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As a common two-dimensional carbon material, graphene has been widely doped into polymers to prepare high-performance dielectric materials. However, the shortcomings of graphene, such as large specific surface area and poor dispersion, limit its further application. Therefore, in this work, to solve the problem regarding the uniform dispersion of graphene in the matrix, in situ polymerization was used to prepare graphene/polyimide films, in which 1,4-diiodobutane was used as a reduction agent to prevent the aggregation of graphene oxide (GO) during imidization. High dielectric constant composite films were obtained by adjusting the ratio of 1,4-diiodobutane in GO. The results show that the resulting graphene/polyimide composite film possessed a dielectric constant of up to 197.5, which was more than 58 times higher than that of the polyimide (PI) film. Furthermore, compared to the pure PI film, the composite films showed better thermal stability and mechanical properties. Thermal performance tests showed that the 1,4-diiodobutane added during the preparation of the composite film was thermally decomposed, and there was no residue. We believe our preparation method can be extended to other high dielectric composite films, which will facilitate their further development and application in high power density energy storage materials. [ABSTRACT FROM AUTHOR]

In terms of new-generation energy-storing devices, aqueous zinc-ion batteries (AZIBs) are becoming the prime candidates because of their inexpensive nature, inherent safety, environmental benignity and abundant resources. Nevertheless, due to a restrained selection of cathodes, AZIBs often perform unsatisfactorily under long-life cycling and high-rate conditions. Consequently, we propose a facile evaporation-induced self-assembly technique for preparing V2O3@carbonized dictyophora (V2O3@CD) composites, utilizing economical and easily available biomass dictyophora as carbon sources and NH4VO3 as metal sources. When assembled in AZIBs, the V2O3@CD exhibits a high initial discharge capacity of 281.9 mAh g−1 at 50 mA g−1. The discharge capacity is still up to 151.9 mAh g−1 after 1000 cycles at 1 A g−1, showing excellent long-cycle durability. The extraordinary high electrochemical effectiveness of V2O3@CD could be mainly attributed to the formation of porous carbonized dictyophora frame. The formed porous carbon skeleton can ensure efficient electron transport and prevent V2O3 from losing electrical contact due to volume changes caused by Zn2+ intercalation/deintercalation. The strategy of metal-oxide-filled carbonized biomass material may provide insights into developing high-performance AZIBs and other potential energy storage devices, with a wide application range. [ABSTRACT FROM AUTHOR]

Materials with outstanding mechanical properties and excellent dielectric properties are increasingly favored in the microelectronics industry. The application of polyimide (PI) in the field of microelectronics is limited because of the fact that PI with excellent mechanical properties does not have special features in the dielectric properties. In this work, PI composite films with high dielectric properties and excellent mechanical properties are fabricated by in-situ reduction of fluorinated graphene (FG) in polyamide acid (PAA) composites. The dielectric permittivity of pure PI is 3.47 and the maximum energy storage density is 0.664 J/cm3 at 100 Hz, while the dielectric permittivity of the PI composite films reaches 235.74 under the same conditions, a 68-times increase compared to the pure PI, and the maximum energy storage density is 5.651, a 9-times increase compared to the pure PI films. This method not only solves the problem of the aggregation of the filler particles in the PI matrix and maintains the intrinsic excellent mechanical properties of the PI, but also significantly improves the dielectric properties of the PI. [ABSTRACT FROM AUTHOR]

It is an effective way to develop basswood (Tilia americana, hardwood)-derived thick carbon electrode for high energy density supercapacitors. The wood-derived anisotropic structural carbon electrodes have different transfer kinetics of the electrolyte, which will significantly affect the electrochemical performance especially at high current density. Therefore, the relationship between the sectional wood-derived electrodes and the electrochemical performance of supercapacitors were systematically studied. The results show that the high specific surface area (542 m2 g−1) of cross-sectional wood-derived carbon contributes to the excellent electrochemical performance (specific/area capacitance ~ 3040 mF cm−2/118 F g−1 at 1 mA cm−2, cycle stability ~ 82.2% after 10,000 cycles at 50 mA cm−2, and capacitive contribution of 76.64% at 5 mV s−1), which is attributed to the hierarchical porous structure and easily allows electrolytes to enter the interior even at high current density. This work provides a fundamental understanding of the dynamic behaviors of electrolyte at different wood sections, and it is expected to be extended to other wood species and wood-like structures for energy storage applications. [ABSTRACT FROM AUTHOR]

Flax fibers, with abundant resources and a low cost, are an excellent precursor of carbon fibers for supercapacitors. At present, they are very attractive for designing electrodes with high electrochemical performance via a simple and green way. Hence, we systemically control the specific surface area and pore structure of flax-based carbon fibers by impregnating them with zinc chloride (ZnCl2) solution. The results show that the dehydration and expansion effects of ZnCl2 affect the microstructure, which is directly related to the specific capacitance. After activation, the optimized electrode exhibited the highest specific capacitance of 105 F g−1 at a current density of 1 A g−1, which has been improved by more than 10 times compared to that of pure-flax based carbon fibers. Moreover, they also show an excellent cycling stability of 98.7% after 10 000 cycles, even at a high current density of 10 A g−1. These results further demonstrate that flax-based electrodes have potential to be applied to some relevant energy storage applications in the future. [ABSTRACT FROM AUTHOR]

Designing energy storage devices from thick carbon electrodes with high areal/volumetric energy density via a simple and green way is very attractive but still challenging. Cellulose, as an excellent precursor for thick carbon electrodes with abundant sources and low cost, is usually activated by a chemical activator and pyrolysis route to achieve high electrochemical performance. However, there are still some problems to be addressed, such as the harsh activation conditions, easy collapse of porous structures, and the high cost. Herein, a 3D self‐supporting thick carbon electrode derived from wood‐based cellulose is proposed for high areal and volumetric energy density of supercapacitor from a mild, simple, and green enzymolysis treatment. Benefiting from the high specific surface area (1418 m2 g−1) and abundant active sites on the surface of wood‐derived hierarchically porous structures and enzymolysis‐induced micropores and mesopores, the assembled symmetry supercapacitor from the thick carbon electrode can realize the high areal/volumetric energy density of 0.21 mWh cm−2/0.99 mWh cm−3 with excellent stability of 86.58% after 15 000 long‐term cycles at 20 mA cm−2. Significantly, the simple and universal strategy to design material with high specific surface area, provides a new research idea for realizing multi‐functional application. [ABSTRACT FROM AUTHOR]

[Display omitted] The flexible and self-healing supercapacitors (SCs) are considered to be promising smart energy storage devices. Nevertheless, the SCs integrated with flexibility, lightweight, pattern editability, self-healing capabilities and desirable electrochemical properties remain a challenge. Herein, an all-in-one self-healing SC fabricated with the free-standing hybrid film (TCMP) composed of the 2,2,6,6-tetramethylpiperidin-1-yloxy-oxidized cellulose nanofibers (TOCNs) carried carbon nanotubes (CNTs), manganese dioxide (MnO 2) and polyaniline (PANI) as the electrode, polyvinyl alcohol/sulfuric acid (PVA/H 2 SO 4) gel as the electrolyte and dynamically cross-linked cellulose nanofibers/PVA/sodium tetraborate decahydrate (CNF/PB) hydrogel as the self-healing electrode matrix is developed. The TCMP film electrodes are fabricated through a facile in-situ polymerization of MnO 2 and PANI in TOCNs-dispersed CNTs composite networks, exhibiting lightweight, high electrical conductivity, flexibility, pattern editability and excellent electrochemical properties. Benefited from the hierarchically porous structure and high mechanical properties of TOCNs, excellent electrical conductivity of CNTs and the desirable synergistic effect of pseudocapacitance induced by MnO 2 and PANI, the assembled SC with an interdigital structure demonstrated a high areal capacitance of 1108 mF cm−2 at 2 mA cm−2, large areal energy density of 153.7 μWh cm−2 at 1101.7 μW cm−2. A satisfactory bending cycle performance (capacitance retention up to 95 % after 200 bending deformations) and self-healing characteristics (∼90 % capacitance retention after 10 cut/repair cycles) are demonstrated for the TCMP-based symmetric SC, delivering a feasible strategy for electrochemical energy storage devices with excellent performance, designable patterns and desirable safe lifespan. [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile "chemical blowing" strategy is developed to expand the dense and micron-scale thickness walls into interconnected carbon nanosheets. • Zn(NO 3) 2 is proved to functioned as blowing agent, precursor of template, activator, and nitrogen dopant. • The optimized thick carbon monolith with high-mass loading (∼30 mg cm−2) delivers encouraging capacitive performance in low-temperature. Biomass-derived carbon materials are promising electrode materials for capacitive energy storage. Herein, inspired by the hierarchical structure of natural wood, carbon monoliths built up by interconnected porous carbon nanosheets with enriched vertical channels were obtained via zinc nitrate (Zn(NO 3) 2)-assisted synthesis and served as thick electrodes for capacitive energy storage. Zn(NO 3) 2 is proved to function as expansion agent, activator, dopant, and precursor of the template. The dense and micron-scale thickness walls of wood were expanded by Zn(NO 3) 2 into porous and interconnected nanosheets. The pore volume and specific surface area were increased by more than 430 %. The initial specific capacitance and rate performance of the optimized carbon monolith was approximately three times that of the pristine dense carbon framework. The assembled symmetric supercapacitor possessed a high initial specific capacitance of 4564 mF cm−2 (0–1.7 V) at −40 °C. Impressively, the robust device could be cycled more than 100,000 times with little capacitance attenuation. The assembled zinc-ion hybrid capacitor (0.2–2 V) delivered a large specific capacitance of 4500 mF cm−2 at −40 °C, approximately 74 % of its specific capacitance at 25 °C. Our research paves a new avenue to design thick carbon electrodes with high capacitive performance by multifunctional Zn(NO 3) 2 for low-temperature applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two basic design strategies for 3D COFs: high valency and functionalization. • 3D COFs: building blocks, topology, linkage, and PSM strategy. • Applications in adsorption and separation, catalysis, stimulus response, conduction and energy storage. • The challenges and opportunities are proposed for future research. Covalent organic frameworks (COFs) are a class of porous crystalline organic materials. The dynamic chemistry of covalent bonding and the applications of COFs have made great progress already. Three-dimensional (3D) COFs have attracted much attention in recent years because of their more diverse spatial structures and interconnected pore properties. High valency and functionalization are two key strategies of 3D COFs design, including the development of building blocks, topology, linkage and post synthetic modification strategy. As a result, the diversity of COF spatial structures is significantly extending and various applications in energy, environment, biology and chemical catalysis are developing. In this review, we summarized the recent articles about 3D COFs in the field of framework design, function development and applications, and put forward the critical strategies and comment, the future perspectives of the field are also prospected. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pore size shows significant effect on the capacitive performance of biomass-derived porous carbon materials. • Pore characteristics are influenced by the probe molecules and the corresponding calculation models. • The microstructure of biomass derived porous carbon is influenced by the structure and components of precursor and synthesis method. • Challenges are existing and new strategies are required to boost the capacitance performance of biomass derived porous carbon. As the world's demand for green energy storage systems continues to increase, electrochemical double-layer supercapacitors based on porous carbon electrodes are receiving more attention than ever. Porous carbon materials can be designed and synthesized from biomass residues/extracts through various technologies, which realizes the value-added utilization of biomass and meets the targets of circular economy. Pore characteristics are particularly important for the capacitive performance of carbon-based electrodes. This review outlines the biomass-derived porous carbon materials and their corresponding capacitive properties, which are divided into biomass-derived ultra/super-microporous carbon, mesoporous carbon, macroporous carbon and hierarchical porous carbon according to the category of pore size. The synthesis methods, pore characteristic testing probes/calculation models and capacitance performance are discussed in detail, and the corresponding advantages and bottlenecks are pointed out critically. Emphasis is laid on the research status and development trend of biomass-derived hierarchical porous carbon materials, including the effects of the structure and composition of biomass precursors, advanced nanotechnologies and the proportion of various pores in carbonaceous products on the capacitance performance. Finally, the coping strategies are proposed for the further development of high capacitance biomass-derived porous carbon materials. [ABSTRACT FROM AUTHOR]

Structural and compositional optimization are considered as vital strategies to improve the capacitive properties of carbon-based electrodes. Inspired by the abundant vertically aligned micron-sized low-tortuosity porous channels of natural wood, a facile, low-energy, and efficient approach that anchors N/O-codoped carbon nanotubes on the inner and outer surfaces of carbonized wood matrix through in-situ chemical vapor deposition is proposed. The as-prepared thick carbon monoliths have unique three-dimensional hierarchically porous structures, interconnected conductive networks, and rich N/O-containing species, consequently endowing the electrodes with ultrahigh mass loading and inspiring capacitive properties. Representatively, the CNTs@CW-800 electrode (∼56 mg cm−2) improves the specific capacitance to 6620.3 mF cm−2 (118.5 F g−1, 82.8 F cm−3) at 2 mA cm−2. And the robust electrode exhibits an outstanding cycle stability even after 20,000 charge/discharge cycles at 30 mA cm−2 (5.4% decay). Furthermore, the maximum specific capacitance and energy density of the assembled symmetric supercapacitor are 4120.0 mF cm−2 (51.5 F cm−3, 42.9 F g−1) and 0.6 mWh cm−2 (6.3 mWh cm−3, 6.0 Wh kg−1), respectively. The above strategies will open up a new path for the value-added utilization of renewable resources and the efficient preparation of low-cost and high-performance energy storage and conversion devices. [Display omitted] • An efficient in-situ CVD method was proposed to design thick carbon electrodes. • N/O-CNTs were grown on the inner/outer surfaces of wood-derived carbon skeleton. • The wood-based thick electrodes possessed ultrahigh mass-loading of ∼56 mg cm−2. • The assembled symmetric supercapacitor exhibited encouraging capacitive properties. [ABSTRACT FROM AUTHOR]

Low conductivity of metal oxide electrode and low specific capacitance of carbon electrode restrict the further commercial application of supercapacitors. Manganese oxides/carbon composites were prepared by a simple method using homemade porous carbon and KMnO 4 as raw materials. The composites have both high capacitance of metal oxides and high conductivity of carbon due to Mn-O-C interaction. The optimized composite electrode exhibited an incredible ultra-high specific capacitance of 550, 520, 481, 402, and 318 F/g at the current densities of 1, 2, 3, 5, and 10 A/g, respectively. Moreover, the assembled asymmetric supercapacitor (ASC) device obtains an astonishing energy density of 50.2 Wh/kg at a power density of 800 W/kg, while 90.5 % capacitance after 10,000 cycles is still maintained. Meanwhile, ASC devices show great potential applications in energy storage, such as lighting 35 lights and running an electronic stopwatch. This material will promote the development of manganese/carbon composite supercapacitors for its simple preparation methods, ultra-high performance, and is expected to be a promising candidate for commercially large-scale applications. [Display omitted] • Manganese oxides/carbon composite with splendid specific capacitance was prepared by a simple method. • The assembled asymmetric supercapacitor (ASC) device obtains an astonishing energy density of 50.2 Wh/kg (800 W/kg). • The ASC device shows excellent cycling stability with a capacitance remaining of 90.5 % after 10,000 cycles. [ABSTRACT FROM AUTHOR]

Renewable cellulose-based papers are considered as a good resource for energy storage devices owing to their interlaced microfibrillar structure and high electrolyte absorptivity. Herein, an all-cellulose-based solid-state high-rate supercapacitor assembled with cellulose paper-derived self-supporting porous carbon electrodes and filter paper separator is designed. Benefiting from ingenious surface chemistry and pore structure engineering, the electrodes possess interconnected network structure, hierarchical pores, and appropriate N/O doping levels. The electrode demonstrates high specific capacitance (222.2 F g−1 at 0.2 A g−1), prominent rate capability (120.1 F g−1 at 100 A g−1), and outstanding cyclic stability (98.7 % capacitance retention after 20,000 cycles at 80 A g−1), which surpass most of cellulose-based self-supporting carbon electrodes ever reported. By integrating the well-designed electrodes with a piece of filter paper separator, the assembled symmetric solid-state supercapacitor (1.2 V) achieves an encouraging specific capacitance of 115.0 F g−1 along with an impressive energy density of 22.9 Wh kg−1 and a maximum power density of 15.9 kW kg−1. Moreover, the symmetric supercapacitor with 1 M Et 4 NBF 4 organic electrolyte (3 V) delivered a maximum energy density and power density of 62.5 Wh kg−1 and 54.9 kW kg−1, respectively. This study proposes a design concept of all-cellulose-based solid-state supercapacitors, which presents a promising direction toward environmentally friendly and sustainable energy storage technology. [Display omitted] • A facile solvothermal reaction and carbonization/activation route was proposed to tailor pore and surface characteristics. • All-cellulose-based symmetric supercapacitor was designed by integrating N/O-CP-50 electrodes and filter paper separator. • Excellent comprehensive performance was achieved for N/O-CP-50-based symmetric supercapacitor. • The typical all-cellulose-based solid-state devices balance the cost and performance of portable electronic devices. [ABSTRACT FROM AUTHOR]

• Anisotropic cellulose nanofibril/silver nanowire materials are constructed via a directional freeze-drying method. • The existence of AgNWs reinforces the solar-thermal energy conversion and storage capacity. • The ss-CPCMs exhibit improved thermal conductivity, thermal stability and recyclability. • This work provides insights into the thermal transmission mechanism in anisotropic supporting materials. Improving the thermal stability and energy storage density of phase change materials (PCMs) in thermal energy storage systems is a key task for their practical applications in industrial production. Whereas, limited by the inherently inferior heat transfer and unsatisfactory visible light response capability, PCMs exhibit extremely low thermal storage/release capability, inhibiting their developments. Herein, we constructed porous cellulose nanofibril (CNF)/silver nanowire (AgNW) hybrid supporting materials possessing the highly ordered structure and characteristically anisotropic thermal transmission capacity by directional freeze-drying, in order to encapsulate octadecanol (OCO) and octodecane (OCC) by vacuum impregnation method. Profited by the infrequently anisotropic structures and high thermal conductivity AgNWs, CNF/AgNW hybrid materials present dissimilar thermal transmission rates in the transverse and longitudinal directions. The close contact of AgNWs to CNFs allows the energy harvesting by solar-excited AgNWs to rapid transfer to CNFs, which increases the phonon propagation of the cellulosic material lattice and implements the improvement of the thermal transmission ability of the hybrid carriers. The obtained series of composite PCMs show an improved thermal conductivity (enhanced by 72.7%), and thermal enthalpy is comparatively approaching the theoretical value. Rejoicingly, the composites are thermally and durably stable. This novel-innovative targeted functional strategy provides insights into the thermal transmission mechanism in anisotropic supporting materials, and the resulting shape-stable composite PCMs (ss-CPCMs) can be employed as promising candidates for renewable thermal energy storage systems in virtue of their characteristic comprehensive performances. [ABSTRACT FROM AUTHOR]