Power Density Values Research Articles

Biochar and other carbonaceous materials used in steelmaking: Possibilities and synergies for power generation by direct carbon fuel cell

The objective of this study is the preliminary investigation of the feasibility of using a low-temperature molten hydroxide direct carbon fuel cell as an additional energy source for steel production by electric arc furnace. For this purpose, four carbonaceous materials related to the steel industry (electrographite, coke, torrefied biochar and hydrochar) were selected and characterized to predict their electrical behavior before their actual introduction as fuels. Special attention was paid to both the morphological effect (bulk/pellet or powder) and the chemical composition of the fuels on the electrical performance of the cell. Electrical measurements showed the positive influence of powder morphology, with coke powder having the highest peak power density value (49.6 mW/cm2). Electrographite was found to be useable only as a powder (18.7 mW/cm2), as the high chemical stability of the bulk morphology, provided by the smooth surface and the pitch used as a binder, acted as inhibitors of the carbon oxidation reaction. Although biochar appeared superior to hydrochar when inserted as powder (23.5 vs. 18.2 mW/cm2), the latter showed promising results also inserted as pellet. the latter also showed promising results when inserted as a pellet. Specifically, once inserted within the molten hydrochar, the binder used to produce the hydrochar is removed changing the morphology from pellet to sandy/powdery, negating the penalizing effect of the lower surface to volume of bulk morphology (15.8 vs. 18.2 mW/cm2) and offering the advantage of avoiding the milling process and related fine particulate production from an industrial point of view.

Impacts of lighting and plug load variations on residential building energy consumption targeting zero energy building goals

Mitigating building energy use and carbon emissions in the buildings sector is a globally recognized goal. This is being pursued through the adoption of zero-energy building (ZEB) targets, with formal government regulations and policies actively embraced in domestic marketplaces. However, building assessment methods used for the ZEB certification system in South Korea have garnered substantial critique from building energy engineers and practitioners for their practical applicability. This study investigated energy consumption patterns of single-family residential buildings, focusing on two major energy end-use categories: lighting- and plug-loads. Empirical analyses and field measurement data were used to construct representative profiles of lighting and plug loads, as well as power density values, based on data from existing residential buildings. These distinct profiles of lighting and plug loads were used as input data for a residential ZEB evaluation. The measurement data from 60 detached houses in South Korea was utilized to derive four representative profiles for the category's loads. These profiles were subsequently employed for simulation-based analyses to assess load diversity. A whole-building energy simulation model was developed to conduct annual building energy analyses and assess ZEB certification based on the set and applied load profiles. Results showed that building energy consumption could vary by up to 23% based on different lighting load patterns and by as much as 58% for differing plug load patterns. These findings underline the importance of refining the current domestic ZEB certification process by considering the influence of diverse domestic load profiles on energy consumption and building certification grades.

Binder-free pinecone-like NiSe/MnSe nanostructure arrays via electrochemically controlled one-step synthesis towards high-performance semi-solid-state supercapacitor

Bimetallic selenides with nanostructures have attracted widespread interest to improve the electrochemical properties of supercapacitors due to their intrinsic properties such as high energy storage capacity, stability, and reliability. Herein, we report the novel synthesis of binder-free pinecone-like nanostructure arrays of Ni2MnSe4 on nickel foam via a facile electrodeposition technique. The electrode materials with various stoichiometric ratios of Ni:Mn as NixMn3-xSe4 (x = 1, 2, and 2.5) are synthesized to study the effect on their surface morphology and electrochemical properties. Ni2MnSe4 is optimized with pinecone-like structure arrays formed by intraconnected rough nanosheets (two-dimensional structure) with interconnected microstructures (pinecone structure), which further offers continuous channels for rapid electron/ion transfer and accelerates the diffusion kinetics of the counter ions, thus leading to improved capacitive property of the electrode material. The as-prepared Ni2MnSe4 electrode exhibits the areal capacitance value of 2160 mF cm−2 at 4 mA cm−2 with superior cycling stability (92 % of capacitance retention over 10,000 cycles). Additionally, the Ni2MnSe4 is utilized as a positive electrode for a semi-solid-state hybrid supercapacitor device (SHSC). The assembled SHSC delivers the energy and power density values of 0.15 mWh cm−2 and 15.51 mW cm−2, respectively with excellent prolonged cycling stability.

An in-Situ Study of the Transformation of Hybrid Layered Hydroxides into Metallic Nanocomposites with Interest in Energy Storage Systems

The high increase of energy demand in recent decade and the necessity of reduce the fossil fuel consumption have triggered the interest of the scientific community in the search of 'green' alternatives. Due to the characteristic intermittence of solar and wind technologies, there is a huge effort on the development energy storage systems. Among them hybrid capacitors (HCs) are promising systems due its high energy and power density values, in comparison with Li-ion batteries, that make them ideal for industrial and automobile applications. Battery-like materials such as nanocomposites (NCs) based on metallic nanoparticles (working as pseudo-capacitor based in redox reactions) with a carbon matrix (working as electric double layer capacitors) are key HCs systems itself. These NCs exhibits a notorious enhancement on their electrochemical performance by applying an external magnetic field. [1] Typically, NCs are obtained by the thermal decomposition of hybrid materials under inert atmosphere, as it has been demonstrated for the case of layered double hydroxides (LDHs), layered hydroxides (α-LHs) and metal organic frameworks (MOFs). [1-3] However, there is a lack of information in terms how the thermal transformation takes places.In this work, we present for the first-time an in-situ study about the transformation of hybrid layered hydroxides into NCs. For that, synchrotron measurements of X-ray absorption spectroscopy (XAS) and powder X-ray diffraction (PXRD) are performed for different hybrid layered hydroxides to follow the transformation in terms of oxidation state and crystallinity. These hybrid layered hydroxides will variate on: (i) the layered hydroxide structure and the anion-layer interactions (LDHs vs α-LHs + electrostatic vs covalent), (ii) the cation nature, and (iii) the identity of the organic linkers, to name a few. For instance, in the case of α-LHs, while the LHs structure defines the thermal decomposition, and the organic molecule length controls the quality and quantity of the final carbon matrix at the NCs.[4] Interestingly, in function of the amount of carbon present on the organic molecule, the oxidation state and the formation of the carbon matrix on the final material are conditioned, which imply that there is a minimum amount of carbon to obtain the NCs. In the other hand, for the previous NCs obtained, the electrochemical characterization is performed in pouch cells, applying an external magnetic field throughout the galvanostatic cycles. This assembly prevents the loss of material along the time and during the process, where it is evidenced how the magnetic field improves the electrochemical performance with an increase in the specific capacity of the NCs. In overall, this work introduces fundamental knowledge on the rational design of hybrid layered hydroxides and the subsequent nanocomposites and its performance in energy storage systems.

(Invited) Recent Advances in Thermally Regenerative Batteries: A New Approach for Generating Electrical Power from Low-Grade Heat

Thermally regenerative flow batteries (TRBs) seek to tap into the unused terawatt-hours of low-grade heat that are currently being expelled from industrial plants and stationary power sources each year. Unlike typical flow batteries, TRBs can be recharged using thermal energy, therefore increasing grid efficiency by using an energy stream that is already widely available. This unique feature is accomplished through a thermally recoverable energy carrier that, when added or removed from an electrolyte, dramatically alters the standard electrode potential of an electrode reaction. To date, most TRBs use ammonia as the energy carrier, which lowers the standard electrode potential of their anode reaction by complexing with transition metal ions such as copper, silver, or zinc. Despite the early successes of TRBs relative to other emerging electrochemical technologies trying to harness low-grade thermal energy sources, they still lacked the energy efficiency and power densities needed to be economically viable. The first iterations of TRBs had peak power densities up to 3 mW cm-2 with competitive theoretical energy efficiencies (up to 1 %), but they suffered from extreme coulombic efficiency issues that limited realizable energy production values. Herein, we will discuss recent changes that have greatly improved the performance possible from these systems and discuss persistent challenges that remain to be solved. Coulombic inefficiencies were resolved by replacing unstable deposition-based reactions with all-aqueous alternatives that provided larger cell potentials and coulombic efficiencies for single metal and bimetallic-TRB systems. Electrolyte composition, operating temperature, and membrane transport all strongly influenced energy efficiency and power density limits from these new electrolyte chemistries. Peak power densities up to 100 mW cm-2 and theoretical energy efficiencies up to 12 % were identified through a preliminary survey of possible design choices. However, tradeoffs between attainable power density and energy efficiency limited cell performance values to a fraction of these values. Future work to better control diffusive transport without conductivity losses will be crucial for approaching theoretical battery performance limits.

Novel microporous manganese phosphonate-derived metal oxides as prospective cathode materials for superior flexible asymmetric micro-supercapacitor device

Developing high-power supercapacitors is tremendously relevant to the current energy demand and implementation of renewable energy storage. The template-free microporous organic-inorganic hybrid material manganese phosphonate (MnPIm) and their derivatives heteroatom doped manganese oxides (NP/MnO2500, NP/MnO2700, NP/MnO2900) are synthesized under hydrothermal condition and following the pyrolysis at different temperatures. Due to heteroatoms doped on material, a significant synergistic effect enhances the electrochemical performance in supercapacitor applications. The unique globular morphology with a hollow structure of materials possesses a high surface area, leading to extraordinary specific capacitance. Among these, NP/MnO2700 electrode material displays the superior specific capacitance value of 1362 F g−1 at 1 mV s−1 in three-electrode assembly with 99.6 % retention of its initial capacitance up to the 2000th cycle. It demonstrates the exceptional specific capacitance of 263 F g−1 in two electrode asymmetric device with an energy density of 72.6 Wh kg−1 at the power density of 1306 W kg−1. The NP/MnO2700 material is used to fabricate a flexible asymmetric micro-supercapacitor device (MSC) with an areal capacitance of 32.8 mF cm−2. The energy density of MSC is estimated to be 18.2 μWh cm−2 at the power density value of 65.6 μW cm−2 with 84.2 % retention up to the 5000th cycle.

Electrochemical supercapacitor based on polyaniline/bismuth-doped zinc oxide (PANI/Bi–ZnO) composite for efficient energy storage

The performance of high-rate supercapacitors is greatly controlled by the electrical and morphological properties of electrodes. Owing to its unique behavior, polyaniline (PANI) is considered one of the best materials for storing energy. This study emphasizes the fabrication of PANI and PANI/bismuth-doped zinc oxide (PANI/Bi–ZnO) as electrode materials for high-efficiency supercapacitors. The pure PANI and its composite were synthesized through inverse emulsion polymerization and investigated for structural and morphological characterization using UV/Vis spectroscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. These characterization techniques showed that the fabricated materials were suitable for supercapacitor electrodes with improved structural, thermal, and morphological properties. Electrochemical impedance spectroscopy, galvanostatic charging–discharging, and cyclic voltammetry were used to investigate the electrochemical properties. The PANI-based electrode showed ∼564.23 F/g charge storage capacity with ∼60% of capacitance retention, which correspondingly increased to ∼914.05 F/g and ∼88% in PANI/Bi–ZnO composite even after 10,000 charge–discharge cycles. The PANI/Bi–ZnO composite also displayed remarkably high energy density (∼2189.90 Wh/kg) and power density (∼38480.42 W/kg) values. The fabricated electrode is expected to have a large capacity for storing energy and power in commercial electrochemical electrodes.

Influence of the Electrode Deposition Method of Graphene-Based Catalyst Inks for ADEFC on Performance.

The utilization of graphene as a catalyst support has garnered significant attention due to its potential for enhancing fuel cell performance. However, a critical challenge in electrode production still lies in the electrode preparation technologies and the restacking of graphene sheets, which can greatly impact the fuel cell performance alongside with catalyst development. This study aimed to investigate the impact of different electrode deposition methods for N-rGO-based catalyst inks on catalyst layer morphology, with a specific focus on graphene sheet orientation and its influence on the performance of alkaline direct ethanol fuel cells (ADEFCs). The dispersion behavior and ink stability of the catalysts were assessed using ultraviolet-visible light (UV-vis), ζ potential, and dynamic light scattering techniques. The morphology and physical properties of the gas diffusion electrodes (GDEs) were analyzed through Brunauer-Emmett-Teller measurements, contact angle measurements and scanning electron microscopy (SEM) combined with energy-dispersive spectroscopy. The electrochemical behavior was evaluated both ex-situ, utilizing half-cell GDE measurements, and in situ, through single-cell tests. The N-rGO-based membrane electrode assembly, comprising Pt-free catalysts and a biobased membrane, exhibited outstanding performance in ADEFCs, as evidenced by high maximum power density values and long-term durability. The N-rGO-based membrane electrode assembly has demonstrated remarkable potential for high-performance fuel cells, presenting an exciting avenue for further exploration.

Multifunctional electrochromic hybrid PANI@WO3 core-shell for energy generation and storage

Materials that can be deposited easily and shows multifunctional application are always in demand. Two technologically important materials, polyaniline (PANI) and tungsten trioxide (WO3) have been amalgamated using an uncommon, yet simple, technique of deposition, chronoamperometry to obtain a hybrid core-shell structure and its application in three different areas of electrochromic display, electrocatalysis and energy storage has been investigated. Electrodepositing WO3 and PANI onto highly conducting substrates one on top of other, resulted in formation of PANI (shell), WO3 (Core) (PANI@WO3) electrode resulting in a highly uniform fibrous surface structure. Electrochemistry performed using the conventional three electrode step up suggested a very good charge storing capacity, stability also indicating a pseudo capacitive nature which was later confirmed with the help of Nyquist plot. Besides very good values of areal capacitance (855 mF/cm2), power density (6.5 kW/cm2) and energy density (1.09 kWh/cm2) established its supercapacitive performance. Next, its behaviour as an electrocatalyst was studied by duly plotting polarisation curves and their corresponding Tafel plots. The PANI@WO3 electrode deposited on a transparent electrode exhibited green-blue-yellow-transparent color switching under different bias conditions with a very small voltage of 0.5 V. A fast switching of 0.4 s and a great color contrast of ∼50 % in visible as well IR region were displayed making the electrochemically deposited core-shell a good candidate for multifunctional application in energy generation, storage with an inerrability with smart electrochromic windows.

Flexible interdigitated symmetric solid-state micro-supercapacitors with higher energy density for wearable electronics

Planar interdigitated solid-state supercapacitors are one of the most promising energy storage devices as they offer the merit of fast ionic transportation with minimal charge transfer resistance due to the narrow gap between the interdigitated isolated electrode fingers. This study focuses on fabricating flexible symmetric solid-state supercapacitor devices with high energy and power densities. Specifically, a symmetric SnO2‖PVA-LiClO4‖SnO2 solid-state supercapacitor (SSC) device was fabricated using the electron beam evaporation (e-beam) technique on thin, flexible electrodes in interdigitated (ISSC) and stacked (SSSC) configurations and their electrochemical performances were compared. The ISSC exhibiting pseudo-capacitive behavior achieved a maximum volumetric capacitance of 439.5 F cm−3 at a scan rate of 5 mV S−1. Quantitative calculation of the device's charge storage dynamics reveals that the diffusion-limited Lithium insertion processes predominantly contribute to the capacitance of ISSC. Comparatively, the ISSC outperformed the SSSC with a diffusion coefficient of 2.55 × 10−13 m2s−1 and ac conductivity of 2.2 × 10−2 S m−1, demonstrating excellent energy density and power density values. Furthermore, the ISSC with no adverse effect on its capacitance even when bent at various angles suggesting its suitability for flexible wearable electronic devices.

Characterization of thin metal‐supported solid oxide fuel cells fabricated through atmospheric Plasma spraying

AbstractIn this study, thin molybdenum‐containing, nickel‐based metal‐supported solid oxide fuel cells (MS‐SOFCs) were fabricated through atmospheric plasma spraying and then characterized. We investigated the change in cell performance associated with the reduction of the Ni–Mo support layer thickness from 200 to 80 µm and reduction of the substrate sintering temperature from 1200 to 1000°C. At a cell voltage of 0.6 V, the measured maximum power density values of a 50 × 50 mm2 MS‐SOFC were 313, 581, 890, and 1098 mW cm−2 at 600, 650, 700, and 750°C, respectively. A 100 × 100 mm2 (commercial‐size) MS‐SOFC and an assembled single‐cell MS‐SOFC stack exhibited electric output power values of approximately 33 and 39 W at 700 and 750°C, respectively, and an effective electrode area of 81 cm2. In a long‐term stability test, the commercial‐size cell and single‐cell stack exhibited a degradation rate of approximately 1% after 1000 h of operation at a current density of 250–300 mA cm−2 and temperature of 700°C. Moreover, a five‐cell MS‐SOFC stack demonstrated a stack power of 180.85 W at 3.792 V (446.5 mW cm−2 at 0.758 V) and 750°C.

3D Printing-Enabled Design and Manufacturing Strategies for Batteries: A Review.

Lithium-ion batteries (LIBs) have significantly impacted the daily lives, finding broad applications in various industries such as consumer electronics, electric vehicles, medical devices, aerospace, and power tools. However, they still face issues (i.e., safety due to dendrite propagation, manufacturing cost, random porosities, and basic & planar geometries) that hinder their widespread applications as the demand for LIBs rapidly increases in all sectors due to their high energy and power density values compared to other batteries. Additive manufacturing (AM) is a promising technique for creating precise and programmable structures in energy storage devices. This review first summarizes light, filament, powder, and jetting-based 3D printing methods with the status on current trends and limitations for each AM technology. The paper also delves into 3D printing-enabled electrodes (both anodes and cathodes) and solid-state electrolytes for LIBs, emphasizing the current state-of-the-art materials, manufacturing methods, and properties/performance. Additionally, the current challenges in the AM for electrochemical energy storage (EES) applications, including limited materials, low processing precision, codesign/comanufacturing concepts for complete battery printing, machine learning (ML)/artificial intelligence (AI) for processing optimization and data analysis, environmental risks, and the potential of 4D printing in advanced battery applications, are also presented.

Preliminary Study of Bioelectricity Generation Using Lettuce Waste as Substrate by Microbial Fuel Cells

Agricultural waste negatively impacts the environment and generates economic difficulties for agro-industrial companies and farmers. As a result, it is necessary for an eco-friendly and sustainable alternative to managing this type of waste. Therefore, the research aimed to investigate lettuce waste as an alternative substrate to generate bioelectricity in single-chamber microbial fuel cells (scMFCs). It was possible to report voltage and electric current peaks of 0.959 ± 0.026 V and 5.697 ± 0.065 mA on the fourteenth day, values that were attained with an optimum pH of 7.867 ± 0.147 and with an electrical conductivity of 118.964 ± 8.888 mS/cm. Moreover, as time passed the values began to decline slowly. The calculated value of maximum power density was 378.145 ± 5.417 mW/cm2 whose current density was 5.965 A/cm2, while the internal resistance reported using Ohm’s Law was 87.594 ± 6.226 Ω. Finally, it was possible to identify the Stenotrophomonas maltophilia bacterium (99.59%) on a molecular scale, as one of the microorganisms present in the anodic biofilm. The three microbial fuel cells were connected in series and demonstrated that they were capable of lighting an LED bulb, with a voltage of 2.18 V.

Nickel oxyhydroxide/zinc hydroxide/rGO as a promising candidate for hybrid energy storage and clean energy generation

AbstractMetal hydroxides are the upcoming materials in the field of energy storage applications. In this work, a mixed metal hydroxide‐based carbon composite, that is, nickel oxyhydroxide/zinc hydroxide/rGO, was successfully synthesized through single step hydrothermal process. The synthesized material was thoroughly characterized using x‐ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy and field emission scanning electron microscopy. Detailed electrochemical analysis was performed through cyclic voltammetry, constant current charge‐discharge analysis and electrochemical impedance spectroscopy. The material exhibited impressive values of specific capacitance (541 F/g), energy density (75 Wh/kg) and power density (2592 W/kg). The electrodes were found to be sufficiently robust and reliable. A symmetric storage device was also fabricated using the synthesized composite followed by thorough electrochemical analyses of the same. A flexible piezoelectric nanogenerator was fabricated by impregnating the polymer PVDF with the synthesized composite that yielded an open circuit voltage of ~50 V and power density of 3117 W/m3. This opens up the possibilities of using the developed material in real life applications.

Prediction of electromagnetic power density emitted from GSM base stations by using multiple linear regression

Today, smart phones based on different mobile communication technologies such as GSM, GPRS/EDGE, 3G, 4G, 5G and 6G have become an indispensable element for various services such as communication, entertainment, and banking. In this context, determining the base station power level is important in terms of limit values and public health, especially in places with high power density. In this study, electromagnetic power density of 31 different base stations was measured at 900 MHz frequency at 20, 40 and 60 meters distances from base stations. Since it is practically not possible to measure each base station from every distance, 3 different distances were chosen randomly. Then, using the power density values measured from different distances, electromagnetic power density estimation was made with multiple linear regression (MLR) analysis method for distances at intermediate distances (25, 30, 35, 45, 50 and 55 meters). In this study, MLR analysis method was applied for power density estimation for the first time in the literature and adjusted R-square value above 0.99 was obtained for each intermediate distance.

Comparison of the Electrochemical Performances of Solid Oxide Fuel Cells with Sputtered Thin Barrier Layers Fueled by Hydrogen or Ammonia

We investigated the influence of a fuel change from pure hydrogen to a hydrogen–ammonia mixture at different percentages on the electrochemical behavior of 50 mm in diameter Solid Oxide Fuel Cells (SOFCs) with sputtered thin buffer layers of Gd-doped ceria, varying the working temperatures from 800 °C to 650 °C. The results show that the performances of the cells are not affected by the fuel change for high working temperatures (800 °C and 750 °C). As an example, a power density value of 802 mW∙cm−2 at 1 A∙cm−2 is found when directly feeding the cell with 8 NmL∙min−1cm−2 of ammonia and with an equivalent flowrate of 12 NmL∙min−1cm−2 of H2. These power density output values are higher than those obtained in industrial state-of-art (SoA) SOFCs with screen-printed buffer layers fed with equivalent hydrogen flowrates, thanks to the improved electrochemical performances obtained in the case of cells with sputtered thin buffer layers of Gd-doped ceria. At lower working temperatures (700 °C and 650 °C), slight changes in the electrochemical behavior of the cells are observed. Nevertheless, in this temperature range, we also obtain an output current density value of 0.54 A∙cm−2 in a pure ammonia flowrate of 12 NmL min−1cm−2 at 800 mV and 700 °C, equal to the value observed in SoA button cells with industrial screen-printed GDC barrier layer fueled with 16 NmL∙min−1cm−2 of H2. These results pave the way towards the use of innovative SOFC structures with sputtered thin buffer layers fueled by ammonia.

Designing of manganese-based oxides and oxyhydroxides as positive electrode materials and activated carbon from Phyllanthus emblica as negative electrode material for battery type supercapacitor

Effective energy storage and prompt energy discharge using better catalysts is the cornerstone for clean energy-based applications. Manganese based materials is an abundant, environmentally friendly and low-cost catalyst for supercapacitor applications. In this work, three manganese based systems (β-MnO2, γ-MnOOH and Mn3O4) were synthesised by hydrotermal method. The ability of manganese to interchage it oxidation state through electron transfer reactions made manganese based systems become one of the prominent cathode material for supercapaciter applications. The supercapacitor studies were carried out using Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) analysis. In this work Mn3O4 showed better charge transfer resistence and specific capacity (597 C/g) compared to β-MnO2 and γ-MnOOH. The high surface area (1189.14 m2/g) activated carbon prepared in-house from Phyllanthus emblica was used as negative electrode and Mn3O4 as positive electrode in device fabrication. The cycling stability study of the fabricated device reveals 92% capacity retention after 5000 cycles at 100 mV/s. The Power density value of 800 W/kg and the energy density of 4 W/kg was achieved at a current density 1 A/g.

Supercapacitance performance of novel core/shell poly(m-toluidine)/(Co-Ni) nanoplatelets/nanoneedles nanocomposite

Poly(m-toluidine) (PmT) is a promising polymer material for many applications due to its high electrical conductivity, stability, and ease of synthesis. This work uses PmT/(Co-Ni) nanoplatelets/nanoneedles core/shell composite as an electrode for designing a high-performance supercapacitor. Firstly, nanoneedles of basic Co-Ni compounds composed of cobalt nickel oxide [CNO; Co1.29Ni1.71O4] and cobalt carbonate hydroxide hydrate [CCHH; Co(CO3)0.5(OH)0·.11H2O] were prepared via hydrothermal process. Then, the poly(m-toluidin) [PmT; C7H9N] nanoplatelets were grown on the (Co-Ni) nanoneedles by the in-situ oxidation polymerization method. The elemental composition, crystal structure, and morphology of the PmT/(Co-Ni) electrode were characterized by physicochemical characterization techniques. The supercapacitance performance of the PmT/(Co-Ni) electrode was measured by using cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy in HCl solution. The results show that the specific capacitance of the PmT/(Co-Ni) electrode was measured at a current density of 0.6 A/g reaching 308F/g. while the values of specific power density and specific energy are 720 W/kg and 15.4 W h/kg, respectively. Moreover, the PmT/(Co-Ni) electrode exhibits long-term stability and retained about 98% of its starting capacitance value after thousand cycles. The remarkable electrochemical execution recorded could be ascribed to unique nanoplatelets/nanoneedles architectures and conductive PmT polymer. These encouraging results refer to good performance and high stability of the PmT/(Co-Ni) electrode for potential application in energy storage devices.

Enhancing the Performance of Cobalt‐based Oxide Electrode Material for Asymmetric Supercapacitor Devices

AbstractSupercapattery is an energy storage device which shows high power and energy densities compared to supercapacitors and batteries. A simple and cost‐effective sol‐gel method was used to synthesize the aluminium‐doped cobalt oxide (Al‐Co3O4). The structural, morphological and composition analyses were investigated using X‐ray diffraction (XRD), scanning electron microscopy (SEM), and X‐ray photoelectron spectroscopy (XPS). Further, Brunauer‐Emmett‐Teller (BET) calculations were performed, which showed an enhancement in surface area. The specific capacity of the Al‐doped sample was increased up to 708 C/g compared to the reference sample (Co3O4=420 C/g). A supercapattery device was designed by using the activated carbon as a negative electrode and the Al‐Co3O4 as the positive electrode in two electrode assemblies. The estimated value of the specific capacity of Al‐Co3O4 was 189 C/g. Furthermore, the obtained energy and power density values were 42 Wh/kg and 2080 W/kg, respectively. To investigate the stability, this device was subjected to 5000 charging/discharging cycles that maintained 90 % of its initial capacity. Our findings provide a foundation for improving the performance of energy storage devices.

Can graphite oxide active material achieve commercial supercapacitor level energy and power densities? Binder free coating and WIS electrolyte strategies

Unlike carbon materials such as graphene, reduced graphite/graphene oxide, activated carbon, etc., graphite oxide (GO) is not considered to be a potent active material for energy storage applications. This study proposes a sustainable approach for developing high energy and power density supercapacitors using graphite oxide (GO) active material, viz., binder free coating and water in salt (WIS) electrolyte. The use of 17 m NaClO4 WIS electrolyte ensures an electrochemical stability window of 2.5 V, which surpasses the thermodynamic limit of water electrolysis. In three electrode configuration, the binder free Ni@GO electrode achieved an energy density of 31.2 Wh/kg and a power density of 625 W/kg, with excellent cycle stability of 133.3 % after 1000 charge-discharge cycles. Energy and power densities of Ni@GO electrodes in aqueous electrolytes viz., 6 M KOH (1.5 Wh/kg and 137 W/kg) and 1 M Na2SO4 (12.6 Wh/kg and 349 W/kg) were significantly lower than those in WIS electrolytes. The GO/17 m NaClO4 WIS symmetric supercapacitor achieved energy and power density values of 24 Wh/kg and 1250 W/kg at 0.5 A/g, with 100 % retention of cycle stability after 10,000 charge-discharge cycles. The energy density values achieved through this strategy of binder-free GO/WIS based supercapacitors are consistent with the range reported for other carbon materials, including activated carbon, carbon nanotubes, and reduced graphene oxide. This suggests that the approach has significant potential for developing high-energy-density supercapacitors using GO, which could have practical applications in a variety of fields.