Construction of flexible electrodes based on ternary polypyrrole@cobalt oxyhydroxide/cellulose fiber composite for supercapacitor

Cellulose nanofiber/MXene (Ti3C2Tx)/liquid metal film as a highly performance and flexible electrode material for supercapacitors

In recent times, there has been significant interest in the utilization of cellulose nanofiber (CNF) films as the foundation for supercapacitors due to their three-dimensional structure, flexibility and eco-friendliness. An ultrasonic and vacuum filtration method was used to prepare a hybrid film consisting of MXene (Ti3C2Tx), CNF and liquid metal (LM). The combination of CNF and LM with MXene produces a porous structure with higher electrical conductivity, which facilitates the transportation of ions and electrons within the composition and confers the material with heightened electrochemical properties. The CNF/MXene/LM electrode has a significant area capacitance of 871.3 mF cm-2 at a current density of 5 mA cm-2. The hybrid film demonstrates excellent stability, maintaining a high conductivity of 546.4 S∙cm-1 and retaining 96.9 % capacitance after 2000 cycles at a current density of 10 mA cm-2. By utilizing the thin film as an electrode, a high-performance quasi-solid supercapacitor was fabricated, with a remarkably thin thickness of only 0.319 mm. Supercapacitors show exceptional electrical properties, including a surface-specific capacitance of 188.2 mF cm-2 at a current density of 5 mA cm-2. This study indicates that flexible electrodes made from cellulose nanofiber have extensive potential in the realm of supercapacitors.

MXene (Ti3C2Tx)/cellulose nanofiber/polyaniline film as a highly conductive and flexible electrode material for supercapacitors

In recent years, supercapacitors based on cellulose nanofiber (CNF) films have received considerable attention for their excellent flexibility, lightweight, and unique structure. In this study, MXene (Ti₃C₂T_x) /CNF/polyaniline (PANI) hybrid films with good conductivity and flexibility were prepared by a convenient vacuum filtration method. Combined with PANI, MXene creates an open structure with high conductivity, which facilitates ion and electron transport among the materials and provides the composite with high electrochemical activity. The MXene/CNF/PANI electrode presents a high areal specific capacitance of 2935 mF cm^-2 at the current density of 1 mA cm^-2, excellent cycling stability with high capacitance retention of 94 % after 2000 cycles at 10 mA cm^-2 and high electrical conductivity (634.4 S∙cm^-1). As a further application of this film, it is used as a free-standing electrode to fabricate a quasi-solid-state supercapacitor with high performance, which has an ultra-thin thickness of 0.344 mm, a significantly high areal specific capacitance (522 mF cm^-2) at 5 mA cm^-2, a high areal energy density of 94.7 μWh∙cm^-2 and a high areal power density of 573 μW∙cm^-2. This work shows the great potential of the developed high-performance and flexible cellulose-based composites for fabricating electrodes as well as supercapacitors.

Soft Fiber Electronics Based on Semiconducting Polymer

Fibers, originating from nature and mastered by human, have woven their way throughout the entire history of human civilization. Recent developments in semiconducting polymer materials have further endowed fibers and textiles with various electronic functions, which are attractive in applications such as information interfacing, personalized medicine, and clean energy. Owing to their ability to be easily integrated into daily life, soft fiber electronics based on semiconducting polymers have gained popularity recently for wearable and implantable applications. Herein, we present a review of the previous and current progress in semiconducting polymer-based fiber electronics, particularly focusing on smart-wearable and implantable areas. First, we provide a brief overview of semiconducting polymers from the viewpoint of materials based on the basic concepts and functionality requirements of different devices. Then we analyze the existing applications and associated devices such as information interfaces, healthcare and medicine, and energy conversion and storage. The working principle and performance of semiconducting polymer-based fiber devices are summarized. Furthermore, we focus on the fabrication techniques of fiber devices. Based on the continuous fabrication of one-dimensional fiber and yarn, we introduce two- and three-dimensional fabric fabricating methods. Finally, we review challenges and relevant perspectives and potential solutions to address the related problems.

Polypyrrole/SnCl2 modified bacterial cellulose electrodes with high areal capacitance for flexible supercapacitors

Polypyrrole (PPy)/bacterial cellulose (BC) composite membranes are a promising kind of lightweight and flexible electrodes for supercapacitors. Herein, we explored a facile and efficient electrostatic self-assembly approach to uniformly depositing anion-doped PPy onto positively charged SnCl₂-modifed BC (SBC). The obtained PPy@SBC electrode exhibited a high areal capacitance of 5718 mF cm^-2 at a current density of 0.5 mA cm^-2, a desirable capacitance retention of 83.1% at 5.0 mA cm^-2 and excellent cycling stability (a capacitance retention of 86.8% after 10,000 cycles at 10 mA cm^-2). A symmetric flexible supercapacitor was further assembled with the PPy@SBC electrodes, which delivered outstanding mechanical flexibility with negligible capacitance decay under different bent states. This study shows impressive potential in fabricating high-performance electrodes for flexible supercapacitors.

A Composite Porous Membrane Based on Derived Cellulose for Transient Gel Electrolyte in Transient Lithium-Ion Batteries

The transient lithium-ion battery is a potential candidate as an integrated energy storage unit in transient electronics. In this study, a mechanically robust, transient, and high-performance composite porous membrane for a transient gel electrolyte in transient lithium-ion batteries is studied and reported. By introducing a unique and controllable circular skeleton of methylcellulose to the carboxymethyl cellulose-based membrane, the elastic modulus and tensile strength of the composite porous membrane (CPM) are greatly improved, while maintaining its micropores structure and fast transiency. Results show that CPM with 5% methylcellulose has the best overall performance. The elastic modulus, tensile strength, porosity, and contact angle of the optimized CPM are 335.18 MPa, 9.73 MPa, 62.26%, and 21.22°, respectively. The water-triggered transient time for CPM is less than 20 min. The ionic conductivity and bulk resistance of the CPM gel electrolyte are 0.54 mS cm−1 and 4.45 Ω, respectively. The obtained results suggest that this transient high-performance CPM has great potential applications as a transient power source in transient electronics.

Green and cost-effective synthesis of flexible, highly conductive cellulose nanofiber/reduced graphene oxide composite film with deep eutectic solvent

Developing efficient strategy for nanomaterials dispersion is the key for promoting the utilization of cellulose-based composite in energy storage devices. In this study, an instant synthesis method for cellulose nanofiber (CNF)/reduced graphene oxide (rGO) composite film with a deep eutectic solvent (DES) based on choline chloride and urea as a media is developed. This DES shows favorable abilities of recyclability, materials dispersion, and could adjust the pH value for reaction systems of neutral to alkaline which in favor of electrostatic repulsion arising from deprotonated carboxyl groups at the composite surface. As-obtained films feature excellent flexibility, high electrical conductivity (as high as 26.47 S∙cm^-1) and well electrochemical properties. Furthermore, a little amount of nitrogen atoms (~3.0 at%) could be introduced in the composite at a mild condition. Overall, this approach offers the potential for cost-effective, environmentally friendly and large-scale production of cellulose-based electrode and numerous advanced applications.

Enhanced Supercapacitor Performance Using a Co3 O4 @Co3 S4 Nanocomposite on Reduced Graphene Oxide/Ni Foam Electrodes

To avoid an enormous energy crisis in the not-too-distant future, it be emergent to establish high-performance energy storage devices such as supercapacitors. For this purpose, a three-dimensional (3D) heterostructure of Co₃ O₄ and Co₃ S₄ on nickel foam (NF) that is covered by reduced graphene oxide (rGO) has been prepared by following a facile multistep method. At first, rGO nanosheets are deposited on NF under mild hydrothermal conditions to increase the surface area. Subsequently, nanowalls of cobalt oxide are electro-deposited on rGO/Ni foam by applying cyclic-voltammetry (CV) under optimized conditions. Finally, for the synthesis of Co₃ O₄ @Co₃ S₄ nanocomposite, the nanostructure of Co₃ S₄ was fabricated from Co₃ O₄ nanowalls on rGO/NF by following an ordinary hydrothermal process through the sulfurization for the electrochemical application. The samples are characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The obtained sample delivers a high capacitance of 13.34 F cm^-2 (5651.24 F g^-1 ) at a current density of 6 mA cm^-2 compared to the Co₃ O₄ /rGO/NF electrode with a capacitance of 3.06 F cm^-2 (1230.77 F g^-1 ) at the same current density. The proposed electrode illustrates the superior electrochemical performance such as excellent specific energy density of 85.68 W h Kg^-1 , specific power density of 6048.03 W kg^-1 and a superior cycling performance (86% after 1000 charge/discharge cycles at a scan rate of 5 mV s^-1 ). Finally, by using Co₃ O₄ @Co₃ S₄ /rGO/NF and the activated carbon-based electrode as positive and negative electrodes, respectively, an asymmetric supercapacitor (ASC) device was assembled. The fabricated ASC provides an appropriate specific capacitance of 79.15 mF cm^-2 at the applied current density of 1 mA cm^-2 , and delivered an energy density of 0.143 Wh kg^-1 at the power density of 5.42 W kg^-1 .

Integrated Conductive Hybrid Electrode Materials Based on PPy@ZIF-67-Derived Oxyhydroxide@CFs Composites for Energy Storage

Due to excellent flexibility and hydrophilicity, cellulose fibers (CFs) have become one of the most potential substrate materials in flexible and wearable electronics. In previous work, we prepared cobalt oxyhydroxide with crystal defects modified polypyrrole (PPy)@CFs composites with good electrochemical performance. In this work, we redesigned the crystalline and nanoscale cobalt oxyhydroxide with zeolitic imidazolate frameworks-67 (ZIF-67) as precursor. The results showed that the PPy@ZIF-67 derived cobalt oxyhydroxide@CFs (PZCC) hybrid electrode materials possess far better capacitance of 696.65 F·g⁻¹ than those of PPy@CFs (308.75 F·g⁻¹) and previous PPy@cobalt oxyhydroxide@CFs (571.3 F·g⁻¹) at a current density of 0.2 A·g⁻¹. The PZCC delivers an excellent cyclic stability (capacitance retention of 92.56%). Moreover, the PZCC-supercapacitors (SCs) can provide an energy density of 45.51 mWh cm⁻³ at a power density of 174.67 mWh·cm⁻³, suggesting the potential application in energy storage area.

Frozen-State Polymerization as a Tool in Conductivity Enhancement of Polypyrrole

Polypyrrole (PPy) is oxidatively polymerized in the frozen state at -24 °C in the presence of various organic dyes as morphology guiding agents in order to form homogeneous 1D PPy nanoforms. The freezing polymerization of pyrrole has a significant influence on the electrical conductivity and thermal stability but negligible influence on the yield compared to widely used room temperature polymerization.

Chemistry, Structures, and Advanced Applications of Nanocomposites from Biorenewable Resources

Researchers have recently focused on the advancement of new materials from biorenewable and sustainable sources because of great concerns about the environment, waste accumulation and destruction, and the inevitable depletion of fossil resources. Biorenewable materials have been extensively used as a matrix or reinforcement in many applications. In the development of innovative methods and materials, composites offer important advantages because of their excellent properties such as ease of fabrication, higher mechanical properties, high thermal stability, and many more. Especially, nanocomposites (obtained by using biorenewable sources) have significant advantages when compared to conventional composites. Nanocomposites have been utilized in many applications including food, biomedical, electroanalysis, energy storage, wastewater treatment, automotive, etc. This comprehensive review provides chemistry, structures, advanced applications, and recent developments about nanocomposites obtained from biorenewable sources.