Flexible Capacitors Research Articles

An insight into the influence of Ag/Se nanoparticles on the structural, optical, and electrical properties of Cs/PAM nanocomposites films as application in electrochemical devices

This paper describes a simple, efficient, and promising approach for making nanocomposite polymer systems using chitosan (Cs) and polyacrylamide (PAM) as the host polymer with Ag/Se nanofiller for electrical energy storage uses. The ATR spectroscopy and XRD methods were used to investigate the structure of the prepared samples. The UV–Visible spectroscopy was utilized to investigate the optical properties. Tauc's plot was used to calculate the energy band-gap values of Cs/PAM and Ag/Se nanocomposite films. When Ag/Se ions are included in Cs/PAM blend films, the Urbach energy increase and reduce the optical energy gap, which means the optical properties is improved. The frequency-dependent AC conductivity of the nanocomposites was used to analyze the dynamic ion behavior of all the as- produced films. At varied contents of the Ag/Se nanofiller and at ambient temperatures, the ε′ and ε′′ as well as the M′ and M′′ vs. frequency graphs of the polymer blend, were also reported. The relaxation frequency of the nanocomposites films was determined from the M′′ spectra. With increasing Ag/Se concentration, the ionic conductivity of nanocomposite samples was discovered to rise. The optimized nanocomposites demonstrated optical and ionic conductivity, making them suitable for electrochemical applications such as flexible capacitors, energy storage devices, and separators in batteries.

Improving the comprehensive energy storage performance of composite materials through the coupling effect of AgNbO3/PVDF nanocomposite

AbstractCeramic‐polymer nanocomposites with high energy storage density can achieve excellent energy storage performance and have a wide range of application prospects. Currently, it has been shown that the coupling effects have a great impact on improving the performance of dielectric composites, but increasing the breakdown strength of polymer nanocomposite is still a tremendous challenge to the achievement of high energy density under high voltages. The aim of this paper is to further investigate this problem and obtain AgNbO3/PVDF flexible composites by introducing a small amount of AgNbO3 ultrafine powder prepared by hydrothermal method into poly(vinylidene fluoride) (PVDF). The interfacial coupling effect within this nanocomposite with the coupling effects of nonlinear dielectric materials improves its energy storage capacity and electrical strength resistance. The energy density of the 2 wt% AgNbO3/PVDF composite film was raised to 16.5 J/cm3 at the electric breakdown strength of 391.7 MV/m, and its energy storage capacity is two to three times that of AgNbO3 lead‐free antiferroelectric ceramics. Finite element simulations showed the further enhancement of breakdown strength was ascribed to the local electric field and to the AgNbO3 ultrafine powder which blocked the breakdown path in the nanocomposites and coupling effects occurred with PVDF. Hence, the AgNbO3 ultrafine powder has a positive effect on improving the energy storage performance of flexible composites. The effects of nonlinear dielectric material coupling effects and interfacial coupling effects on the dielectric properties of composite dielectric materials are further investigated, which are important for the development of flexible high energy storage capacitors.

Excellent energy storage properties achieved in PVDF-based composites by designing the lamellar-structured fillers

Polymer-based dielectrics are widely utilized due to the high power density, fast discharging-charging speed and broad operating temperature range. However, suffering from the inherent low energy density, the practical application is restricted. Herein, a novel structure design of lamellar-structured MgO and BiFeO3/MgO (BFO/MgO) fillers is proposed and a series of PVDF-based composites are fabricated. The breakdown strength is significantly improved due to the large heterojunction electric field produced by BFO and MgO. Meanwhile, the large polarization contributes to a high energy storage performance. A high energy density of 9.93 J cm−3 at 409.6 kV mm−1 with energy efficiency of 66% is achieved in 0.9 wt% BFO/MgO-PVDF/PMMA composites. Compared with previous literatures, high energy density is obtained in a relatively low electric field in this work at such trace filling content, which is quite suitable for the long-term electric field application. This work establishes a facile and effective approach for developing the flexible dielectric capacitors with high energy storage capability.

Organic resin based high surface area and N-enriched porous carbon nanosheets for supercapacitors

Organic resins are considered as a kind of promising precursors to prepare carbon materials due to its broad resource, high char yield. Nevertheless, it is still a chanllenge on preparing of electrode materials with large specific surface area, high content of heteroatom doping, and remarkable electrochemical properties from organic resins for supercapacitors. Here we report a efficient and facile synthetic strategy to fabricate ultrahigh specific surface area and N-enriched porous carbon nanosheets (N-PCNs) using g-C3N4 as template, L-Tyrosine-based resin as carbon precursor by hydrothermal polymerization and following KOH activation process. The effects of activator ratio and activation temperature on the morphology, structure and capacitance performance of N-PCNs have been systematacially studied. The prepared N-enriched (4.13 at%) porous carbon nanosheets with ultrahigh specific surface area (3542 m2 g−1) show excellent capacitance performance. The optimized sample presents an excellent specific capacitance of 349 F g−1 at 0.5 A g−1, and can also maintain 218 F g−1 at 50 A g−1, showing an outstanding rate performance. Moreover, the symmetric flexible capacitor assembled by Agar/Na2SO4 gel electrolyte displays a relatively high energy density of 31.4 Wh kg−1 at 225 W kg−1.

How to process P(VDF-TrFE) thin films for controlling short circuits in flexible non-volatile memories

Severe electrical shorting is one of the biggest challenges for the development of flexible non-volatile ferroelectric memories with low operation voltage. In this work, short circuits in flexible ferroelectric capacitors based on copolymer poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)], were explicitly investigated. It was found that processing conditions of P(VDF-TrFE) films have huge effects on electrical shorting conditions. Both deciding factors such as drying temperatures, solvent evaporation rates, and solution concentrations, and plausible factors such as post-drying thermal annealing, were clearly identified. These deciding factors were found to affect short circuits by altering the film porosity, surface roughness, and defect conditions in P(VDF-TrFE) thin films. The detailed correlation of these factors with film porosity were established and explained within the framework of liquid-liquid phase separation. The correlation with the surface roughness and defect conditions were explained with Marangoni convection. The net effects of these factors on electrical shorting conditions are rather complicated because a favorable factor with regards to film porosity may be detrimental in terms of surface roughness and/or defects. So these factors have to been carefully tailored to control short circuits and generate high yields in P(VDF-TrFE) thin film memory devices. Comparative study shows that drying at 80 °C in open air is the optimal condition for processing P(VDF-TrFE) thin films from PGMEA solution. Under this optimal drying condition, a yield of 76% was achieved from large-area devices of about 200 μm × 200 μm with thin P(VDF-TrFE) films of about 200 nm processed with roll-2-roll compatible techniques on plastic substrates. An effective two-step approach to manufacturing P(VDF-TrFE) layers for ferroelectric capacitors with low operation voltage but high yields, is presented. The key information gained from this work on ferroelectric capacitors could be generalized to another type of ferroelectric memories, namely ferroelectric field effect transistors. So it provides researchers and engineers a general guideline on how to control short circuits by processing P(VDF-TrFE) thin films for flexible non-volatile memories.

Flexible Fault Current Adaptation Features of a Novel DC Circuit Breaker Assisted by Superconducting Fault Current Limiters

The high d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> before zero-crossings easily leads to delayed or failed operations for the active current injection mechanical DC circuit breaker, especially for small direct current interruptions. The pre-charging process also makes this type of circuit breaker hard to realize repeat operations economically in the high voltage DC system. This paper proposes a novel DC circuit breaker and its design method that deeply coordinating a superconducting fault current limiter with the active current injection DC circuit breaker. This method significantly reduces d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> before current zero-crossings and enables repeat operations economically. Besides limiting fault currents, the superconducting fault current limiter also charges the resonance capacitor flexibly in the circuit breaker, realizing the injected reverse current keep a constant proportion to the arbitrary fault current. Validations of the flexible capacitor charge and repeat operations are made by simulation and low voltage experiments. The charging times are within 2.5 ms and the reverse current keeps 1.2 to 1.7 times over the fault current under arbitrary conditions. D <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> /d <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> at current zero is reduced by 80% under 30% of rated interruption capacity. Flexible capacitor charge experiments are consistent with the simulation design. The superconducting tapes can recover within 300 ms to support repeat operations.

Reversible and homogenous zinc deposition enabled by in-situ grown Cu particles on expanded graphite for dendrite-free and flexible zinc metal anodes

The rapid development of wearable electronics has boosted the exploration of flexible and safe energy storage devices, such as zinc ion batteries or capacitors; and suppressing the dendrite growth for Zn anode is essential for enhancing their performance. Addressing this, we report a dendrite-free and flexible Zn metal anode (Zn@Cu-Ps/EG) that is based on expanded graphite (EG) decorated with in-situ formed copper particles (Cu-Ps). In this material, the Cu-Ps act as zincophilic seeds that reduce zinc nucleation overpotential, while the EG substrate induces epitaxial electrodeposition of zinc for suppressing dendrite growth. Moreover, the Cu-Ps nail the graphite nanosheets tightly and enhance the mechanical strength and flexibility of the Cu-Ps/EG composite. Consequently, the Zn@Cu-Ps/EG anode exhibits a low Zn deposition overpotential of 142.8 mV and superior cycling performance over 3000 h upon cycling at 10.0 mA cm−2 and 10.0 mAh cm−2. A flexible Zn-ion capacitor equipped with this anode delivers excellent cycling performance for over 1600 cycles at 1.0 A g−1 and stable power output at various bending statuses. This work provides a new approach for designing advanced flexible and dendrite-free Zn metal anodes for energy storage applications.

Flexible lead-free film capacitor based on BiMg0.5Ti0.5O3-SrTiO3 for high-performance energy storage

Flexible dielectric film capacitors with high performance of energy storage has shown great promise as a solution to the flexibility and stability of modern electronics and electric power systems. Herein, a novel relaxor-ferroelectric BiMg0.5Ti0.5O3-xSrTiO3 (BMT-xSTO, x = 0.1, 0.2, 0.3 and 0.4) thin film capacitors are obtained via one-step fabrication on flexible mica substrates. A superior energy storage density of 109.7 J cm−3 and a pretty high efficiency of 80.6% are simultaneously achieved in the BMT-0.3STO film capacitor. At the same time, the energy storage performance can be stable in the temperature range of 25 to 200° C, the wide frequency range of 500 Hz to 10 kHz, and even after 108 electrical cycles. In addition, under the bending radii from 16 mm to 4 mm, there is no obvious variation in performance even after 104 mechanical fatigue cycles, indicating the super flexibility and stability of the film capacitors. The prominent properties of the BMT-based film capacitor are mainly attributed to the improvement of relaxation behavior by introducing appropriate STO, which are explained by the domain evolution via piezo-response force microscopy and phase field simulation. The present work suggests a new way to obtain lead-free and flexible dielectric film capacitors for flexible energy storage technology.

Flexible aqueous asymmetric capacitor with SiC-decorated boron-doped graphene cathode and core–shell SiC@graphene anode

• Core-shell SiC@graphene (Gr) nanoparticles were synthesized as an anode material. • B-doped graphene (BGr) nanosheets embedded with SiC nanoparticles were synthesized. • SiC-BGr electrocatalyzed the NiOOH/NiO redox reaction to improve pseudocapacitance. • SiC-BGr cathode showed the maximum specific capacitance of 1803 mF cm −2 at 4 mA cm −2 . • Aqueous SiC-BGr//SiC@Gr capacitor showed high working voltage and stability. Flexible aqueous pseudocapacitors have the advantages of high specific capacitance, high safety, low cost, and fast ion diffusion. However, the development of such devices is a challenge because of the low stability of the active material and the high interface resistance of the current collector-active material. In this study, we used silicon carbide (SiC)-boron-doped graphene (BGr) nanosheets and core–shell SiC@Gr nanoparticles as the cathode and anode, respectively, and constructed a flexible aqueous asymmetric capacitor (ASC) with a 3 M NaOH/carboxymethyl cellulose hydrogel as the electrolyte. In an aqueous NaOH solution, the optimized SiC-BGr cathode showed a specific capacitance of 1384.3 mF cm −2 (461.4 F g −1 ) at the current density of 3 mA cm −2 (1 A g −1 ), and the core–shell SiC@Gr anode showed a wide potential window of −1.0–0 V. The as-assembled ASC device had a high working voltage of 1.4 V, delivered an excellent capacitance of 337.1 mF cm −2 , and retained 86% of its initial capacitance after 10 000 cycles. Furthermore, the ASC also showed high energy density (57.3 μWh cm −2 ), high power density (6536.9 μW cm −2 ), high bending stability, and applicability at a low temperature of −20 °C. Thus, the preparation of novel SiC-Gr materials can promote the development of flexible aqueous capacitors with high working voltage and good temperature adaptability for application in the field of wearable electronic devices with safety, strong environmental adaptability, and reliable performance.

Redispersed Bi nanoparticles on graphene fiber fabric anode regulated by microwave irradiation for flexible sodium ion capacitors

• Flexible electrode of Bi nanoparticles anchored on graphene fiber fabric is fabricated. • Micro-sized Bi can be redispersed into 20 nm on GFF in 5 s by microwave. • Competitive mechanisms are proposed to dominate the redispersion. • Flexible Bi/GFF anode exhibits superior Na + storage capacity for sodium ion capacitors. Sp 2 dominated carbon supported metal nanoparticles with well-controlled structures are promising for portable electrochemical energy storage device with “triple-high” (energy, power, and cycle) feature, yet remains elusive. We report here a flexible graphene fiber fabric (GFF) with well-dispersed Bi nanoparticles by a facile and efficient microwave (MW) irradiation method. By regulating the irradiation duration and π-π conjugated structure of GFF, the pristine micro-sized Bi particles can be uniformly redispersed on GFF with an average particle size of 20 nm in 5 s. The competitive mechanisms between the MW accumulated energy and surface energy of Bi nanoparticles as well as energy conversion efficiency are proposed to dominate this redispersion and particle size changing process. The entire Bi/GFF composite exhibits good conductivity, flexibility, and superior sodium ion storage specific capacity of 113 mAh g −1 at 30 A g −1 , which are conceptionally demonstrated as an anode for flexible sodium ion capacitors (SICs). The quasi-solid-state SICs exhibit great mechanical-electrochemical stability, integration property, long-term stability, and high energy/power densities. This work offers a model material of sp 2 dominated carbon supported metal nanoparticles with well-controlled structures by an efficient and facile route, demonstrating a potential for flexible, and “triple-high” energy storage device in the future.

SILAR synthesized dysprosium selenide (Dy2Se3) thin films for hybrid electrochemical capacitors

As the necessity of energy storage is continuously increasing, new materials have been investigated for electrochemical energy storage, especially for electrochemical capacitors. These storage devices are rapidly convertible as well as air pollution free. Therefore, a number of materials have been explored as electrode materials for supercapacitors to fulfill different requirements of electrochemical energy storage. Herewith, dysprosium selenide (Dy2Se3) films were prepared using the simple successive ionic layer adsorption and reaction (SILAR) method and characterized using different physico-chemical techniques. The specific capacitance (Cs) of 92 F g−1 was obtained at the current density of 2.85 A g−1 in 1 M LiClO4 electrolyte with a retention of 85% over 5000 galvanostatic charge-discharge (GCD) cycles performed at a current density of 4 A g−1. The flexible solid-state hybrid electrochemical capacitor of configuration Dy2Se3/LiClO4-PVA/MnO2 showed Cs of 83 F g−1 and specific energy of 18 Wh kg−1 at a specific power of 2.7 kW kg−1. This hybrid device retained 92% of capacitance at a device bending angle of 160°. These results demonstrate the facile synthesis of Dy2Se3 and its possible use in electrochemical energy storage applications.

Energy storage behavior in flexible antiferroelectric (Pb0.98,La0.02)(Zr0.95,Ti0.05)O3 thin film capacitors prepared via a direct epitaxial lift-off method

Flexible antiferroelectric (AFE) thin film capacitors are important for foldable and wearable electronics. This work demonstrates a direct epitaxial lift-off method to fabricate flexible epitaxial AFE thin film capacitors using (Pb0.98,La0.02)(Zr0.95,Ti0.05)O3 (PLZT) as an example. The flexible PLZT thin film showed the tetragonal structure with coexisting ferroelectricity and antiferroelectricity. An energy storage density (ESD) of 2.6 J/cm3 with an efficiency of 73% was obtained at the low electric field, and a high ESD of 22 J/cm3 with an efficiency of 33% was achieved at the high electric field. Such energy storage performances could be maintained after 103 bending cycles and 105 charging/discharging cycles. This simple method can be used to compose flexible epitaxial thin film capacitors and even other flexible thin film devices.

In Situ Growth of Ultrathin NiO Nanosheet‐Arrays on MOF‐Derived Porous Co3O4 Scaffolds as High‐Performance Cathode for Asymmetric Supercapacitors

AbstractThe ever‐increasing market for portable and wearable electronic devices creates a demand for high‐efficiency electrochemical energy storage devices with excellent flexibility. Herein, MOF‐derived porous Co3O4 scaffolds as the core, ultrathin NiO nanosheet‐arrays as the shell, well‐aligned core‐shell structured Co3O4@NiO were constructed on carbon cloth (CC/Co3O4@NiO) via facile chemical bath methods. Composition, morphological structure, and electrochemical performance of the hybrid nanomaterials were analyzed in detail. Benefiting from the MOF‐derived porous Co3O4 core, the NiO shell with large specific surface area, and close conductive linkages between the core and shell, CC/Co3O4@NiO presents an outstanding areal capacitance of 3015.1 mF cm−2 (1206 F g−1) at 5 mA cm−2 and an exceptional rate performance. Additionally, the flexible SASC device assembled with the CC/Co3O4@NiO cathode possesses an ultra‐high volumetric energy density of 3.11 mWh cm−3 at a volumetric power density of 116 mW cm−3 with a satisfactory cycling stability (90.1 % of after 10000 cycles). These values are superior to the great majority of the state‐of‐the‐art flexible electrochemical capacitors. Thereby, the core‐shell structured CC/Co3O4@NiO is a promising candidate material for energy storage devices, and this work can provide a reference for the structural design and constructing of electrode materials.

Structural, optical, and dielectric modulus properties of PEO/PVA blend filled with metakaolin

The PEO/PVA blend incorporated by different weight percentages (≤10%) of metakaolin (MK) has been prepared and characterised. The XRD revealed a semicrystalline structure of pure PEO/PVA with peaks indicating the presence of silicon and aluminum in the MK composition. The addition of MK in the blend leads to a decrease in the diffraction peak intensities, confirming that the blend-MK interactions break some PEO/PVA blend domains. The UV–Vis transmittance and reflectance spectra were studied and used to determine optical parameters. The decrease in the band-gap values was demonstrated with the increase in MK to confirm the suitability of MK as a band-gap regulated the optical material in different applications. The obtained values of the optical band gap decrease with the increase of MK concentration due to the defect levels that correlate to the sample's density of localized states. The higher values of ε′ found at a lower frequency related to the effect of the dominant contribution of the interfacial polarization due to the accumulation of charges, whereas the higher values of ε″ at the lower frequency were related to an increase in the energy loss in the composite films. The Cole-Cole plot displays semicircles at the lower frequency range with a linear increase at the intermediate and higher frequency due to the grain boundary and the relaxation process. The values of the real part (σ′) are lower than that of the corresponding values of the imaginary part (σ″). Applied an electric field causes polarized films and the ability to store an electric charge. Therefore, these composites may be used in flexible capacitors.

One-pot synthesis of hexafluorobutyl acrylate hyperbranched copolymer for graphene/poly(vinylidenefluoride-trifluoroethylene- chlorofluoroethylene) dielectric composite

Dielectric polymer film capacitor is rapidly emerging as next-generation energy storage for advanced engineering applications because of its lightweight, low cost, and processability. Further increasing energy density of polymer film with high charge–discharge efficiency is prevalent research spotlight. The filler/polymer composite with compatible interface is proved as an effective strategy to improve the energy storage capability of dielectric film. In this work, we designed hyperbranched hexafluorobutyl acrylate copolymer as miscible interface in graphene/fluoropolymer dielectric composite. A facile one-pot method was adopted to synthesize hyperbranched polyethylene grafted hexafluorobutyl acrylate (HBPE-g-HFBA) copolymer, which was adsorbed on surface of nanosheets by non-covalent interaction during exfoliation of natural graphite. The graphene/poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) composite was prepared by solution casting. The interfacial polarization is enhanced with the improved compatibility of composite that is due to the chemical similarity between hexafluorobutyl acrylate segments and fluoropolymer matrix. The energy density of 0.1 wt% nanocomposite achieves 5.0 J cm−3 with charge–discharge efficiency of 78.1% at 250 MV m−1. This work provides an optional route for non-covalent functionalization of graphene and the development of flexible polymer film capacitor with large energy storage capability.

Barium titanate-enhanced hexagonal boron nitride inks for printable high-performance dielectrics

Printed electronics have been attracting significant interest for their potential to enable flexible and wearable electronic applications. Together with printable semiconductors, solution-processed dielectric inks are key in enabling low-power and high-performance printed electronics. In the quest for suitable dielectrics inks, two-dimensional materials such as hexagonal boron nitride (h-BN) have emerged in the form of printable dielectrics. In this work, we report barium titanate (BaTiO3) nanoparticles as an effective additive for inkjet-printable h-BN inks. The resulting inkjet printed BaTiO3/h-BN thin films reach a dielectric constant (ε r) of ∼16 by adding 10% of BaTiO3 nanoparticles (in their volume fraction to the exfoliated h-BN flakes) in water-based inks. This result enabled all-inkjet printed flexible capacitors with C ∼ 10.39 nF cm−2, paving the way to future low power, printed and flexible electronics.

Anisotropic fluid with phototunable dielectric permittivity

Dielectric permittivity, a measure of polarisability, is a fundamental parameter that dominates various physical phenomena and properties of materials. However, it remains a challenge to control the dielectric permittivity of materials reversibly over a large range. Herein, we report an anisotropic fluid with photoresponsive dielectric permittivity (200 < ε < 18,000) consisting of a fluorinated liquid-crystalline molecule (96 wt%) and an azobenzene-tethered phototrigger (4 wt%). The reversible trans-cis isomerisation of the phototrigger under blue and green light irradiation causes a switch between two liquid-crystalline phases that exhibit different dielectric permittivities, with a rapid response time (<30 s) and excellent reversibility (~100 cycles). This anisotropic fluid can be used as a flexible photovariable capacitor that, for example, allows the reversible modulation of the sound frequency over a wide range (100 < f < 8500 Hz) in a remote manner using blue and green wavelengths.

Structural design of flexible interdigital capacitor based upon 3D printing and spraying process

Traditional substrates of metallic interdigital electrodes (IEs) are rigid and undeformable, flexible interdigital capacitors are therefore appealing as strain sensors. In this study, interdigital capacitors were parametrically designed by 3D printing and encapsulated by spraying process. The interdigital circuits of the structure were printed with conductive silicone rubber filled with silver-coated glass fiber and carbon fiber, and the circuits were encapsulated with polydimethylsiloxane. Herein, the interdigital-flexible structures were parametrically designed and firstly served as capacitive sensor, namely flexible interdigital capacitive sensors (FICSs). The spaces between IEs, are extremely sensitive to strain, therefore provide the capacitors with excellent electromechanical behaviors. The optimized FICS benefited for a wide working range of strain (0%∼45%), high sensitivity (gauge factor = 2.7) to a tiny strain of 0.3%, stable working duration at different stretching speeds (18 mm min−1, 36 mm min−1 and 72 mm min−1), prolonged service life (>800 cycles), as well as excellent capability to detect human movement (bulging, grasping and bending). Response mechanism of the FICS was modeled based upon its microstructure evolution, including the distances between IEs and the fillers migration. The printed FICSs with optimized structure provide a comprehensive thought in the design of electronics, further would inspire the branch of 3D printed electronics.

Self-powered and flexible integrated solid-state fiber-shaped energy conversion and storage based on CNT Yarn with efficiency of 5.5%

Self-powered and flexible integrated solid-state fiber-shaped photo capacitors (SS-FPCs), which combine energy-harvesting and energy-storage functions in a single device, have drawn a lot of attention as potential applications in wearable electronics. Herein, a flexible carbon nanotube yarn (CNTY) with improved mechanical and electrical properties is used as a shared electrode to create SS-FPCs. In addition, CNTY was doped into n- and p-type using polyethyleneimine (PEI) and iron (III) chloride (FeCl3) to improve the electrocatalytic behavior of CNTY, respectively. The optimized SS-FPC based on p-type material-doped CNTY, which integrates the high specific capacitance of the solid-state fiber-shaped electrochemical energy storage (SS-FES) unit with 78.26 mF cm−2 and a high power conversion efficiency (PCE) of the solid-state fiber-shaped dye-sensitized solar cells (SS-FDSSCs) unit with 5.50%, exhibits a remarkable overall energy conversion efficiency of up to 4.69% and excellent discharging time of about 6 min owing to the synergistic action of the two units. Compared to traditional integrated power systems, our self-powered and flexible integrated SS-FPCs are lightweight, flexible, affordable, and suitable for special applications, especially fabric for wearable electronics.

Flexible multilayer lead-free film capacitor with high energy storage performances via heterostructure engineering

The immense potential of flexible energy storage materials applied in wearable electronic devices has stimulated a lot of science researches on manufacturing technology and performance optimization. Herein, an all-inorganic flexible ferroelectric film with multilayer heterostructure is prepared based on Mn doped Bi0.5Na0.5TiO3BiNi0.5Zr0.5O3 (Mn:BNT-BNZ) and Bi0.5Na0.5TiO3BiZn0.5Zr0.5O3 (BNT-BZZ) relaxor ferroelectrics. A win-win situation of breakdown strength and polarization is achieved in the Mn:BNT-BNZ/BNT-BZZ multilayer film with the stacking period N = 3, of which energy density and efficiency reach 80.4 J/cm3 and 62.0% respectively. It is proposed that the excellent energy storage performances are attributed to the synergistic effect of the electric field amplification effect, interface blocking effect and the polarization coupling effect based on the multilayer heterostructure. Moreover, the flexible ferroelectric film exhibits outstanding temperature (25–205 °C), frequency (0.5–5 kHz) stability and antifatigue property (1 × 108 cycles), and can well maintain stable performance at different tensile/compressive bending radii (10–5 mm) and even after 104 bending cycles with a fixed bending radius of 3 mm. This work opens up a promising route to the development of flexible energy storage materials.