Single Supercapacitor Research Articles

Stretchable supercapacitors made with plasticine/graphene/CeNdNiO2 composite electrodes

Mechanically strong, flexible and deformable supercapacitors (SCs) are of particular interest for the wearable electronics. Therefore, stretchable dual SCs composed of two single devices were fabricated and studied in this research. Soft SC electrodes were made of plasticine decorated with graphene microplates and had cylindrical shape. To enhance the capacitance of the devices, Ce0.8Nd0.1Ni0.1O2-δ (CNNO) particles were added as redox material in the SC electrodes. Electrochemical tests were performed for the single SCs made only with graphene electrodes and produced capacitances/energy-densities of 178–215 F g−1/24–30 W h kg−1. When the single graphene supercapacitors are connected in-series, a maximum specific capacitance/energy density of 370.9 F g−1/51.4 W h kg−1 is obtained. The single SCs made with CNNO particles had higher specific capacitances/energy-densities of 326–436 F g−1/45–61 W h kg−1. The SCs made with CNNO were connected in-series and in-parallel, producing specific capacitances/energy densities of 257.1 F g−1/35.7 W h kg−1 and 516 F g−1/71.7 W h kg−1, respectively. Thus, incorporating the CNNO particles to the SCs enhanced their capacitance by 51–144%. According to the CV curves, the current densities are increased from 6 to 15 A g−1 to 37 A g−1 when the single devices are connected in-parallel. If the single devices are connected in-series, the output voltages of the supercapacitors increased from 1 to 1.3 V. The devices were also subjected to stretching at 25% and the capacitance dropped by 90–96.5% because the electrodes were broken. However, the devices were unstretched and the capacitance was recovered by ≈ 40–60%. If those last devices are heated at 50 °C, the SC electrodes are totally repaired, and the capacitance is even 12–33% higher in comparison with the original capacitance for the non-stretched device. Additionally, absorbance, Raman and XPS analyses revealed the presence of oxygen vacancies, Ce3+/Ce4+, Nd0/Nd1+/Nd3+ and Ni0/Ni2+/Ni3+, which worked as redox centers for the charge storage. In summary, the results presented here demonstrate that our stretchable SC can operate in-series or in-parallel connection and their electrodes can be re-built after applying heat. The cost of those SCs is drastically reduced because they are made with plasticine and due to their flexibility and stretchability, they are good candidates for wearable applications, which require deformable devices.

Vertically Layered Multi‐Pair Interdigital Electrodes within a Single Sheet of Paper for High Energy Density

AbstractA paper‐based supercapacitor (SC) is a promising flexible energy storage device for wearable electronics. Paper is an alternative flexible substrate to conventional substrates such as metal foil or plastics. Paper's porous structure can be applied as a large surface area of electrode to store more charge. Paper can also be used as a separator between each electrode. We propose a simple method for vertically integrating a multi‐pair of interdigital electrodes within only a single sheet of paper. The integrated multi‐electrodes were fully separated because of a removable wax barrier. The integrated multi‐pair interdigital electrodes in a paper were used as ultra‐thin SCs combined in parallel. With an inner space of paper, the device volume can be reduced with high energy density while preserving flexibility. The energy density was 86.58 μWh cm−2, which is three orders of magnitude higher energy density than a single SC at the same size.

Modeling, Simulation, and Characterization of a Supercapacitor in Automotive Applications

In the energy storage field, supercapacitors (SCs) are gaining more and more attention thanks to features, such as high-power density, high life cycles, and lack of maintenance. In this article, an improved SC three-branch model, which considers the residual charge phenomenon, is presented. The procedure to estimate the model parameters and the related experimental setup are presented. The parameter estimation procedure is repeated for several SCs of the same type. The average parameters are, then, obtained and used as initial guesses for a recursive least squares optimization algorithm to increase the accuracy of the model. The model of a single SC is, then, extended to SC banks, testing different configurations and operating conditions. The simulation results, obtained in the MATLAB/Simulink environment for both the single SC and the different SC bank configurations, are validated with experimental tests to assess the model accuracy.

A stretchable and self-healable conductive hydrogels based on gelation/polyacrylamide/polypyrrole for all-in-one flexible supercapacitors with high capacitance

Conductive polymeric hydrogels have aroused growing attentions for their promising applications in wearable electronics. It is still necessary to harmonize their mechanical and electrochemical properties for the real applications. Here we report novel conductive hydrogels with a sandwich-like structure, in which gelatin/polyacrylamide (Gel/PAAM) double network are served as robust scaffold and polypyrrole (PPy) nanoclusters were firmly embedded in the two sides of the Gel/PAAM hydrogel. The obtained Gel/PAAM/PPy hydrogels have shown a skin-like stretchable and high conductivity under various deformations. Significantly, the PPy content in the Gel/PAAM/PPy hydrogels can be easily regulated for the use in flexible all-in-one supercapacitors (SCs). The optimized device showed an exceptional specific capacitance of 363.75 mF/cm2, a high energy density of 32.33 μW h/cm2 at power density of 400 μW/cm2, as well as a promising cyclic stability of 82% capacitance retention after 2000 cycles. Besides, the working potential window and output current density can be extended by assembling the single SC into series and parallel connection. What’ more, the device possesses very stable electrochemical performance under bending, compressing, stretching conditions and even after healing process. This work proposes a feasible approach for preparation of novel PPy-based conductive hydrogels that might provide a viable source for all-flexible electronic devices.

Laser-Graving-Assisted Fabrication of Foldable Supercapacitors for On-Chip Energy Storage.

Planar supercapacitors (SCs) have been regarded as promising energy devices for on-chip electronics and they should be evaluated by areal performances due to the very limited available areas. However, these SCs usually suffer from inevitable size increase for the requirement of substrates, current collectors, and sealants. This work presents a kind of freestanding, foldable, and quasi-solid-state SCs that single SC units were stacked in the thickness direction with a common electrode to reduce their occupied areas. The foldable SCs can be fabricated in desired patterns by laser graving and their areal performances increase linearly with the assembled units. The energy density of a 5-unit foldable SC is 177.9 μWh cm-2 at the power density of 2.78 mW cm-2, and it outperforms most planar SCs. Therefore, this work provides a new reference to improve the areal properties of on-chip SCs from the device design aspect.