Knitting Controllable Oxygen-Functionalized Carbon Fiber for Ultrahigh Capacitance Wire-Shaped Supercapacitors

Flexible composite films constructed of MXene/cellulose nanofibers/natural fiber-based activated carbon fibers for high-performance flexible supercapacitors

Traditional activated carbon fibers (CF) based supercapacitors suffer from low mechanical strength, inherent brittleness that induces stress concentrations, and bulky architectures from binder/conductive additive requirements. To overcome these limitations, cellulose nanofibers (CNF) are synergistically integrated with Ti₃C₂Tₓ MXene and CF, forming a mechanically reinforced composite film via hydrogen bonding and van der Waals interactions. The CNF/CF network expands the interlayer spacing of MXene, which enhances the ion-accessible surface area and enables rapid ion transport. The resulting Ti₃C₂Tₓ/CNF/CF composite film demonstrates exceptional electrochemical performance, achieving a specific capacitance of 420.99 F g-1 at 0.5 A g-1, with 84.56 % retention at 10 A g-1. As a self-supporting flexible electrode (0.49 mm thickness), it delivers an areal capacitance of 214 mF cm-2 at 0.3 mA cm-2 and an energy density of 14.5 μWh cm-2 at 30.2 μW cm-2. The hierarchical CNF/CF network simultaneously suppresses MXene restacking through spatial confinement while optimizing mechanical flexibility and stress distribution via interfacial bonding. This assembly strategy enables scalable fabrication of ultrathin MXene-based supercapacitors suitable for flexible electronics and grid-scale storage systems.

Self-Templating Synthesis of Mesoporous Carbon Cathode Materials for High-Performance Lithium-Ion Capacitors

Lithium-ion capacitors (LICs) have attracted considerable interest because of their excellent power and energy densities. However, the development of LICs is limited by the low capacity of the cathode and the kinetics mismatch between the cathode and anode. In this work, mesoporous carbon materials (MCs) with uniform pore sizes were prepared using magnesium citrate as the raw material through a self-templating method. During the carbonization process, MgO nanoparticles generated from magnesium citrate act as a template, resulting in a more orderly pore structure. The resultant MCs demonstrate a high specific surface area of 1673 m2 g-1 and an abundance of small mesopores, which significantly accelerated ion migration within the electrolyte and expedited the formation of electric double layers. Benefiting from these advantages, the MCs cathode demonstrates a high reversible specific capacity, excellent cycling stability, and rate performance. The assembled MCs-based LIC provides a high energy density of 152.2 Wh kg-1 and a high power density of 14.3 kW kg-1. After 5000 cycles, a capacity retention rate of 80 % at the current density of 1 A g-1 is obtained. These results highlight the excellent potential of MCs as a cathode material for LICs.

Fabrication of a symmetric supercapacitor device using MnO2/cellulose nanocrystals/graphite electrodes via sputtering for energy storage

The growing commercialization of flexible electronic goods has led to increased interest in flexible wearable energy storage devices, particularly supercapacitors. The development of supercapacitive electrodes from low-cost, sustainable, and renewable materials is essential for promoting a green and eco-friendly approach. Cellulose nanocrystals (CNCs) with unique properties and structures hold the potential to produce a 3-D network-based electrode, which is necessary to utilize high-quality carbon materials. Integration of metal oxides on the CNCs/graphite surface exhibits excellent structural stability due to CNCs and electrical characteristics of the graphite substrate. In this work, we demonstrate a self-standing MnO2/CNCs/graphite-based hybrid electrode with excellent supercapacitance for energy storage. An MnO2 thin film was produced using the radio frequency (RF) magnetron sputtering technique, while CNCs were extracted from sugarcane bagasse. The MnO2/CNCs/graphite hybrid electrode and device demonstrated superior electrochemical performance in 1 M Na2SO4 electrolyte. It offered a 1.2 V potential window with an areal capacitance of 149 mF cm-2, energy density of 75 mW h cm-2 at 2 mA cm-2, and a power density of 2977 μW cm-2 with a low solution resistance of 5.67 Ω, comparable to the very high value of CNCs, i.e., Rs 6.13 KΩ. Moreover, the MnO2/CNCs/graphite device demonstrated outstanding cyclic retention, i.e., 85.27% after 15 000 cycles, owing to the structural stability imparted by CNCs, making it a great contender as supercapacitors.

Disruption of the Conjugated π-Electron System of Graphene Oxides Diminishes Their Microwave Reactivity

Graphenes and graphene-based adsorbents have the potential to be thermally regenerated by microwave irradiation due to their electronic mobility and propensity to absorb microwaves. This article investigates the effect of oxidation on their ability to heat during microwave irradiation in conjunction with their ability to adsorb a polycyclic aromatic hydrocarbon. For this, a series of graphene oxides (GOs) were synthesized, and their chemical properties and surface structures were analyzed systematically. As the oxidation levels increased, the microwave reactivity of GOs decreased notably. This was attributed to the disruption of the sp2-hybridized basal plane despite the introduction of polar oxygen-containing functional groups. The findings of this work indicated the role of the conjugated π-electron system on microwave reactivity, possibly posing a juxtaposition with the influence of polar C-O bonds on dielectric reactivity. In addition, the adsorption of the model compound decreased by oxidation, confirming the decrease in π-π electron donor-acceptor interactions and the increase in the formation of water clusters around oxygen-containing functional groups. This study provides the first mechanistic insight into the relationship between the conjugated π-electron network of graphenes and their microwave reactivity. It paves the way for utilizing microwave irradiation to regenerate spent graphenic adsorbents for water treatment.

High-Performance Zinc-Ion Hybrid Supercapacitor from Guilin Sanhua Liquor Lees-Derived Carbon Materials

Aqueous zinc-ion hybrid supercapacitors (ZHSCs) have attracted considerable attention because they are inexpensive and safe. However, the inadequate energy densities, power densities, and cycling performance of current ZHSC energy-storage devices are impediments that need to be overcome to enable the further development and commercialization of this technology. To address these issues, in this study, we prepared carbon-based ZHSCs using a series of porous carbon materials derived from Sanhua liquor lees (SLPCs). Among them, the best performance was observed for SLPC-A13, which exhibited excellent properties and a high-surface-area structure (2667 m2 g-1) with abundant micropores. The Zn//SLPC-A13 device was assembled by using 2 mol L-1 ZnSO4, SLPC-A13, and Zn foil as the electrolyte, cathode, and anode, respectively. The Zn//SLPC-A13 device delivered an ultrahigh energy density of 137 Wh kg-1 at a power density of 462 W kg-1. Remarkably, Zn//SLPC-A13 retained 100% of its specific capacitance after 120,000 cycles of long-term charge/discharge testing, with 62% retained after 250,000 cycles. This outstanding performance is primarily attributed to the SLPC-A13 carbon material, which promotes the rapid adsorption and desorption of ions, and the charge-discharge process, which roughens the Zn anode in a manner that improves reversible Zn-ion plating/stripping efficiency. This study provides ideas for the preparation of ZHSC cathode materials.

Thin carbon nanotube coiled around thick branched carbon nanotube composite electrodes for high-performance and flexible supercapacitors

TCNT/BCNT composites are designed for flexible supercapacitors that exhibit exceptional cycling performance and remarkable flexibility over 10 000 cycles under bending.

Hierarchical nickel oxalate superstructure assembled from 1D nanorods for aqueous Nickel-Zinc battery

Hierarchical superstructures in nano/microsize can provide improved transport of ions, large surface area, and highly robust structure for electrochemical applications. Herein, a facile solution precipitation method is presented for synthesizing a hierarchical nickel oxalate (Ni-OA) superstructure composed of 1D nanorods under the control of mixed solvent and surfactant of sodium dodecyl sulfate (SDS). The growth process of the hierarchical Ni-OA superstructure was studied and indicated that the product had good stability in mixed solvent. Owing to smaller size, shorter pathway of ion diffusion, and abundant interfacial contact with electrolytes, hierarchical Ni-OA superstructure (Ni-OA-3) showed higher specific capacity than aggregated micro-cuboids (Ni-OA-1) and self-assembled micro/nanorods (Ni-OA-2). Moreover, the assembled Ni-OA-3//Zn battery showed good cyclic stability in aqueous electrolytes, and achieved a maximum energy density of 0.42 mWh cm^-2 (138.75 Wh kg^-1), and a peak power density of 5.36 mW cm^-2 (1.79 kW kg^-1). This work may provide a new idea for the investigation of hierarchical nickel oxalate-based materials for electrochemical energy storage.