RESUMEN
Plastic film capacitors are widely used in pulse and energy storage applications because of their high breakdown strength, high power density, long lifetime, and excellent self-healing properties. Nowadays, the energy storage density of commercial biaxially oriented polypropylene (BOPP) is limited by its low dielectric constant (~2.2). Poly(vinylidene fluoride) (PVDF) exhibits a relatively high dielectric constant and breakdown strength, making it a candidate material for electrostatic capacitors. However, PVDF presents significant losses, generating a lot of waste heat. In this paper, under the guidance of the leakage mechanism, a high-insulation polytetrafluoroethylene (PTFE) coating is sprayed on the surface of a PVDF film. The potential barrier at the electrode-dielectric interface is raised by simply spraying PTFE and reducing the leakage current, and then the energy storage density is increased. After introducing the PTFE insulation coating, the high-field leakage current in the PVDF film shows an order of magnitude reduction. Moreover, the composite film presents a 30.8% improvement in breakdown strength, and a 70% enhancement in energy storage density is simultaneously achieved. The all-organic structure design provides a new idea for the application of PVDF in electrostatic capacitors.
RESUMEN
Scalable and cost-effective fabrication of three-dimensional (3D) boron carbon nitride (BCN) microspheres was first demonstrated by hydrothermal and annealing methods. In particular, the specific surface area of 3D-BCN-4 reached 1390.12 m2 g-1 and had a high hierarchical pore structure. An all-printed solid-state flexible microsupercapacitor (MSC) based on 3D-BCN-4 microspheres as an electrode material was fabricated for the first time by a screen printing method, which also provided efficacious properties. The single MSC areal capacitance reached 41.6 mF cm-2. Furthermore, the remarkable mechanical flexibility was also achieved for the device with evidence that no obvious capacitance loss occurred even upon bending to 180°, and the device had a 93.3% capacitance retention after 1000 cycles. In addition, the maximum energy density reached 0.00832 mW h cm-2, and the highest power density was 2 mW cm-2. These results show the synthesis of 3D-BCN by a facile and effective method with excellent electrochemical performance, which should provide a promising direction to wearable energy storage devices.
RESUMEN
Construct dielectric films with high energy density and efficiency are the key factor to fabricate high-performance dielectric film capacitors. In this paper, an all organic composite film was constructed based on high dielectric polymer and linear dielectric polymer. After the optimized polycondensation reaction of a linear dielectric polymer aromatic polythiourea (ArPTU), the proper molecular weight ArPTU was obtained, which was introduced into poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (PVDF-TrFE-CFE) terpolymer for a composite dielectrics. The results indicate that the addition of ArPTU molecules reduces the dielectric loss and improves the breakdown field strength of the PVDF-TrFE-CFE effectively. For the PVDF-TrFE-CFE/ArPTU (90/10) composite film, the maximum energy density about 22.06 J/cm3 at 407.57 MV/m was achieved, and high discharge efficiency about 72% was presented. This composite material can be casted on flexible substrate easily, and PVDF-TrFE-CFE/ArPTU organic composite films having high energy density, high breakdown field strength, low dielectric loss, and higher discharge efficiency are obtained. This is an unreported exploration about high energy density organic dielectric films based on PVDF-TrFE-CFE matrix and linear polymer dielectrics, and the findings of this research can provide a simple and scalable method for producing flexible high energy density materials for energy storage devices.
RESUMEN
High performance dielectric polymer materials are a key point for energy storage capacitors, especially film capacitors. In this paper, a sandwich-structured polymer film is constructed to achieve high energy density and high efficiency. High dielectric materials of poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) doped with barium titanate (BaTiO3) are used as the outer layer to achieve a high dielectric constant, and a boron nitride nanosheet (BNNS) layer is inserted between P(VDF-HFP)/BaTiO3 to obtain a high breakdown field strength of composite films. The results indicate that when the doping amount of the BaTiO3 nanoparticles reaches 10 wt% and the mass fraction of the BNNS layer is 0.75 wt%, a significant improvement of energy storage performance is obtained. The energy storage density of the P(VDF-HFP)/BaTiO3/BNNSs composite film can reach 8.37 J cm-3, which is higher than 6.65 J cm-3 of the pure P(VDF-HFP) film. Compared with the P(VDF-HFP) film doped with BaTiO3, significant improvement of the breakdown field strength (about 148.5%) is achieved and the energy storage density increases 235% accordingly, resulting from the inserted BNNSs layer blocking the growth of electrical branches and suppressing leakage current. This novel sandwich-structured film shows promising future applications for high performance dielectric capacitors.
RESUMEN
The three-dimensional (3D) porous nanostructures have shown attractive promise for flexible microsupercapacitors due to their merits of more exposed electrochemical active sites, higher ion diffusion coefficient, and lower charge-transfer resistance. Herein, a highly opened 3D network of reduced graphene oxide/poly(3,4-ethylenedioxythiophene) (rGO/PEDOT) was constructed through the laser-assisted treatment and in situ vapor phase polymerization methods, which can be employed with gel electrolyte to prepare flexible microsupercapacitors, without conductive additives, polymer binder, separator, or complex processing. These porous open network structures endow the obtained microsupercapacitors with a maximum specific capacitance (35.12 F cm-3 at 80 mA cm-3), the corresponding energy density up to 4.876 mWh cm-3, remarkable cycling stability (with only about 9.8% loss after 4000 cycles), and excellent coulombic efficiency, which are comparable with most previous reported rGO-based microsupercapacitors. Additionally, the microsupercapacitors connected in series/parallel have been conveniently fabricated, followed by being integrated with solar cells as efficient energy harvesting and storage systems. Moreover, the working voltage or energy density of microsupercapacitors array can be easily tailored according to the practical requirements and this work provides a promising approach to prepare high-performance flexible micro-energy device applied in the wearable electronics accordingly.
RESUMEN
We report chemical in situ deposition of conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) on reduced graphene oxide (rGO) nanosheets through a simple hydrothermal polymerization method. The functional groups on graphene oxide (GO) were directly employed as an oxidant to trigger the polymerization of 3,4-ethylenedioxythiophene (EDOT), and the GO nanosheets were reduced into rGO accordingly in an aqueous environment. Well anchoring of ultrathin PEDOT on rGO through this oxidant-free method was confirmed by UV-Vis spectrum, FT-IR spectrum, SEM, and TEM analysis. The obvious enhancement of conductivity was observed after the covering of PEDOT on rGO, and this composite showed high conductivity about 88.5 S/cm. The electrochemical performance results revealed that rGO/PEDOT composite electrode exhibits high specific capacitance about 202.7 F/g. The good synergetic effect between PEDOT and rGO also makes sure highly stable reversibility of composite electrode during charging/discharging process, and more than 90% initial capacitance retains after 9000 times cycles. In addition, the electrode based on rGO/PEDOT deposited on the cotton fabric shows excellent flexible ability with the evidence that 98% of the initial capacitance of electrode maintained after three thousands of free bending, which shows promising energy storage performance for flexible devices. .
RESUMEN
A novel electrode material incorporating renewable biomass-derived juglone biomolecules with commercial activated carbon (AC) granules has been through simple ultrasonic dispersion and dissolution-recrystallization and was found to exhibit good electrochemical performance. The juglone biomolecules are prepared by an ultrasound-assisted extraction method from abandoned walnut peel, which decreases pollution and increases economic efficiency. Through the dissolution-recrystallization process with AC, a hierarchical structure with nanosized juglone particles was obtained, and the AC particles worked as scaffolding to strengthen the slight biomolecules, thus expanding the active sites and effectively reducing the dissolution of the active materials. The pseudocapacitance fading mechanism was investigated by ex situ FTIR measurement and the porous structure ensures that the composite electrode has an enhanced specific capacitance of 248 F g-1 compared to 172.8 and 62.5 F g-1 for the respective AC and juglone samples. Besides, the excellent cyclic stability (retained 75% after 3000 charge-discharge cycles) was demonstrated. The highest area-specific capacitance of the composites was 1300 mF cm-2. An asymmetric supercapacitor based on this composite electrode was assembled with an AC electrode as the counter electrode and exhibited good cyclic performance at a voltage of 1.2 V (retained 77% after 3000 charge-discharge cycles), which provides a high energy density of 12 W h kg-1 at a power density of 0.18 kW kg-1 and a high power density of 2 kW kg-1 at an energy density of 9 W h kg-1. This work explores the application of biomolecule-based composites in energy storage devices and provides a potential strategy for constructing environmentally friendly electrodes.