Search Results (172)

Developing electrocatalysts that are efficient and durable for the oxygen evolution reaction (OER) is essential for improving the energy efficiency of alkaline water splitting. Spinel-type transition-metal oxides have emerged as promising non-noble alternatives; however, their catalytic performance is often limited by sluggish charge transport and insufficient utilization of active sites. Herein, we present a systematic comparative study of electrodeposited Co₃O₄ (CO-300) and Cu-substituted Co₂CuO₄ (CCO-300) nanosheet films directly grown on Ni foam. Structural, morphological, and spectroscopic analyses reveal that Cu²⁺ integration into Co-oxide spinel lattice modifies the local electronic environment and produces a more open and interconnected nanosheet architecture, thereby enhancing conductivity and increasing the density of accessible redox-active sites. As a result, the optimized CCO-300 exhibits superior catalytic performance at higher current densities, along with a smaller Tafel slope (44 mV dec^–1), a larger electrochemically active surface area (ECSA), and reduced charge-transfer resistance compared to CCO-300, indicating accelerated reaction kinetics and improved electron-ion transport. Furthermore, the multistep chronopotentiometry measurements and long-term stability tests over 100 h at current densities of 10 and 250 mA cm^–2 highlight the excellent operational stability of the CCO-300 catalyst. Full article

In this study, thin molybdenum nitride (MoN_x) layers were directly synthesized on molybdenum foil via thermal treatment under an NH₃ atmosphere, and their phase evolution, structural characteristics, and electrochemical performance were investigated. The thickness and morphology of the MoN_x layers were controlled by varying ammonolysis time and temperature, while subsequent annealing in N₂ converted the nitride layer into MoO₂. Meanwhile, oxidation in air yielded crystalline MoO₃ layers. X-ray diffraction and X-ray photoelectron spectroscopy confirmed progressive oxidation of molybdenum, with Mo 3d binding energies increasing in the sequence of Mo < MoN_x < MoO₂ < MoO₃, consistent with their nominal oxidation states. Electrochemical characterization revealed that both MoN_x/Mo and MoO₂/Mo electrodes exhibit notable pseudocapacitive behavior in 0.5 M H₂SO₄ electrolyte, with areal specific capacitances reaching up to 520 mF cm⁻² at 10 mV s⁻¹. Increasing layer thickness led to enhanced capacitance, likely due to an increase in the electrochemically accessible surface area and the extension of ion diffusion pathways. MoO₂-coated samples showed stronger faradaic contribution and superior rate capability compared to MoN_x counterparts, along with a gradual shift from predominantly electric double-layer capacitance toward hybrid pseudocapacitive charge storage mechanisms. Full article

The escalating demand for high-performance energy storage devices has driven extensive research into flexible electrode materials for supercapacitors. Integrating structured carbon nanomaterials with flexible substrates to construct binder-free electrode architectures represents a promising strategy for improving supercapacitor capacitance and rate capability. However, achieving stable, binder-free integration of structure-controlled nanostructured carbon materials with flexible substrates remains a critical challenge. In this study, we report a direct synthesis approach for one-dimensional (1D) carbon nanofibers (CNFs) on commercial flexible carbon fabric (CF) via chemical vapor deposition (CVD). The resulting CNFs exhibit two typical average diameters—approximately 25 nm and 50 nm—depending on the growth temperature, with both displaying highly graphitized structures. Electrochemical characterization of the CNFs/CF composites in 1 M H₂SO₄ electrolyte revealed typical electric double-layer capacitor (EDLC) behavior. Notably, the 25 nm-CNFs/CF electrode achieves a high specific capacitance of 87.5 F/g, significantly outperforming the 50 nm-CNFs/CF electrode, which reaches 50.2 F/g. Compared with previously reported carbon nanotube CNTs/CF electrodes, the 25 nm-CNFs/CF electrode exhibits superior capacitance and lower resistance. Full article

Fiber-based and fabric batteries signify a groundbreaking development in energy storage, allowing for the straightforward incorporation of power sources into wearable fabrics, intelligent apparel, and adaptable electronics. In this study, we introduce a novel strategy for one-step fabrication of a flexible lithium titanate oxide (Li₄Ti₅O₁₂, LTO) anode directly on a copper current collector via electrospinning, eliminating the need for high-temperature post-processing. Based on our previous work with electrospun nanofiber cathodes and carbon-based current collector, we prepared the LTO electrode using polyethylene oxide (PEO) as a binder and carbon additives to enhance mechanical integrity and conductivity. LTO fiber mats detached from the current collector were found to endure multiple instances of bending, twisting, and folding without any structural damage. LTO/Li cells incorporating electrospun fiber LTO electrodes with 72 wt% active material loading deliver a high capacity of 170 mAh g⁻¹ at 0.05 C. In addition, they demonstrate excellent cycling stability with a capacity loss of only 0.01% per cycle over 200 cycles and maintain a capacity of 160 mAh g⁻¹ at 0.1 C. The scalability of the heat-treatment-free method for fabricating flexible LTO anodes, together with the improved mechanical durability and electrochemical performance, offers a promising route toward the development of next-generation flexible and wearable energy storage devices. Full article

This study reports a binder-free, catalyst-free method for fabricating vertically aligned carbon nanotubes (VACNTs) directly on copper (Cu) foil using plasma-enhanced chemical vapor deposition (PECVD) for electrochemical double-layer capacitor (EDLC) applications. This approach eliminates the need for catalyst layers, polymeric binders, or substrate pre-treatments, simplifying electrode design and enhancing electrical integration. The resulting VACNTs form a dense, uniform, and porous array with strong adhesion to the Cu substrate, minimizing contact resistance and improving conductivity. Electrochemical analysis shows gravimetric specific capacitance (C_grav) and areal specific capacitance (C_areal) of 8 F g⁻¹ and 3.5 mF cm⁻² at a scan rate of 5 mV/s, with low equivalent series resistance (3.70 Ω) and charge transfer resistance (0.48 Ω), enabling efficient electron transport and rapid ion diffusion. The electrode demonstrates excellent rate capability and retains 92% of its initial specific capacitance after 3000 charge–discharge cycles, indicating strong cycling stability. These results demonstrate the potential of directly grown VACNT-based electrodes for high-performance EDLCs, particularly in applications requiring rapid charge–discharge cycles and sustained energy delivery. Full article

A novel process for the synthesis of binder-free, porous nickel/polythiophene-functionalized sulfur (Ni/S-PTh) composite cathodes for lithium–sulfur (Li–S) batteries is introduced in this paper. Initially, a polyvinyl butyl polymer scaffold is 3D printed, then coated with a graphite-based conducting layer, and, finally, it is pulse-plated for nickel deposition to produce a high-surface-area, mechanically stable current collector. S-PTh particles are afterwards co-deposited into the Ni matrix through composite electrodeposition. After the dissolution of the polymer template, the resulting self-standing electrodes still maintain porous structure with uniform sulfur distribution and a distinct transition between the dense Ni layer and the Ni/S-PTh composite layer. Electrochemical characterization of the Ni/S-PTh composite cathodes by galvanostatic cycling at C/10 rate results in an initial specific discharge capacity of ~1120 mAh·g⁻¹ and a specific capacity of ~910 mAh·g⁻¹ after 200 cycles, resulting in a high capacity retention of ~81 %. For our novel approach, no steps at high temperatures or toxic solvents are involved and the need for polymer binders and conductive additives is avoided. These results demonstrate the potential of composite electrodeposition in combination with 3D printing for producing sustainable, high-performance sulfur cathodes with tunable architecture. Full article

The potential of silicon carbide (SiC) as a promising high-capacity and stable anode material is hindered by poor electronic conductivity and slow lithium diffusion kinetics. Here, we report a one-step laser chemical vapor deposition (LCVD) process to directly synthesize porous graphene@SiC heterostructures on carbon fiber substrates. This in situ method yields an integral, binder-free electrode architecture that enhances mechanical robustness against pulverization. A critical feature of this heterostructure is the built-in electric field at the graphene–SiC interface, which is revealed by theoretical calculations to significantly accelerate charge transport and lithium-ion diffusion. The resulting anode delivers a high reversible capacity of 668 mAh·g⁻¹ after 100 cycles at 0.1 A·g⁻¹. More remarkably, a unique multi-stage activation mechanism is discovered, leading to an unprecedented capacity rebound to 735 mAh·g⁻¹ after cycling at rates up to 5 A·g⁻¹. This activation process is observed to accelerate with increasing current density in the 0.1–2 A·g⁻¹ range. Furthermore, post-cycling analysis via XRD, TEM, and XPS confirms both the structural durability of the electrode and a reversible lithium intercalation mechanism, providing a critical foundation for the future design of high-performance LIB anodes. Full article

Aqueous zinc-ion batteries (AZIBs) have gained significant attention as promising candidates for next-generation energy storage systems, especially in mobile robotics, due to their inherent safety, environmental friendliness, and low cost. However, the practical application of AZIBs is often hindered by slow Zn²⁺ diffusion and the poor structural stability of the cathode materials under high-rate or long-term operation. To address these challenges, a defect-engineered, binder-free MnO₂ electrode, with a MnO₂ loading of 1.35 mg·cm⁻², is synthesized via in situ hydrothermal growth of ultrathin MnO₂ nanosheets directly on a 3D conductive nickel foam scaffold, followed by reductive annealing to introduce abundant oxygen vacancies. These oxygen-rich defect sites significantly enhance Zn²⁺ adsorption, improve charge transfer kinetics, and contribute to enhanced pseudocapacitive behavior, further improving overall electrochemical performance. The intimate contact between the MnO₂ and Ni substrate ensures efficient electron transport and robust structural integrity during repeated cycling. With this synergistic architecture, the MnO₂@Ni electrode achieves a high specific capacity of 122.9 mAh·g⁻¹ at 1 A·g⁻¹, demonstrating excellent cycling durability with 94.24% capacity retention after 800 cycles and nearly 99% coulombic efficiency. This study offers a scalable strategy for designing high-performance, structurally stable Zn-ion battery cathodes with improved rate capability, making it a promising candidate for energy-intensive mobile robotic and flexible electronic systems. Full article

This work presents a method for preparing an Fe₂O₃/MWCNT/Al composite electrode without the use of a binder. Synthesizing the composite material directly on conductive substrates allows one to obtain ready-made supercapacitor electrodes characterized by high values of specific capacity, as well as resistance to numerous charge/discharge cycles. Using an array of multi-walled carbon nanotubes (MWCNTs) as a conductive base for the synthesis of iron oxide allows for the production of a composite material that combines the positive properties of both materials. The Fe₂O₃/MWCNT/Al composite was formed using electrochemical oxidation of the MWCNT/Al material in a mixture of 0.1 M aqueous solution of Fe(NH₄)₂(SO₄)₂ (iron ammonium sulfate) and 0.08 M CH₃COONa (sodium acetate) in a 1:1 ratio. The proposed approaches to fabricating composite electrodes provide excellent performance characteristics, namely high cyclic stability and fast response time. For the first time, an Fe₂O₃/MWCNT/Al composite was obtained using electrochemical oxidation of Fe²⁺ on the surface of MWCNTs grown directly on aluminum foil. The specific capacitance of the obtained composite material reaches 175 F/g at a scanning rate of 100 mV/s. The capacity loss during cyclic measurements does not exceed 25% after 10,000 charge/discharge cycles. Full article

Designing advanced electrode architectures with tailored morphology and redox synergy is essential for achieving high-performance supercapacitive energy storage. In this study, a PVP-assisted hydrothermal approach was employed to synthesize binder-free NiCo₂O₄ nanostructured electrodes directly on nickel foam substrates. By modulating the PVP concentration (0.5–2 wt%), hierarchical flower-like nanosheets were engineered, with the NiCo-P₁ sample (1 wt% PVP) exhibiting an optimized structure, superior electroactive surface area, and enhanced ion accessibility. Comprehensive electrochemical analysis revealed that NiCo-P₁ delivered an outstanding areal capacitance of 36.5 F/cm² at 10 mA/cm², along with excellent cycling stability over 15,000 cycles with 80.97% retention. Kinetic studies confirmed dominant diffusion-controlled redox behavior with high OH⁻ diffusion coefficients and minimal polarization. An asymmetric pouch-type supercapacitor device (NiCo-P₁//AC) exhibited a wide operating window of 1.5 V, achieving a remarkable areal capacitance of 187 mF/cm², energy density of 0.058 mWh/cm², and capacitive retention of 78.78% after 5000 cycles. The superior performance is attributed to the synergistic integration of mixed-valence Ni and Co species, engineered nanosheet morphology, and low interfacial resistance. This work underscores the significance of surfactant-directed design in advancing cost-effective, high-performance electrodes for next-generation flexible energy storage technologies. Full article

Thin films of manganese–nickel–cobalt oxide with graphene (G@MNCO) were deposited on copper foam using electrochemical deposition. NiCo₂O₄ is the main phase in these films. As the proportion of graphene in the precursor solution increases, the oxygen vacancies in the samples also increase. The microstructure of these samples evolves into hierarchical vertical flake structures. Cyclic voltammetry measurements conducted within the potential range of 0–1.2 V reveal that the electrode with the highest graphene content achieves the highest specific capacitance, approximately 475 F/g. Furthermore, it exhibits excellent cycling durability, maintaining 95.0% of its initial capacitance after 10,000 cycles. The superior electrochemical performance of the graphene-enhanced, manganese-doped nickel–cobalt oxide electrode is attributed to the synergistic contributions of the hierarchical G@MNCO structure, the three-dimensional Cu foam current collector, and the binder-free fabrication process. These features promote quicker electrolyte ion diffusion into the electrode material and ensure robust adhesion of the active materials to the current collector. Full article

Slurry-cast (SLC) electrode manufacturing faces problems such as thickness limitation and material stratification, which are caused by applying toxic organic solvents. Solvent-free electrode technology, as a sustainable alternative, could get rid of issues generated by solvents. In this study, dual-layer NCM811 solvent-free electrodes (DLEs) are fabricated via an electrostatic powder deposition method with an active material-rich upper layer to provide high energy output, while the more binder–conductor content base layer improves conductivity and contact with current collectors. The dual-layered structure overwhelms the single-layer electrode (SE) with stable cycling performance caused by more regulated pore structures. DLE maintains 74% capacity retention after 100 cycles at 0.3 C, while the SLC shows only 60% capacity retention. Additionally, DLE shows excellent rate performance at various rates, with 207.3 mAh g⁻¹, 193.9 mAh g⁻¹, 173.9 mAh g⁻¹, 157.3 mAh g⁻¹, and 120.4 mAh g⁻¹ at 0.1 C, 0.2 C, 0.5 C, 1.0 C, and 2.0 C, respectively. The well-designed DLE cathodes exhibit superior discharge-specific capacities, rate performance, and improved cycling stability than traditional SLC cathodes. It enlightens the path toward new structure innovations of solvent-free electrodes. Full article

In this study, a Zn(CN)₂–V₂O₃–C composite cathode was synthesized via AC electrophoretic deposition (EPD) and evaluated for application in aqueous zinc-ion batteries (ZIBs). Here, we report for the first time a binder-free Zn(CN)₂–V₂O₃–C composite cathode, using AC-EPD to create an ultrathin architecture optimized for probing the electrode–electrolyte interface without interference from additives or bulk effects. The composite combines Zn(CN)₂ for structural support, V₂O₃ as the redox-active material, and carbon for improved conductivity. X-ray diffraction confirmed the presence of Zn(CN)₂ and V₂O₃ phases, while scanning electron microscopy revealed a uniform, ultrathin film morphology. Electrochemical analysis demonstrated a hybrid charge storage mechanism with a b-value of 0.64, indicating both capacitive and diffusion-controlled contributions. The electrode delivered a high specific capacity (~250 mAh/g at 500 mA/g) with stable cycling performance. These results highlight the potential of metal–organic framework-derived composites for high-performance ZIB cathodes. The composite is especially effective when prepared via AC-EPD, which yields ultrathin, uniform films with strong adhesion and low agglomeration. This enhances energy storage performance and provides a reliable platform for focusing on interfacial charge storage, excluding the effect of binders on electrochemical performance. Full article

Lithium-ion batteries (LIBs) with high power, high capacity, and support for fast charging are increasingly favored by consumers. As a commercial electrode material for power batteries, LiFePO₄ was limited from further wide application due to its low conductivity and lithium-ion diffusion rate. The development of advanced architectures integrating rational conductive networks with optimized ion transport pathways represents a critical frontier in optimizing the performance of cathode materials. In this paper, a novel self-supporting cathode material (designated as LFP@LVP-CES) was synthesized through an integrated coaxial electrospinning and controlled pyrolysis strategy. This methodology directly converts LiFePO₄, Li₃V₂(PO₄)₃, and polyacrylonitrile (PAN)) into flexible, binder-free cathodes with a hierarchical structural organization. The 3D carbon nanofiber (CNF) matrix synergistically integrates LiFePO₄ (Li/Fe/PO_x) and Li₃V₂(PO₄)₃ (Li/V/PO_x) nanoparticles, where CNFs act as a conductive scaffold to enhance electron transport, while the PO_x polyanionic frameworks stabilize Li⁺ diffusion pathways. Morphological characterizations (SEM and TEM) revealed a 3D cross-connected carbon nanofiber matrix (diameter: 250 ± 50 nm) uniformly embedded with active material particles. Electrochemical evaluations demonstrated that the LFP@LVP-CES cathode delivers an initial specific capacity of 165 mAh·g⁻¹ at 0.1 C, maintaining 80 mAh·g⁻¹ at 5 C. Notably, the material exhibited exceptional rate capability and cycling stability, demonstrating a 96% capacity recovery after high-rate cycling upon returning to 0.1 C, along with 97% capacity retention over 200 cycles at 1 C. Detailed kinetic analysis through EIS revealed significantly reduced R_ct and increased Li⁺ diffusion. This superior electrochemical performance can be attributed to the synergistic effects between the 3D conductive network architecture and dual active materials. Compared with traditional coating processes and high-temperature calcination, the preparation of controllable electrospinning and low-temperature pyrolysis to some extent avoid the introduction of harmful substances and reduce raw material consumption and carbon emissions. This original integration strategy establishes a paradigm for designing freestanding electrode architectures through 3D structural design combined with a bimodal active material, providing critical insights for next-generation energy storage systems. Full article