Strontium phosphide-polyaniline composites for high performance supercapattery devices

ABSTRACTIn this study, graphene oxide (GO) was chemically reacted with sodium borohydride (NaBH4) to form reduced graphene oxide (rGO). rGO, Montmorillonite nanoclay, and polyvinylcarbazole (PVK) were used to form a ternary nanocomposite via chemical reaction. These nanocomposite qualities were described via scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy-attenuated transmission reflectance (FTIR-ATR). In addition, these materials were used in supercapacitor device as an active material to test electrochemical performances via cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). The rGO/nanoclay/PVK nanocomposite shows significantly improved specific capacitance (Csp = 168.64 Fg−1) compared to that of rGO (Csp = 63.26 Fg−1) at the scan rate of 10 mVs−1 by CV method. The enhanced capacitance results in high power density (P = 5522.6 Wkg−1) and energy density (E = 28.84 Whkg−1) capabilities of the rGO/nanoclay/PVK nanocomposite material. The addition of nanoclay and PVK increased the specific capacitance of rGO material due to a dopant effect for supercapacitor studies. Ragone plots were drawn to observe energy and power density of supercapacitor devices. The Csp of rGO/nanoclay/PVK nanocomposite has only 86.4% of initial capacitance for charge/discharge performances obtained by CV method for 5000 cycles.

A critical review of recent advancements in zinc based metal organic framework nanocomposites and their derivatives for supercapacitor applications with future perspectives and challenges

Biomass-based carbonaceous materials derived from Musa Sapientum have gained much attention in recent years for their application in energy storage devices, especially supercapacitors. In the present work, we synthesized carbonaceous material from banana peel as the biomass precursor by using a pyrolysis method carried out at various temperatures (600, 800, and 1000 °C). The characterization of the prepared carbonaceous materials BP600, BP800 and BP1000 was done by using different characterization techniques such as FTIR, XRD, FE-SEM, and TEM, studies. The electrochemical study of the synthesized material was carried out by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) electrochemical impedance spectroscopy (EIS). The supercapacitive performance of the material was studied using a 3-electrode system with 3M KOH as an electrolyte. As a result, the BP600 exhibited a better specific capacitance with higher energy and power densities along with a maximum cyclic stability of 16,000 cycles. To show the practical applicability of the material BP 600, two electrode system studies were carried out as well, which showed preferentially good values for specific capacitance with appreciable power and energy density values. The study provides us with a green approach for the fabrication of non-toxic, low-cost, and environmentally friendly potential porous carbonaceous electrode materials by converting bio-waste into a clean and renewable source of energy.

Graphene–MnO 2 and graphene asymmetrical electrochemical capacitor with a high energy density in aqueous electrolyte

PANI/MWCNT nanocomposite supercapacitor electrodes were synthesized by in-situ microwave plasma polymerization of aniline in the presence of MWCNT-COOH. The SEM image of the composite illustrates the formation of the core-shell MWCNT-PANI ordered structure that has a strong effect on the electrical conductivity and porosity, in addition to the appearance of agglomerated polymerized islands. The electrochemical performance of PANI/MWCNT composite was evaluated with respects to the obtained specific capacitance, energy and power density, and cyclic stability, using cyclic voltammetry, galvanostatic charge/discharge at a constant current and electrochemical impedance spectroscopy. The highest obtained specific capacitance was 112 F/g at a charging current density of 1.6 A/g, provides the highest energy density of 34.8 Wh/Kg and a power density of 1670 W/Kg. While the highest achieved power density was 8381 W/Kg with an energy density of 12.8 Wh/Kg. The delivered energy density crossed the threshold energy density limit of the battery, which meets the scientific motivation to use supercapacitor as an independent energy source.

The intermittent nature of many renewable energy sources such as wind and solar, coupled with fluctuations in energy demand, creates a pressing need for efficient, low-cost energy storage technologies. Supercapacitors are promising candidates to play a role in next-generation energy storage systems. They have a higher power density and better cycle life (although lower energy density) than batteries making them ideal for rapid energy storage and deployment [1]. Activated carbon is a favoured electrode material due to high surface area, although low conductivity requires use of a conductive additive (often carbon black), reducing available surface area for charge storage. In contrast, the high conductivity and specific surface area of graphene has made it a promising material for electrochemical double layer supercapacitors (EDLCs) [2], however, performance is limited by restacking of the graphene sheets, reducing available surface area.In this work, high-shear exfoliated few layer graphene (FLG) [3] is investigated both as an electrode material and as a conductive additive/interfacial layer for EDLCs. FLG suspensions were produced under a variety of exfoliation conditions, with platelet thickness and linear dimension determined from Raman spectroscopy based on metrics developed by Backes et al. [4] and through scanning electron microscopy (SEM).The FLG suspensions were used in three ways: i) to create thin ‘graphene paper’ electrodes; ii) as a conductive additive, mixed into the activated carbon electrode material; iii) deposited onto the back of (and diffused within) activated carbon electrodes. These electrodes were investigated by Raman spectroscopy and Scanning Electron Microscopy, before being assembled into symmetric two-terminal aqueous cells then evaluated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS), and their electrochemical performance related to structure and composition.As expected, pure FLG electrodes often showed excellent low series resistance values, however specific capacitance was low, due to restacking. Directly mixing 5% FLG into activated carbon as a conventional conductive additive led to a specific capacitance of 63 F/g (from CV at 10 mV/s), and a series resistance of 19 W (from GCD at 1 A/g) - markedly inferior to those with 5% carbon black as a conductive additive (95 F/g and 2 Ohm) and inferior even to electrodes with no conductive additive (87 F/g and 10 Ohm).However, post fabrication deposition/infusion of FLG offers comparable performance to carbon black (90 F/g and 1 Ohm) at 7% FLG by weight. As the quantity of FLG is increased the specific capacitance decreases sharply. This behaviour is attributed to FLG restacking on the rear of the electrode, so adding mass whilst providing limited additional capacitance, and compression of the electrode.Adding high-shear exfoliated FLG to activated carbon electrodes shows promise for obtaining the benefits of both materials. At present, FLG/activated carbon electrodes can match the performance of those produced from activated carbon with a carbon black conductive additive and, with further optimization, we expect will be able to exceed them.Figure: a) Cross sectional SEM image of activated carbon electrode with graphene interfacial layer; b) magnified cross sectional SEM image of graphene interfacial layer; c) cyclic voltammograms at 10 mV/s of the different electrodes mentioned in the abstract.

Magnetron sputtered tungsten di-sulfide: An efficient battery grade electrode for supercapattery devices

Graphene-based electrodes are of great interest for developing high performance electrochemical double-layer capacitors (EDLCs) due to their excellent electrochemical properties, low electric resistance and unique structures. Meanwhile, EDLCs have become more attractive not only to offer high power and energy densities but also to withstand a harsh temperature ranges [1]. Since temperature effects can be crucial to estimate the rational evaluation of degradation, energy efficiency and lifetime, it requires better understanding of temperature-dependent electrochemical properties especially at electrode/electrolyte interfaces. In this study, the performance of an EDLC, assembled with two identical graphene electrodes and the 1M Et4NBF4/PC electrolyte in a coin cell, is systemically characterized under various operating temperature conditions, ranged from -30 °C to 60 °C. Graphene deposition is carried out by using the vacuum filtration method. This method yields an electrically strong conductive and thermally stable nano-structured graphene paper [2]. Electrochemical characterization techniques including cyclic voltammetry (CV), constant charging/discharging (CCD) and electrochemical impedance spectroscopy (EIS) are performed to evaluate capacitance retention, energy and power densities, internal resistance variation and interfacial processes at the double-layer region. In addition, EIS data is simulated with the proposed electric equivalent circuit in order to investigate the temperature dependency on interfacial reactions with respects to mass transfer (diffusion) and electrode kinetics (charge transfer) [3]. Each reaction is represented by electrical resistive elements in the equivalent circuit, and its values are correlated with the activation energy to quantitatively rationalize the observed behaviour of diffusion and the charge transfer kinetics with temperature.

The effects of different activating agents on the physical and electrochemical properties of activated carbon electrodes fabricated from wood-dust of Shorea robusta

A hybrid PEMFC/supercapacitor device with high energy and power densities based on reduced graphene oxide/Nafion/Pt electrode

A mild hydrothermal process is applied to synthesize hydrous ruthenium–tin binary oxides (Ru0.7Sn0.3O2·nH2O) with good capacitive performance in alkaline system. Then, a symmetric electrochemical capacitor (EC) is fabricated based on the as-synthesized Ru0.7Sn0.3O2·nH2O material and 1 M KOH aqueous electrolyte. Electrochemical performance of the symmetric EC is investigated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy tests. Electrochemical tests demonstrate that the symmetric EC surprisingly can operate with a high upper cell voltage limit of 1.45 V in 1 M KOH electrolyte. Maximum specific capacitance and energy density of the symmetric aqueous EC are approximately 160 F/g and 21 Wh/kg, respectively, delivered at a current density of 1.25 A/g. And the specific energy density decreases to approximately 15 Wh/kg when the specific power density increases up to approximately 1,770 W/kg. The promising specific energy and power densities are obtained simultaneously for the unwonted symmetric EC due to its larger operating potential range. Moreover, the symmetric EC exhibits electrochemical stability with 85.2% of the initial capacitance over consecutive 1,000 cycle numbers.

Recent advances in utilizing graphene-based materials for flexible supercapacitor electrodes

Lithium-Ion Batteries receive growing attention because of their potentially high energy and power density, which are important requirements for automobile applications. Reports agreed that the positive electrode is hereby the performance limiting cell component. NxMyCz (nickel manganese cobalt spinel) is one of the most promising cathode materials, both due to its rather high operating voltage and to either high power or energy density [1]. Hereby, a compromise between high power (thin layers and, i.e., high porosity) and high energy density (thick layers and, i.e., low porosity) has to be reached, in particular for automotive applications. This demands for an extended understanding of the interplay between microstructure parameters and chemical stoichiometry of NMC cathodes on cell performance characteristics. In this study, two NMC - cathodes recovered from commercial high energy and high power cells are analyzed (i) by SEM and X-ray tomography and (ii) by Electrochemical Impedance spectroscopy (EIS). By evaluating the impedance spectra measured at 0 to 40°C and at SOC 0 to SOC 100 by the distribution function of relaxation times (DRT) [2], a physically motivated transition line model [3] was established. The microstructure parameters required for a quantitative analysis of the electrochemical loss processes were obtained by X-ray tomography data. Additionally, the exact composition is determined by energy dispersive X-ray spectroscopy (EDX) investigations The results confirm, that a NMC electrode custom tailored for high energy density is rather thick (70 µm) and made of large low-porous agglomerates of primary particles, as described in [4]. The significant difference between the NMC cathode of a high energy and a high power cell however is not, as expected, a significantly higher porosity, but a sophisticated combination of small carbon black particles and elongated carbon black fibers, enabling high discharge currents. The tortuosity of the electrode pores, which represent the transport pathways for the liquid electrolyte, is low for the high power cell, which raises the effective electrolyte conductivity significantly, when compared to the high energy cell [4]. Furthermore the high power cell features a special compound of two different NxMyCz active materials. By including all the results from EIS, DRT, X-ray tomography and EDX, an evaluation of the influence of composition and microstructure on performance characteristics of the NxMyCz cathodes will be presented.

Asymmetric hybrid supercapacitors integrating transition metal oxides with carbonaceous electrodes have attracted significant attention for advanced energy storage applications due to their ability to combine high energy density with rapid power delivery. In this study, an Al/Nb 2 O 5 cathode and a Cu/graphene oxide (GO) anode were fabricated via slurry casting and electrophoretic deposition (EPD), respectively, and assembled with a paper separator in aqueous potassium hydroxide (KOH) electrolytes of varying concentrations (1, 2, and 3 M). Structural and morphological analyses confirmed the orthorhombic phase of Nb 2 O 5 and the uniform deposition of GO films. Galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) measurements revealed a strong dependence of electrochemical performance on electrolyte concentration. The device operating in 2 M KOH exhibited the most favorable balance between energy and power densities, achieving a specific capacitance of 30.7 F g −1 , energy density of 36.5 Wh kg −1 , and power density of 295 W kg −1 , with a relaxation time constant of 0.634 ms. In contrast, 1 M KOH provided moderate energy storage capability, while 3 M KOH suffered from reduced capacitance due to increased viscosity and ion–ion interactions. Comparative analysis with literature data highlights the competitive performance of the Al/Nb 2 O 5 //Cu/GO configuration, particularly in terms of energy–power trade‐off. These findings underscore the critical role of electrolyte optimization and electrode design in advancing hybrid supercapacitors for sustainable energy storage applications.

The growing demand for efficient energy storage systems, particularly in portable electronics and electric vehicles, has led to increased interest in supercapacitors, which offer high power density, rapid charge/discharge rates, and long cycle life. However, improving their energy density without compromising performance remains a challenge. In this study, we developed novel 3D-printed reduced graphene oxide (rGO) electrodes coated with polyaniline (PANI) to enhance their electrochemical properties. The rGO 3D-printed electrodes were fabricated using direct ink writing (DIW), which allowed precise control over thickness, ranging from 4 to 24 layers. A unique ink formulation was optimized for the printing process, consisting of rGO, cellulose acetate (CA) as a binder, and acetone as a solvent. The PANI coating was applied via chemical oxidative polymerization (COP) with up to five deposition cycles. Electrochemical testing, including cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS), revealed that 12-layer electrodes with three PANI deposition cycles achieved the highest areal capacitance of 84.32 mF/cm2. While thicker electrodes (16 layers and beyond) experienced diminished performance due to ion diffusion limitations, the composite electrodes demonstrated excellent cycling stability, retaining over 80% of their initial capacitance after 1500 cycles. This work demonstrates the potential of 3D-printed PANI/rGO electrodes for scalable, high-performance supercapacitors with customizable architectures.