Facile green synthesis of silver nanodendrite/cellulose acetate thin film electrodes for flexible supercapacitors

High-Performance 3D Nanostructured Silver Electrode for Micro-Supercapacitor Application

In the current energy crisis scenario, the development of renewable energy forms such as energy storage systems among the supercapacitors is an urgent need as a tool for environmental protection against increasing pollution. In this work, we have designed a novel 3D nanostructured silver electrode through an antireplica/replica template-assisted procedure. The chemical surface and electrochemical properties of this novel 3D electrode have been studied in a 5 M KOH electrolyte. Microstructural characterization and compositional analysis were studied by SEM, energy-dispersive X-ray spectroscopy, XRD technique, and Kripton adsorption at -198 °C, together with cyclic voltammetry and galvanostatic charge-discharge cycling measurements, Coulombic efficiency, cycle stability, and their leakage current drops, in addition to the self-discharge and electrochromoactive behavior, were performed to fully characterize the 3D nanostructured electrode. Large areal capacitance value of 0.5 F/cm2 and Coulombic efficiency of 97.5% are obtained at a current density of 6.4 mA/cm2 for a voltage window of 1.2 V (between -0.5 and 0.8 V). The 3D nanostructured silver electrode exhibits excellent capacitance retention (95%) during more than 2600 cycles, indicating a good cyclic stability. Additionally, the electrode delivers a high energy density of around 385.87 μWh/cm2 and a power density value of 3.82 μW/cm2 and also displays an electrochromoactive behavior. These experimental results strongly support that this versatile combined fabrication procedure is a suitable strategy for improving the electrochemical performances of 3D nanostructured silver electrodes for applications as micro-supercapacitors or in electrochemical devices.

Cellulose nanocrystal-coated TEMPO-oxidized cellulose nanofiber films for high performance all-cellulose nanocomposites

High performance biopolymer films are of great interest as effective alternatives to non-biodegradable and petroleum-based polymer films. However, most natural biopolymer films possess weak mechanical and poor gas barrier properties, limiting their applicability. In this work, we developed all-cellulose nanocomposite films through a simple vacuum filtration process, using cellulose nanocrystals (CNCs) and 2,2,6,6-tetramethylpiperidine-1-oxy-oxidized cellulose nanofibers (TEMPO-CNFs). The TEMPO-CNFs were employed to construct a transparent, free-standing substrate matrix and the CNCs were used as a coating material to improve the mechanical and water vapor barrier properties of the final material. We have demonstrated that the top and bottom CNCs-coated TEMPO-CNF substrates (CNC/TEMPO-CNF/CNC) have excellent mechanical and good water vapor barrier properties. The resulting CNC/TEMPO-CNF/CNC films revealed a high tensile strength of 114 MPa and a low specific water vapor transmission rate (SWVTR) of 19 g∙mm/m²∙day. In addition, the CNC/TEMPO-CNF/CNC films were resistant to various solvents including water, ethanol, tetrahydrofuran (THF), and acetone. This type of high performance cellulose nanocomposite can be used as a renewable material for a broad range of potential applications.

Carbon threads sweat-based supercapacitors for electronic textiles

Flexible and stretchable energy-storage batteries and supercapacitors suitable for wearable electronics are at the forefront of the emerging field of intelligent textiles. In this context, the work here presented reports on the development of a symmetrical wire-based supercapacitor able to use the wearer’s sweat as the electrolyte. The inner and outer electrodes consists of a carbon-based thread functionalized with a conductive polymer (polypyrrole) which improves the electrochemical performances of the supercapacitor. The inner electrode is coated with electrospun cellulose acetate fibres, as the separator, and the outer electrode is twisted around it. The electrochemical performances of carbon-based supercapacitors were analyzed using a simulated sweat solution and displayed a specific capacitance of 2.3 F.g⁻¹, an energy of 386.5 mWh.kg⁻¹ and a power density of 46.4 kW.kg⁻¹. Moreover, cycle stability and bendability studies were performed. Such energy conversion device has exhibited a stable electrochemical performance under mechanical deformation, over than 1000 cycles, which make it attractive for wearable electronics. Finally, four devices were tested by combining two supercapacitors in series with two in parallel demonstrating the ability to power a LED.

Nanocellulose/polypyrrole aerogel electrodes with higher conductivity via adding vapor grown nano-carbon fibers as conducting networks for supercapacitor application

Nanocellulose-based conductive materials have been widely used as supercapacitor electrodes. Herein, electrode materials with higher conductivity were prepared by in situ polymerization of polypyrrole (PPy) on cellulose nanofibrils (CNF) and vapor grown carbon fiber (VGCF) hybrid aerogels. With increase in VGCF content, the conductivities of CNF/VGCF aerogel films and CNF/VGCF/PPy aerogel films increased. The CNF/VGCF₂/PPy aerogel films exhibited a maximum value of 11.25 S cm⁻¹, which is beneficial for electron transfer and to reduce interior resistance. In addition, the capacitance of the electrode materials was improved because of synergistic effects between the double-layer capacitance of VGCF and pseudocapacitance of PPy in the CNF/VGCF/PPy aerogels. Therefore, the CNF/VGCF/PPy aerogel electrode showed capacitances of 8.61 F cm⁻² at 1 mV s⁻¹ (specific area capacitance) and 678.66 F g⁻¹ at 1.875 mA cm⁻² (specific gravimetric capacitance) and retained 91.38% of its initial capacitance after 2000 cycles. Furthermore, an all-solid-state supercapacitor fabricated by the above electrode materials exhibited maximum energy and power densities of 15.08 W h Kg⁻¹, respectively. These electrochemical properties provide great potential for supercapacitors or other electronic devices with good electrochemical properties.

The electrochemical performances of nanocellulose-based electrode materials were improved via building nano-carbon conducting networks.

Nanowires of polyaniline festooned silver coated paper electrodes for efficient solid-state symmetrical supercapacitors

This paper demonstrates a facile strategy for the development of nanosilver decorated polyaniline coated (PAg) paper-based electrodes for the fabrication of solid-state symmetrical supercapacitors. PAg based printing paper was developed through a two-step process involving initial silver nucleation and growth on the paper followed by aniline polymerization. The developed electrically conductive paper exhibited a highly porous structure and excellent mechanical stability. Further symmetrical supercapacitors having the configuration PAg/electrolyte/PAg were fabricated and evaluated for electrochemical performance such as specific capacitance (483 F g⁻¹ and 613 F g⁻¹ in aqueous 1 M H₂SO₄ and PVA–H₂SO₄ gel electrolytes respectively), energy density (69.56 and 85.13 W h kg⁻¹), and power density (243.44 and 405.375 W kg⁻¹) and cycling stability (90% of its capacitance retention even after 2000 cycles), exhibiting excellent performance under various bending conditions. All these exciting results suggest that the developed paper-based flexible solid-state energy device can serve as an efficient, sustainable, and low-cost energy storage system for portable microelectronic devices which are expected to revolutionize the perception of energy-storage devices in the electronics industry.

This paper demonstrates a facile strategy for the development of nanosilver decorated polyaniline coated (PAg) paper-based electrodes for the fabrication of solid-state symmetrical supercapacitors.