Superior Capacitive Performance Research Articles

Scalable Dual In Situ Synthesis of Polyester Nanocomposites for High-Energy Storage.

Incorporating ultralow loading of nanoparticles into polymers has realized increases in dielectric constant and breakdown strength for excellent energy storage. However, there are still a series of tough issues to be dealt with, such as organic solvent uses, which face enormous challenges in scalable preparation. Here, a new strategy of dual in situ synthesis is proposed, namely polymerization of polyethylene terephthalate (PET) synchronizes with growth of calcium borate nanoparticles, making polyester nanocomposites from monomers directly. Importantly, this route is free of organic solvents and surface modification of nanoparticles, which is readily accessible to scalable synthesis of polyester nanocomposites. Meanwhile, uniform dispersion of as ultralow as 0.1 wt% nanoparticles and intense bonding at interfaces have been observed. Furthermore, the PET-based nanocomposite displays obvious increases in both dielectric constant and breakdown strength as compared to the neat PET. Its maximum discharged energy density reaches 15 J cm-3 at 690 MV m-1 and power density attains 218 MW cm-3 under 150 Ω resistance at 300 MV m-1, which is far superior to the current dielectric polymers that can be produced at large scales. This work presents a scalable, safe, low-cost, and environment-friendly route toward polymer nanocomposites with superior capacitive performance.

Ionic thermoelectricity of salt-free PVA-hydrogel

As polyvinyl alcohol (PVA) hydrogels have shown a high potential as an ionic thermoelectric generator, this paper aims to study the thermoelectric (TE) power of salt-free PVA hydrogel. Ionic thermoelectric performance, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) are measured at different relative humidities. Findings show that salt-free PVA hydrogels can achieve a relatively high Seebeck (9.26 mV K−1) using only surrounding moisture. Hydrogels with low PVA content have a more stable TE output than hydrogels with high PVA content in high relative humidity conditions. Embedded Ni-foam-CNT electrodes stabilize performance, reduce noise, and provide superior capacitance, resistance, and thermoelectric performance over direct drop-casting of CNT on hydrogels. Recommended operating relative humidity (RH) ranges between 40 % and 60 %, while recommended PVA content ranges from 10 % to 15 % mass ratio of PVA in water. The results pave the way for using PVA hydrogels as thermoelectric devices in biocompatible applications.

Understanding Electrolyte Ion Size Effects on the Performance of Conducting Metal-Organic Framework Supercapacitors.

Layered metal-organic frameworks (MOFs) have emerged as promising materials for next-generation supercapacitors. Understanding how and why electrolyte ion size impacts electrochemical performance is crucial for developing improved MOF-based devices. To address this, we investigate the energy storage performance of Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with a series of 1 M tetraalkylammonium tetrafluoroborate (TAABF4) electrolytes with different cation sizes. Three-electrode experiments show that Cu3(HHTP)2 exhibits an asymmetric charging response with all ion sizes, with higher energy storage upon positive charging and a greater charging asymmetry with larger TAA+ cations. The results further show that smaller TAA+ cations demonstrate superior capacitive performances upon both positive and negative charging compared to larger TAA+ cations. To gain further insights, electrochemical quartz crystal microbalance measurements were performed to probe ion electrosorption during charging and discharging. These reveal that Cu3(HHTP)2 has a cation-dominated charging mechanism, but interestingly indicate that the solvent also participates in the charging process with larger cations. Overall, the results of this study suggest that larger TAA+ cations saturate the pores of the Cu3(HHTP)2-based electrodes. This leads to more asymmetric charging behavior and forces solvent molecules to play a role in the charge storage mechanism. These findings significantly enhance our understanding of ion electrosorption in layered MOFs, and they will guide the design of improved MOF-based supercapacitors.

A novel Co9S8–MoS2 nanosheet arrays@HCSs with superior capacitive and cycling performance for hybrid supercapacitor

Due to high conductivity and electrochemical activity, transition metal sulfides and their complexes have emerged as attractive electrode materials for supercapacitors. Herein, heterostructures of Co9S8–MoS2 nanosheet arrays on the hollow carbon spheres (HCSs) with yolk-shell structure (Co9S8–MoS2 NSAs@HCSs) are synthesized by a hydrothermal method and in-situ sulfurization of silicates. This core-shell structure can effectively improve the conductivity and reaction kinetics, resulting in a notable improvement in the cycling and capacity properties. The Co9S8–MoS2 NSA@HCSs electrode has an outstanding cycle stability (96.9 %) after 10, 000 cycles at 10 A g−1 and a high specific capacity of 804C g−1 at 1 A g−1. The effects of solution concentration and sulfurization time on the microstructures and electrochemical properties of the electrode are also investigated. Furthermore, the hybrid supercapacitor (HSC) is assembled with Co9S8–MoS2 NSA@HCSs (positive electrode) and HCSs (negative electrode). Additionally, the HSC delivers 98.2 % of cycling stability after 10, 000 cycles at 10 A g−1. The energy density of 45.6 Wh kg−1 can be obtained at the power density of 770.4 W kg−1.

Effect of carbonization temperatures on the synthesis of biocarbon from Borassus flabellifer fruit fiber for capacitive energy storage

AbstractBorassus flabellifer (Palmyra) fruit fiber (PFF) was extracted and converted into biocarbon materials at different carbonization temperatures of 400°C, 600°C, and 800°C under N2 atmosphere for 1 h. The physicochemical properties of obtained biocarbon materials were investigated via CHNS, SEM‐EDX, FTIR, RAMAN, XRD, BET‐specific surface area, and TGA techniques. The obtained results were correlated with the capacitive energy storage application of biocarbon materials. The highest specific surface area of 46.36 m2 g−1 was observed for the biocarbon materials obtained at 800°C, which also showed superior capacitive performances. The specific capacitances of PFF‐derived biocarbon materials obtained at 400°C, 600°C, and 800°C are respectively found to be 28.58, 37.07, and 45.76 F g−1 at 1 A g−1 employing 1M KOH as electrolyte. The biocarbon materials obtained at 800°C showed the highest specific energy and power of 1.99 and 261 W kg−1 at 1 A g−1.

Co-sputtering construction of Gd-doped WO3 nano-stalagmites film for bi-funcional electrochromic and energy storage applications

Gd-doped WO3 nano-stalagmites (GW-NSs) film has been successfully prepared on indium-doped tin oxide (ITO)-coated glass substrates by co-sputtering deposition. Gd dopants can facilitate the vertically-aligned growth of WO3 nano-stalagmites on the WO3-nanoparticle seed layer. The microstructure analysis shows that the GW-NSs film with optimized aspect ratio and array density is fabricated with Gd/W = 0.6 % in atomic ratio. Such GW-NSs electrode (active area: 1 × 1.5 cm2) exhibits large transmittance modulation (ΔT = 52.7 % at 633 nm), high coloration efficiency (87.3 cm2 C−1 at 633 nm), fast switching speed (5.9/13.1 s for coloration/bleaching), large diffusion coefficient (9.52 × 10−10 cm2 s−1) and long-term cycling stability (>2000) under an applied voltage of ± 1.0 V, which can be attributed to a shorten Li+ diffusion distance and a large-area contact with the electrolyte. Importantly, the GW-NSs film also shows superior capacitive performance (calculated areal capacitance of 8.44 mF cm−2 at 0.4 mA cm−2) and long-term cyclic stability (capacitance retention rate is 87.4 % after 2000 cycles). Furthermore, we fabricated the bifunctional smart window device combined with NiO counterpart electrode, which has the ability to visually monitor the level of stored energy from rapid and reversible coloration, indicating the potential applications of GW-NSs in both electrochromic and energy-storage fields.

Electron-interactive 1D porous vertical NiCo2O4 nanowire and 3D N-doped graphene aerogel enable high hydroxyl-ion adsorption capacity for superior energy storage

Supercapacitors are a kind of highly efficient energy-storage device with long cycle life and high power density, however, their specific capacitance is insufficient for further application and development. In this work, a novel composite with one-dimensional (1D) NiCo2O4 nanowire arrays (NiCo2O4-NWA) vertically supported on three-dimensional (3D) nitrogen-doped graphene aerogel (NGA) is designed and facilely realized by hydrothermal reaction and thermal treatment. The NiCo2O4 nanowires, with length of ∼1 μm and diameter of ∼25 nm, display a porous structure and are regularly arranged on both sides of the sheets in nitrogen-doped graphene aerogel. The aerogel-supporting NiCo2O4 nanowires demonstrate a remarkably high specific capacitance of 2742 F g−1 at 1 A g−1, and an outstanding cyclic stability with capacitance retention of 90% even after 10,000 cycles at 80 A g−1. The density functional theory calculation shows the narrow band gap (0.32 eV) and strong electronic interaction and hydroxyl-ion adsorption effect of NiCo2O4 supported on NGA, resulting in superior specific capacitance and energy storage performance. The 3D nitrogen-doped graphene aerogel supporting 1D nanowire arrays represent a promising high-performance electrode material for application in the supercapacitors and other electrochemical energy-conversion and storage equipment.

The optimal micro- and meso-pores oriented development of Eucommia ulmoides oliver wood derived activated carbons for capacitive performance

The optimization of pore characteristics is of pivotal importance for enhancing the capacitive performance of activated carbons (ACs) in supercapacitor applications. This study delved into the impact of porous structures, developed through varying activation temperatures (350–850 ֩C), on capacitive performance of wood derived activated carbons (ACs). Our findings revealed that AC350, possessing the highest micropore surface area (Smicro) of 903.38 m2 g-1 and a micropore volume (Vmicro) of 0.43 cm3g-1, exhibited the lowest specific capacitance (SC) of 13 Fg-1. This suggests that a higher SC is not significantly associated with a greater quantity of micropores. Conversely, AC850, with a peak Smeso of 1472.89 m2 g-1 and Vmeso of 1.24 cm3g-1, demonstrate a SC of only 83 Fg-1, indicating that the higher SC is not significantly correlated with an increased amount of mesopores either. However, AC650 displayed an optimal SC of 123 Fg-1, with an ideal Smeso/Smicro ratio of 2.16 and Vmeso/Vmicro ratio of 5.50. This underscores that the superior capacitive performance of ACs based electrode materials is intricately linked to an effective amalgamation of micro- and meso-pores. By strategically manipulating the pore composite structure to augment the charge storage capability of activated carbon electrode materials, we can enhance the energy density of capacitors. This advancement is poised to further propel the application of biomass-derived activated carbon and its composite capacitor technology in energy storage domains.

Superior Cyclic Stability and Capacitive Performance of Cation- and Water Molecule-Preintercalated δ-MnO2/h-WO3 Nanostructures as Supercapacitor Electrodes.

The large number of active sites in the layered structure of δ-MnO2 with considerable interlayer spacing makes it an excellent candidate for ion storage. Unfortunately, the δ-MnO2-based electrode has not yet attained the exceptional storage potential that it should demonstrate because of disappointing structural deterioration during periodic charging and discharging. Here, we represent that stable Na ion storage in δ-MnO2 may be triggered by the preintercalation of K ions and water molecules. Furthermore, the sluggish reaction kinetics and poor electrical conductivity of preintercalated δ-MnO2 layers are overcome by the incorporation of h-WO3 in the preintercalated δ-MnO2 to form novel composite electrodes. The composites contain mixed valence metals, which provide a great number of active sites along with improved redox activity, while maintaining a fast ion transfer efficiency to enhance the pseudocapacitance performance. Based on our research, the composite prepared from preintercalated δ-MnO2 with 5 wt % h-WO3 provides a specific capacitance of up to 363.8 F g-1 at a current density of 1.5 A g-1 and an improved energy density (32.3 W h kg-1) along with an ∼14% increase in capacity upon cycling up to 5000 cycles. Hence, the interaction between the preintercalated δ-MnO2 and h-WO3 nanorods results in satisfactory energy storage performance due to the defect-rich structure, high conductivity, superior stability, and lower charge transfer resistance. This research has the potential to pave the way for a new class of hybrid supercapacitors that could fill the energy gap between chemical batteries and ideal capacitors.

Silver-decorated SrTiO3 nanoparticles for high-performance supercapacitors and effective remediation of hazardous pollutants.

SrTiO3/Ag nanocomposites were synthesized using a facile wet impregnation method, employing rigorous experimental techniques for comprehensive characterization. XRD, FTIR, UV, PL, FESEM, and HRTEM were meticulously utilized to elucidate their structural, functional, morphological, and optical properties. The electrochemical performance of the SrTiO3/Ag nanocomposite was rigorously assessed, revealing an impressive specific capacitance of 850 F/g at a current density of 1A. Furthermore, the photocatalytic activity of the SrTiO3/Ag nanocomposite was rigorously examined using methylene blue (MB) dye, and the results were outstanding. After 120min of UV irradiation, the nanocomposite exhibited an exceptional MB dye degradation efficiency exceeding 88%. The SrTiO3/Ag nanocomposite represents an exemplary catalyst in terms of efficiency, cost-effectiveness, environmental compatibility, and reusability. The electron and superoxide radicals play a chief role in the MB dye degradation process. The inclusion of Ag within the SrTiO3 matrix facilitated the formation of a conductive nano-network, ultimately resulting in superior capacitive and photocatalytic performance.

Rational design of electrochemical energy storage and thermal energy storage double network aerogel for in-situ temperature regulation of supercapacitors

During the charging/discharging process, a large amount of heat is constantly generated inside the supercapacitor. Therefore, thermal management of supercapacitors is crucial. In this work, a calcium alginate/polyaniline/polyethylene glycol (CA/PANI/PEG) double network multifunctional aerogels were prepared for thermal energy storage and electrochemical energy storage Due to the strong hydrogen bonding between PANI and CA and ionic cross-linking between CA molecular chains, the CA/PANI double network structure can be used to solidify PEG. CA/PANI/PEG aerogels can form stable porous network structures with excellent properties. For example, due to the in-situ thermal management of CA/PANI/PEG, CA/PANI/PEG exhibits a higher specific capacitance than the traditional PANI-based electrode at 55 °C. More importantly, the CA/PANI/PEG aerogel not only possessed a high enthalpy of phase transition (162.1 J/g) but also showed superior capacitive performance (175 mF/cm2 at 0.1 mA/cm2 at 55 °C). After 10,000 charge/discharge cycle tests, it can maintain 84.5 % of the initial capacitance. This study opens up a new way for the development and application of PCMs in the thermal management of supercapacitors.

Unifying and Suppressing Conduction Losses of Polymer Dielectrics for Superior High-Temperature Capacitive Energy Storage.

Superior high-temperature capacitive performance of polymer dielectrics is critical for the modern film capacitor demanded in the harsh-environment electronic and electrical systems. Unfortunately, the capacitive performance degrades rapidly at elevated temperatures owing to the exponential growth of conduction loss. The conduction loss is mainly composed of electrode and bulk-limited conduction. Herein, the contribution of surface and bulk factors is unified to conduction loss, and the loss is thoroughly suppressed. The experimental results demonstrate that the polar oxygen-containing groups on the surface of polymer dielectrics can act as the charge trap sites to immobilize the injected charges from electrode, which can in turn establish a built-in field to weaken the external electric field and augment the injection barrier height. Wide bandgap aluminum oxide (Al2 O3 ) nanoparticle fillers can serve as deep traps to constrain the transport of injected or thermally activated charges in the bulk phase. From this, at 200 °C, the discharged energy density with a discharge-charge efficiency of 90% increases by 1058.06% from 0.31 J cm-3 for pristine polyetherimide to 3.59 J cm-3 for irradiated composite film. The principle of simultaneously inhibiting the electrode and bulk-limited conduction losses could be easily extended to other polymer dielectrics for high-temperature capacitive performance.

Template-Induced Ni(OH)2 Nanosheet-Constructed Hierarchically Porous Aerogel Boosts Superior Specific Capacitance and Rate Performance for Supercapacitors

Template-Induced Ni(OH)₂ Nanosheet-Constructed Hierarchically Porous Aerogel Boosts Superior Specific Capacitance and Rate Performance for Supercapacitors

Facile synthesis of bead-chain structured MWCNTs@CeO2 with oxygen vacancies-rich for promoting electrochemical energy storage

The extraordinary properties of metal oxides (MOs) have led to their increasing recognition as a potential material for energy storage systems, along with exceptional performance enhancement. Given the inherently finite electronic conductivity exhibited by most metallic oxides, commonly employed strategies to overcome this limitation involve their integration with conducting carbon materials or the introduction of oxygen vacancies. Herein, bead-chain structured MWCNTs@CeO2 with abundant oxygen vacancies (BC MWCNTs@Ov-CeO2) was successfully synthesized by utilizing chain-like MWCNTs to string together bead-like CeO2 nanoparticles, through a facile solvothermal approach. In particular, MWCNTs are neither covalently nor non-covalently modified, substantially simplifying fabrication procedures. The incorporation of carbon nanotubes and the abundance of oxygen vacancies effectively enhance charge storage dynamics, leading to significant improvements in conductivity and electrochemical properties beyond those previously reported CeO2-based composites. BC MWCNTs@Ov-CeO2 exhibited an impressive specific capacitance of 421.1 F g−1 at 1 A/g, outperforming pure CeO2 by 286%, demonstrating its superior capacitance performance. According to various theoretical and experimental investigations, it has been firmly established that the presence of conductive networks and oxygen vacancies significantly enhances the electrochemical properties of MOs. This research emphasizes the importance of understanding oxygen vacancies in electrode materials, providing a systematic approach for the development of future energy storage devices.

Silicon-oxy-carbide intercalated three-dimensional graphene hybrid membrane for all-solid-state supercapacitors

The demand for high-performance energy storage solutions has driven research towards advanced electrode materials. In this study, a graphene-based hybrid membrane, containing intercalated silicon-oxy-carbide (SiOC), was fabricated using a novel method that combines flow-directed assembly and vapour reduction. This hybrid membrane not only enhances electrolyte transport owing to its three-dimensional network structure but also capitalises on the synergistic advantages of graphene and SiOC owing to strong coupling forces. When compared to individual graphene and SiOC, the resulting flexible all-solid-state symmetric supercapacitor device (ASSSs) demonstrated superior capacitance performance, in terms of a high power density of 8000 W·kg−1 at an energy density of 17.5 W·h·kg−1 and a high energy density of 86.8 W·h·kg−1 at 600 W·kg−1, all within a wide potential window of 0–2.0 V. This innovative methodology has far-reaching implications, offering a straightforward and efficient strategy for designing and preparing three-dimensional (3D) graphene-based membrane electrodes with potential applications in flexible energy storage devices.

2D Germanane‐MXene Heterostructures for Cations Intercalation in Energy Storage Applications

AbstractHeterostructures offer an exceptional possibility of combining individual 2D materials into a new material having altered properties compared to the parent materials. Germanane (GeH) is a 2D material with many favorable properties for energy storage and catalysis, however, its performance is hindered by its low electrical conductivity. To address the low electrochemical performance of GeH, a heterostructure of GeH and Ti3C2Tx is fabricated. The Ti3C2TX is a layered material belonging to the family of MXenes. The resulting heterostructure (GeMXene) at a defined mass ratio of GeH and Ti3C2Tx shows superior capacitive performance that surpasses that of both pristine materials. The effect of the size of cations and anions for intercalation into GeMXene in different aqueous salt solutions is studied. GeMXene allows only cation intercalation, which is evidenced by the gravimetric electrochemical quartz crystal microbalance (EQCM) technique. The capacitive performance of the GeMXene is compared in neutral, acidic, and alkaline electrolytes to determine the best electrochemical performance. This unleashes the potential use of GeMXene heterostructure in different electrolytes for supercapacitors and batteries. This work will pave the way to explore the heterostructures of other 2D materials such as novel MXenes and functionalized germanane for highly energy‐storage efficient systems, and beyond.

A green approach for synthesis of an efficient nano pebbles-like BiVO4@C electrode for supercapacitor application

A simple, sustainable, cost-effective, and environmentally benign BiVO4@C electrode is developed via an in-situ bio-mediated green SILAR approach. The optimized synthesis and electrochemical characterization of a BiVO4@C and BiVO4 electrode are reported. The in-situ incorporation of carbon in the BiVO4 (BiVO4@C) was determined by Raman, XPS, and FTIR spectroscopy. The BiVO4@C electrode demonstrates a large specific surface area (106.7 m2 g−1), higher charge storage, superior capacitive performance, longer discharge time, and excellent cycling stability when compared to BiVO4. The flexible solid-state symmetric supercapacitor (SSC) device using BiVO4@C electrode material with PVA/KOH electrolyte gel delivered maximum specific capacitance (Csp) (154.6 F g−1) and energy density of 42.0 Wh kg−1 at a power density of 571.6 W kg−1. Moreover, the symmetric device exhibited cycle stability of 5000 cycles with 97.4 % capacitance retention paving the way for developing sustainable supercapacitors for commercial application.

High capacitance performance of hierarchically SiO2 self-doped porous activated carbon derived from palm empty fruit bunches

Porous activated carbon derived from empty fruit bunch (EFB) has garnered significant attention as an electrode material for supercapacitors due to its low cost, abundance, and sustainability in real energy storage applications. However, there is still room for improvement in their performance compared to other renewable biomass resources. In our study, we successfully converted EFB biomass into porous activated carbon with outstanding performance, achieving a remarkably high specific capacitance of 459.28 F/g at 0.5 A/g, along with a moderate specific surface area (SSA) of 1215.38 m2/g. Furthermore, the quasi-solid-state supercapacitor assembled from the AC700 sample demonstrated excellent energy density, reaching 15.39 Wh/kg at a power density of 50 W/kg. Additionally, it exhibited remarkable cycling stability, with a capacitance retention of 93 % after 10,000 cycles. These exceptional results were achieved by simply adjusting the activation temperature. We utilized KOH as the activating agent and carbonized it at temperatures of 600 °C, 700 °C, and 800 °C for 2 h under an N2 atmosphere. The superior capacitive performance of the AC700 sample can be attributed to the combined effects of its high SSA, surface functional groups, and optimal pore size distribution. The optimum activation temperature of 700 °C resulted in the formation of porous activated carbon with the most structural defects, as well as an appropriate distribution of micropores (63.41 %) and mesopores (31.70 %), facilitating ion diffusion and providing multiple sites for charge storage. Additionally, the AC700 sample exhibited the highest SiO2 content, measuring at 34.33 %, and the lowest contact angle of 75°. The presence of SiO2 in the carbon framework promotes the formation of more hydrophilic active sites, thereby enhancing the pseudocapacitance performance and facilitating sufficient wetting between the electrolyte and electrode interface.

Supercapacitor electrode material derived from copper hydrogen phosphate nano pellets

Herein, the authors disclose for the first time the synthesis of copper hydrogen phosphate (Cu(HPO4)) material for supercapacitor applications. First, we synthesized Cu(HPO4) by a facile chemical bath deposition (CBD) method and then it was characterized by several physicochemical techniques. The fabricated Cu(HPO4) electrode showed superior capacitive performance of 874F/g at 0.1 A/g of current density. Further, Cu(HPO4) electrode retains a maximum of 93.2% of its original specific capacitance retention over 5,000 galvanostatic charge–discharge (GCD) cycles.

Scalable Polyimide-Organosilicate Hybrid Films for High-Temperature Capacitive Energy Storage.

High-temperature polymer dielectrics have broad application prospects in next-generation microelectronics and electrical power systems. However, the capacitive energy densities of dielectric polymers at elevated temperatures are severely limited by carrier excitation and transport. Herein, a molecular engineering strategy is presented to regulate the bulk-limited conduction in the polymer by bonding amino polyhedral oligomeric silsesquioxane (NH2 -POSS) with the chain ends of polyimide (PI). Experimental studies and density functional theory (DFT) calculations demonstrate that the terminal group NH2 -POSS with a wide-bandgap of Eg ≈ 6.6eV increases the band energy levels of the PI and induces the formation of local deep traps in the hybrid films, which significantly restrains carrier transport. At 200°C, the hybrid film exhibits concurrently an ultrahigh discharged energy density of 3.45Jcm-3 and a high gravimetric energy density of 2.74Jg-1 , with the charge-discharge efficiency >90%, far exceeding those achieved in the dielectric polymers and nearly all other polymer nanocomposites. Moreover, the NH2 -POSS terminated PI film exhibits excellent charge-discharge cyclability (>50000) and power density (0.39MWcm-3 ) at 200°C, making it a promising candidate for high-temperature high-energy-density capacitors. This work represents a novel strategy to scalable polymer dielectrics with superior capacitive performance operating in harsh environments.