Improved-quality graphene films via the synergism of large nanosheet aligning and nanotube bridging for flexible supercapacitors.

Scalable production of reduced graphene oxide (rGO) films with high mechanical-electrical properties are desirable candidates for wearable electronics devices and energy storage applications. Removing structural incompleteness such as wrinkles or voids in the graphene films generated from the assemble process would greatly optimize their mechanical properties. However, the densely stacked graphene sheets in the films degrades their ionic kinetics and thus limits their development. Here, a horizontal-longitudinal-structure modulating strategy is demonstrated to produce enhanced mechanical, conductive and capacitive graphene films. Typically, two-dimensional (2D) large graphene sheets (LGS) induce regular stacking of GO during assembling process to reduce wrinkles, while one-dimensional (1D) single-walled carbon nanotubes (SWCNT) bridge with graphene sheets to strengthen the multidirectional intercalation and reduce GO layer restacking. The simultaneous incorporation of LGS and SWCNT synergistically makes fine microstructure with improving the alignment of graphene sheets, increasing continuous conductive pathways to facilitate electron transport, and enlarging interlayer spacing to promote the electrolyte ion diffusion. As a result, the obtained graphene films are flat and exhibit signally reinforced mechanical properties, electrical conductivity (38727 S m-1), as well as specific capacitance (232 F g-1) as supercapacitor electrodes than those of original rGO films. Moreover, owing to the comprehensive improved properties, the flexible gel supercapacitor assembled by the graphene film-based electrodes shows high energy density, good flexibility and excellent cycling stability (93.8% capacitance retention after 10000 cycles). This work provides a general strategy to manufacture robust graphene structural materials for energy storage applications in flexible and wearable electronics.

Cellulose nanofiber-based hybrid hydrogel electrode with superhydrophilicity enabling flexible high energy density supercapacitor and multifunctional sensors.

Flexible hybrid hydrogels (GO/AC/CNFn) with a 3D porous network structure and superhydrophilic property are synthesized by cross-linking and self-assembling graphene oxide (GO) and activated carbon (AC) with cellulose nanofiber (CNF) during microwave hydrothermal process. In this ternary composite hydrogel, CNF molecular chains bridge GO sheets to build the 3D skeleton and anchor AC particles within GO nanosheets, forming ordered architecture of GO/AC/CNFn hydrogel that simultaneously possesses high flexibility and excellent mechanical integrity. When using this hydrogel as additive-free electrode, the presence of AC provides developed porous structure and density to promote high volumetric capacitance, while the heteroatom nitrogen groups tune the surface property of the composite with increased electrical conductivity. Benefited from the optimized structure, GO/AC/CNF1 electrode delivers an ultra-high mass specific capacitance of 627 F/g and volume specific capacitance of 618 F/cm3 at 0.5 A/g in three-electrode system in 1 M H2SO4 electrolyte, which is kinetically demonstrated to be essentially originated from the capacitive contributions. The energy density reaches 32.2 Wh/kg at a power density of 150 W/kg for the fabricated flexible solid-state symmetric supercapacitor. Moreover, the obtained flexible device could sensitively response at varied physiological signals, shedding fresh lights on their potential applications in signal sensors and portable electronics.

Chitosan-based high-performance flexible supercapacitor via "in-situ co-doping/self-regulation-activation" strategy.

The construction of N, P co-doped hierarchically porous carbons (NPHPC) by a facile and green approach is crucial for high-performance energy storage but still an enormous challenge. Herein, an environment-friendly "in-situ co-doping, self-regulation-activation" strategy is presented to one-pot synthesize NPHPC using a phytic acid-induced polyethyleneimine/chitosan gel (PEI-PA-CS) as single precursor. NPHPC displayed a specific surface area of up to 1494 m2 g-1, high specific capacitance of 449 F g-1 at 1 A g-1, outstanding rate capability and cycling durability in a wide temperature range (-20 to 60 °C). NPHPC and PEI-PA-CS electrolyte assembled symmetric quasi-solid-state flexible supercapacitor presents superb energy outputs of 27.06 Wh kg-1 at power density of 225 W kg-1. For capacitive deionization (CDI), NPHPC also exhibit an excellent salt adsorption capacity of 16.54 mg g-1 in 500 mg L-1 NaCl solution at a voltage of 1.4 V, and regeneration performance. This study provides a valuable reference for the rational design and synthesis of novel biomass-derived energy-storage materials by integrating phytic acid induced heteroatom doping and pore engineering.

Femtosecond Laser Direct Writing of Flexible Electronic Devices: A Mini Review.

By virtue of its narrow pulse width and high peak power, the femtosecond pulsed laser can achieve high-precision material modification, material additive or subtractive, and other forms of processing. With additional good material adaptability and process compatibility, femtosecond laser-induced application has achieved significant progress in flexible electronics in recent years. These advancements in the femtosecond laser fabrication of flexible electronic devices are comprehensively summarized here. This review first briefly introduces the physical mechanism and characteristics of the femtosecond laser fabrication of various electronic microdevices. It then focuses on effective methods of improving processing efficiency, resolution, and size. It further highlights the typical progress of applications, including flexible energy storage devices, nanogenerators, flexible sensors, and detectors, etc. Finally, it discusses the development tendency of ultrashort pulse laser processing. This review should facilitate the precision manufacturing of flexible electronics using a femtosecond laser.

Constructing a 3D Ion Transport Channel-Based CNF Composite Film with an Intercalated Structure for Superior Performance Flexible Supercapacitors.

The weak stiffness, huge thickness, and low specific capacitance of commonly utilized flexible supercapacitors hinder their great electrochemical performance. Learning from a biomimetic interface strategy, we design flexible film electrodes based on functional intercalated structures with excellent electrochemical properties and mechanical flexibility. A composite film with high strength and flexibility is created using graphene (reduced graphene oxide (rGO)) as the plane layer, layered double metal hydroxide (LDH) as the support layer, and cellulose nanofiber (CNF) as the connection agent and flexible agent. The interlayer height can be adjusted by the ion concentration. The highly interconnected network enables excellent electron and ion transport channels, facilitating rapid ion diffusion and redox reactions. Moreover, the high flexibility and mechanical properties of the film achieve multiple folding and bending. The CNF-rGO-NiCoLDH film electrode exhibits high capacitance performance (3620.5 mF cm-2 at 2 mA cm-2), excellent mechanical properties, and high flexibility. Notably, flexible all-solid assembled CNF-rGO-NiCoLDH//rGO has an extremely high area energy density of 53.5 mWh cm-2 at a power density of 1071.2 mW cm-2, along with cycling stability of 89.8% retention after 10 000 charge-discharge cycles. This work provides a perspective for designing high-performance energy storage materials for flexible electronics and wearable devices.

Pseudocapacitive Kinetics in Synergistically Coupled MoS2-Mo2N Nanowires with Enhanced Interfaces toward All-Solid-State Flexible Supercapacitors.

Pseudocapacitive kinetics in rationally engineered nanostructures can deliver higher energy and power densities simultaneously. The present report reveals a high-performance all-solid-state flexible symmetric supercapacitor (FSSC) based on MoS2-Mo2N nanowires deposited directly on stainless steel mesh (MoS2-Mo2N/SSM) employing DC reactive magnetron co-sputtering technology. The abundance of synergistically coupled interfaces and junctions between MoS2 nanosheets and Mo2N nanostructures across the nanocomposite results in greater porosity, increased ionic conductivity, and superior electrical conductivity. Consequently, the FSSC device utilizing poly(vinyl alcohol)-sodium sulfate (PVA-Na2SO4) hydrogel electrolyte renders an outstanding cell capacitance of 252.09 F·g-1 (44.12 mF·cm-2) at 0.25 mA·cm-2 and high rate performance within a wide 1.3 V window. Dunn's and b-value analysis reveals significant energy storage by surface-controlled capacitive and pseudocapacitive mechanisms. Remarkably, the symmetric device boosts tremendous energy density ∼10.36 µWh·cm-2 (59.17 Wh·kg-1), superb power density ∼6.5 mW·cm-2 (37.14 kW·kg-1), ultrastable long cyclability (∼93.7% after 10,000 galvanostatic charge-discharge cycles), and impressive mechanical flexibility at 60°, 90°, and 120° bending angles.

Cross-Linked Polyacrylic-Based Hydrogel Polymer Electrolytes for Flexible Supercapacitors.

Hydrogel polymer electrolytes (GPEs), as an important component of flexible energy storage devices, have gradually received wide attention compared with traditional liquid electrolytes due to their advantages of good mechanical, bending, and safety properties. In this paper, two cross-linked GPEs of poly(acrylic acid-co-acrylamide) or poly(acrylic acid-co-N-methylolacrylamide) with NaNO3 aqueous solution (P(AA-co-AM)/NaNO3 or P(AA-co-HAM)/NaNO3) were successfully prepared using radical polymerization, respectively, using acrylic acid (AA) as the monomer, N-methylolacrylamide (HAM) or acrylamide (AM) as the comonomer, and N, N-methylenebisacrylamide (MBAA) as the cross-linking agent. We investigated the morphology, glass transition temperature (Tg), ionic conductivities, mechanical properties, and thermal stabilities of the two GPEs. By comparison, P(AA-co-HAM)/NaNO3 GPE exhibits a higher ionic conductivity of 2.00 × 10-2 S/cm, lower Tg of 152 °C, and appropriate mechanical properties, which are attributed to the hydrogen bonding between the -COOH and -OH, and moderate cross-linking. The flexible symmetrical supercapacitors were assembled with the two GPEs and two identical activated carbon electrodes, respectively. The results show that the flexible supercapacitor with P(AA-co-HAM)/NaNO3 GPE shows good electrochemical performance with a specific capacitance of 63.9 F g-1 at a current density of 0.2 A g-1 and a capacitance retention of 89.4% after 3000 charge-discharge cycles. Our results provide a simple and practical design strategy of GPEs for flexible supercapacitors with wide application prospects.

Mechanically Robust and Highly Conductive Poly(ionic liquid)/Polyacrylamide Double-Network Hydrogel Electrolytes for Flexible Symmetric Supercapacitors with a Wide Operating Voltage Range.

Flexible electronic devices, such as supercapacitors (SCs), place high demands on the mechanical properties, ionic conductivity, and electrochemical stability of electrolytes. Hydrogels, which combine flexibility and the advantages of both solid and liquid electrolytes, will meet the demand. Here, we report the synthesis of novel poly(ionic liquid)/polyacrylamide double-network (DN) (PIL/PAM DN) hydrogel electrolytes containing different metal salts via a two-step γ-radiation method. The resultant Li2SO4-1.0/PIL/PAM DN hydrogel electrolyte possesses excellent mechanical properties (tensile strength of 3.64 MPa, elongation at break of 446%) and high ionic conductivity (24.1 mS·cm-1). The corresponding flexible SC based on the Li2SO4-1.0/PIL/PAM DN hydrogel electrolyte (SC-Li2SO4) presents improved ion diffusion, ideal electrochemical double-layer capacitor behavior, good rate capability, and excellent cyclic stability. Moreover, symmetric SC-Li2SO4 achieves a wide operating voltage range of up to 1.5 V, with a maximum energy density of 26.0 W h·kg-1 and a capacitance retention of 94.1% after 10,000 galvanostatic charge-discharge cycles, owing to the deactivation of free water molecules by the synergistic effect of PIL, PAM, and SO42-. Above all, the capacitance of SC-Li2SO4 is well-maintained after overcharge, overdischarge, short circuit, extreme temperature, compression, and bending tests, indicating its high security and flexibility. This work reveals the enormous application potential of PIL-based conductive hydrogel electrolytes for flexible electronic devices.

Pseudocapacitive Storage in Molybdenum Oxynitride Nanostructures Reactively Sputtered on Stainless-Steel Mesh Towards an All-Solid-State Flexible Supercapacitor.

Exploiting pseudocapacitance in rationally engineered nanomaterials offers greater energy storage capacities at faster rates. The present research reports a high-performance Molybdenum Oxynitride (MoON) nanostructured material deposited directly over stainless-steel mesh (SSM) via reactive magnetron sputtering technique for flexible symmetric supercapacitor (FSSC) application. The MoON/SSM flexible electrode manifests remarkable Na+-ion pseudocapacitive kinetics, delivering exceptional ≈881.83 F g-1 capacitance, thanks to the synergistically coupled interfaces and junctions between nanostructures of Mo2N, MoO2, and MoO3 co-existing phases, resulting in enhanced specific surface area, increased electroactive sites, improved ionic and electronic conductivity. Employing 3D Bode plots, b-value, and Dunn's analysis, a comprehensive insight into the charge-storage mechanism has been presented, revealing the superiority of surface-controlled capacitive and pseudocapacitive kinetics. Utilizing PVA-Na2SO4 gel electrolyte, the assembled all-solid-state FSSC (MoON/SSM||MoON/SSM) exhibits impressive cell capacitance of 30.7 mF cm-2 (438.59 F g-1) at 0.125 mA cm-2. Moreover, the FSSC device outputs a superior energy density of 4.26 µWh cm-2 (60.92 Wh kg-1) and high power density of 2.5 mW cm-2 (35.71 kW kg-1). The device manifests remarkable flexibility and excellent electrochemical cyclability of ≈91.94% over 10,000 continuous charge-discharge cycles. These intriguing pseudocapacitive performances combined with lightweight, cost-effective, industry-feasible, and environmentally sustainable attributes make the present MoON-based FSSC a potential candidate for energy-storage applications in flexible electronics.

Li Salt Assisted Highly Flexible Carbonaceous Ni3N@polyimide Electrode for an Efficient Asymmetric Supercapacitor.

This work used a highly flexible, sustainable polyimide tape as a substrate to deposit ductile-natured carbonaceous Ni3N (C/Ni3N@polyimide) material for supercapacitor application. C/Ni3N was prepared using a co-sputtering technique, and this method also provided better adhesion of the electrode material over the substrate, which is helpful in improving bending performance. The ductile behavior of the sputter-grown electrode and the high flexibility of the polyimide tape provide ultimate flexibility to the C/Ni3N@polyimide-based supercapacitor. To achieve optimum electrochemical performance, a series of electrochemical tests were done in the presence of various electrolytes. Further, a flexible asymmetric supercapacitor (NC-FSC) (C/Ni3N//carbon@polyimide) was assembled by using C/Ni3N as a cathode and a carbon thin film as an anode, separated by a GF/C-glass microfiber soaked in optimized 1 M Li2SO4 aqueous electrolyte. The NC-FSC offers a capacitance of 324 mF cm-2 with a high areal energy density of 115.26 µWh cm-2 and a power density of 811 µW cm-2, with ideal bending performance.

Nanocellulose/carbon nanotube/manganese dioxide composite electrodes with high mass loadings for flexible supercapacitors.

The increasing commercialization of flexible electronic products has sparked a rising interest in flexible wearable energy storage devices. Supercapacitors are positioned as one of the systems with the most potential due to their distinctive advantages: high power density, rapid charge and discharge rates, and long cycle life. However, electrode materials face challenges in providing excellent mechanical strength while ensuring sufficient energy density. This study presents a method for constructing a flexible composite electrode material with high capacitance and mechanical performance by electrochemically depositing high-quality manganese dioxide (MnO2) onto the surface of a nanocellulose (CNF) and carbon nanotube (CNT) conductive film. In this electrode material, the CNF/CNT composite film serves as a flexible conductive substrate, offering excellent mechanical properties (modulus of 3.3 GPa), conductivity (55 S/cm), and numerous active sites. Furthermore, at the interface between MnO2 and the CNF/CNT substrate, C-O-Mn bonds are formed, promoting a tight connection between the composite materials. The assembled symmetric flexible supercapacitor (FSC) demonstrates impressive performance, with an areal specific capacitance of 934 mF/cm2, an energy density of 43.10 Wh/kg, a power density of 166.67 W/kg and a long cycle life (85 % Capacitance retention after 10,000 cycles), suggesting that they hold promise for FSC applications.

Flexible All-Solid-State Asymmetric Supercapacitors Based on PPy-Decorated SrFeO3-δ Perovskites on Carbon Cloth.

The defective structure and high oxygen vacancy concentration of SrFeO3-δ perovskite enable fast ion-electron transport, but its low conductivity still hinders the high electrochemical performance. Herein, to enhance the conductivity of SrFeO3-δ-based electrodes, polypyrrole-modified SrFeO3-δ perovskite on carbon cloth (PPy@SFO@CC) has been successfully fabricated by electrodeposition of polypyrrole (PPy) on the surface of SFO@CC. The optimal PPy700@SFO@CC electrode exhibits a specific capacitance of 421 F g-1 at 1 A g-1. It was found that the outside PPy layer not only accelerates the electron transport and ion diffusion but also creates more oxygen vacancies in SrFeO3-δ, enhancing the charge storage performance significantly. Moreover, the NiCo2O4@CC//PPy700@SFO@CC device maintains a specific capacitance of 63.6% after 3000 cycles, which is ascribed to the weak adhesion forces between the active materials and carbon cloth. Finally, the all-solid-state flexible supercapacitor NiCo2O4@CC//PPy700@SFO@CC is constructed with PVA-KOH as the solid electrolyte, delivering an energy density of 16.9 W h kg-1 at a power density of 984 W kg-1. The flexible supercapacitor retains 69% of its specific capacitance after 1000 bending and folding times, demonstrating a certain degree of foldability. The present study opens new avenues for perovskite oxide-based flexible all-solid-state supercapacitors.

Regenerated silk protein based hybrid film electrode with large area specific capacitance, high flexibility and light weight towards high-performance wearable energy storage.

Planar wearable supercapacitors (PWSCs) have sparked intense interest owing to their hopeful application in smart electronics. However, current PWSCs suffered from poor electrochemical property, weak flexibility and/or large weight. To relieve these defects, in this study, we fabricated a high-performance PWSC using silk protein derived film electrodes (PPy/RSF/MWCNTs-2; RSF, PPy and MWCNTs represent regenerated silk film, polypyrrole and multi-walled carbon nanotubes, respectively, while 2 is the mass ratio of silk to MWCNTs), which were developed by 'dissolving-mixing-evaporating' and in situ polymerization. In three-electrode, PPy/RSF/MWCNTs-2 showed a superb area specific capacitance of 8704.7 mF cm-2 at 5 mA cm-2, which surpassed numerous reported PWSC electrodes, and had a decent durability with a capacitance retention of 90.7 % after 5000 cycles. The PPy/RSF/MWCNTs-2 derived PWSC showed a largest energy density of 281.3 µWh cm-2 at 1660.1 µW cm-2, and a power density as high as 13636.4 µW cm-2 at 125.6 µWh cm-2. Furthermore, impressive capacitive-mechanical stability with a capacitance retention of 92 % under bending angles from 0 to 150 was depicted. Thanks to the rational and affordable preparation, our study for the first time prepared RSF electrode that had great capacitive property, high mechanical flexibility and light weight, simultaneously. The encouraging results can not only open up a new path to manufacture high-performance flexible electrodes, but may also help to realize the high-value-added utilization of silk.

Expanded Carbon Nanotube Fiber at the Liquid-Air Interface for High-Performance Fiber-Based Supercapacitors and Electrochemical Sensors.

Carbon nanotube fibers (CNTFs) are widely utilized in flexible and wearable electronics due to their outstanding electrical and mechanical properties. However, the spinning process of CNTFs has limited the CNTs from exposure, leading to an ultralow usage efficiency of individual CNTs. Here, we propose an electrochemical expansion strategy of a single CNTF at the liquid-air interface, forming a macroscopic spindle-shaped CNTF (SS-CNTF) with an enlarged volume of up to 5000-fold upon the spindle. The obtained spindle-shaped structure endows CNTF with a high specific surface area together with excellent conductivity and good mechanical properties. Therefore, the SS-CNTF-based devices exhibit outstanding performances both in energy storage (electrical double-layer supercapacitor, energy density: 11.22 Wh kg-1, power density: 203.9 kW kg-1) and electrochemical sensing (ascorbic acid: 1.26 µA µM-1 cm-2; dopamine: 103.91 µA µM-1 cm-2; uric acid: 11.53 µA µM-1 cm-2). The novel architecture of SS-CNTF prepared by one-step electrochemical expansion at the liquid-air interface enabled its high performance in multiple applications, providing new insight into the development of CNTF-based devices.

"Improving with using" effect and mechanism analysis of electrodeposited poly(1,5-diaminoanthraquinone)/carbon cloth electrode for high-performance flexible supercapacitors.

As a robust and conductive substrate, carbon cloth (CC) has been modified with various pseudocapacitive materials to boost its electrochemical performance in flexible supercapacitors. Here, poly(1,5-diaminoanthraquinone) (PDAA) electrodeposited CC electrodes were developed and much higher areal specific capacitance was obtained in comparison with the functionalized CC (FCC). Most importantly, an unusual phenomenon of "improving with using" was found for the optimized one, FCC@PDAA-3, which exhibited the increased capacitance retention from 150.4% to 194.8% with increasing the number of cycles from 10,000 to 50,000. Such extraordinary cyclic life was mainly ascribed to the doping and electropolymerization of the encapsulated 1,5-diaminoanthraquinone (DAA) in the immobilized PDAA during the electrochemical cycles. These findings are expected to contribute to a deeper understanding of the pseudocapacitive materials evolution during long charging/discharging cycles, favoring the design of long-life supercapacitors for practical application.

Highly Conductive and Reusable Cellulose Hydrogels for Supercapacitor Applications.

We report Na-Alginate-based hydrogels with high ionic conductivity and water content fabrication using poly (3,4-ethylene dioxythiophene) (PEDOT): poly (4-styrene sulfonic acid) (PSS) and a hydrogel matrix based on dimethyl sulfoxide (DMSO). DMSO was incorporated within the PEDOT:PSS hydrogel. A hydrogel with higher conductivity was created through the in-situ synthesis of intra-Na-Alginate, which was then improved upon by H2SO4 treatment. Field emission scanning electron microscopy (FESEM) was used to examine the surface morphology of the pure and synthetic hydrogel. Structural analysis was performed using Fourier-transform infrared spectroscopy (FTIR). Thermogravimetric analysis (TGA), which examines thermal properties, was also used. A specific capacitance of 312 F/g at 80 mV/s (energy density of 40.58 W/kg at a power density of 402.20 W/kg) at 100 DC mA/g was achieved by the symmetric Na-Alginate/PEDOT:PSS based flexible supercapacitor. The electrolyte achieved a higher ionic conductivity of 9.82 × 10-2 and 7.6 × 10-2 Scm-1 of Na-Alginate and a composite of Na-Alginate/PEDOT:PSS at 25 °C. Furthermore, the supercapacitor Na-Alginate/PEDOT:PSS//AC had excellent electrochemical stability by showing a capacity retention of 92.5% after 3000 continuous charge-discharge cycles at 10 mA current density. The Na- Alginate/PEDOT:PSS hydrogel displayed excellent flexibility and self-healing after re-contacting the two cut hydrogel samples of electrolyte for 90 min because of the dynamic cross-linking network efficiently dissipated energy. The illumination of a light-emitting diode (LED) verified the hydrogel's capacity for self-healing.

Rapid fabrication of tough sodium alginate/MXene/poly(vinyl alcohol) dual-network hydrogel electrolytes for flexible all-solid-state supercapacitors.

With the rapid development of flexible portable devices, polymer-based hydrogel electrolytes have drawn tremendous attention and widespread interest to replace conventional liquid electrolytes. Herein, an eco-friendly, low cost and fast method was adopted to synthesize novel cross-linked dual-network hydrogel electrolytes (PVA/SA/MXene-NaCl) within 5 min due to the formation of borate bonds. The unique dual-network structure of hydrogel enabled hydrogel electrolytes to efficiently dissipate energy under deformation and the formation of borate bonds endowed hydrogel with self-healing ability. Benefited from the introduction of NaCl and MXene, the hydrogels displayed a high ionic conductivity (40.8 mS/cm) and enhanced mechanical strength (650 kPa). Notedly, the flexible supercapacitor with low concentration of NaCl (0.3 mol L-1) delivered a superior areal capacitance of 130.8 mF cm-2 at 1 mA cm-2 and 106.2 mF cm-2 at 3 mA cm-2, and simultaneously offered remarkable capacitance retention under the state of bending, self-healing (five cycles), compression and stretching. Moreover, as-assembled supercapacitor maintained about 88.9 % of its original capacitance and 90.5 % of Coulombic efficiency after 5000 charge-discharge cycles. Our research presented a simple and universally pathway to prepare flexible energy storage devices with excellent mechanical and electrochemical properties.

Inorganic-Organic Double Network Ionogels Based on Silica Nanoparticles for High-Temperature Flexible Supercapacitors.

Herein, we demonstrate an inorganic-organic double network gel electrolyte consisting of a silica particle network and a poly-2-hydroxyethyl methacrylate network in which 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquids are confined. The as-synthesized double network ionogel electrolytes exhibited high ion conductivity of 3.8 to 12.8 mS cm-1 over a wide temperature range of 30 to 150 °C and mechanical integrity with a maximum toughness of 1.8 MJ m-3 at 30 °C. These remarkable properties of the ionogel were associated with the formation of an optimal physical network of the silica nanoparticles in the colloidal dispersion. Accordingly, a flexible supercapacitor using ionogel electrolytes and reduced graphene oxide electrodes delivered energy and power densities of 48 Wh kg-1 and 4 kW kg-1, respectively, even at a high temperature of 120 °C, demonstrating excellent long-term stability that retains 93% of the initial capacitance even over 10,000 charge/discharge cycles at 120 °C.

Scalable Solution Phase Synthesis of 2D Siloxene via a Two-Step Interlayer Expansion Process.

Two-dimensional (2D) siloxene is attracting considerable research interest recently principally owing to its inherent compatibility with silicon-based semiconductor technology. -The synthesis of siloxene has been mostly limited to multilayered structures using traditional topochemical reaction procedures. Herein, we report high-yield synthesis of single to few-layer siloxene nanosheets by developing a two-step interlayer expansion and subsequent liquid phase exfoliation procedure. Our protocol enables high-yield production of few-layer siloxene nanosheets with a lateral dimension of up to 4 µm and thickness ranging from 0.8 to 4.8 nm, corresponding to single to a few layers, well stabilized in water. The atomically flat nature of exfoliated siloxene can be exploited for the construction of 2D/2D heterostructure membranes via typical solution processing. We demonstrate highly ordered graphene/siloxene heterostructure films with synergistic mechanical and electrical properties, which deliver noticeably high device capacitance when assembled into a coin cell symmetric supercapacitor device structures. Additionally, we demonstrate that the mechanically flexible exfoliated siloxene-graphene heterostructure enables its direct use in flexible and wearable supercapacitor applications.

Preparation of lignin-based hydrogels, their properties and applications.

Polymers obtained from biomass are a concerning alternative to petro-based polymers because of their low cost of manufacturing, biocompatibility, ecofriendly and biodegradability. Lignin as the second richest and the only polyaromatics bio-polymer in plant which has been most studied for the numerous applications in different fields. But, in the past decade, the exploitation of lignin for the preparation of new smart materials with improved properties has been broadly sought, because lignin valorization plays one of the primary challenging issues of the pulp and paper industry and lignocellulosic biorefinery. Although, well suited chemical structure of lignin comprises of many functional hydrophilic and active groups, such as phenolic hydroxyls, carboxyls and methoxyls, which provides a great potential to be applied in the preparation of biodegradable hydrogels. In this review, lignin hydrogel is covered with preparation strategies, properties and applications. This review reports some important properties, such as mechanical, adhesive, self-healing, conductive, antibacterial and antifreezing properties were then discussed. Furthermore, herein also reviewed the current applications of lignin hydrogel, including dye adsorption, smart materials for stimuli sensitive, wearable electronics for biomedical applications and flexible supercapacitors. Overall, this review covers recent progresses regarding lignin-based hydrogel and constitutes a timely review of this promising material.