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Flexible graphene‐based paper electrodes (FGPEs) are a new class of study and the research on this electrode material has been carried out for approximately ten years. FGPEs have many advantages compared to classical solid electrodes such as being flexible, foldable, adaptable to flexible electronics, being cut, easily shaped, and effective and adjustable modification. In this work, the applicability of FGPEs modified with polyindole (PIN) thin films and zinc oxide nanoparticles (ZnO‐NPs) to energy‐storage systems as a supercapattery design is presented, and especially the limitations of ZnO‐NPs for energy‐storage applications are revealed to inform researchers working for a similar purpose. Capacitance calculations have been performed using both cyclic voltammetry (CV) and galvanostatic charge‐discharge (GCD) experiments. It was observed that the rGO/PIN paper demonstrated almost 30 times more energy‐storage capacity than that of the rGO/PIN/ZnO paper due to the electrochemical instability of ZnO‐NPs on the flexible electrode platform at the applied potential region in 1.0 M HClO4 solution. The rGO/PIN paper with a highly flexible property exhibited an energy density of 74.5 W h cm−2 and a power density of 2258 W cm−2 at a current density of 2.2 mA cm−2, revealing hopeful results for future modular and flexible approaches. [ABSTRACT FROM AUTHOR]

Carbon paper has been synthesized by paper making process followed by composite formation, and further chemically oxidized by immersing into a mixture of sulphuric acid and potassium dichromate to be used as an electrode for supercapacitor applications. XRD and Raman spectra were used to analyze the structure, and the defects in the samples respectively, in due course of oxidation. FESEM images revealed the morphology of oxidized samples to be rougher, which contributes towards increased active sites for reaction. The sample (COCP‐60) optimized via electrochemical studies, was further tested in various electrolytes to study the electrode/electrolyte interaction. It delivered a highest areal capacitance of 6.02 F/cm2 (231.5 F/g) in acidic electrolyte at a current density of 5 mA/cm2 (0.19 A/g). This findings were further corroborated by surface and diffusion contribution studies wherein it was found that diffusion is more profound with acidic electrolyte. The supercapacitor device fabricated with COCP‐60 electrode delivered an energy density of 0.41 Wh/cm2 at 2.83 W/cm2 power density with coulombic efficiency of 98 %, and cyclic stability of ∼90 % for over 5000 cycles. [ABSTRACT FROM AUTHOR]

As newly emerging energy storage devices, supercapacitors are being investigated thoroughly by researchers. Free-standing electrode is one of the major research focuses in this area, which not only avoids the use of resistive binders but also simplifies device assembly. The study describes the synthesis and study of carbon fiber-based carbon carbon composite paper (heat treated to different temperatures) as a free-standing supercapacitor electrode. Due to the inert nature of carbon paper, it was activated to create defect sites and to increase the specific surface area. Electrochemical studies suggested that activated carbon paper heat treated to 750°C (ACP-750) exhibited the highest areal capacitance of 11.4 F/cm2 (422.2 F/g) at the current density 2.5 mA/cm2 (0.09 A/g), probably due to the generation of larger number of defect sites (as depicted by XRD and RAMAN studies). ACP-750 electrode was used to fabricate the solid-state symmetric supercapacitor device that exhibited an energy density 0.77 Wh/cm2 at a power density of 2.34 W/cm2. The electrode was allowed to age (ACPA-750), after which it exhibited enhanced specific capacitance of 16.8 F/cm2 (622.2 F/g) at a current density 2.5 mA/cm2. ACPA-750//ACPA-750 device delivered maximum energy density of 1.66Wh/cm2 at a power density of 3 W/cm2. The device exhibited a coulombic efficiency of 96.1% and capacitance retention of 89% after 10,000 cycles. Carbon paper was activated to produce defect sites and to enhance the specific surface area because of its inert nature. The effect of ageing can be observed by the enhancement in the specific capacitance value of 16.8 F/cm2 (622.2 F/g) at 2.5 mA/cm2. At a power density of 3 W/cm2, the ACPA-750//ACPA-750 symmetrical supercapacitor device achieved a maximum energy density of 1.66 Wh/cm2 along with 89 % of initial capacitance retention after 10,000 charge-discharge cycles. [Display omitted] • Carbon paper was developed as free standing supercapacitor electrode. • Activation of carbon paper enhanced the defect sites and the surface area. • A solid-state supercapacitor device was fabricated using activated carbon paper. • The device delivered an energy density of 1.66Wh/cm2 @ 3 W/cm2 power density. • After 5000 cycles devices coulombic efficiency is 98.3%, capacity retention is 95%. [ABSTRACT FROM AUTHOR]

The design of high‐performance electrode material without compromising energy and power density is critical for the advancement in hybrid electric vehicle technology. In this perspective, we have fabricated a MnO2 loaded activated charcoal‐based electrode on graphite paper as an endeavour to improve the energy storage capabilities. The electrode material is synthesized by employing a sustainable route and the structural, microstructural, and textural properties have been investigated. The electrochemical performance for energy storage is evaluated and the fabricated electrode on graphite paper exhibits remarkably high‐power density (811 W kg−1) maintaining high energy density (106 Wh kg−1) at the same time, along with high gravimetric specific capacitance value of 768 F g−1 at 2 mA cm−2. The obtained results demonstrate the excellent performance of the electrode material, suggesting MnO2 loaded activated charcoal as a prospective electrode material to meet the demand of hybrid electric vehicles as well as to contribute to our transitioning towards low‐to‐zero carbon emission technology. [ABSTRACT FROM AUTHOR]

In this study, a redox reaction is employed to synthesize manganese oxide (Mn3O4) nanoparticles using potassium permanganate as a precursor in the presence of diethyl amine. The structural characterization reveals the formation of the tetragonal phase of Mn3O4 nanoparticles with a space group of I41/amd. A free‐standing Mn3O4‐based paper electrode is fabricated and its electrochemical performances are investigated. The electrode exhibits a maximum specific capacitance value of ~353 F g−1 and an areal capacitance of ~530 mF cm−2 at a current density of 0.2 A g−1. A symmetric supercapacitor‐based device is also designed using Mn3O4 nanoparticles as an active material in a gel electrolyte configuration. The Mn3O4 device achieves specific and areal capacity values of ~208 mAh g−1 and 260 mA cm−2, respectively, at a current density of 0.3 A g−1. The device delivers maximum energy and power density values of ~104 Wh kg−1 and ~220 W kg−1, respectively, with ~92 % specific capacity retention at 0.3 A g−1 after 5000 cycles. The above results suggest that the Mn3O4‐based device has the potential for energy storage applications. [ABSTRACT FROM AUTHOR]

The MXene-modified papers with high-uniform loading of polypyrrole and excellent conductivity have been fabricated via a multiple self-assembly and in-situ polymerization strategy, which achieves boosting areal capacitance. [Display omitted] • Multiple self-assembly and in-situ polymerization strategy is proposed tofabricate paper-based supercapacitors. • Alternate adsorption of MXene and polypyrrole on paper yields an ultra-high polypyrrole loading of 10.0 mg/cm2. • The paper-based supercapacitor shows a boosting areal capacitance of 2316 mF/cm2. Despite the intriguing features of freestanding flexible electronic devices, such as their binder-free nature and cost-effectiveness, the limited loading capacity of active material poses a challenge to achieving practical high-performance flexible electrodes. We propose a novel approach that integrates multiple self-assembly and in-situ polymerization techniques to fabricate a high-loading paper-based flexible electrode (MXene/Polypyrrole/Paper) with exceptional areal capacitance. The approach enables polypyrrole to form a porous conductive network structure on the surface of paper fiber through MXene grafting via hydrogen bonding and electrostatic interaction, resulting in an exceptionally high polypyrrole loading of 10.0 mg/cm2 and a conductivity of 2.03 S/cm. Moreover, MXene-modified polypyrrole paper exhibits a more homogeneous pore size distribution ranging from 5 to 50 μm and an increased specific surface area of 3.11 m2/g. Additionally, we have optimized in-situ polymerization cycles for paper-based supercapacitors, resulting in a remarkable areal capacitance of 2316 mF/cm2 (at 2 mA/cm2). The capacitance retention rate and conductivity rate maintain over 90 % after undergoing 100 bends.The maximum energy density and cycling stability are characterized to be 83.6 μWh/cm2 and up to 96 % retention after 10,000 cycles. These results significantly outperform those previously reported for paper-based counterparts. Overall, our work presents a facile and versatile strategy for assembling high-loading, paper-based flexible supercapacitors network architecture that can be employed in developing large-scale energy storage devices. [ABSTRACT FROM AUTHOR]

A high-performance paper electrode is fabricated through coating polypyrrole (PPy) on ordinary laboratory filter paper via a traditional interfacial polymerization method with perchloric acid (HClO4) as a dopant. Owing to the superior mechanical flexibility and environmental stability of the free standing PPy paper, the robust electrode displays an ultrahigh capacitance of 1650 mF cm−2 and remarkable cyclic stability of losing 11.66% after cycling for 10000 times in a three-electrode system. More importantly, the areal specific capacitance has only decreased by 0.08% after five months. Furthermore, by employing the synthesized PPy papers as electrodes and the PVA-H2SO4 gel as electrolyte, the assembled all-solid-state supercapacitor with an areal specific capacitance of 566.5 mF cm−2 is achieved, corresponding to an areal energy density of 38.55 μW h cm−2 and power density of 0.17 mW cm−2. These results suggest that the simple synthesis of PPy paper electrode pave a promising way to exploit flexible and durable energy storage applications. [ABSTRACT FROM AUTHOR]

Energy storage devices (ESD) which are intended to power electronic devices, used in close contact of human skin, are desirable to be safe and non-toxic. In light of this requirement, Zn based energy storage devices seem to provide a viable pathway as they mostly employ aqueous based electrolytes which are safe and non-toxic in their functioning. Additionally, having a flexible ESD will play a crucial role as it will enable the ESD to conform to the varying shapes and sizes of wearable electronics which they energize. In this work, we have developed an inkjet-printed Zinc ion battery (IPZIB) with planar electrode configuration over bond paper substrate. Zn has been used as the negative electrode, MnO2 is used as the positive electrode with Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as the active binder. Conducting tracks of reduced graphene oxide (rGO) are used to construct the current collector on the paper substrate. The fabricated IPZIB delivered a high discharge capacity of 300.14 mAh g−1 at a current density of 200 mA g−1. The energy density of the IPZIB is observed as 330.15 Wh kg−1 at a power density of 220 W kg−1 and retains an energy density of 94.36 Wh kg−1 at a high power density of 1650 W kg−1. Finally, we have demonstrated the capability of the IPZIB to power a LED at various bending and folding conditions which indicates its potential to be used in the next generation flexible and wearable electronic devices. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) derived nanostructures receive immense research focus due to its high porosity, conductivity, and structural tailrolability features. In this work, porous Zeolitic Imidazole Framework‐67 (ZIF‐67) to synthesize cobalt phosphide/carbon composite (ZCoPC) that serves as a positive electrode is utilized. Furthermore, porous and conductive office paper derived carbon (OPC) are utilized as a negative electrode to make a hybrid system. The metalloid characteristics, high conductivity, and good porosity of ZCoPC material makes it a high‐performance battery like electrode. ZCoPC electrode achieves maximum specific capacity of 192.6 mAh g−1 at 1 A g−1 using 1 m potassium hydroxide (KOH) electrolyte. Furthermore, surface and diffusion charge participation investigation are also undergone for ZCoPC electrode that helps in determining the actual charge dynamics occurring in the electrode. In addition, a supercapattery device is assembled using ZCoPC as battery electrode and OPC as supercapacitor electrode. The as fabricated OPC//ZCoPC hybrid supercapattery device delivers extraordinary energy density of 31.6 Wh kg−1 with a power density of 700 W kg−1 and also a long cycle life of 92.3% even after 10,000 charge–discharge cycles. Hence, these outcomes demonstrate that the synergy of porous MOF derived metal phosphide and OPC electrodes are beneficial for supercapattery devices. [ABSTRACT FROM AUTHOR]

A novel strategy is proposed to enhance the electrochemical performance of polypyrrole (PPy)‐coated cellulose paper (PCP)‐based supercapacitor by increasing the reaction interface between hydrophobic pyrrole and hydrophilic FeCl3 solution. Paper is pretreated with regenerated cellulose (RC) to increase its specific surface area, which lays the foundation for increasing the reaction interface between pyrrole and FeCl3 in the following in situ polymerization while providing more adsorption sites for PPy. The RC‐pretreated paper is first impregnated with pyrrole, followed by removing surplus pyrrole occupied by the internal pores of paper prior to the impregnation of FeCl3 solution, aiming to increase the reaction interface between pyrrole and FeCl3 solution. Consequently, the as‐prepared PCP electrode exhibits a PPy loading of 4.2 mg cm−2, which is twofold higher than unpretreated PCP electrodes (2 mg cm−2). Moreover, a solid‐state supercapacitor assembled with PCP electrodes presents a 58 mF cm−2 areal capacitance at 2 mA cm−2 (equivalent to 140.5 F g−1 at 0.5 A g−1), a 33.1 µWh cm−2 energy density at a power density of 0.60 mW cm−2, and excellent cycling stability with a capacitance retention of 91.6% after 10 000 CV cycles. This work offers a new insight toward improving the electrochemical performance of PCP‐based supercapacitor. [ABSTRACT FROM AUTHOR]

The local and global aspects of the Casimir effect for a scalar field in the presence of a point-like impurity were treated in our papers (Fermi and Pizzocchero in Symmetry 10(2):38, 2018; Fermi in Mod. Phys. Lett. A 35(03):2040008, 2020), using the zeta regularization method. A paper by Ziemian, recently published in (Ann. Henri Poincaré 22:1751–1781, 2021), discusses the Casimir effect for a scalar field in presence of one or two, extended or point-like impurities, using the Herdegen–Stopa approach. Ziemian claims that his result for the energy density with a single point-like impurity differs from that derived in Fermi and Pizzocchero (2018), ascribing the mismatch to a basic conceptual discrepancy. In the present work, we show that the formula in Ziemian (2021) for the energy density in the presence of a point-like impurity coincides (upon amending minor computational errors) with the formula of Fermi and Pizzocchero (2018) for the same quantity. In order to make our discussion self-contained, in the present paper we also survey some basic facts related to Fermi and Pizzocchero (2018), Fermi (2020), Ziemian (2021). This survey includes Schrödinger's operators with point-like interactions, as described in the celebrated book (Solvable models in quantum mechanics, Springer, New York, 1988) by Albeverio et al., the zeta regularization method for a canonically quantized scalar field and the implementation of point-like interactions in this setting. [ABSTRACT FROM AUTHOR]

[Display omitted] • Preparation of hierarchical porous hollow carbon fiber paper with oxygen vacancies. • Construct a multi-layered pores electrode, with a specific surface area of 205.58 m2 g−1. • The OV-TiO 2-X @HPHCFP electrode shows a high areal capacitance of 1608.2 mF cm−2 at 2 mA cm−2. • The dual OV double electrolytes supercapacitor delivers a high potential of 2.5 V and an energy density of 0.196 Wh cm−2. The inherent limited energy density in supercapacitors constitutes a substantial impediment to their widespread adoption and large-scale production. In this study, we have devised a novel cathodic electrode denoted as OV-TiO 2-X @HPHCFP, featured with rich oxygen vacancies and its hierarchical porous hollow structure. The OV-TiO 2-X @HPHCFP cathode manifests an impressive areal capacitance of 1608.2 mF cm−2 at the current density of 2 mA cm−2, coupled with a remarkable capacitance retention of 97.7 % after 10,000 charge–discharge cycles. Theoretical calculations corroborate that the presence of oxygen vacancies enhances the conductivity of the electrode, facilitating expedited charge transfer kinetics. Furthermore, the electrode integrated into a double electrolyte flexible supercapacitor configuration, denoted as OV-TiO 2-X @HPHCFP//PVA-Na 2 SO 4 /PVA-LiCl//OV-MoO 3-Y @CFP, operated at an effective potential of 2.5 V, can yield an energy density of 1.96 × 10−1 mWh cm−2 at a power density of 1.25 mW cm−2. This investigation thereby delineates a promising strategy for the development of supercapacitors that can attain elevated operational potentials with concomitant enhancements in energy density. [ABSTRACT FROM AUTHOR]

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The lithium-sulfur battery (LSB) is a highly promising energy storage system with merits of exceptional theoretical specific capacity and energy density. However, challenges including insufficient sulfur conductivity, volume expansion, and the polysulfide shuttle effect result in rapid capacity decay and limited cycle life of the LSB, which significantly hinders its development. Inspired by the structure and forming process of paper, a fiber double network skeleton was constructed using flexible pulp fiber (PF) and highly conductive carbon fiber (CF). Following the principles of wet end chemistry in papermaking, MXene nanosheets with high adsorption and catalytic capacity for polysulfides were self-assembled on the surfaces of PF and CF to fabricate composite paper-based materials. The interwoven mesh of PF exhibited strong binding force and stable structure, providing support and protection for the CF interwoven mesh, resulting in a composite material with abundant porosity and excellent structural stability. Moreover, the CF interweaving network combined with an overlaid MXene interweaving network established an effective three-dimensional conductive pathway. When utilized as a self-supporting cathode in LSB, this composite paper-based material demonstrated outstanding cyclic stability. Under conditions of sulfur load at 2.3 mg·cm−2 and discharge at 0.2 C, the specific discharge capacity remained at 952 mAh·g−1 after 200 cycles with a capacity retention rate reaching 95.4%. The CF/PF@Mxene (CPCMX) also exhibited excellent tensile strength measured at 7.19 MPa while maintaining exceptional flexibility and electrolyte wettability. This research presents a highly promising solution for advancing the development of LSB with superior cycle stability. [ABSTRACT FROM AUTHOR]

Most of the newer forms of carbon materials being demonstrated as potential anodes for lithium-ion batteries suffer a serious drawback in terms of their commercial perspectives due to their failure in the retention of a flat plateau in the charging/discharging profile. Here we present a facile and low-cost approach for the fabrication of solvent-free, binder-free anode material for the practical usage. A filter paper was coated with graphite using a pencil lead followed by pyrolysis (PyPF) and tested for its electrochemical performance. Galvanostatic charge/discharge experiments as carried out in half-cell configuration exhibited a specific capacity of 342 mAhg−1 with a constant plateau at 156 mAg−1 with 98% coulombic efficiency. This clearly shows the potential and competency of the material to be an inexpensive commercial anode. The role of graphite coating on filter paper was clearly manifested in the comparative studies with only pyrolyzed filter paper. Furthermore, full cell studies were performed using PyPF as anode and carbon coated LiFePO 4 as a cathode. A specific capacity of 120 mAhg−1 at C/5 rate with 141 WhKg−1 energy density with the retention of constant plateau and minimal polarization further emphasize the proficiency of PyPF as an anode for a commercial lithium-ion battery. Image 1 • An eco-friendly, binder-free and freestanding anode is developed for practical lithium ion battery. • Favorable plateau in the charge/discharge profile with minimal polarization is obtained. • A small quantity of graphitic carbon derived from pencil lead remarkably engender excellent charge/discharge profile. • Full cell study puts that this anode in scope of commercial lithium ion batteries. [ABSTRACT FROM AUTHOR]

Abstract As promising energy storage equipment, Zn-air battery exhibits the advantage of high energy density, lightweight and compact structure over other rechargeable batteries, which is an ideal choice for electric vehicles. For Zn-air battery, the activity of air cathode plays an important role in its performance. Here, we report the fabrication of Co 3 O 4 based bulky electrode with three-dimensional mesoporous carbon as matrix, which originates from cheap filter paper precursor. This electrode exhibits excellent activity and durability in oxygen reduction (ORR) and oxygen evolution reaction (OER) process, which possesses small half-wave potential (ORR 1/2 = 0.811 V) and low overpotential (OER 10 = 1.518 V) for ORR and OER, respectively. With this electrode as air cathode directly, a rechargeable Zn-air battery is assembled successfully. During discharge process, the maximum power density of this Zn-air battery achieves 71 mW cm−2. Furthermore, it also exhibits high specific capacity (828 mAh g−1 at 20 mA cm−2, 544 mAh g−1 at 50 mA cm−2) and small voltage gap (0.91 V at 10 mA cm−2) in charge and discharge process. As a rechargeable battery, it also shows promising stability after long time charge-discharge experiments. Thus, we find out a simple and convenient method to fabricate cheap and effective bi-functional air cathode for rechargeable Zn-air battery. Graphical abstract A Co 3 O 4 electrode was fabricated with Co(NO 3) 2 ·6H 2 O and filter paper as precursors, which exhibits excellent ORR and OER activities. It was employed as air cathode in Zn-air battery. fx1 Highlights • Filter paper was employed as precursor to fabricate Co 3 O 4 electrode. • 3D mesoporous electrode with N-doped carbon as matrix is obtained. • The electrode exhibits excellent ORR and OER activities. • The electrode is employed as air cathode in Zn-air battery directly. [ABSTRACT FROM AUTHOR]

Stretchable micropower sources with high energy density and stability under repeated tensile deformation are key components of flexible/wearable microelectronics. Herein, through the combination of strain engineering and modulation of the interlayer spacing, freestanding and lightweight MXene/bacterial cellulose (BC) composite papers with excellent mechanical stability and a high electrochemical performance are first designed and prepared via a facile all-solution-based paper-making process. Following a simple laser-cutting kirigami patterning process, bendable, twistable, and stretchable all-solid-state micro-supercapacitor arrays (MSCAs) are further fabricated. As expected, benefiting from the high-performance MXene/BC composite electrodes and rational sectional structural design, the resulting kirigami MSCAs exhibit a high areal capacitance of 111.5 mF cm−2, and are stable upon stretching of up to 100% elongation, and in bent or twisted states. The demonstrated combination of an all-solution-based MXene/BC composite paper-making method and an easily manipulated laser-cutting kirigami patterning technique enables the fabrication of MXene-based deformableall-solid-state planar MSCAs in a simple and efficient manner while achieving excellent areal performance metrics and high stretchability, making them promising micropower sources that are compatible with flexible/wearable microelectronics. [ABSTRACT FROM AUTHOR]

In this study, nanosized zeolitic imidazolate framework‐8 (ZIF‐8) crystal has been produced on the universitetet i oslo‐66 (UiO‐66) metal–organic framework (MOF) to make core–shell structure using a layer‐by‐layer deposition method. In comparison to the pristine UiO‐66 and ZIF‐8, the core–shell MOF exhibits superior performance in terms of specific capacitance. This enhanced performance is attributed to its remarkable ability to facilitate the rapid diffusion of electrolyte ions through nanosized ZIF‐8 and enhance the electron transfer process involving the inner and outer metal ions within the UiO‐66@ZIF‐8 structure. Remarkably, the core–shell structure achieves an impressive specific capacitance of 588.8 F g−1 at a current density of 0.5 A g−1 using 1 m sulfuric acid (H2SO4) aqueous electrolyte. Additionally, the UiO‐66@ZIF‐8 core–shell material is demonstrated as a positive electrode, coupled with activated carbon (AC) derived from waste tissue paper serving as the negative electrode, in the fabrication of an asymmetric supercapacitor (ASC) device. At a power density of 400 W kg−1, this assembled asymmetric device delivers a notably high energy density of 53 Wh kg−1 along with a cyclic stability of 94.8% after 10 000 cycles. This study substantiates the superior performance of the UiO‐66@ZIF‐8 core–shell MOF structure as a highly effective supercapacitor electrode material, surpassing the performance of its pristine MOF counterparts. [ABSTRACT FROM AUTHOR]

The design and preparation of a reduced graphene oxide (rGO) paper electrode with a reinforced concrete structure is an effective strategy to improve the mechanical properties of flexible electrodes. Therefore, PEDOT:PSS is added as a binder, toughening and conductive agent. CNTs, with good mechanical properties, are added to enhance the strength. Fe2O3 nanoparticles are added to increase the energy storage. According to these assumptions, we successfully prepared a flexible hydrophilic paper electrode with rGO nanosheets, PEDOT:PSS, CNTs and Fe2O3 nanoparticles by a constant temperature vacuum drying method. In addition, the assembled symmetrical supercapacitor exhibits a high capacitance of 1924 mF cm−3 at 1 mA cm−3, an excellent energy density of 35.6 W h kg−1 (at 166 W kg−1) and a remarkable cycle stability of 98.2% retention over 10 000 cycles at 1 mA cm−2. [ABSTRACT FROM AUTHOR]

Sodium‐carbon dioxide (Na‐CO2) batteries are regarded as promising energy storage technologies because of their impressive theoretical energy density and CO2 reutilization, but their practical applications are restricted by uncontrollable sodium dendrite growth and poor electrochemical kinetics of CO2 cathode. Constructing suitable multifunctional electrodes for dendrite‐free anodes and kinetics‐enhanced CO2 cathodes is considered one of the most important ways to advance the practical application of Na‐CO2 batteries. Herein, RuO2 nanoparticles encapsulated in carbon paper (RuCP) are rationally designed and employed as both Na anode host and CO2 cathode in Na‐CO2 batteries. The outstanding sodiophilicity and high catalytic activity of RuCP electrodes can simultaneously contribute to homogenous Na+ distribution and dendrite‐free sodium structure at the anode, as well as strengthen discharge and charge kinetics at the cathode. The morphological evolution confirmed the uniform deposition of Na on RuCP anode with dense and flat interfaces, delivering enhanced Coulombic efficiency of 99.5% and cycling stability near 1500 cycles. Meanwhile, Na‐CO2 batteries with RuCP cathode demonstrated excellent cycling stability (>350 cycles). Significantly, implementation of a dendrite‐free RuCP@Na anode and catalytic‐site‐rich RuCP cathode allowed for the construction of a symmetric Na‐CO2 battery with long‐duration cyclability, offering inspiration for extensive practical uses of Na‐CO2 batteries. [ABSTRACT FROM AUTHOR]

Summary: Miniaturization of devices, combined with other features such as portability, proneness to automation, rapid performance, amenability to integration, multiplexing, and cost‐effectiveness, is rapidly increasing for various sensing and energy harvesting applications. One such emerging area is the development of microfluidic fuel cell on cellulose papers, which has enormous scope to optimize its performance. This is primarily because such devices eliminate the need for membranes as well as external pumps since they have built‐in colaminar flow embedded capillaries. Such peripherals are usually used in conventional microfluidic fuel cells, which are fabricated using methods like photolithography, PDMS lithography, and 3D printing. This paper presents investigations on microfluidic paper–based fuel cells (MPFCs) with different cellulose absorbent pads for their performance optimization. Herein, the MPFC utilizes formic acid as fuel, oxygen from quiescent air as oxidant, and sulfuric acid as electrolyte for conducting ionic exchange under colaminar flow. The electrodes are realized through simple pencil strokes depositing a thin layer of graphite. The porous graphite electrodes act as diffusion agents breathing oxygen directly from the atmospheric air. Such an MPFC configuration, costing less than US $1, was optimized to achieve maximum energy density by examining various combinations of absorbent pads with different grades of cellulose papers. It is seen that the maximum open circuit potential is 0.46 V, while the maximum current and power densities are 1505.66 μAcm−2 and 173.97 μWcm−2, respectively, with a grade 6 absorbent pad. Such performance can be further enhanced by investigating MPFCs with various graphite pencils with a diverse number of strokes at different concentration levels. [ABSTRACT FROM AUTHOR]

In this study, graphene oxide paper is obtained via vacuum‐assisted filtration of graphene oxide solution to prepare self‐standing electrodes for supercapacitors. Simultaneous reduction and N‐doping of graphene oxide paper are performed by chemical reduction followed by thermal annealing. Influence of different reduction techniques on the electrochemical properties of the self‐standing papers is investigated. N‐doped reduced graphene oxide papers are decorated with iron oxide nanoparticles to increase the energy density of the material. Increasing the amount of iron oxide nanoparticles in the composite paper results in enhanced capacitance. In the galvanostatic charge‐discharge measurements, iron oxide/N‐doped reduced graphene oxide electrode exhibits specific capacitance of 203 F g−1 at 0.5 mA cm−2. This value is remarkable since the electrode has a high mass loading of 2 mg cm−2, which shows that the electrode can be used for practical purposes. Moreover, these electrodes operate in a wide potential window (1.6 V) and exhibit 79 % capacitance retention at 10000 cycles. [ABSTRACT FROM AUTHOR]

Smaller volume/weight and higher output power/energy density are always the goals of electrochemistry energy devices. Here, a simple strategy is proposed to prepare an integrated gas diffusion electrode (GDE) with high conductivity through skin electroplating. The skin electroplating is the combination of magnetron sputtering and spatial confinement electroplating. The electroplated metal obtained by skin electroplating is uniformly, continuously, and tightly attached to the surface of carbon paper like a layer of skin. Uniform and continuous electroplating metal layer endows the integrated electrode excellent conductivity with the square resistance as low as 27 mΩ sq−1. In application, the self‐breathing fuel cell with 1 cm2 active area can harvest ultrahigh volume specific power density (20.9 kW L−1). Additionally, the weight of the fuel cell stack (23 W) with the integrated electrode is only 20 g, which is only 7% of the commercial stack with the same power. The mass specific power density reaches 1150 W kg−1, which is 15 times of the commercial stack. Outstandingly, the stack can charge 4 mobile phones at the same time. More importantly, the skin electroplating provides an effective strategy to improve the specific power density of other energy devices including Zn‐air batteries, Li‐air batteries, and so on. [ABSTRACT FROM AUTHOR]

A helium (He) dielectric barrier discharge plasma jet (DBD jet) was used for the first time for treating graphite foil as the current collector of a paper-based fluidic aluminum-air battery. The main purpose was to improve the distribution of the catalyst layer through modification and functionalization of the graphite foil surface. The plasma functionalized the graphite foil surface to enhance the wettability where the more hydroxyl could be observed from XPS results. The 30 s-He DBD jet treatment on the graphite foil significantly improved the battery performance. The best current density of 85.6 mA/cm2 and power density of 40.98 mW/cm2 were achieved. The energy density was also improved to 720 Wh/kg. [ABSTRACT FROM AUTHOR]

• Nacre-like FG/Al energetic paper was designed and prepared. • A significantly enhanced energy and pressure output are obtained. • FG/Al energetic papers shown self-propagate combustion reaction at micro-scale. • The chemical reaction mechanism was distinctly elucidated. • FG/Al energetic paper displayed high flexibility and strain. Developing functional devices requires energetic materials with comprehensive performance including high energy density, excellent chemical reactivity and mechanical properties. Herein, an effective strategy inspired by nacre-like architecture was employed to construct new fluorographene (FG)/nano-aluminum (Al) energetic paper through a vacuum filtration induced self-assembly process. FG/Al energetic paper showed ultrahigh reactivity and high flexibility owing to combined effect of the nacre-like architecture and interfacial interaction. FG/Al energetic paper exhibited significantly enhanced energy output (3257.7 J/g) and self-propagate combustion reaction with high pressure output at micro-scale. Chemical reaction mechanism was distinctly elucidated based on reactive molecular dynamics simulations and the combustion products of FG/Al energetic paper. More interestingly, FG/Al energetic paper displayed high flexibility and strain (5.39%) reported for the first time. The bio-inspired route provides a promising approach to design advanced energetic materials for applications in transportation, aerospace, and military industries. [ABSTRACT FROM AUTHOR]

Zinc–air batteries proffer high energy density and cyclic stability at low costs but lack disadvantages like sluggish reactions at the cathode and the formation of by-products at the cathode. To resolve these issues, a new perovskite material, CaCu3Ti4O12 (CCTO), is proposed as an efficacious electrocatalyst for oxygen evolution/reduction reactions to develop zinc–air batteries (ZAB). Synthesis of this material adopted an effective oxalate route, which led to the purity in the electrocatalyst composition. The CCTO material is a proven potential candidate for energy applications because of its high dielectric permittivity (ε) and occupies an improved ORR-OER activity with better onset potential, current density, and stability. The Tafel value for CCTO was obtained out to be 80 mV dec−1. The CCTO perovskite was also evaluated for the zinc–air battery as an air electrode, corresponding to the high specific capacitance of 801 mAh g−1 with the greater cyclic efficiency and minimum variations in both charge/discharge processes. The highest power density (Pmax) measured was 127 mW cm−2. Also, the CCTO based paper battery shows an excellent performance achieving a specific capacity of 614 mAh g−1. The obtained results promise CCTO as a potential and cheap electrocatalyst for energy applications. [ABSTRACT FROM AUTHOR]

A nanoflower structure of Zn 0. 7 6 Co 0. 2 4 S directly grown on carbon fiber papers (CFP) was successfully designed by a mild two-step hydrothermal method. Benefiting from their fascinating structural features, Zn 0. 7 6 Co 0. 2 4 S/CFP electrode exhibits a maximum specific capacitance of 300 F g − 1 at current density of 1 A g − 1 and 84% capacitance retention after 5,000 cycles at current density of 5 A g − 1 . Subsequently, Zn 0. 7 6 Co 0. 2 4 S/CFP//AC all-solid-state asymmetric supercapacitor (ASC) device is assembled and able to illuminate the red LEDs. ASC devices deliver a maximum energy density of 9.59 W h kg − 1 at a power density of 750 W kg − 1 . Therefore, this impressive result demonstrates that the nanoflower Zn 0. 7 6 Co 0. 2 4 S have promising applications in the development of high-performance supercapacitors. Zn0.76Co0.24S/CFP was obtained using two-step hydrothermal method. Its microstructure presents a novel nanoflower arrays. The synergistic effect between Zn0.76Co0.24S nanoflower and CFP improves the electrons transport efficiency, conductivity and structural stability of the hybrid. The as-prepared Zn0.76Co0.24S/CFP electrode delivers a specific capacitances of 300 F g−1 and exhibits an excellent cycling stability (retaining 84% after 5000 cycles) as well as a high energy density of 9.59 W h kg−1. [ABSTRACT FROM AUTHOR]

A simple and scalable direct laser machining process to fabricate MXene-on-paper coplanar microsupercapacitors is reported. Commercially available printing paper is employed as a platform in order to coat either hydrofluoric acid-etched or clay-like 2D Ti3C2 MXene sheets, followed by laser machining to fabricate thick-film MXene coplanar electrodes over a large area. The size, morphology, and conductivity of the 2D MXene sheets are found to strongly affect the electrochemical performance due to the efficiency of the ion-electron kinetics within the layered MXene sheets. The areal performance metrics of Ti3C2 MXene-on-paper microsupercapacitors show very competitive power-energy densities, comparable to the reported state-of-the-art paper-based microsupercapacitors. Various device architectures are fabricated using the MXene-on-paper electrodes and successfully demonstrated as a micropower source for light emitting diodes. The MXene-on-paper electrodes show promise for flexible on-paper energy storage devices. [ABSTRACT FROM AUTHOR]

Graphene oxide–modified poly (vinyl alcohol)/sodium sulfate-sodium molybdate (GO/PVA-Na2SO4-Na2MoO4, GPSS) gel polymer electrolyte and nickel molybdate (NiMoO4) electrode are integrated to fabricate carbon paper (CP) supercapacitor to improve capacitance performance. GO in PVA gel can introduce an effective ion transport pathway to improve ionic conductivity of gel polymer electrolyte. The ionic conductivity increases from 3.73 mS cm−1 for PVA-Na2SO4 to 6.46 mS cm−1 for GO/PVA-Na2SO4 at optimal GO mass ratio of 0.6% in GO/PVA gel. It also obviously increases from 4.33 mS cm−1 for PVA-Na2SO4-Na2MoO4 to 28.86 mS cm−1 for GO/PVA-Na2SO4-Na2MoO4. Both Na2MoO4 electrolyte and NiMoO4 electrode show reversible redox electroactivity to provide superior pseudocapacitance. Accordingly, the CP supercapacitor using GPSS gel shows specific capacitance of 41.67 mF cm−2 and energy density of 70.02 mWh m−2 at 0.5 mA cm−2, presenting higher performance than 15.91 mF cm−2 and 26.74 mWh m−2 using GO/PVA-Na2SO4 gel. Furthermore, the NiMoO4/CP supercapacitor using GPSS gel shows even higher specific capacitance of 78.18 mF cm−2 and energy density of 131.39 mWh m−2 at 0.5 mA cm−2. It also exhibits high cycling capacitance retention of 85% at 0.5 mA cm−2 for 1000 cycles. The improved capacitance performance of CP supercapacitor using Na2MoO4 gel polymer electrolyte and NiMoO4 electrode is ascribed to reversible redox reaction of Mo(VI)/Mo(V), Mo(VI)/Mo(IV), and Ni(II)/Ni(III). The NiMoO4/CP supercapacitor using GO/Na2MoO4 gel polymer electrolyte becomes desirable for the promising application in energy storage devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polyformamide-derived carbon nanowire arrays are in-situ synthesized as N-containing carbon coatings for cellulose-based carbon fibers. • The green H 2 O 2 solution acts as both dopant and activator. • The assembled solid-state symmetric supercapacitor yields encouraging capacitive properties. • This work paves a cost-effective and universal avenue toward structural and compositional engineering of electrodes in energy-related devices. Free-standing porous carbon have risen to prominent electrode materials for high-rate solid-state supercapacitors, yet they are still plagued by uneconomical petrochemical feedstocks, tedious slurry-casting processes, and suboptimal performance. Herein, a dual‐strategy of combining free-standing nitrogen-doped carbon nanowire array coating and pore engineering is designed to boost the performance of cellulose-derived carbon electrodes. Polyformamide-derived carbon nanowire arrays are in-situ synthesized as N-containing carbon coatings for cellulose-based carbon fibers. More intriguingly, H 2 O 2 activation further enhances the hierarchical porous structure. Benefiting from the synergistic effect of free-standing feature, high electrolyte compatibility, interconnected conductive fiber networks, well-developed hierarchical porous structure and stable heteroatom-doped carbon coatings, the designed electrodes possess high accessibility of electrolyte ions and effective ion/electron transport channels. Thus, the specific capacitance reaches 275.6 F g−1 at 0.5 A g−1 for aqueous supercapacitor. The solid-state symmetric supercapacitor demonstrates the specific capacitance of 126.5 F g−1 at 0.5 A g−1 with the capacitance retention of 64.5% even when the current densities increased by 40-folds. Their promising energy density (17.5 Wh kg−1) and power density (12.3 kW kg−1) closing to the state-of-the-art biomass-derived free-standing solid-state symmetric supercapacitors. This breakthrough symbolizes a step forward in the advancement of biomass as high‐performance electrodes for supercapacitors. [ABSTRACT FROM AUTHOR]

One-dimensional Cu(OH) 2 nanorods and two-dimensional 1T-MoS 2 nanosheets have attracted attention due to their attractive electrochemical properties. However, 1T-MoS 2 nanosheets tend to agglomerate and transform to 2H-MoS 2 , resulting in a decrease in electrochemical performance. In this study, flexible electrodes with 3D hetero-nanostructures are constructed by growing Cu(OH) 2 nanorod arrays and loading 1T-MoS 2 nanosheets on carbon fiber paper made of chopped carbon fibers as a conductive flexible substrate. The flower-shaped 1T-MoS 2 nanosheets with increased interlayer spacing are conducive to the rapid diffusion and insertion of electrolyte, while the conductive copper hydroxide nanorod array and carbon fiber paper can facilitate electron transport. The 1T-MoS 2 /Cu(OH) 2 @CFP based electrode has a high areal capacitance of 1124.0 mF cm−2 at 1 mA cm−2 and excellent cycle stability (with 98.3% capacitance retention after 10000 charge-discharge cycles). Furthermore, a flexible asymmetric solid-state supercapacitor (FASSC) device based on the as-prepared 1T-MoS 2 /Cu(OH) 2 @CFP electrode exhibits an energy density of 0.130 mWh cm−2 at a power density of 0.375 mW cm−2. The capacitance of FASSC device remains 90.8% of the initial value after 20000 cycles. In addition, the CFP substrate can be bent at a large angle and folded into different shapes, which makes 1T-MoS 2 /Cu(OH) 2 @CFP based electrodes suitable for flexible and portable electronics. [Display omitted] • 3D 1T-MoS 2 /Cu(OH) 2 hetero-nanostructure was grown on flexible CFP were constructed. • The 3D hetero-nanostructure offers rich electroactive sites for Faradaic reactions. • The 1T-MoS 2 /Cu(OH) 2 @CFP electrode shows a high areal capacitance of 1124.0 mF cm−2. • The assembled hybrid supercapacitor delivers a high energy density of 0.130 mWh cm−2. [ABSTRACT FROM AUTHOR]

Paper manufacture is a very energy-intensive industry and generates a large amount of waste such as paper mill sludge (PMS). Given that the current PMS disposal ways ( e.g. , incineration and landfilling) are not eco-friendly and costly, establishing an appropriate PMS disposal platform including energy recovery is crucial to making more environmentally benign and economically viable industrial paper manufacturing process. In this respect, this study places a great emphasis on investigating the influence of CO 2 on pyrolysis of PMS by systematical analysis of major three-phase pyrolytic products, such as gases and tar, under N 2 and CO 2 atmospheres. It was validated that using CO 2 as a reaction medium in pyrolysis of PMS not only increased the production of CO (a major constituent of syngas) by ∼1000% but also decreased the amount of tar by 23%. The increase in CO production and decrease in tar formation likely resulted from reactions between CO 2 and volatile organic compounds (VOCs) generated from thermal decomposition of PMS, which could be expedited by catalytic effects of minerals contained in PMS. The results shown in this paper could be applied to design green paper manufacturing processes efficiently utilizing a potent greenhouse gas, CO 2 . [ABSTRACT FROM AUTHOR]

With the increasing demand for flexible energy-storage systems, mulberry paper has emerged as a suitable flexible substrate because its mechanical strength and chemical stability surpass that of A4 commercial printing papers. Mulberry paper can withstand deformation because of its high holocellulose content and low lignin content. Moreover, it is hydrophilic, which is advantageous for a simple dip-coating process. Herein, we propose a hybrid nanocomposite-coated mulberry paper, synthesized by dip-coating, as an electrode for flexible energy-storage devices. The electrode was successively coated with silver nanowires (AgNWs), carbon nanotubes, and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate. The synergetic effect of the electric double-layer and pseudocapacitive materials as well as AgNWs, is to act as a current collector and increases conductivity, resulting in a gravimetric energy density of 14.64 W h kg−1 and gravimetric power density of 2.69 kW kg−1 at a current density of 1 A g−1. This paper focuses on the fabrication of mulberry-paper-based electrodes with hybrid nanocomposite coatings and presents the electrochemical performance of the as-fabricated electrodes. These electrodes can be used in eco-friendly energy-storage devices because of the superiority of mulberry paper over commercial printing paper. [ABSTRACT FROM AUTHOR]

Organic molecule stabilized manganese stannate (MnSnO 3) perovskite nanoparticles were synthesized using a complexion strategy route. The Rietveld refinement analysis confirmed the formation of orthorhombic structure of manganese stannate with the space group of Pnma. Free standing manganese stannate electrode was fabricated on paper based flexible substrate and investigated the electrochemical performances. The maximum specific capacitance and areal capacitance delivered by electrode were ∼ 183 F/g and ∼ 487 mF/cm2, respectively, at the current density of 0.2 A/g, with an excellent capacitance retention ∼ 93% for 103 cycles at 0.6 A/g. A symmetric supercapacitor was fabricated using the MnSnO 3 as active material on positive and negative electrodes in solid state gel electrolyte configuration. The device achieved the specific capacity value ∼ 156 mAh/g at 0.1 A/g with the energy density and power density of ∼ 10 Wh/kg and ∼ 22 kW/kg, respectively, at 0.5 A/g. These results suggested that manganese stannate nanoparticles are promising candidates for high-performance supercapacitor application. [Display omitted] • Organic molecule stabilized manganese stannate perovskite nanoparticles. • Flexible Au-coated paper based free-standing electrode and symmetric device were fabricated for supercapacitor applications. • Diffusive control mechanism dominated the overall charge storage process. • The fabricated device exhibited excellent stability for energy and power storage performance. [ABSTRACT FROM AUTHOR]

• Three-dimensional WO 2 /MoO 2 @P, N-CNTs were prepared by the Self-template method. • Highly conductive and hollow structure of WO 2 /MoO 2 @P, N-CNTs avoided aggregation of NiCo-LDH. • IMSC devices were prepared by fully screen-printed technology. • IMSCs demonstrated excellent energy density (0.0590 mWh cm−2), cycling stability (100% capacity retention after 10,000 cycles) and mechanical stability (lighting the bulb under extremely distorted conditions). In-plane micro-supercapacitors (IMSCs) have greater promise for use in flexible wearable electronics than traditional stacked configurations due to their ease of integration and conformability. Nickel-cobalt layered double hydroxide (NiCo-LDH) has garnered significant interest as a stellar material for supercapacitors because of its affordable price, regular morphology, and high theoretical capacity. Unfortunately, the intrinsic poor conductivity of LDH materials prevents supercapacitors from achieving long-term stable cycling and the desired energy density. This research successfully applies the self-templated approach to prepare carbon nanotubes (CNTs) with heterogeneous architectures and numerous phase interfaces, thereby mitigating this disadvantage. Carbon nanosheets adorned with WO 2 and MoO 2 nanoparticles assemble the CNT with a typical three-dimensional structure. When combined with LDH in a suitable ratio, the composite electrode's conductivity significantly improves, providing increased capacity and cycling stability. Compared to commercial CNTs, the larger size of the prepared WO 2 /MoO 2 @P, N-CNTs serves a superior supporting and connecting role, thereby preventing the NiCo-LDH from aggregating. Under the best conditions, the composite electrode demonstrates a capacity of 1237 C/g at 1 A g−1 and an optimal capacity retention of more than 92%. For the IMSC devices, the composite materials as the positive electrode achieve an energy density of 0.0590 mWh cm−2, and no capacity degradation is observed after 10,000 cycles. In addition, bending tests have demonstrated the mechanical stability of the IMSCs. Therefore, this strategy of mixing highly conductive WO 2 /MoO 2 @P, N-CNTs can effectively improve the conductivity of the composite material and the mechanical properties of the overall device. Furthermore, this concept can be further extended to the preparation and application of other wearable devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Developing free-standing MFCPs electrode by simple and efficient strategy. • In ether electrolyte, the highest ICE is up to 96.3%. • The storage sodium behavior of MFCPs is "adsorption-intercalation-filling" process. • The pseudo-graphitic structure helps to obtain ultra-high ICE and rate-capability. Hard carbon (HC) is praised as the state-of-the-art anode material for sodium ion batteries (SIBs). However, developing HC anode with both ultra-high initial Coulombic efficiency (ICE) and superb rate performance is still one of the most critical challenges in practical application. Herein, the renewable filter papers were directly converted into a series of free-standing and flexible microfiber carbon papers (MFCPs) as practical additive-free anode for SIBs, adopting a simple graphite plate-assisted pyrolysis tactics. In ether electrolyte, the obtained MFCPs (at pyrolysis temperature > 1100 ℃) achieve an ICE>95%, one of the top values in the HC ranking list. Excitingly, the practical powers of MFCPs also reflect in the greater superior rate capability (251.2 mAh g−1 at 1 A g−1) compared to traditional materials and excellent cycle life (217.3 mAh g−1 after 500 cycles at 1 A g−1). Moreover, when assorted with an O3-Na(NiFeMn) 1/3 O 2 cathode, the pouch full cell delivers a splendid energy density of 246 Wh kg−1 with superb cycle life. Importantly, mechanism analysis reveals that three-stage storage sodium behavior of MFCPs: adsorption, intercalation and filling. Interestingly, sodium ions in ether electrolyte insert the interlayer as naked Na+ form instead of solvated Na+, revealing high ICE and rate-capability depends on pseudo-graphitic structures with high-level ordered degree. This work provides an extensible practical HC anode and insights in the sodium storage mechanism of HC in ether electrolyte.. [ABSTRACT FROM AUTHOR]

The rapid development of the portable and wearable devices has inspired the ever-growing pursuit of flexible energy storage equipment which can power these devices. Here, rice paper (RP) was integrated with a homemade LGS-polypyrrole (LGS-PPy) ink and commercial pen ink in order to construct a flexible electrode of a supercapacitor via a facial dip-coating method. The obtained RP/LGS-PPy ink/Pen ink composites showed a high areal specific capacitance of 1568 mF/cm2 at 0.2 mA/cm2, owing to the uniform deposition of a LGS-PPy layer which was covered by the pen ink coating. Furthermore, the assembled symmetric supercapacitor fabricated from the RP/LGS-PPy ink/Pen ink electrode exhibited impressive electrochemical performances in terms of specific capacitance (317.5 mF/cm2 at 2 mA/cm2), power density (846 μW/cm2 at the energy density of 23.5 μWh/cm2), and life times (82.1% capacitance retention after 5000 cycles). In addition, the capacitance of the as-prepared device remained essentially unchanged even after bending at 180°, thus demonstrating this device's outstanding flexibility. The low cost of raw materials, robust fabrication strategy as well as the moderate performances make the RP-based supercapacitor a promising candidate for future flexible energy storage devices. [Display omitted] • RP/LGS-PPy ink/pen ink was constructed via a facial dip-coating method. • The RP-based electrode exhibited outstanding desirable areal specific capacitance and excellent cycling stability. • The RP-based electrode demonstrated impressive flexibility. • The assembled supercapacitor showed superior energy density and power density. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li-S) batteries appear to be one of the most promising energy-storage devices owing to the unparalleled theoretical specific energy, relatively inexpensive price and abundant resources. Despite these attractive features, the practical performances of sulfur cathode still remain a lot of challenges, such as the electrical insulating nature of S and Li 2 S, huge volume change during cycling, notorious shuttle effect of lithium polysulfide intermediates (LiPSs), sluggish redox kinetics and construction of thick electrodes with high sulfur loading. Here, CoFe 2 O 4 nanoparticles anchored on the carbon nanotube (CNT) paper is proposed as free-standing sulfur host to address the issues. The cross-linking CNT network can serve as conductive matrix and accommodate volume change upon cycling simultaneously. Meanwhile, the CoFe 2 O 4 nanoparticles are capable of effectively anchoring LiPSs to suppress the shuttle effect and accelerating LiPSs conversion to boost redox kinetics. Moreover, the free-standing paper electrode without any binder is conducive to constructing stable cathode with high sulfur loading. In consequence, the well-designed S/CoFe 2 O 4 /CNT paper cathodes deliver impressive electrochemical performance, demonstrating an initial discharge capacity of 755.3 mAh g−1 and remaining a high reversible capacity of 642.6 mAh g−1 after 400 cycles at 2 C with an inconspicuous decay of 0.04% per cycle. The bimetallic oxide CoFe 2 O 4 nanoparticles anchored on the carbon nanotube paper is proposed as free-standing sulfur host with enhanced polysulfide trapping and catalytic effects for advanced Li-S batteries. [Display omitted] • Binder-free host realizes high sulfur loading and energy density for Li-S battery. • CoFe 2 O 4 /CNT paper inhibits the polysulfide shuttling via strong chemical interaction. • CNT-anchored CoFe 2 O 4 catalytically promotes the polysulfide conversion kinetics. • The Li-S battery with S/CoFe 2 O 4 /CNT cathode exhibits enhanced capacity and stability. [ABSTRACT FROM AUTHOR]

Thin, lightweight, stackable, solid-state supercapacitors are in great demand in the electronics industry because of their use in miniaturized devices. Herein, we report a simple and novel strategy to fabricate ultra-thin, lightweight, and stackable symmetric supercapacitors using MnO 2 -incorporated carbon nanotube (CNT)-web paper. SEM and TEM analyses revealed a uniform nanometer-scale coating of MnO 2 on the individual fibers of the CNT-web paper after simple deposition at room temperature. The network structure of free-standing conductive CNT-web paper provides a short diffusion path, allowing for complete utilization of MnO 2 in the charge storage process. A MnO 2 /CNT-web paper electrode showed an excellent areal capacitance of 135 mF cm −2 at 5 mV s −1 with a remarkable capacitance retention of 95% after 10,000 cycles. A symmetric solid-state supercapacitor containing MnO 2 /CNT-web paper displayed a high areal capacitance of 57 mF cm −2 with an energy density of 0.018 mWh cm −2 and a capacitance retention as high as 86% after 10,000 cycles. In addition, the voltage and capacitance were tripled by simply stacking three symmetric supercapacitors and connecting them in series and in parallel, respectively. We are optimistic that the excellent performance of the ultra-thin CNT-web paper-based supercapacitors demonstrated here will facilitate the development of compact supercapacitor banks in the near future. [ABSTRACT FROM AUTHOR]

The development of Fe 2 O 3 with high conductivity and energy density is crucial for practical utilizations of supercapacitors. Here, we demonstrated the preparation of novel Fe 2 O 3 /graphene oxide paper (Fe 2 O 3 /GP) hybrid electrode for high density supercapacitors. Due to the characteristic features of large surface areas and fast electron transportation, the specific areal capacitance of the Fe 2 O 3 /GP was around 3.08 F cm −2 at the charge-discharge current density of 5 mA cm −2 , which is nearly 14 times of the Fe 2 O 3 /carbon paper (Fe 2 O 3 /CP, 0.22 F cm −2 ). More importantly, the Fe 2 O 3 /GP hybrid electrode also retained about 95% of the initial capacitance after long-term cyclic process. These findings would help us to develop high effective and stable materials for energy storage devices. [ABSTRACT FROM AUTHOR]

BACKGROUND: Two‐ and three‐dimensional porous activated carbon (C)‐based symmetrical supercapacitors show great potential for extraordinary gravimetric performance as sustainable energy storage. However, the applications of portable and microdimensional supercapacitors are limited by their low volumetric performance stemming from reduced density resulting from increased porosity and high fabrication costs. This study aimed to demonstrate the high gravimetric–volumetric performance of symmetrical supercapacitors from biomass‐based porous carbon‐sources materials through an environmentally benign development method. Unique porous C sourced from TENERA‐type palm oil stick waste was prepared using potassium hydroxide (KOH) as an activating agent. The electrode set resembled a solid plate with an encapsulation density of ≈1.40 g cm−3. RESULT: The study used superior gravimetric–volumetric electrode materials, including an adjusted specific surface area of 934 m2 g−1, single‐doped optimization, and a hollow paper‐stack‐like morphological structure with a high C content of 91%. The results showed that the best electrode in the 1 mol L−1 H2SO4 electrolytes exhibited a high gravimetric capacitance of 233 F g−1 and an extraordinary volumetric capacitance of 326 F cm−3 at 1 A g−1. Furthermore, their coulombic efficiency was ≈99.1% at 10 A g−1. The symmetrical electrode device performed a high gravimetric–volumetric energy density of 19.03 Wh kg−1 and 26.6 Wh L−1 at a maximum output power density of 1.7 kW kg−1 and 1.9 kW L−1, respectively. CONCLUSION: These results indicate that the applied method development and the C‐biomass‐based electrode material design could achieve a high, well‐matched gravimetric–volumetric performance balance in symmetric supercapacitor devices. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Fiber supercapacitors are promising energy storage devices for potential application in wearable and miniaturized portable electronics, which currently suffer from difficulties in achieving high capacitance and energy density synchronously owing to the limited specific surface area of the electrode materials and material incompatibility between the two electrodes. Herein, a strategy is developed for the manufacture of coaxial asymmetric fiber supercapacitors by wrapping a core of PVA‐KOH gel electrolyte‐coated Ni(OH)2@NiCo2O4/CNT fibers with MoS2@Fe2O3/CNT paper. The as‐prepared coaxial fiber asymmetric supercapacitors exhibit a specific capacitance of 373 mF cm−2 (at a current density of 2 mA cm−2) and energy density of 0.13 mW h cm−2 (at a power density of 3.2 mW cm−2), and also show good rate capability, long cycle life, and excellent flexibility. This work provides the possibility for the practical application of fiber supercapacitors in wearable and portable energy storage equipment. [ABSTRACT FROM AUTHOR]

Paper-based microfluidics (lab on paper) emerges as an innovative platform for building small-scale devices for sensing, diagnosis, and energy storage/conversions due to the power-free fluidic transport capability of paper via capillary action. Herein, we report for the first time that paper-based microfluidic concept can be employed to fabricate high-performing aluminum–air batteries, which entails the use of a thin sheet of fibrous capillary paper sandwiched between an aluminum foil anode and a catalyst coated graphite foil cathode without using any costly air electrode or external pump device for fluid transport. The unique microfluidic configuration can help overcome the major drawbacks of conventional aluminum–air batteries including battery self-discharge, product-induced electrode passivation, and expensive and complex air electrodes which have long been considered as grand obstacles to aluminum–air batteries penetrating the market. The paper-based microfluidic aluminum–air batteries are not only miniaturized in size, easy to fabricate and cost-effective, but they are also capable of high electrochemical performance. With a specific capacity of 2750 A h kg−1 (@20 mA cm−2) and an energy density of 2900 W h kg−1, they are 8.3 and 12.6 times higher than those of the non-fluidic counterpart and significantly outperform many other miniaturized energy sources, respectively. The superior performance of microfluidic aluminum–air batteries originates from the remarkable efficiency of paper capillarity in transporting electrolyte along with O2 to electrodes. [ABSTRACT FROM AUTHOR]

The surface charge and space charge accumulation in paper used in oil–paper insulation system may distort electric field distribution and lead to the flashover and breakdown of insulation system. In this paper, the effect of gas-phase fluorination on the surface charge and space charge characteristics of oil-impregnated Nomex paper was investigated. Nomex T410 was fluorinated at 25 °C using F2/N2 mixtures with 20% F2 in volume at 0.05 MPa for 15, 30 and 45 min. Fourier Transform Infrared Spectroscopy (FTIR) proved that the molecular chain scission and cleavage occurred during gas-phase fluorination. Furthermore, the surface charge and space charge characteristic of the original and fluorinated oil-impregnated paper were measured using an electrostatic voltmeter and Pulsed Electroacoustic (PEA) equipment respectively. Furthermore, the hole and electron trap distribution of the samples were obtained by Isothermal Surface Potential Decay (ISPD) model. The results showed that both the positive and negative charge decay rates were accelerated by gas-phase fluorination and the hole, electron trap energy and density of the fluorinated samples were reduced by fluorination. It is suggested that the space charge dissipation was also accelerated by fluorination, indicating that gas-phase fluorination is an effective approach to modify the charge dynamics of oil-impregnated Nomex paper. [ABSTRACT FROM AUTHOR]

In the field of advanced energy storage, nanostructured Polyaniline (PANI) based materials hold a special place. Extensive studies have been done on the application of PANI in supercapacitors, however, the structure–property relationship of these materials is still not understood. This paper presents a detailed characterization of the novel sodium phytate doped 3D PANI nanofibers anchored on different types of carbon paper for application in supercapacitors. An excellent relationship between the structures and properties of the synthesized samples was found. Remarkable energy storage characteristics with low values of solution, charge transfer and polarization resistance and a specific capacitance of 1106.9 ± 1.5 F g−1 and 779 ± 2.6 F g−1 at current density 0.5 and 10 Ag−1, respectively, was achieved at optimized conditions. The symmetric supercapacitor assembly showed significant enhancement in both energy density and power density. It delivered an energy density of 95 Wh kg−1 at a power of 846 W kg−1. At a high-power density of 16.9 kW kg−1, the energy density can still be kept at 13 Wh kg−1. Cyclic stability was also checked for 1000 cycles at a current density of 10 Ag−1 having excellent retention, i.e., 96%. [ABSTRACT FROM AUTHOR]

• Issue of low energy density of VRFB is addressed by modifying electrode surface. • Highly functionalized nanopores are formed on the surface of thin carbon papers. • Surface area, wettability and electrode/electrolyte contact is highly improved. • Electrolyte utilization for cell having modified electrodes is improved by 110%. • 27 Wh L−1 more energy is harvested with 29% higher energy efficiency at 50 mA cm−2. Low energy density of a vanadium redox flow battery (VRFB) due to limited solubility and stability of vanadium ions constrains its wide spread applications and this issue becomes more critical by low active surface areas of electrodes and mass transport limitations of active species on the electrodes that lead to low electrolyte utilization. In this study the issue of low energy density is addressed by improving the electrode performance through modifying the surface properties and morphology of thin (0.19 mm thick) carbon paper electrodes instead of commonly used several millimeters thick carbon felts. Surface functionalization and pore formation of carbon paper are carried out using a catalytic etching method at high temperaturewhere the diameters of nanopores are controlled by tuning the etching conditions. The synergistic effects of thin, nanoporous and functionalized carbon paper result in more effective electrode/electrolyte interaction and the less mass transport resistance. Therefore, the zero-gap VRFB cell employing the nanoporous electrodes displays remarkable performance improvement in terms of electrolyte utilization by 110%, discharge energy density by 155% and energy efficiency by 29% as compared to the one using pristine electrodes at a current density of 50 mA cm−2. The results imply that the more energy can be harvested by employing nanoporous and functionalized carbon paper electrodes having larger active surface areas. [ABSTRACT FROM AUTHOR]

[Display omitted] • Aramid-based energy storage capacitor was synthesized by a convenient method. • Electrical breakdown strength was optimized by the interface engineering. • Good dielectric constant thermal stability from RT to 300 °C was achieved. • Our finds promoted the energy storage capacitors in commercial use. Polymer-based dielectric energy storage capacitors show more potential than conventional rigidity ceramic-based capacitors. Recent studies were classified into two categories: the excellent room temperature performance in poly (vinylidene fluoride) (PVDF) systems and the enhanced thermal stability in polyimide-based systems. Only now, however, both of them are still far from commercial use because of their inferior heat resistance or poor processability. By adding BaTiO 3 (BT) particles in maturely used aramid nanofibers, we synthesized the aramid nanofiber (ANF)/BT-based flexible paper capacitors through a convenient industrialized technology in this work. Due to the intrinsic laminated structure of ANF and the uniform distribution of BT particles, the composite film with BT addition of 8 vol% exhibits outstanding dielectric thermal stability. With the help of the interfacial resistance in the organic–inorganic interface, which protected the ANF matrix from being breakdown too early by optimizing the electrical field distribution, a high and stable energy storage density of 6.70 J/cm3 was obtained in ANF/BT5. In addition, excellent energy storage frequency stability with ultrafast discharge speed was also achieved. This work offered a highly repeatable way to synthesize commercially used flexible capacitors, bridging the lab investigation and commercial use in high-power density energy storage polymers. [ABSTRACT FROM AUTHOR]

Marked by high energy density and low material cost, lithium sulfur batteries are considered to be one of the most promising energy storage devices. However, the poor electrochemical performance impedes their practical application. In this work, MoS 2 is decorated on carbon nanotubes paper (CNTP) through magnetron sputtering technique to fabricate interlayers for high-performance lithium sulfur batteries. Due to the catalysis of MoS 2 on the conversion of sulfur species, lithium sulfur batteries present enhanced electrochemical performance. The initial discharge capacity reaches 1233 mA h g −1 and maintains 850 mA h g −1 after 100 cycles at 0.5C even the sulfur loading is about 3.4 mg cm −2 . In addition, the coulombic efficiency is over 96% among all 100 cycles. [ABSTRACT FROM AUTHOR]

In recent era of modern and bendable technology, energy dearth arises as a paramount subject around the globe with a dire demand of flexible and lightweight energy storage devices. This study targets fabrication of reduced graphene oxide (rGO) and utility of abundantly available, cost effective, and environment friendly lignocelluloses (LC) fibers extracted from Carica papaya source, as a binder to bind active material (rGO) as robust and compact paper sheet. Fabricated samples were analyzed by X-ray diffraction for crystallographic analysis, Scanning electron microscopy, Transmission electron microscope for morphology, Fourier transform infrared spectroscopy for structural bonding, and Raman spectroscopy for vibrational modes. Robust and bendable rGO/LC paper electrode was tested for energy storage application by employing in different characterizations, i.e., cyclic voltammetry for capacitive behavior, galvanostatic charge–discharge for symmetric EDLC, and electrochemical impedance spectroscopy for resistive charge kinetics, respectively. rGO/LC composite sheet employed as working electrode in 3-electrode CV measurements and revealed specific capacitance of 591 F/g at a scan rate of 5 mV/s by keeping the undistorted shape of voltammograms at higher scan rates which present it as a suitable candidate for modern flexible and energy storage devices. rGO/LC-based symmetric cell revealed the highest specific capacitance of 228 F/g at applied current density of 0.1 A/g, the energy density of 6.3 Wh/kg, and power density of 129 W/kg, respectively. rGO/LC-based symmetric cell confirmed the cycling stability by revealing capacitance retention of 82% after 200 cycles. It can conclude that biomass-based rGO paper sheet can be a potential candidate as environmentally safe with remarkable electrochemical activity in energy storage applications. [ABSTRACT FROM AUTHOR]