Search Results (1,521)

Two semiflexible piezoelectric composite plate structures were developed, incorporating 1 × 9 and 2 × 9 arrays of PZT elements mounted on brass discs and mechanically secured by pop rivets within a thin plastic foil spacer positioned between two copper-clad PCB layers. This configuration provides reliable electrical contact, adequate mechanical compliance, and efficient conversion of mechanical vibration energy into electrical energy. In addition, a multifunctional thermoelectric device was realized, consisting of four cubic modules arranged around a rectangular tube and enabling both handheld operation and coupling to hot or cold surfaces. Each cube is equipped with optimized finned heat sinks and integrates four thermoelectric elements on each face. Experimental results show that each cube generates approximately 6 mW, when handheld and with icy water injected into the central tube, demonstrating its suitability as a compact and versatile thermal energy harvester. Under low-light conditions, a solar panel is supplemented by this hybrid piezoelectric–thermoelectric energy harvesting system that combines the output of a piezoelectric composite plate with the dual outputs of a thermoelectric device using an electronically isolated summing block to ensure source decoupling. Energy storage and management are implemented using a capacitor buffer for the piezoelectric device, two voltage boosters for the thermoelectric outputs, and an automatic ultra-low-power pulse width modulation buck regulator for charging supercapacitors at 5 V. Full article

The explosive demand for flexible wearable and portable devices imposes stringent requirements on the mechanical, energy storage, and sensing properties of functional materials. Although two-dimensional (2D) transition metal carbides and nitrides (MXene) possess high conductivity and pseudocapacitance, their severe self-restacking and intrinsic brittleness restrict their practical applications. Herein, a facile vacuum filtration and hot-pressing densification strategy is proposed to fabricate nacre-inspired MXene-based films. By incorporating one-dimensional (1D) high-aspect-ratio TEMPO-oxidized cellulose nanofibrils (TOCNFs), the self-restacking of MXene is effectively suppressed. The optimal M20F5 composite film exhibits a coordinated electromechanical balance, maintaining an electrical conductivity of 1.07 × 10⁶ S m⁻¹ while enduring 2124 folding cycles. For energy storage, the assembled symmetric supercapacitor delivers a specific capacitance of 828.92 F g⁻¹ at 0.5 mA cm⁻² and maintains an energy density of 13.75 Wh kg⁻¹ at a power density of 9500 W kg⁻¹. Furthermore, acting as a piezoresistive sensor, the film achieves reliable detection, spanning from bimodal gait recognition to subtle physiological pulses. This work establishes a viable material design strategy for next-generation supercapacitors and intelligent wearable systems. Full article

Metal–organic frameworks (MOFs) are crystalline porous materials made of metal nodes coordinated by organic linkers. Their high surface areas, tunable pore sizes, adjustable chemical environments, and modular design make MOFs promising for two main application domains: environmental remediation and energy conversion or storage. In this review, we explore the applications of both newly designed MOFs and MOF-derived materials. These applications include catalysis, electrocatalysis, sensing, pollutant removal, batteries, supercapacitors, and other hybrid energy devices. We attempt to correlate MOF structure with key parameters, such as metal centers, ligands, defects, and porosity, to performance. We also discuss the future use of MOFs in real-world devices. This depends on overcoming challenges such as scalability, conductivity, stability, and environmental safety. Full article

This paper introduces a new combination of hybrid energy storage in a split-shaft wind energy conversion system based on a hydraulic transmission system. In the hybrid energy storage, a flywheel, supercapacitor, and battery are integrated into the wind energy conversion system with minimal additional supporting hardware. The split-shaft configuration allows the direct connection of the flywheel to the doubly fed induction generator (DFIG) shaft without a power electronic converter. The principal operation and minimization of this hybrid storage, as well as the energy management strategy, are explained. The goal is to smooth out output power fluctuations using the response surface method. A 1.5 MW hydraulic wind turbine is simulated in Matlab 23, and the hybrid storage is configured and optimized. The direct connection of the flywheel facilitates reaching a suitable level of smoothness at a reasonable cost. The proposed configuration is compared with conventional storage, and the results demonstrate that the integrated hybrid energy storage reduces the annualized storage cost by 71%. Full article

In this work, we employed an easy hydrothermal method to prepare CuO and ZnO, as well as the prepared composite nanostructured electrodes of CuO@ZnO for supercapacitor applications. The systematic electrochemical performance evaluation of the prepared materials was conducted by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). CuO@ZnO nanocomposite reflected the best charge storing behavior with a specific capacitance of 513 F/g, followed by pristine CuO (190 F/g) and ZnO (416 F/g). The composite also demonstrated 25.67 Wh/kg and 400 W/kg for energy density and power density, respectively, suggesting improved electrochemical performance. Besides, the areal and volumetric capacitances were 0.77 F/cm² and 4.81 F/cm³, respectively, supported by the structural integrity and enhancement in electroactive materials utilization of the electrode material. Kinetic analysis showed that b values of the samples had mixed capacitive/diffusion-controlled charge storage, while higher diffusion coefficients and standard rate constants were apparent for ion transport or redox kinetics. EIS results showed a 2.14 Ω solution resistance, indicative of a decreased electrical resistivity. An asymmetric supercapacitor device fabricated by CuO@ZnO as the positive electrode and activated carbon (AC) as the negative electrode provided the specific capacitance of 48.57 F/g, energy density of 15.17 Wh/kg, and power density of 535 W/kg. After 10,000 cycles, the capacitance of the device was 76%, indicating good long-term stability. Full article

The increasing global demand for high-performance, reliable, and sustainable energy storage systems has accelerated the development of supercapacitors as technologies capable of bridging the performance gap between conventional capacitors and batteries. Supercapacitors combine rapid charge–discharge capability, high power density, and exceptional cycle life through charge storage mechanisms based on ion adsorption and fast surface redox reactions at the electrode–electrolyte interface. This review examines the fundamental operating principles, charge storage mechanisms, electrode materials, mechanical and functional properties, fabrication methods, and engineering applications of modern supercapacitors. Carbon-based materials, metal oxides, conducting polymers, MXenes, sulfides, nitrides, borides, and emerging hybrid systems are critically compared in terms of capacitance, energy density, cycling stability, and mechanical robustness. Additionally, recent advances in scalable manufacturing approaches, including thin-film deposition and printing technologies, are discussed alongside key challenges such as limited energy density, interfacial instability, mechanical degradation, electrolyte compatibility, and large-scale processing. By consolidating recent developments across materials science, electrochemistry, and device engineering, this review provides insight into future directions for next-generation high-performance supercapacitor technologies. 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

Magnetic materials have demonstrated considerable potential for applications in the field of energy storage. Spinel-type CoFe₂O₄ possesses both good redox activity and structural stability, but its magnetism may affect the electrochemical performance. During the high-temperature carbonization and activation processes, the magnetism is significantly weakened, thereby exerting only a limited effect on device performance. To address the issues of high cost and poor environmental friendliness of traditional electrode materials, two types of waste biomass, namely banana peels and sunflower seed shells, were employed as carbon sources for the preparation of Y-doped CoFe₂O₄/carbon composites in this study. Y-doped CoFe₂O₄/banana peel carbon was used as the positive electrode, while Y-doped CoFe₂O₄/sunflower seed shell carbon was used as the negative electrode. The results indicate that the CoFe₂O₄/BPC cathode doped with 0.4% Y has the best performance, with a specific capacitance of 1788 F/g at 1 A/g and a retention rate of 98% after 10,000 cycles. In addition, the SSPC anode exhibited a specific capacitance of 350 F/g and excellent cycling stability. The assembled device achieved a specific capacitance of 190 F/g at 1 A/g and a capacitance retention rate of 83.6% after 10,000 cycles at 5 A/g, demonstrating good energy density, power density and cycling stability. This research provides experimental evidence for the development of low-cost supercapacitors based on biomass. Full article

Conventional liquid springs enable storage of energy in the form of interfacial tension at forcibly wetted lyophobic surfaces. The pressure–volume work performed to compress the liquid into a poorly wettable porous medium is recovered during spontaneous expulsion when pressure falls below the capillary pressure characteristic of a given system. Our study explores generalizations to easily wettable materials where liquid infiltration is opposed solely by steric hindrance exerted on liquid molecules in micro-sized pores. The concept is exemplified in molecular simulations of prototypical model systems with methanol intruding narrow slits between hydrocarbon or graphene surfaces. While these materials show significant wetting propensities at macroscopic interfaces with liquid methanol, substantial compression is required to wet molecular-sized pores barely accommodating a monolayer of liquid molecules. The observed O(10³) bar intrusion pressures secure stored energy densities competitive with supercapacitors and amenable to improvement. Wall–liquid attraction and small pore diameters lead to intrusion–expulsion pathways along cooperative-adsorption isotherms. The process avoids abrupt liquid/vapor transitions and associated nucleation barriers, responsible for cycle hysteresis in experiments with water in hydrophobic capillaries. Using open ensemble (Grand Canonical) Monte Carlo sampling, we identify the range of porosities supporting reversible energy storage/recovery operation in lyophilic media; the results can assist with the design of molecular spring devices with competitive storage and power capacities in pragmatic contexts. Full article

Standalone photovoltaic DC energy systems must maintain bus voltage stability without grid support; however, abrupt load variations can cause a DC-bus voltage drop, reducing system reliability and disturbing connected equipment. Although battery-based energy storage is effective for long-duration power balancing, its response to instantaneous disturbances can be limited. This study proposes an energy stability strategy using supercapacitor-based ride-through control and required capacity sizing for fast DC-bus voltage support. The proposed controller continuously monitors the DC-bus voltage and, when a voltage drop is detected, immediately triggers supercapacitor discharge to compensate for the power deficit until the bus recovers. In addition, a design formulation is derived to estimate the required compensation energy, ride-through time, and minimum capacitance based on the expected power deficit, allowable DC-bus voltage drop, and initial supercapacitor voltage. Simulation results under step changes in load resistance show that the supercapacitor sized by the proposed method maintains the DC-bus voltage close to its reference value within the specified limit. Hardware experiments further validate the ride-through operation and show good agreement between the predicted and measured compensation times. Full article

Polymer-engineered MXene composites have emerged as a versatile materials platform for electrochemical energy storage, offering a means to address key limitations associated with ion transport, structural instability, and interfacial reactivity. This review provides a unified perspective on how polymer integration modifies the structure–transport–stability relationships of MXene-based systems across Na-ion batteries, aqueous Zn-ion batteries, and supercapacitors. In Na-ion systems, polymer-mediated interlayer engineering and porosity control improve ion accessibility and mitigate diffusion limitations arising from the large ionic radius of Na⁺. In aqueous Zn-ion systems, polymer electrolytes and interfacial layers regulate Zn²⁺ solvation and deposition behavior, suppressing dendritic growth and parasitic reactions. In supercapacitors, polymer–MXene hybrids establish coupled ionic–electronic transport pathways and mechanically compliant architectures, enabling stable electrochemical performance under high-rate and deformable conditions. Particular emphasis is placed on the underlying mechanisms responsible for suppressing oxidation, preserving structural integrity, and extending cycle life, including interfacial passivation, desolvation regulation, and structural confinement. These coupled effects govern long-term electrochemical stability across different energy storage systems. Finally, recent advances in operando characterization, data-driven materials design, and scalable processing are discussed in the context of future development. By linking material design strategies to fundamental mechanisms, this review outlines a coherent framework for the rational development of polymer–MXene composites toward practical energy storage applications. Full article

Bismuthene, a two-dimensional elemental material with high theoretical capacity and favorable electronic properties, has emerged as a promising candidate for sustainable energy storage systems. This review summarizes recent advances in bismuthene-based materials for lithium-, sodium-, and potassium-ion batteries, aqueous rechargeable batteries, and supercapacitors, with a focus on their structure–property relationships, including ion diffusion, alloying behavior, and cycling stability. Strategies such as defect engineering, heterostructure design, and three-dimensional architectures are highlighted for enhancing electrochemical performance. Beyond technical performance, we discuss the economic potential of bismuthene through levelized cost analysis, as well as its sustainability implications in terms of energy efficiency, environmental impact, materials sustainability and lifecycle stability. This review highlights the integration of advanced energy materials into sustainability assessment frameworks, bridging laboratory-scale innovation with practical and environmentally responsible energy storage applications. Full article

Conventional strategies for synthesizing porous structures generally depend on template-based methods, which involve not only excessive consumption of templating agents but also the use of hazardous chemicals, such as hydrofluoric acid or strong alkalis. Therefore, designing an effective and convenient strategy to fabricate porous SnO₂ is of significant practical relevance. Herein, we developed a top-down strategy to fabricate SnO₂ electrode via a thermal oxidation gas-release route, resulting in a bulk 3D hierarchical architecture with interconnected porous channels. Employing a bottom-up strategy, the gel precursors of these porous SnO₂ materials were synthesized on a large scale via a simple, surfactant- and template-free route, in accordance with green chemistry principles. The results show that the porous SnO₂(300) electrode materials possess a high specific surface area and exhibit favorable electrochemical energy-storage performance, achieving a high specific capacitance of 267.31 F g⁻¹ at a current density of 1 A g⁻¹. Furthermore, based on the gel electrolyte of PVA/KOH, an asymmetric supercapacitor device assembled using porous SnO₂(300) materials as the positive electrode and activated carbon as the negative electrode (denoted as P-SnO₂//AC) achieves an energy density of 32.49 Wh kg⁻¹ at the power density of 718.97 W kg⁻¹. This work presents a simple, cost-effective, environmentally friendly and scalable approach to synthesize SnO₂ materials with an advanced structural design. Full article

Photovoltaic (PV)-storage systems operating in weak grids are affected by high grid impedance, transient voltage disturbances, and measurement noise, which can degrade frequency regulation, increase converter current stress, and impose high-frequency current fluctuations on the battery. To address these issues, this paper proposes a multi-timescale transient-state sensing and signal-processing framework for grid-forming PV-hybrid storage systems. The proposed framework combines three coordinated functions. First, a frequency-domain HESS power-decoupling mechanism separates high-frequency transient power components and assigns them to the supercapacitor, while the battery mainly handles low-frequency energy variations. Second, a voltage-deviation-driven adaptive virtual inductance is introduced to increase the equivalent output impedance during voltage-sag events and reduce transient inrush current. Third, a noise-resilient frequency sensing strategy based on a filtered frequency derivative and a dead-band for false-trigger suppression is developed to reduce noise-induced false triggering in adaptive inertia and damping control. Comparative simulations indicate that under the tested weak-grid conditions, the proposed method reduces the transient inrush-current peak by 53.2%, decreases the maximum dynamic frequency deviation by approximately 75%, and improves the active-power regulation speed by more than 50%. These results indicate that the proposed sensing-oriented framework can improve transient response while reducing converter and battery current stress in PV-storage systems connected to high-impedance grids. Full article

This paper presents the design and validation of an adaptive islanding detection method (AIDM) for an AC/DC hybrid microgrid integrated with a hybrid energy storage system (HESS) comprising a supercapacitor and a battery. The proposed AIDM combines dual-tree complex wavelet transform (DTCWT), synthetic minority oversampling technique (SMOTE), and long short-term memory (LSTM) network to effectively detect islanding and non-islanding conditions in the microgrid following faults/disturbances. Fault and disturbance signals are captured at the point of common coupling, following which they are extracted and decomposed using DTCWT. The SMOTE algorithm is employed for data preprocessing to balance the dataset and enhance the accuracy of the intelligent classifier. Finally, LSTM is used for training and testing the AIDM for different faults/disturbance classification and detection. Two categories of datasets, $T_{D1}$ and $T_{D2}$, are used for testing the AIDM. The results obtained from MATLAB/Simulink show that datasets incorporated with HESS achieve higher detection accuracy of 100% compared to datasets without HESS with average accuracy of 99.77% under sudden load increase. It is also established that the proposed AIDM maintains robustness when exposed to noise signals, confirming its reliability under noisy conditions. Full article