LDHs prepared by coprecipitation (848 F/g and ∼5.1 %). Furthermore, an asymmetric NiV-LDHs//activated carbon supercapacitor (ASC) is assembled, which can yield a remarkable energy density of 75.8 μWh/cm2 at a power density of 0.80 mW/cm2, and two ASCs in series can illuminate a red light (2.5 V) for more than 270 s. Therefore, this study proposes a facile and economic strategy to prepare 3D nanomaterial for advanced and flexible printable energy storage devices.

The Self-Adhesive Properties of Carbon Activated-Like Shape Coin Derived From Palmae Plant Waste and Used as High-Performance Supercapacitor Electrodes

Abstract Synthesized biomass-based carbonaceous materials from Palmae plant wastes with self-adhesive properties, converted into coin-like shapes, are used as supercapacitor electrodes with high power and energy density, high specific capacitance, excellent electrical conductivity, low cost, and environmentally friendly. Therefore, this study aims to investigate a simple and cost-effective method to generate porous carbon activation from Palmae plant waste biomass, namely areca leaf midrib (ALM). Activated carbon (AC) material derived from ALM was obtained through precarbonization, alkaline chemical activation, and two-step pyrolysis, namely carbonization and physical activation at 600 °C and 700 °C in the N2 as well as CO2 atmosphere, respectively. Its physical properties show an sp2 structure with high graphitization or amorphousness and two sloping peaks in the hkl plane at an angle of 2θ, approximately 24 deg and 44 deg. The electrochemical properties of AC supercapacitor cells derived from ALM biomass have the highest specific capacitance value of 216 F g−1 at a scan rate of 1 mV s−1 in a two-electrode system. Furthermore, the cell obtained a maximum energy density of 11 W h kg−1 and a power density of 196 W kg−1, respectively. Therefore, this study recommends an innovative and environmentally safe approach for producing high-performance supercapacitor cell electrodes for energy storage without adding nanomaterials and externally doped heteroatoms.

The Effects of Graphene Oxide and Reduced Graphene Oxide Conductive Additives on Activated Carbon Supercapacitors

With their relative ease of production and coupled strong surface functionality and electrical conductivity properties, graphene oxide (GO) and reduced graphene oxide (rGO) are exciting, yet overlooked, graphene-like additive prospects for activated carbon (AC) electrodes in supercapacitors. In this work, we incorporated small amounts of synthesized GO and rGO in AC electrodes via a simple mixing procedure to explore their effects. In addition to materials characterizations, symmetric supercapacitors were made from these electrodes and tested across current densities ranging from 0.1–10 A g−1 and across 10,000 additional charge-discharge cycles at 2 A g−1. Performance measurements indicate that GO and rGO enhance the rate resistance and capacity, respectively, of AC electrodes, but these effects are modest and do not prevent increases in internal resistance over the course of 10,000 cycles. The overall ineffectuality of GO and rGO is reasoned to be due to their isolation and infrequency as a result of the relatively impotent distribution method used.

Preparation and Application of Graphene and Derived Carbon Materials in Supercapacitors: A Review

Graphene has recently attracted a wide range of research interests due to its rigorous two-dimensional structure and extraordinary electrical, thermal and mechanical properties. As a conductive agent, an activated carbon supercapacitor can obtain better performance. This paper summarizes the latest research progress, mainly from two aspects: (1) the preparation of an activated carbon base for a supercapacitor based on waste sugar solution and the relationship between pore structure and activation parameters, and (2) the application of the two-dimensional materials graphene and its composite materials in electric double-layer capacitors, graphene–polymer composite tantalum capacitors, graphene–transition metal oxide composite tantalum capacitors, and asymmetric super capacitors. The studies found that graphene and its composite materials have obvious advantages in improving the cycle efficiency, conversion rate, and energy density of supercapacitors, the overall energy efficiency of mechanical systems, and the chemical properties of nanoelectronics. Therefore, it is urgent to summarize these works in order to promote the next development. Graphene is expected to be effectively and environmentally quantified in the near future, and its application in supercapacitors will be further expanded and matured.

An asymmetric MnO2|activated carbon supercapacitor with highly soluble choline nitrate-based aqueous electrolyte for sub-zero temperatures

• Eutectic of choline nitrate and water maintains liquid state down to -100°C. • MnO 2 /carbon supercapacitor at 1.8 V operates down to -40°C. • Charge compensation in MnO 2 by the nitrate ions in presence of bulky choline cations. MnO 2 |activated carbon supercapacitors are attractive power devices that rival the electric double-layer capacitors (EDLCs) due to high reachable voltage. However, they greatly suffer from performance loss at low temperature as most of aqueous electrolytes freeze below ca. -10°C. Here, a concentrated choline nitrate-based (5 mol/L aqueous ChNO 3 ) electrolyte is applied to extend the working temperature range due to its eutectic-like properties. In such electrolyte, water acts as hydrogen bond donor for nitrate anion and low hydration energy for large choline cations favors ionic transport. The MnO 2 /CNT composite electrode with a hierarchical structure has been synthesized by hydrothermal process. The presence of CNTs as core component facilitates the electron conduction, while the two-dimensional MnO 2 flakes grown on the surface provide electrolyte transport pathways and improve the interfacial processes (pseudocapacitive charge/discharge). Thanks to the low hydration of choline cation, the individual activated carbon (AC, negative) and MnO 2 /CNT (positive) electrodes are charged symmetrically up to a cell voltage of 1.8 V. Overall, due to the wide electrochemical stability window (∼2.0 V) and anti-freezing properties of ChNO 3 -based aqueous electrolyte and the hierarchical design of the MnO 2 /CNT composite, the asymmetric supercapacitor operates down to -40 °C and displays excellent energy and coulombic efficiency with no loss of performance after several thousand cycles. This work provides a new possibility on the low temperature application of high voltage supercapacitors.

Production of nanoarchitectonics corncob activated carbon as electrode material for enhanced supercapacitor performance

Corncob was utilized as a low-grade and abundant material for the production of activated carbon through impregnation with potassium carbonate (K2CO3) at different ratios (1:1 to 1:3). The impregnated samples were activated at different temperatures (500 °C to 800 °C) and activated carbons were used to fabricate electrodes for energy storage. The results revealed that increasing activation temperature and K2CO3 tailored the surface area (489–884 m2/g), morphological, and topography of the activated carbon to propagate higher energy storage via a predominantly electric double layer (EDL) mechanism. The capacitive performance of the materials obtained at different temperatures is in the order of 650 °C > 500 °C > 800 °C. In 3-electrode cells, a specific capacitance of 325 F/g was reached at a 5 mV/s scan rate. The energy retention and columbic efficiency after 10,000 charge/discharge cycles were maintained at 88 % and 100 %, respectively. The corncob activated carbon material presented specific energy of 9.9 Wh/kg at 0.25 A/g, which is higher than many reported studies on activated carbon supercapacitors under similar conditions.

Sustainable utilization method of using coal gasification fine ash to prepare activated carbon for supercapacitor

To solve the problems of resource waste and environmental pollution from coal gasification fine ash (CGFA), it is necessary to develop a high-value and sustainable utilization technology. In this study, a sustainable utilization method for CGFA to prepare activated carbon supercapacitor (AC-SC) was proposed for the first time. AC-SC with a high specific surface area was successfully fabricated via a facile deashing pretreatment and subsequent KOH activation. Results showed that with increasing KOH dosage, the specific surface area of AC-SC samples, "C–O or O C–O" functional groups content, and disorder in carbon skeleton increased. Among them, the AC-SC sample (D-800-1-5) with a carbon source to KOH mass ratio of 1:5, activation temperature of 800 °C, and activation time of 1 h showed an ideal micropore-mesoporous composite type pore structure. Moreover, the BET surface area of the sample was 2224.62 m 2 g −1 . The specific capacitance of the D-800-1-5 sample was 124.06 F g −1 @ 0.5 A g −1 , and the capacitance retention rate was as high as 128.7% after 10,000 charge-discharge cycles. These results revealed that D-800-1-5 exhibited excellent capacitance characteristics and rate performance, and proved the feasibility of CGFA as a carbon source for the preparation of AC-SC. The proposed method provided a new technical route for the high value and sustainable utilization of CGFA. • An activated carbon supercapacitor was prepared from coal gasification fine ash. • A technical route for high-value and sustainable use of coal gasification fine ash was proposed. • The method was more facile than the traditional preparation processes. • The BET surface area of the D-800-1-5 sample was 2224.62 m 2 g −1 . • The capacity retention of the material was 128.7% after 10000 cycles.

Macroporous Graphene Frameworks for Sensing and Supercapacitor Applications

Abstract3D architectures based on graphene have triggered a great deal of interest in energy, sensing, and environmental applications. This work describes, a simple electrochemical approach for the direct deposition of a functionalized graphene framework by utilizing electrostatic interactions between graphene oxide (GO) and a cationic surfactant. The surfactant improves the adsorption of GO sheets on the electrode surface, allowing the integration of individual graphene sheets into 3D structures with large electrochemically active surface area. Without using binders or conductive additives, the current approach leads to supercapacitors with high specific capacitance (320 F g−1) and areal capacitance (≈400 mF cm−2 for two electrode cells with single‐sided coatings), which compares favorably to commercial activated carbon supercapacitors. Moreover, the supercapacitors demonstrate low internal resistance (≈1 Ω cm−2), excellent cycling stability (no loss observed after 10 000 cycles) while also maintaining superior rate capability. In another application, these frameworks were successfully implemented as an electrochemical sensor for the simultaneous determination of small biomolecules including ascorbic acid, dopamine and uric acid with high sensitivity, selectivity and reproducibility. This work provides a simple, yet effective, strategy for the fabrication of macroporous electrodes with superior chemical, structural, and electrical properties that are desirable for a broad range of applications.

2.5 V High‐Performance Aqueous and Semi‐Solid‐State Symmetric Supercapacitors Enabled by 3 m Sulfolane‐Saturated Aqueous Electrolytes

Aqueous electrolytes show the potential of application for high‐performance supercapacitors. However, their limited operating voltages set limits for widespread applications. Herein, the feasibility of applying the sulfolane (SL)‐saturated 3 m LiTFSI aqueous electrolytes for supercapacitors is shown. These electrolytes possess high conductivities and wide electrochemical stable windows (ESWs), demonstrating the potential applications in high‐voltage supercapacitors. Activated carbon//3 m LiTFSI SL/Water //activated carbon supercapacitor is assembled to possess a high voltage of 2.5 V and outstanding capacitive performance (106 F g−1 at 0.5 A g−1, >10 000 cycles). Also, a high areal capacitance up to 1.52 F cm−2 is obtained by applying a high mass loading electrode (13.06 mg cm−2). Furthermore, a flexible symmetric semi‐solid‐state supercapacitor (2.5 V) is fabricated. Impressive performance can be obtained. Thus, the finding suggests a promising electrolyte design for high‐voltage aqueous supercapacitors.

An efficient and versatile biopolishing strategy to construct high performance zinc anode

Conventional strategies for highly reversible Zn anodes usually involve complex and time-consuming production processes of current collectors, expensive and toxic electrolyte additives, or the introduction of inactive materials in protective layer. Here, we develop a fast, facile, and environmentally friendly biopolishing method to prepare dendrite-free Zn anodes, which merely involves the simple immersion of Zn foil in a biocompatible cysteine aqueous solution. The ravine structure formed by sulfhydryl etching for 30 min not only increases the electroactive area of Zn anode but also regulates the distribution of electric field and Zn ions, ensuring the homogeneous deposition and stripping of Zn ions. The biopolished Zn anode can be operated steadily for 2,000 h with a low voltage hysteresis at a current density of 1 mA·cm−2. In addition, Zn anodes with a cycle life of 500 h can be built by soaking for only 5 min, proving the high efficiency of the proposed method. This strategy is generalized to substances with sulfhydryl groups for polishing Zn electrodes with improved performance. The cysteine-polished Zn//activated carbon supercapacitor can stably run for 20,000 cycles without obvious capacity attenuation. The proposed strategy shows potential for producing advanced Zn anodes.