Search Results (171)

This paper reviews the research progress of supercapacitors (SCs), including the influence of electrode materials on energy storage mechanism and performance, and life prediction. Supercapacitors show application potential in many fields due to their high-power density, fast charge–discharge capability, long cycle life, and environmental protection characteristics. In this paper, the energy storage mechanism of the double-layer capacitor, pseudocapacitor, and asymmetric supercapacitor are discussed. New electrode materials, such as carbon-based materials, metal oxides, and conductive polymers, are reviewed based on the performance optimization measures that are involved in the microstructure design of electrode materials, and integrate the rule prediction of supercapacitors into comprehensive learning. When designing and using supercapacitors, we should not only pay attention to their life but also pay attention to their remaining service life in real time. The paper also mentions the progress of life prediction technology, which is of great significance to improve the reliability and maintenance efficiency of energy storage equipment, and ensure the long-term stable operation of energy storage systems. Future research directions include increasing energy density, extending life, adapting to extreme environments, developing flexible and wearable devices, intelligent management, and reducing costs. Full article

The emergence of electrically conductive polymeric materials has revolutionized the landscape of sustainable energy technologies, presenting unprecedented opportunities for advancing both photovoltaic conversion systems and electrochemical energy-storage platforms. These remarkable macromolecular materials exhibit distinctive characteristics including adjustable electronic band structures, exceptional mechanical adaptability, solution-phase processability, and cost-effective manufacturing potential. This extensive review provides an in-depth examination of the fundamental principles governing charge carrier mobility in conjugated polymer systems, explores diverse synthetic methodologies for tailoring molecular architectures, and analyzes their transformative applications across multiple energy technology domains. In photovoltaic technologies, electrically conductive polymers have driven major advancements in organic solar cells and photoelectrochemical systems, significantly improving energy conversion efficiency while reducing manufacturing costs. In electrochemical energy storage, their integration into supercapacitors and rechargeable lithium-based batteries has enhanced charge storage capability, accelerated charge–discharge processes, and extended operational lifespan compared with conventional electrode materials. This comprehensive analysis emphasizes emerging developments in hybrid composite architectures that combine conductive polymers with carbon-based nanomaterials, metal oxides, and other functional components to create next-generation flexible, lightweight, and wearable energy systems. By synthesizing fundamental materials chemistry with device engineering perspectives, this review illuminates the transformative potential of electrically conductive polymers in establishing sustainable, efficient, and resilient energy infrastructures for future technological landscapes. Full article

The rapid advancement of wearable technology has created an increasing demand for efficient, high-performance energy storage systems that also offer key characteristics such as flexibility, lightweight, and durability. Among the emerging materials, polymer hydrogels have garnered significant attention due to their unique combination of viscoelasticity, low density, and tunable porous nanostructures. These materials exhibit adaptable surface and structural properties, making them promising candidates for next-generation flexible and wearable energy storage devices. This work provides an overview of recent progress and innovations in the application of polymer hydrogels for the development of flexible energy storage systems. The intrinsic three-dimensional architecture and porous morphology of these hydrogels offer a versatile platform for constructing high-performance supercapacitors, rechargeable batteries, and personal thermal management devices. Various types of polymer hydrogels and their principal fabrication methods are discussed in detail, along with the structural factors that influence their electrochemical and mechanical performance. Furthermore, recent advancements in integrating polymer hydrogel materials into wearable and flexible technologies—such as energy storage devices, thermal regulation systems, and multifunctional energy platforms—are comprehensively reviewed and analyzed. Full article

Functionalized hydrogels represent an emerging class of smart materials being explored for advancing next-generation wearable technologies, owing to their flexibility, biocompatibility, stimuli-responsiveness, and tunable properties. This review provides an overview of recent developments in hydrogel-based wearables, highlighting their potential to enhance adaptive, multifunctional, and environmentally sustainable devices and textiles. It begins by examining progress in wearable sensors, energy storage and harvesting, biosignal monitoring, and smart textiles, as well as the associated challenges, including limited battery life, inadequate skin adhesion, user discomfort, and constrained functionality. The review further explores the synthesis, fabrication techniques, properties, and types of hydrogels tailored for wearable technologies, followed by a detailed discussion of their applications in smart batteries, supercapacitors, sensors, nanogenerators, fabrics and hybrid systems. It also highlights integrating artificial intelligence (AI) and the Internet of Things (IoT) to improve designs; enhance performance through real-time monitoring, data analytics, and user interaction; and expand functionality. Also, it analyzes key limitations of current hydrogels—particularly in energy density, dehydration resistance, fatigue behaviour, and large-scale reproducibility—and outlines strategies based on hierarchical material design, sustainable and biodegradable formulations, and standardized testing and regulatory alignment. The review concludes by affirming the role of hydrogel-based technologies in shaping the future of wearable innovations across healthcare, lifestyle, and beyond and outlines promising research directions. Full article

Self-powered strain sensing technology represents a pivotal frontier in overcoming the energy constraints of wearable electronics, thereby enabling their long-term intelligence and operational autonomy. This review systematically summarizes recent advances in integrated strain sensing systems, with a particular focus on three primary strategies for achieving self-powered functionality: integration with energy storage devices (e.g., flexible supercapacitors and microbatteries); integration with energy harvesters (e.g., triboelectric and piezoelectric nanogenerators); and advanced systems that synergistically combine energy harvesting, storage, and management modules. The article begins by outlining the fundamental working mechanisms and key performance parameters of strain sensors. It then provides a detailed analysis of the material systems, innovative structural designs, operational mechanisms, and applications in health monitoring and human-computer interaction associated with the different self-powered strategies. Finally, the review critically examines the persistent challenges in this field, including energy balance, mechanical robustness, and environmental stability, and offers perspectives on future research directions such as multimodal energy harvesting, intelligent data processing, and the development of biocompatible materials. This work aims to serve as a valuable reference for advancing the practical implementation of truly autonomous and wearable strain sensing systems. Full article

The rapid development of wearable technology has spurred considerable interest in hydrogels, which are hydrophilic three-dimensional polymer networks known for their remarkable flexibility. Nevertheless, their application in flexible electronics has been constrained by inferior mechanical and physical properties. As an emerging flexible material, dual-network hydrogels possess high mechanical strength, self-healing capability, excellent fatigue resistance, and electrical conductivity, showing great potential for use in flexible electronics. This article systematically reviews the design and performance optimization strategies of dual-network hydrogels. It reviews the advancements in their applications in flexible electronic devices, including bodily fluid biomarker sensors, flexible energy storage devices, health monitoring sensors, and physical motion sensors. The potential future challenges and opportunities for dual-network hydrogel materials are also discussed. This review aims to provide a theoretical foundation for developing next-generation dual-network hydrogels for flexible electronics and to promote their practical implementation in this field. Full article

This study explores the fabrication and electrochemical performance of flexible NiCo₂O₄-based pseudo-capacitor electrodes, inkjet-printed onto flexible Kapton substrates. To circumvent the insulating nature of Kapton, a thin Au interlayer (20 nm) was introduced, significantly enhancing electrical conductivity. The effect of NiCo₂O₄ mass loading, ranging from 0.1 to 0.5 mg cm⁻², was investigated. Optimal performance was achieved at a loading of 0.3 mg cm⁻² on Au/Kapton substrates, yielding a specific capacitance of 520 F g⁻¹ at 3.3 A g⁻¹ and 90% capacitance retention after 1000 charge–discharge cycles. These results confirm that inkjet-printed NiCo₂O₄ electrodes, when combined with a conductive interlayer, exhibit excellent pseudo-capacitive behavior on flexible, non-conductive substrates. This approach demonstrates the feasibility of scalable, low-temperature fabrication techniques for high-performance flexible energy storage devices, suitable for emerging wearable technologies. 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

Polymer materials have become promising candidates for next-generation energy storage, with structural tunability, multifunctionality, and compatibility with a variety of device platforms. They have a molecular design capable of customizing ion and electron transport routes, integrating redox-active species, and enhancing interfacial stability, surpassing the drawbacks of traditional inorganic systems. New developments have been made in multifunctional polymers that have the ability to combine conductivity, mechanical properties, thermal stability, and self-healing into a single scaffold system, which is useful in battery, supercapacitor, and solid-state applications. By incorporating polymers with carbon nanostructures, ceramics, or two-dimensional materials, hybrid polymer nanocomposites improve electrochemical performance, durability, and mechanical compliance, and the solid polymer electrolytes, as well as artificial solid electrolyte interphases, resolve dendrite growth and safety issues. The multifunctionality also extends to flexibility, stretchability, and miniaturization, which implies that polymers are suitable for use in wearable devices and biomedical devices. At the same time, sustainable polymer innovation focuses on bio-based feedstocks, which can be recycled, and green synthesis pathways. Polymer discovery using artificial intelligence and machine learning is faster than standard methods, predicts structure–property–performance relationships, and can be rationally engineered. Although there are difficulties in stability during long periods, scalability, and trade-offs between indeedness and mechanical endurance, polymers are a promising avenue with regard to dependable, safe, and sustainable power storage. This review presents the molecular strategies, multifunctional uses, and prospects, where polymers are at the center of the next-generation energy technologies. Full article

With environmental pollution and energy shortages becoming increasingly severe, developing efficient energy conversion and storage technologies is crucial. Cu₂Se has garnered significant attention as a thermoelectric material due to its abundant raw materials, low cost, and high thermoelectric figure of merit (ZT). This paper reviews the synthesis methods and application progress of Cu₂Se in the energy field. Regarding synthesis, various methods such as solid-state synthesis, hydrothermal synthesis, and ion exchange can be employed to control its microstructure and properties. In applications, Cu₂Se demonstrates significant potential in thermoelectric conversion by harnessing the Seebeck effect to convert waste heat into electricity. Simultaneously, its high carrier mobility and favorable electrochemical properties make it promising for energy storage systems like sodium-ion batteries and aqueous batteries. Furthermore, this material holds considerable potential in emerging fields such as flexible wearable devices and high-efficiency thermoelectric power generation systems. Future research should continue optimizing its comprehensive properties to advance the practical application of Cu₂Se in energy conversion and storage. Full article

Conductive polymer hydrogels have attracted extensive attention in wearable devices, soft machinery, and energy storage due to their excellent mechanical and conductive properties. However, their preparation is often complex, expensive, and time-consuming. Herein, we report a facile precipitation method to prepare conductive polymer composite hydrogels composed of poly(acrylic acid) (PAA), poly(vinyl alcohol) (PVA), and poly(3,4-ethylenedioxythiophene) (PEDOT) via straightforward solution blending and centrifugation. During the preparation, PEDOT, grown along the PAA template, is uniformly dispersed in the hydrogel matrix. After shaping and rinsing, the PEDOT/PAA/PVA hydrogel shows good mechanical and electrical properties, with a conductivity of 4.065 S/m and a Young’s modulus of 311.6 kPa. As a strain sensor, it has a sensitivity of 1.86 within 0–100% strain and a response time of 400 ms. As a bioelectrode, it exhibits lower contact impedance than commercially available electrodes and showed no signs of skin irritation in the test. The method’s versatility is confirmed by the observation of similar performance of hydrogels with different compositions (e.g., polyaniline (PANI)/PAA/PVA). These results demonstrate the broad applicability of the method. Full article

Intrinsically stretchable polymer ionic conductors (PICs) hold significant application prospects in fields such as flexible sensors, energy storage devices, and wearable electronic devices, serving as promising solutions to prevent mechanical failure in flexible electronics. However, the development of PICs is hindered by an inherent trade-off between mechanical robust and electrical properties. Cellulose, renowned for its high mechanical strength, tunable chemical groups, abundant resources, excellent biocompatibility, and remarkable recyclability and biodegradability, offers a powerful strategy to decouple and enhance mechanical and electrical properties. This review presents recent advances in cellulose-based polymer ionic conductors (CPICs), which exhibit exceptional design versatility for flexible electrodes and strain sensors. We systematically discuss optimization strategies to improve their mechanical properties, electrical conductivity, and environmental stability while analyzing the key factors such as sensitivity, gauge factor, strain range, response time, and cyclic stability, where strain sensing refers to a technique that converts tiny deformations (i.e., strain) of materials or structures under external forces into measurable physical signals (e.g., electrical signals) for real-time monitoring of their deformation degree or stress state. Full article

This work provides the first demonstration of FFTCCV as a dual-purpose method, serving both as a real-time diagnostic tool and as a phase- and morphology-engineering strategy. By adjusting the scan rate, FFTCCV directs the crystallographic evolution of Ni (OH)₂ on Ni foam—stabilizing α-nanoflakes at 0.7 V·s⁻¹ and β-platelets at 0.007 V·s⁻¹—while simultaneously enabling electrode-resolved ΔQ tracking and predictive state-of-health (SoH) monitoring. This approach enabled the precise regulation of electrode morphology and phase composition, yielding high areal capacitance (546.5 mF·cm⁻² at 5 mA·cm⁻²) with ~75% retention after 3000 cycles. These improvements advance the development of high-performance micro-supercapacitors, facilitating their integration into wearable and miniaturized devices where compact and durable energy storage is required. Beyond performance enhancement, FFTCCV also enabled continuous monitoring of capacitance during extended operation (up to 40,000 s). By recording both anodic and cathodic responses, the method provided time-resolved insights into device stability and revealed characteristic signatures of electrode degradation, phase transitions, and morphological changes. Such detection allows recognition of early failure pathways that are not accessible through conventional testing. This monitoring capability functions as an embedded health sensor, offering a pathway for predictive diagnosis of supercapacitor failure. Such functionality is particularly important for energy-driven actuators and smart materials, where uninterrupted operation and preventive maintenance are critical. FFTCCV therefore provides a scalable strategy for developing energy-autonomous microsystems with improved performance and real-time state-of-health monitoring. Full article

The development of portable and wearable electronics has promoted the advancement of fiber supercapacitors (FSCs), but their low energy density still limits their application in flexible devices. Herein, we incorporated micron-sized graphene dispersions at varying concentrations into the polyaniline (PANI) precursor solution prepared via electrochemical polymerization and subsequently electrodeposited PANI/graphene composites onto the surface of carbon nanotube (CNT) fibers, ultimately obtaining fibrous PANI/graphene@CNT composite electrodes. This electrode material not only exhibits the superior electrochemical activity characteristic of conducting polymers synthesized by electrochemical polymerization but also possesses a relatively high specific surface area. Furthermore, we fabricated coaxial fiber supercapacitors using PANI/graphene@CNT composite fibers and CNT films as the positive and negative electrode materials, respectively. The maximum energy density and power density could reach 160.5 µWh cm⁻² and 13 mW cm⁻² respectively, proving its excellent energy storage and output capabilities. More importantly, the prepared CFASC device showed remarkable mechanical and electrochemical durability. Even after 3000 bending cycles, it retained 89.77% of its original capacitance, highlighting its promising applicability in the realm of flexible electronics. The resulting devices demonstrate excellent electrochemical performance and mechanical stability. Full article

Energy harvesting (EH) is a rapidly evolving domain that is primarily focused on capturing and converting ambient energy sources into more convenient and usable forms. These sources, which range from traditional renewable sources such as solar or wind power to thermal gradients and vibrations, present an alternative to typical power generation. The temptation to use energy harvesting systems is in their potential to power low-power devices, such as environment monitoring devices, without relying on conventional power grids or standard battery implementations. This improves the sustainability and self-sufficiency of IoT devices and reduces the environmental impact of conventional power systems. Applications of EH include wearable health monitors, wireless sensor networks, and remote structural sensors, where frequent battery replacement is impractical. However, these systems also face challenges such as intermittent energy availability, limited storage capacity, and low power density, which require innovative design approaches and efficient energy management. The paper provides a general overview of the subsystems present in the energy harvesting systems and a comprehensive overview of the energy transducer technologies used in energy harvesting systems. Full article