Search Results (1,426)

The increasing demand for lithium-ion batteries (LIBs) raises concerns about the security of critical raw material supply and the management of hazardous waste. Efficient recycling can alleviate these issues by transforming spent batteries into high-value secondary materials for the circular economy. Industrial recycling has traditionally focused on the recovery of nickel (Ni) and cobalt (Co), whereas lithium (Li) recovery has often been sidelined due to technical complexities and fluctuating economic incentives. To meet the European Union (EU) Batteries Regulation target of 80% lithium recovery by the end of 2031, technically effective and economically viable lithium recovery strategies are required. This study investigates the use of food-grade sucrose as an organic reductant for the targeted recovery of lithium from NMC622 and NCA battery materials. The process combines sucrose-assisted reductive roasting with selective water leaching. The effects of roasting temperature, holding time, sucrose dosage, and heating rate were systematically evaluated and optimised. Under the best conditions of 600 °C, 15 min, 15 wt% sucrose, and a heating rate of 20 °C/min, lithium leaching efficiencies of 93.2% and 87.6% were achieved for separated NMC622 cathode material and NMC622-derived black mass, respectively. The method was also applicable to NCA-based black mass, reaching 83.7% lithium recovery under the same conditions. Mechanistic analysis revealed that lithium release was strongly controlled by the extent of transition metal reduction. Cobalt was fully reduced to its metallic state under all tested conditions. However, maximum lithium recovery required nickel to be reduced to metallic Ni and manganese-containing phases to be converted to MnO. The sucrose-assisted roasting process was rapid and holding times longer than 15 min decreased lithium recovery. This decrease was caused by the formation of poorly soluble lithium-containing phases, such as LiF and Li₃PO₄. F composition analysis showed the black mass (1.06 wt%) and anode fractions (2.26 wt%) to contain significantly more F than the cathode fraction (0.46 wt%), hence leading to the 5% Li leaching efficiency difference between cathode and black mass fractions under most conditions tested. Overall, these results demonstrate that sucrose-assisted reductive roasting, followed by selective water leaching, provides a rapid and effective route for high-efficiency lithium recovery from NMC- and NCA-based battery materials. Full article

To solve the drawbacks of conventional long-cycle wear tests for miniature standing- wave linear ultrasonic motors, an accelerated equivalent wear model and test system were proposed in this work. After primary screening of multiple pair materials, graphite and Al₂O₃ were adopted to modify epoxy films. The optimal friction pair is composed of 6061 hard anodic oxidation film and ECA105 composite film. The matched pair exhibits excellent driving stability and low wear loss, with fatigue wear as the main wear form. Graphite and Al₂O₃ exert synergistic anti-wear and load-bearing effects via forming a stable transfer film on the friction interface. Experimental results confirm that the accelerated test is equivalent to a full-life durability test. The presented method and optimized friction pair can effectively guide the development of high-performance ultrasonic motors. Full article

Quaternary β-Ti-xTa-xZr-xNb (TTZN) alloys (x = 10, 20, and 30 wt%) were surface-modified by plasma electrolytic oxidation (PEO) to improve their surface properties. This treatment promotes the incorporation of bioactive ions, such as Ca and P, and favors the formation of a porous anodic surface resulting from the oxidation of the precursor metals. This study investigated how the addition of alloying elements (Zr, Ta, and Nb) influences oxide formation, PEO-induced pore morphology, wettability, and coating hardness. The surfaces were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), Vickers microhardness testing, and wettability analysis. XRD analysis revealed that the TTZN10 alloy exhibited crystalline TiO₂ phases in the form of anatase and rutile. In contrast, the TTZN20 and TTZN30 alloys exhibited only cubic ZrO₂ diffraction peaks, while no TiO₂ peaks were detected within the detection limits of the XRD technique. Micrographs showed micrometric pores on all alloy surfaces. The TTZN20 alloy exhibited the highest porosity (31.8%), which correlated with lower hydrophilicity (θ = 79°) and high surface free energy (67 mJ/m²). After PEO treatment, all surfaces exhibited high hardness values ranging from 491 to 561 HV. The highest hardness was observed for TTZN10, attributed to the mixed anatase/rutile TiO₂ phase composition. Full article

In this study, hexagonal titanium dioxide nanotubes (hTNTs) fabricated by sonoelectrochemical anodization were thermally modified in air to investigate the influence of annealing temperature and heating/cooling rate on phase evolution, structural stability and electrochemical behavior. The samples were annealed at 450 °C, 550 °C, and 650 °C for 2 h using heating/cooling rates of 6 °C/min, 10 °C/min, and 20 °C/min. The hexagonal nanotubular morphology remained preserved after thermal treatment. However, increasing annealing temperature and heating/cooling rate promoted crack formation due to the thermally induced stress relaxation and phase transformation. The anatase content increased with increasing heating/cooling rate, indicating kinetically limited anatase-to-rutile transformation, whereas annealing at 650 °C promoted partial rutile formation. Electrochemical studies demonstrated that annealing temperature and heating/cooling rate affected the electrochemical behavior of hTNTs through different mechanisms. Increasing annealing temperature promoted structural ordering and partial anatase-to-rutile transformation, leading to reduced current response and enhanced electrochemical stability. In contrast, heating/cooling rate significantly affected impedance behavior and diffusion-related processes, indicating changes in charge transfer kinetics and ion transport within the nanotubular oxide layer. The results demonstrate that thermal treatment kinetics play an important role in controlling the phase composition and electrochemical behavior of hTNTs, providing insight into the thermal optimization of hexagonal TiO₂ nanotubes for advanced functional applications. Full article

Silicon (Si) is a leading anode candidate for next-generation lithium-ion batteries owing to its high theoretical capacity (~4200 mAh/g), but its >300% volumetric expansion during lithiation causes particle pulverization, loss of electrical contact, and continuous solid electrolyte interphase (SEI) reformation, resulting in rapid capacity fade. Here, we report a single-walled carbon nanotube (SWNT)-templated porous Si/SiO₂ core–shell cylindrical hybrid anode synthesized by combining block copolymer-directed sol–gel assembly with controlled magnesiothermic reduction. SWNT bundles act as a three-dimensional structural template that directs the formation of a continuously interconnected cylindrical porous network, a geometry difficult to obtain by conventional particle-based compositing. The controlled, partial magnesiothermic reduction intentionally preserves residual amorphous SiO₂ within the porous shell as an electrochemically inactive mechanical buffer that suppresses Si volume expansion and stabilizes the electrode. A side-by-side comparison with a fully reduced, SiO₂-free counterpart of identical architecture isolates the role of the SiO₂ buffer in achieving long-term cycling stability. The SWNT-porous Si/SiO₂ hybrid delivers a reversible capacity of 1133 mAh/g in the first cycle and retains 90% of its initial capacity after 200 cycles at 1 C with 99.7% Coulombic efficiency, together with a rate capability of 482 mAh/g at 5 C. Post-cycling cross-sectional analysis confirms minimal electrode-level swelling (~2 μm) after 200 cycles, demonstrating the structural efficacy of the SWNT-templated porous architecture combined with the SiO₂ buffer for structurally stable Si anodes. Full article

The development of sustainable electrocatalysts for clean energy by modifying biomass-derived activated carbon with nitrogen and transition metals is presented. Activated carbon (AWC) material was obtained using alder wood char as a precursor, while nitrogen and cobalt or copper nanoparticles were incorporated with the aim of creating efficient materials for hydrazine oxidation (HzOR) and direct hydrazine–hydrogen peroxide fuel cells (DHHPFC, N₂H₄–H₂O₂). The composition, structure, and surface morphology of the created materials were examined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and inductively coupled plasma optical emission spectroscopy (ICP-OES). The activity of the AWC, AWC–Co–N, and AWC–Cu–N catalysts for HzOR was investigated using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). N₂H₄–H₂O₂ fuel-cell tests were performed by applying the catalysts as both the anode and cathode. It was found that all materials retained a hierarchical porous carbon framework, while metal incorporation altered surface compactness. Cobalt doping produced well-dispersed Co nanoparticles and abundant Co–N–C coordination sites, whereas Cu introduction resulted in moderately compact structures with uniformly distributed Cu-based nanoparticles. Electrochemical measurements demonstrated that both metal dopants enhanced HzOR activity, with the catalytic performance following the order of AWC–Co–N > AWC–Cu–N > AWC. Fuel-cell testing further confirmed this trend: AWC–Co–N achieved the highest maximum power density (30.4 mW cm⁻²), outperforming AWC–Cu–N (17.7 mW cm⁻²). These results identify AWC–Co–N as a highly effective bifunctional electrocatalyst for DHHPFCs. Full article

Biomass-derived carbons are promising sustainable anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) because biomass is renewable, abundant, low-cost, and naturally diverse in composition and morphology. Lignocellulosic frameworks, intrinsic heteroatoms, and biomass-derived inorganic species can be converted through carbonization, activation, graphitization, and doping into carbon architectures with tunable porosity, carbon ordering, and surface chemistry. This review first summarizes the compositional and structural features of biomass precursors and explains how processing conditions convert them into carbon frameworks. Recent advances in biomass-derived carbon anodes are then discussed by comparing the distinct design requirements for LIBs and SIBs. For LIBs, accessible surface area, hierarchical porosity, heteroatom-derived active sites, and improved electronic conductivity are generally beneficial for enhancing Li⁺ storage and rate capability. In contrast, SIB hard carbons require controlled surface exposure, expanded turbostratic spacing, and closed or latent pores to improve Na⁺ storage reversibility and initial Coulombic efficiency. These comparisons emphasize that biomass-derived carbon anodes should be designed according to system-specific storage mechanisms rather than a universal carbon design strategy. Full article

Mass-based circularity indicators, such as ISO 59020:2024, quantify material recovery as a share of total throughput but do not account for chemical composition or functional performance, as a consequence of their sector-agnostic design. In copper metallurgical systems, trace tramp elements (e.g., As, Sb, Bi, Fe, Sn, Ni) present in WEEE-derived scrap, anode slimes, and refinery residues can significantly reduce electrical conductivity. Even at nominal purities of ≥99.7 wt.% Cu, conductivity may drop to 85.0–88.0% IACS, as illustrated by selected reported cases—a level of functional degradation that remains undetected by mass-based accounting. Analysis of Grade A cathode standards (EN 1978:2022, LME Cu-CATH-1, ASTM B115-10:2021) shows that impurity limits as low as 2 ppm (Bi) constrain the achievable share of secondary feed in closed-loop recycling. For a specific flash-smelting–refinery configuration, modeling indicates that secondary feed shares above approximately 30% may lead to impurity accumulation beyond the stated specification constraints unless low-impurity primary copper is introduced. This study introduces the Quality-Adjusted Circularity Indicator (QACI), a conceptual, specification-constrained indicator framework that applies a dilution factor f_dil derived from a binary blending mass balance to adjust ISO 59020:2024 inflow-based circularity indicators using a feed-composition blending constraint anchored to Grade A specification limits. The QACI functions as a feed-composition screening indicator operating at the anode blending stage and does not represent a correction of the full electrorefining system. Parametric scenario analysis across six stylized impurity configurations shows that, at identical mass-based circularity (C_mass = 25%), the QACI ranges from 7.1% to 25.0%. This corresponds to a 1.3- to 3.5-fold difference between the mass-based and quality-adjusted indicator values under the stated feed-composition assumptions, illustrating the potential overestimation introduced when feed-quality constraints are not considered. This ratio quantifies the divergence between two indicator values under stylized conditions and should not be interpreted as a directly measured fold-difference in actual loop-closure performance. Positioned within the ISO 59020:2024 Annex C complementary method space, the QACI is positioned as a first-order screening approach of existing circularity metrics that may inform future research discussion of quality-differentiated approaches in EU secondary metals policy. Full article

Lithium-ion batteries with high energy density and long cycle life have been widely used as secondary batteries in electric vehicles and energy storage systems. With the growing demand for high energy density in lithium-ion batteries, silicon-based materials, which possess a high theoretical specific capacity (4200 mAh g⁻¹), are regarded as core candidates for anode materials. However, Si-based materials undergo severe volume expansion (up to 300%), which leads to the collapse of the electrode structure, inducing pulverization of the active material and capacity loss, thereby hindering the commercial application of silicon-based materials. To address these issues, scholars from various countries have developed many silicon-based materials with different compositions and three-dimensional structures, and have made some research progress. This review first elaborates on the lithium storage mechanisms and advantages of diverse silicon-based anode materials by taking Si, SiO_x, SiN_x, and SiP_x as representative examples with distinct characteristics. Subsequently, from the two aspects of dimensional design (0D, 1D, 2D and 3D) and architecture design (core–shell, sandwich-like and network structure), the design strategies for various silicon-based anode structures and their enhancement on electrochemical performance are analyzed. Finally, this review elucidated the challenges faced by silicon-based anodes from the perspectives of mechanism elucidation, structural customization, industrialization, and full-cell applications. It also proposed future development directions for silicon anodes by combining actual challenges and focusing on aspects such as structure optimization, machine learning, advanced characterization techniques, and mechanistic analysis. Full article

This paper presents the design, structural optimization, and two-dimensional (2D) technology computer-aided design (TCAD) simulation of a gallium nitride (GaN) vertical Merged P-i-N/Schottky (MPS) diode incorporating a multi-drift-layer doping profile, composite SiO₂/Si₃N₄ passivation, and field-plate (FP) termination. The proposed device is constructed on an n⁺-GaN substrate with a three-sub-layer n-type drift region and a p-GaN/p⁺-GaN anode region. Systematic TCAD simulations are performed to investigate the dependences of key performance metrics—including knee voltage (V_knee), specific on-resistance (R_on), breakdown voltage (BV), reverse leakage current (J_leak), and Baliga’s figure of merit (BFOM)—on the Schottky metal work function, multi-drift-layer doping concentration, drift-layer thickness, Schottky-to-PN contact length ratio (γ_w), operating temperature, and reverse recovery switching transients. Results demonstrate that the MPS architecture effectively decouples forward conduction loss from reverse blocking capability, overcoming the conventional R_on–BV trade-off. The optimal doping profile (n_mm = 2 × 10¹⁵, n_m = 2 × 10¹⁵, n = 1 × 10¹⁶ cm⁻³) achieves a BFOM of ~31.97 GW·cm⁻² with BV ≈ 5.98 kV and R_on ≈ 1.12 mΩ·cm². Joint doping–thickness optimization further identifies a graded doping profile (n_mm = 2 × 10¹⁵, n_m = 5 × 10¹⁵, n = 1 × 10¹⁶ cm⁻³) combined with layer thicknesses (T_nmm, T_nm, T_n) = (4.49, 5, 20) μm as the overall optimum, achieving BFOM = 55.36 GW·cm⁻² (BV = 6.61 kV, R_on = 0.79 mΩ·cm²)—a +73% improvement, governed by the punch-through/field-stop design principle. The optimal contact ratio of γ_w = 1.33 yields a BFOM of 38.71 GW·cm⁻². Temperature analysis confirms a positive BV temperature coefficient due to drift-region-limited avalanche breakdown, and the BFOM improves monotonically from 33.31 to 37.82 GW·cm⁻² between 200 K and 450 K. Mixed-mode switching simulations show that increasing γ_w substantially reduces reverse recovery charge (Q_rr), demonstrating the strong potential of the proposed MPS diode for high-voltage, high-frequency, and high-temperature power electronic applications. Full article

Graphite is widely used as an anode in lithium-ion batteries (LIBs); however, its limited capacity restricts the energy density enhancement. Si-based anodes offer much higher capacity, but their significant volume changes during repeated lithiation and delithiation generate mechanical stress and can damage the electrode/current-collector interface. Herein, high-strength nanotwinned Cu (NT-Cu) was fabricated and employed as current collectors for carbon-coated Si/β-Si₃N₄-based anodes. The electroplated 5 μm-thick NT-Cu foils exhibited tensile strength exceeding 760 MPa. The role of the Cu current collector was investigated by comparing NT-Cu foils with different mechanical properties and commercial Cu foils. The results show that electrochemical performance was not governed by UTS alone; instead, a balanced combination of tensile strength, ductility, and surface morphology was important for improving cycling stability and rate capability. To further improve cycling retention, artificial graphite was incorporated into the Si/β-Si₃N₄ composite. Using a 5 μm electroplated NT-Cu foil and a Si/β-Si₃N₄/artificial graphite composite anode, the pouch cell retained 81.51% of its capacity and delivered 267.3 mAh g⁻¹ after 206 cycles. These results demonstrate the potential of NT-Cu for improving the stability of Si-containing LIB anodes. Full article

Inorganic mercury ions (Hg²⁺) are highly toxic, posing a threat to aquatic ecosystems and human health. In this study, iron phthalocyanine (FePc) was anchored onto the surface of MXene via a self-assembly strategy to construct an FePc/MXene-x (F/M-x) heterostructure. Characterization by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption (BET) confirmed that the high specific surface area and good conductivity of MXene effectively inhibited FePc aggregation and increased the exposure of active sites. The F/M-x composite was then modified onto a glassy carbon electrode (GCE) to fabricate an electrochemical sensor, and the detection performance for Hg²⁺ was evaluated using square-wave anodic stripping voltammetry (SWASV). Under optimized conditions (pH = 5.0, accumulation at −1.2 V for 180 s), the F/M-100/GCE exhibited a linear range of 0.1–1.0 μM, a sensitivity of 19.02 μA/μM, and a detection limit of 5.9 nM. The sensor showed good anti-interference ability against coexisting metal ions such as Cd²⁺, Cu²⁺, and Pb²⁺, with a batch-to-batch RSD of 2.03% and a long-term stability RSD of 2.49%. Spike recovery experiments in real water samples (lake water and groundwater) verified the accuracy of the method. This study provides a new electrochemical platform for the rapid detection of trace Hg²⁺ in water environments. Full article

Hydrogen peroxide fuel cells have emerged as a promising class of electrochemical energy conversion device owing to the dual redox character of H₂O₂, its liquid-phase storage, and its ability to operate in air-free environments. In this work, a dual-compartment direct H₂O₂ fuel cell using a Prussian Blue cathode and a tantalum anode, separated by a Nafion 115 proton exchange membrane, was systematically characterized and optimized with respect to electrolyte pH and ionic composition. The influence of pH on OCV was investigated independently in each compartment across the range of pH 2 to 12. In the tantalum compartment, OCV increased non-linearly with pH from 573 mV to 808 mV, driven by the enhanced electrochemical reactivity of the system under alkaline conditions. In the Prussian Blue compartment, OCV decreased from 676 mV to 199 mV with increasing pH, reflecting the instability of the material in alkaline conditions. The effect of the electrolyte ionic composition on average current density was subsequently investigated by varying the concentrations of NaCl and Dy(NO₃)₃. Increasing NaCl from 0 to 2.5 M produced an increase in current density from 0.414 mA/cm² to 0.973 mA/cm², consistent with ohmic resistance reduction through improved ionic conductivity. The addition of Dy(NO₃)₃ produced a positive response with an optimal concentration of $0.05$ M, at which current density reached 1.08 mA/cm², before declining sharply. Under the fully optimized conditions, pH 12 in the tantalum compartment, pH 2 in the Prussian Blue compartment, 0.3 M H₂O₂, 2.0 M NaCl, and 0.05 M Dy(NO₃)₃, the cell produced an OCV of 724 mV and a peak power density of 0.283 mW/cm² at a current density of 0.8 mA/cm². These results demonstrate that meaningful electrochemical performance can be achieved in a dual-compartment H₂O₂ fuel cell without the use of precious metal catalysts and highlight electrolyte engineering as an effective strategy for improving cell output in this class of device. Full article

Driven by the “Dual Carbon” goals, supercapacitors have become critical energy storage devices for new energy electric vehicles. In this paper, a ZnFe₂O₄@ZnCo₂O₄ core–shell cathode was prepared by a hydrothermal method followed by high-temperature annealing, and an AC@PANI composite anode was synthesized through in situ polymerization. The materials were characterized by SEM, TEM, XRD, XPS, nitrogen adsorption–desorption and electrochemical tests. The ZnFe₂O₄ rod-like core provides mechanical stability, whereas the ZnCo₂O₄ nanosheet shell increases the specific surface area and exposes more active sites. The cathode delivers 2133 F/g at 1 A/g with 94.4% retention after 10,000 cycles. The anode reaches 398 F/g at 1 A/g. The cathode delivers 2133 F/g at 1 A/g with 94.4% retention after 10,000 cycles. The anode reaches 398 F/g at 1 A/g. The assembled ZnFe₂O₄@ZnCo₂O₄//AC@PANI hybrid supercapacitor works in a wide voltage range of 0–1.6 V. It exhibits a specific capacitance of 157 F/g at 1 A/g and a high energy density of 54.7 Wh/kg at a power density of 1600 W/kg. The device retains 91.4% of its initial capacity after 10,000 charge–discharge cycles. This study offers a promising strategy for high-performance automotive supercapacitors. Full article