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Owing to the increasing low-carbon demand, environmentally friendly supercapacitors with low temperature resistance have attracted increasing attention. Herein, biomass hydrogels were successfully fabricated by covalently cross-linked lignin (Lig) with soy protein isolate (SPI) and assembled into supercapacitors. The performance of hydrogel electrolytes and the electrochemical performance of supercapacitors were studied systematically. The hydrogel electrolyte achieved the highest ionic conductivity of 0.086 S cm−1 with 50% addition of SPI. The supercapacitor displayed an excellent specific capacitance of 150.80 F g−1 at room temperature. Importantly, over 10,000 charge-discharge cycles, the capacitance retention rate maintained more than 73.5%, and the coulombic efficiency was around 100%. Besides, the electrochemical performance of the supercapacitors at low temperature was investigated as well. Even at −20 °C, the flexible supercapacitor could keep a specific capacitance of 135.71 F g−1, with a capacitance retention rate up to 90% of room temperature, indicating a prominent resistance at subzero temperature. Overall, this work lays a foundation for the preparation of environmentally friendly and low temperature resistant solid-state supercapacitors, which is conducive to the practical application under harsh environments. [ABSTRACT FROM AUTHOR]

High performance disulfonated poly(arylene ether sulfone)/poly(ethylene oxide) (SPAES/PEO) composite membranes were prepared by a simple method such as a novel separator saturated by the lithium sulfate (Li2SO4) aqueous electrolyte for application in supercapacitors (SCs). As prepared composite membranes exhibit excellent mechanical properties and thermal stabilities, which are beneficial for the safety in potential applications, meanwhile, the addition of PEO on membrane also enhanced the affinity with electrolyte and the ion conduction for lithium salts. In addition, the SC cell was fabricated with optimized SPAES/PEO composite membrane and activated carbon electrodes with Li2SO4 aqueous electrolyte. The obtained SC with the SPAES/PEO separator revealed a specific capacitance of 142.5 F g−1 at a current density of 0.1 A g−1. Furthermore, the energy density of the SC was promoted to 19.04 Wh kg−1 due to the wide working voltage range of the neutral electrolyte, and the SC exhibited an excellent coulombic efficiency of almost 99% and nearly 100% cycling retention after 5000 galvanostatic charge/discharge cycles. All of these results indicated that SPAES/PEO composite membrane is suitable as a novel separator for SC. [ABSTRACT FROM AUTHOR]

A series of poly(aryl ether sulfone) copolymers containing quaternary ammonium moieties were obtained by polymerization of methylated copolymers, followed by bromination and derivatization with quaternary-ammonium groups. The copolymer membranes exhibited excellent thermal stability and mechanical properties. Symmetric supercapacitor single cells based on activated carbon and quaternary ammonium functionalized poly(aryl ether sulfone) membranes were fabricated into a three-layer structure: activated carbon electrode//quaternary ammonium functionalized poly(aryl ether sulfone) separator//activated carbon electrode and characterized by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy in 6 M KOH aqueous solution. The coulombic efficiency of the supercapacitor was as high as 95% over 5000 cycles. The effect of different degree of quaternization of PAES copolymer separators on thermal and mechanical properties of separators and performance of the symmetric supercapacitor single cells were investigated. [ABSTRACT FROM AUTHOR]

The low energy density of supercapacitors, especially supercapacitors based on aqueous electrolytes, is the main factor limiting their application, and the energy density is closely related to the operating potential window of the supercapacitor. The polymer electrolyte is the main contributor to the safe operation and good ion conductivity of the supercapacitor. In this study, a crosslinked quaternized poly(arylene ether sulfone) (PAES) membrane was prepared via crosslinking during membrane formation with a thermal‐only treatment and applied in an electric double‐layer capacitor (EDLC). The pre‐prepared PAES membrane formed a polymer electrolyte with 1 mol/L Li2SO4 and was then fabricated into an EDLC single cell. The properties of both the membrane and ELDC were investigated. The preferred cPAES‐N‐0.2 polymer electrolyte showed an ionic conductivity of 1.18 mS/cm. The optimized EDLC exhibited a single‐electrode gravimetric capacitance of 104.92 F/g at a current density of 1.0 A/g and a high operating potential window (1.5 V); it, thereby, achieved a high energy density of 8.20 W h/kg. The EDLC also exhibited excellent cycling properties over 3000 charge–discharge cycles. The crosslinked structures promoted the tensile strength and thermal stability of the PAES membranes; this was accompanied by a slight decrease in the ionic conductivity. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47759. [ABSTRACT FROM AUTHOR]

Soy protein isolate (SPI) is one of the most abundant plant proteins in nature. Enormous studies have been carried out on SPI-based materials, however, the application for energy storage devices is still limited due to its fiddly film forming process and lack of electrochemical performance. Herein, we presented a SPI-based polymer electrolyte by grafting modification with the hydrophilic functional monomer acrylamide (AM). The optimized gel polymer electrolyte (GPE) exhibited an excellent ionic conductivity up to 5.10 mS cm−1, which was greatly higher than gel polymer electrolyte based on original pure SPI (1.84 mS cm−1). More significantly, supercapacitors constructed by grafting-modified SPI delivered a specific capacitance of 141.74 F g−1 at 1.0 A g−1 and exhibited high capacitance retention of 95% after 8000 charge−discharge cycles. Beyond that, redox-active polymer electrolyte based on grafting-modified SPI combining with KI enormously improved the energy density of supercapacitor up to 27.52 Wh kg−1 at a current density of 0.5 A g−1. This work provided a novel and facile strategy to obtain a high-performance SPI-based polymer electrolyte and laid an experimental foundation for the high-value application of SPI in the field of energy storage devices. [Display omitted] • SPI was converted to a biomass-based GPE with Li 2 SO 4 for 0–1.5 V potential window. • Grafting modified SPI provided GPE a higher ionic conductivity up to 5.10 mS cm−1. • SC-SPI-g-PAM has a 53.4% increase in capacitance compared to SC-SPI at 1.0 A g−1. • Redox-active KI enhanced the energy density of supercapacitor to 27.52 Wh kg−1. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dual cross-linked hydrogel was prepared with modified lignin at room temperature. • The hydrogel electrolyte has excellent freezing resistance and ionic conductivity. • The supercapacitor provides excellent electrochemical performance at −40 ℃. • The anti-freezing hydrogel can be also applied as a sensor. Hydrogel electrolytes have the dual functions of electrolyte and separator and combine the advantages of liquid and solid electrolytes, making them one of the most ideal candidates for supercapacitors and sensors. However, hydrogel electrolytes are prone to deactivate when the operating temperature is too low. Therefore, dual cross-linked hydrogels with chemical bonds and multiple noncovalent interactions were prepared at room temperature using activated modified lignin. Dual cross-linked hydrogel had excellent mechanical performance and fatigue resistance, whose tensile elongation could reach 700 %. Because the hydrogel contained a concentrated alkaline solution, the electrolyte achieved excellent freezing resistance and a high ionic conductivity of 0.345 S cm−1 (−40 ℃, 0.044 S cm−1). Supercapacitors assembled with the hydrogel electrolyte demonstrated a high specific capacitance of 210 F g−1 (−40 ℃, 176 F g−1) at 1.0 A g−1. Furthermore, the hydrogel electrolyte exhibited good electrochemical properties not only in alkaline environments but also in neutral and acidic conditions. The hydrogel could also act as a flexible sensor with a sensitivity of 1.34 within a 100 % strain, making it a promising material for wearable sensors to monitor joint activities in the human body. [ABSTRACT FROM AUTHOR]

An organic-organic self-assembly hydrothermal synthesis strategy coupled with carbonization is reported to fabricate nitrogen-doped ordered mesoporous carbon microspheres (N-OMCMs) from m -aminophenol-formaldehyde resin. The obtained N-OMCMs possess high-surface-area ordered mesoporous structure, moderate nitrogen content and micrometer-sized sphere-like morphology. And the N-OMCMs exhibit a large specific capacitance up to 288 F g −1 , excellent rate performance (222 F g −1 at 20 A g −1 ) and long-term stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bio-based hydrogel is multifunctional with adhesion and low temperature resistance. • The hydrogel electrolyte showed good ionic conductivity (0.06 S cm−1). • The lignin-based supercapacitor can withstand large bending and compression. • Supercapacitors can maintain a high capacitance retention rate of 76.2 % at −40 °C. For the development of supercapacitors, multifunctional hydrogel electrolytes with flexibility, robust adhesiveness and low-temperature resistance have attracted increasing interest. Lignin is the most abundant renewable aromatic biopolymer in nature, however, it has not gained appropriate attention for hydrogel electrolytes due to its insolubility and lack of flexibility. Herein, an all-bio-based hydrogel is constructed by covalently cross-linked lignin (Lig) with interpenetrating gelatin in alkaline solutions. The multifunctional hydrogel electrolytes with a high ionic conductivity of 0.06 S cm−1, robust adhesiveness and anti-freezing properties are designed. The optimized flexible supercapacitor constructed by Lig/Gelatin hydrogel electrolyte shows a remarkable specific capacitance of 145.14F/g and a high energy density of 4.86 W h kg−1 at 0.5 A g−1 at room temperature. It can retain a comparable specific capacitance of 110.6F/g at 0.5 A g−1 even at −40 °C. The multifunctional lignin-based hydrogel has promising potential for supercapacitors under a broad range of environmental conditions. With this effective strategy, lignin can potentially be used in multifunctional energy storage devices. [ABSTRACT FROM AUTHOR]

Soybean protein isolate (SPI) has good reactivity, hydrophilicity and film-forming properties, but its electrochemical performance is poor when used as a polymer electrolyte matrix. The graft-modification of the SPI using polyacrylic acid (PAA) allows the introduction of strong hydrophilic carboxyl groups into the SPI molecular chains. This enables the SPI to effectively absorb electrolytes in the subsequent electrolyte adsorption process, resulting in a modified polymer electrolyte. The resulting constructed supercapacitor can operate stably in a voltage window of 0–2 V and exhibit excellent electrochemical behavior with a high single electrode specific capacitance up to 293.08 F g−1 and an energy density of 38.76 W h kg−1 at a power density of 734.38 W kg−1, which is much better than SPI-based supercapacitor. This simple, low-cost and environmentally friendly approach has a great potential for the development of high-performance supercapacitor with high voltage window, high specific capacitance and high energy density. [Display omitted] • GPE was prepared based on soybean protein isolate grafted by polyacrylic acid. • GPE-SPI-g-PAA exhibited excellent electrolyte/electrode interface performance. • SC-SPI-g-PAA could be operated stably in a potential window of 0–2 V. • SC-SPI-g-PAA could provide a high energy density up to 38.76 W h kg−1. [ABSTRACT FROM AUTHOR]