Search

Optimizing areal capacitance for supercapacitors (SCs) using cyclic voltammetry (CV) involves complex, iterative experiments. Multiple tests are necessary to account for variations in electrode–electrolyte interactions and environmental factors, ensuring thorough characterization. However, this process is time consuming and labor intensive. This study leverages machine learning (ML) to streamline the procedure by generating reliable synthetic data, thereby reducing the time and resources required by traditional methods. The reproducibility of synthetic data makes it a valuable tool for research and validation. Various ML models are used for synthetic data generation, selected based on the characteristics of the real data. This research specifically employs the XGBoost (XGB) ML model to introduce variations in scan rates, enriching the dataset within the range of 5–600 mV/s. Results show that ML algorithms effectively preserve the statistical properties of CV data for laser‐induced graphene (LIG) SCs, evidenced by a high R2 value of 0.97 for the synthetic dataset, confirming the data's fidelity. Additionally, the study introduces a Python module for calculating areal capacitance, facilitating assessment in both real and synthetic datasets. This approach accelerates SC analysis while maintaining data integrity, paving the way for future research and development. [ABSTRACT FROM AUTHOR]

When graphene oxide (GO) was reduced, the stacking of reduced graphene oxide (rGO) sheets would lead to far lower of its specific capacitance than the theoretical value of graphene. In order to solve this problem, we use tannic acid (TA) to modify the rGO layered film by vacuum filtration of the mixture of GO and TA in solution, and then mild thermal reduction at 180℃. Due to the rich redox active functional groups of TA, the introduction of TA can not only alleviate the stacking of rGO sheets and promote the reduction process of GO at relatively low temperature, but also provide additional pseudocapacitance. When used for two-electrode symmetrical supercapacitor in 6 M KOH electrolyte, the TrGO-0.5 gives areal capacitance of 525 mF cm−2, and energy density of 72.2 uWh cm−2 at power density of 250.9 uW cm−2. It also has capacitance retention of 91.7% after 10,000 charging/discharging cycles at current density of 4 mA cm−2. The TrGO-0.5 based button cell with 2 M 1-ethyl-3-methylimidazole tetrafluoroborate (EMIMBF4) as electrolyte shows the practical application to light up three LEDs. [ABSTRACT FROM AUTHOR]

Thickening of electrodes is crucial for maximizing the proportion of active components and thus improving the energy density of practical energy storage cells. Nevertheless, trade-offs between electrode thickness and electrochemical performance persist because of the considerably increased ion transport resistance of thick electrodes. Herein, we propose accelerating ion transport through thick and dense electrodes by establishing an immobile polyanionic backbone within the electrode pores; and as a proof of concept, gel polyacrylic electrolytes as such a backbone are in situ synthesized for supercapacitors. During charge and discharge, protons rapidly hop among RCOO− sites for oriented transport, fundamentally reducing the effects of electrode tortuosity and polarization resulting from concentration gradients. Consequently, nearly constant ion transport resistance per unit thickness is achieved, even in the case of a 900-μm-thick dense electrode, leading to unprecedented areal capacitances of 14.85 F cm−2 at 1 mA cm−2 and 4.26 F cm−2 at 100 mA cm−2. This study provides an efficient method for accelerating ion transport through thick and dense electrodes, indicating a significant solution for achieving high energy density in energy storage devices, including but not limited to supercapacitors. [ABSTRACT FROM AUTHOR]

Flexible electronic products, with their characteristics of flexibility and wearability, have attracted significant attention and have become an important direction in the research and development of the electronics industry. Planar micro-supercapacitors (MSCs) with flexible composite electrodes can provide reliable energy support for these products, propelling their further development. The research employed a quick, effective, and environmentally friendly method of laser scribing to create shape-controllable flexible composite electrodes on composite films of Poly(3,4-ethylenedioxythiophene) and graphene oxide (PEDOT/GO), which were subsequently assembled into MSCs. An analysis of the composite electrode morphology, structure, and elemental distribution was conducted through the utilization of SEM, TEM, and XPS techniques. Following this, a comprehensive evaluation of the electrochemical performance of the flexible MSCs was carried out, which included cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and assessment of cyclic stability. The analysis of the CV results indicated that the MSCs achieved the areal capacitance of 5.78 mF/cm2 at 5 mV/s. After 5000 cycles at a current density of 0.05 mA/cm2, the capacitance retention rate was 85.4%. The high areal capacitance and strong cycle stability of MSCs highlight the potential of PEDOT/reduced graphene oxide (PEDOT/rGO) electrodes in electrode applications. [ABSTRACT FROM AUTHOR]

Two-dimensional transition-metal carbides and nitrides "MXenes" have demonstrated great potential as electrode materials for electrochemical energy storage systems. This is especially true for delaminated Ti3C2Tx, which already shows outstanding gravimetric and volumetric capacitance, with areal capacitance limited by thickness (only a few microns). However, the performance of multilayer Ti3C2Txhas been more modest. Here, we report on using metal cation (viz., Na+, K+, and Mg2+) pre-intercalated multilayer Ti3C2Txas electrodes for aqueous supercapacitors. These electrodes are scalable and amenable to roll-to-roll manufacturing, with adjustable areal loadings of 5.2 to 20.1 mg/cm2. K-Ti3C2Txexhibited the highest capacitances at different scan rates. A gravimetric capacitance comparable to that of delaminated MXene of up to 300 F/g was achieved for multilayer K-Ti3C2Txbut with an outstanding ultra-high areal capacitance of up to 5.7 F/cm2, which is 10-fold higher than the 0.5 F/cm2of delaminated MXene and exceeds the 4.0 F/cm2of microengineered MXene electrodes.

The MXene-modified papers with high-uniform loading of polypyrrole and excellent conductivity have been fabricated via a multiple self-assembly and in-situ polymerization strategy, which achieves boosting areal capacitance. [Display omitted] • Multiple self-assembly and in-situ polymerization strategy is proposed tofabricate paper-based supercapacitors. • Alternate adsorption of MXene and polypyrrole on paper yields an ultra-high polypyrrole loading of 10.0 mg/cm2. • The paper-based supercapacitor shows a boosting areal capacitance of 2316 mF/cm2. Despite the intriguing features of freestanding flexible electronic devices, such as their binder-free nature and cost-effectiveness, the limited loading capacity of active material poses a challenge to achieving practical high-performance flexible electrodes. We propose a novel approach that integrates multiple self-assembly and in-situ polymerization techniques to fabricate a high-loading paper-based flexible electrode (MXene/Polypyrrole/Paper) with exceptional areal capacitance. The approach enables polypyrrole to form a porous conductive network structure on the surface of paper fiber through MXene grafting via hydrogen bonding and electrostatic interaction, resulting in an exceptionally high polypyrrole loading of 10.0 mg/cm2 and a conductivity of 2.03 S/cm. Moreover, MXene-modified polypyrrole paper exhibits a more homogeneous pore size distribution ranging from 5 to 50 μm and an increased specific surface area of 3.11 m2/g. Additionally, we have optimized in-situ polymerization cycles for paper-based supercapacitors, resulting in a remarkable areal capacitance of 2316 mF/cm2 (at 2 mA/cm2). The capacitance retention rate and conductivity rate maintain over 90 % after undergoing 100 bends.The maximum energy density and cycling stability are characterized to be 83.6 μWh/cm2 and up to 96 % retention after 10,000 cycles. These results significantly outperform those previously reported for paper-based counterparts. Overall, our work presents a facile and versatile strategy for assembling high-loading, paper-based flexible supercapacitors network architecture that can be employed in developing large-scale energy storage devices. [ABSTRACT FROM AUTHOR]

Transition metal materials (TMs) show promise as active materials for energy storage applications due to their excellent conductivity and electrochemical activity. In this study, amorphous nickel boride (a-NiB) was deposited onto high surface area templates comprising carbon nanowalls (CNW) and silicon nanowires (SiNWs) using a simple, cost-effective electroless process, for use as electrodes in electrochemical capacitors (ECs). The electrochemical performance of the electrodes was found to be influenced by the type of template used for the a-NiB deposition. Areal capacitances of 204.4 mF·cm−2 and 165.7 mF·cm−2 at a scan rate of 5 mV·s−1 were measured for CNWs-NiB and SiNW-NiB electrodes, respectively. In addition, both types of electrode materials displayed excellent charging/discharging stability after 10,000 cycles. A solid-state symmetric EC assembled with a CNW-NiB electrode exhibited a high areal capacitance of 42 mF·cm−2 at a high current density of 12 mA·cm−2. The CNW-NiB-based ECs can also deliver a high energy density of 19.1 mWh·cm−2 at 0.64 W·cm−2 with charging/discharging stability over 10,000 consecutive cycles. [ABSTRACT FROM AUTHOR]

Lignin is a waste product in the paper industry and lignocellulosic biorefineries, in addition to being the second most abundant renewable biopolymer on Earth. Valorization of useless lignin into high value‐added advanced materials not only helps address the environmentally detrimental biowaste but also satisfies the societal need for energy. While lignin has been converted into porous carbon, made into slurry, and pasted onto metal forms as an electrode for lithium‐ion batteries and supercapacitors, there remains issues with how to scale up the process while achieving great area and mass capacitances in the fabricated lignin‐carbon electrodes. In this work, a thick freestanding electrode coupled by lignin carbon and sodium without any binder and additives was fabricated demonstrating a specific area capacitance of 19.7 F cm−2 at a current density of 1 mA cm−2, which is the highest among to date reported freestanding lignin carbon electrodes with similar thickness. This excellent electrochemical performance originates from high electro‐positivity and oxygen content promoted by the sodium. This work brings a new strategy towards lignin utilization and energy storage through coupling lignin carbon and alkali metals. [ABSTRACT FROM AUTHOR]

Over the past few years, the flexible quasi-solid-state zinc-ion hybrid supercapacitors (FQSS ZHSCs) have been found to be ideal for wearable electronics applications due to their high areal capacitance and energy density. The assembly of desirable ZHSCs devices that have promising practical applications is of high importance, whereas it is still challenging to assemble ZHSCs devices. In this study, a ZHSC that exhibited ultrahigh areal capacitance and high stability was developed by using an active carbon cloth (ACC) cathode, which could improve ionic adsorption. The as-obtained ACC cathode had an energy storage mechanism due to the electrical double-layer capacitive behavior of Zn2+, which was accompanied by the dissolution/deposition of Zn4SO4(OH)6·5H2O. The ACC//Zn@ACC ZHSC device exhibited an areal capacitance of 2437 mF cm−2 (81 F cm−3, 203 F g−1 under the mass of ACC with ∼12 mg cm−2) at 1 mA cm−2, an areal energy density of 1.354 mWh cm−2 at 1 mW cm−2, as well as high stability (with an insignificant capacitance decline after 20000 cycles), which was demonstrated to outperform the existing ZHSCs. Furthermore, the assembled flexible device still had competitive capacitance, energy density and service life when integrated into a FQSS ZHSC. When applied in practice, the device could achieve high mechanical flexibility, wearable stability and output. This study can inspire the development of the FQSS ZHSC device to satisfy the demands for wearable energy storage devices with high performance.

A combination of high mass loading and efficient utilization of electroactive materials is crucial for simultaneously enhancing the energy and power densities of energy storage devices. This is exemplified herein using cobalt nickel layered double hydroxides nanosheets (CoNi‐LDHs) directly grown on copper nanowires (Cu NWs) standing quasi‐vertically on carbon cloth (CC) to yield a multi‐core‐shell CoNi‐LDHs/Cu NWs/CC as the supercapacitor electrode that exhibits a high areal capacitance of 5.55 F cm−2 (corresponding to a gravimetric capacitance of 1209.15 F g−1) at a large current density of 10 mA cm−2. Such superior rate capability is attributed to the high packing density of CoNi‐LDHs in the electrode, benefitting from the large specific surface area of Cu NWs/CC. Additional contribution stems, on the other hand, from the facile charge transfer kinetics resulted from the elimination of binder from the electrode coupled with the mesopores between not only Cu NWs but also CoNi‐LDHs nanosheets, and the macropores between the carbon fiber of CC. Benefitting from such exceptional rate performance is the supercapacitor built on CoNi‐LDHs/Cu NWs/CC as the positive electrode coupled with bismuth subcarbonate (Bi2O2CO3) as the negative electrode capable of delivering outstanding power density of 13.31 mW cm−2 and energy density of 0.35 mWh cm−2. [ABSTRACT FROM AUTHOR]

Here in, we report electrodeposited Mn3O4 thin film doped with various level of Zn dopant (0≤x≤5.0,%), on a layer of indium tin oxide (ITO) on glass substrate. The deposition route involves the use of two-electrode electrochemical cell system comprising graphite and the substrate as counter and working electrodes, respectively. Some surface properties such as those of morphological, crystal structure, optical, electrical and electrochemical were studied to evaluate the films’ potentials in energy conversion and storage devices. Microstructural studies revealed the films grew with isotropic morphology of good tetragonal shaped crystal structure with even distribution and possessing required surface area on the substrate surfaces. Raman prominent peak at 659 cm −1 wave number indicates a typical A1gRaman vibrating mode of Mn2+in a Mn3O4 spinel structure. The crystallite size and microstrain values were found varying from 38 to 43 nm and 5.6 × 10−3 to 3.2 × 10−3, with respect to increase in dopant content, respectively. Energy band gap and Urbach energy were varied from 3.28 to 2.68 eV and 1.59 to 2.17 eV with increasing level of dopant content, accordingly. Electrochemical charge storage area capacitance (12.62 to 21.35 mF cm −2)/capacity (5.1 to 8.1μAh cm −2) and rate capability of Mn3O4 electrode were found to improve with Zn dopant. The work therefore discusses the tailoring of band absorption and supercapacitive characteristic of electrodeposited Mn3O4 thin film with Zn-doping for enhanced energy application.

The 3D printing technique offers huge opportunities for customized thick‐electrode designs with high loading densities to enhance the area capacity in a limited space. However, key challenges remain in formulating 3D printable inks with exceptional rheological performance and facilitating electronic/ion transport in thick bulk electrodes. Herein, a hybrid ink consisting of woody‐derived cellulose nanofibers (CNFs), multiwalled carbon nanotubes (MWCNTs), and urea is formulated for the 3D printing nitrogen‐doped thick electrodes, in which CNFs serve as both dispersing and thickening agents for MWCNTs, whereas urea acts as a doping agent. By systematically tailoring the concentration‐dependent rheological performance and 3D printing process of the ink, a variety of gel architectures with high geometric accuracy and superior shape fidelity are successfully printed. The as‐printed gel architecture is then transformed into a nitrogen‐doped carbon block with a hierarchical porous structure and superior electrochemical performance after freeze‐drying and annealing treatments. Furthermore, a quasi‐solid‐state symmetric supercapacitor assembled with two interdigitated carbon blocks obtained by a 3D printing technique combined with a nitrogen‐doping strategy delivers an energy density of 0.10 mWh cm−2 at 0.56 mW cm−2. This work provides guidance for the formulation of the printable ink used for 3D printing of high‐performance thick carbon electrodes. [ABSTRACT FROM AUTHOR]

Understanding the configuration and properties of the simplest lithium‐ion crystal, the Li‐Cl crystal, is essential for developing Li‐based electrochemical energy storage and conversion devices. Under ambient conditions, LiCl in a 1:1 stoichiometry is the only known stable form of the Li‐Cl crystal, and the corresponding crystals are insulating. Here, using cryo‐electron microscopy (cryo‐EM) and X‐ray photoelectron spectroscopy (XPS), this work reports a novel abnormal 2D Li2Cl crystal in ultra‐thin reduced graphene oxide (rGO) membranes by simply soaking the rGO membrane in unsaturated LiCl solution under ambient conditions and showed its high‐resolution image. Unexpectedly, such Li2Cl crystal presents metallic properties rather than insulating properties. Using vacuum filtration of the unsaturated LiCl solution through rGO membranes, this work prepares the rGO membranes with high content Li2Cl, displaying a high areal capacitance of 220 mF cm−2. Remarkably, the Li2Cl‐rGO membranes also exhibit heterostructure property and piezoelectricity. For the excess Li and unique electrical characteristics, these Li2Cl‐rGO membranes can be used as a humidity sensor. These findings point to possibilities for creating new Li‐based materials and fabricating novel high‐performance electronic devices, transistors, and sensors. [ABSTRACT FROM AUTHOR]

Self-supporting electrode materials with the advantages of a simple operation process and the avoidance of the use any binders are promising candidates for supercapacitors. In this work, carbon-based self-supporting electrode materials with nanosheets grown on Al foil were prepared by combining hydrothermal reaction and the one-step chemical vapor deposition method. The effect of the concentration of the reaction solution on the structures as well as the electrochemical performance of the prepared samples were studied. With the increase in concentration, the nanosheets of the samples became dense and compact. The CNS-120 obtained from a 120 mmol zinc nitrate aqueous solution exhibited excellent electrochemical performance. The CNS-120 displayed the highest areal capacitance of 6.82 mF cm−2 at the current density of 0.01 mA cm−2. Moreover, the CNS-120 exhibited outstanding rate performance with an areal capacitance of 3.07 mF cm−2 at 2 mA cm−2 and good cyclic stability with a capacitance retention of 96.35% after 5000 cycles. Besides, the CNS-120 possessed an energy density of 5.9 μWh cm−2 at a power density of 25 μW cm−2 and still achieved 0.3 μWh cm−2 at 4204 μW cm−2. This work provides simple methods to prepared carbon-based self-supporting materials with low-cost Al foil and demonstrates their potential for realistic application of supercapacitors. [ABSTRACT FROM AUTHOR]

Negatrodes with wide negative operating voltage, high electrochemical storage capacity, and intrinsic metal ion intercalation abilities are vital to the continuous development of storage devices with simultaneous energy and power density improvement. Herein, we report binder-less coating of non-stoichiometric vacancy-implanted Nb 2 O 5-x as carbon additive-free negatrode on FTO substrate for asymmetric supercapacitor and sodium ion capacitor applications. The negatrode was fabricated through vacuum-less and low-temperature solvothermal-assisted electro-coating technique and yielded several orders of enhancement in its areal capacitance and retained ca. 90 % of its capacity after 5000 cycles of charge-discharge in aqueous Na+ electrolyte. The solvothermal treated electro-coated electrode (STT_Nb 2 O 5-x) achieved an areal capacitance of 22.58 mF/cm2, which was far higher than those of hydrothermal-treated electro-coated HTT_Nb 2 O 5 and Nb 2 O 5 electrodes. The solvothermal treatment simultaneously enhanced the electro-coated samples' impedance properties and mass load through oxygen vacancy implantation and re-crystallization of the electro-coated Nb 2 O 5 layer, respectively. This study presented a facile and energy-efficient technique of direct coating of defect-enhanced pseudocapacitive nanomaterials for the fabrication of electrochemical storage devices. • Binder-free coating of carbon additive-free Nb 2 O 5-x was achieved through solvothermal-assisted electro-coating. • A simultaneous increase in donor concentration and mass load of Nb 2 O 5-x was achieved via low-temperature synthesis. • Lowered values of impedance parameters and increased areal capacity were attained. • High-performing negatrode with wide negative operating potential was demonstrated. [ABSTRACT FROM AUTHOR]

• The introduction of Co 3 O 4 effectively prevented the collapse of MXene and increased the specific surface area of the electrode material. • Introducing Co 3 O 4 into MXene, the composite electrode material exhibits excellent electrochemical performance. • The Co 3 O 4 synthesized through a simple hydrothermal method exhibits a regular petal-like appearance after sintering. The development of high-performance electrode materials is crucial for advancing supercapacitor technology. The two-dimensional layered structure of MXene (Ti 3 C 2 T x) presents high conductivity, abundant surface functional groups and accessible ion interaction between layers. However, the MXene suffers from the layer aggregation. To overcome this issue, we synthesized a composite material combining MXene with cobalt oxide (Co 3 O 4) to enhance electrochemical performance in supercapacitors. MXene's two-dimensional layered structure, high conductivity, and abundant surface functional groups allow for efficient ion intercalation, while Co 3 O 4 contributes high theoretical capacitance and rich oxidation states. The resulted MXene/Co 3 O 4 composite exhibits an impressive areal capacitance of 6.456F/cm2 at a current density of 3 mA/cm2, maintaining 90.52 % capacitance retention at 30 mA/cm2, and 81.37 % capacity after 5000 charge–discharge cycles. Additionally, the asymmetric supercapacitor (ASC) device fabricated using the MXene/Co 3 O 4 composite achieves a power density of 6.41 mW/cm2 at an energy density of 0.37 mWh/cm2, with 82.3 % capacitance retention after 5000 cycles. These results demonstrate that the MXene/Co 3 O 4 composite material is a promising candidate for high-performance supercapacitors, offering significant improvements in rate capability and long-term cycling stability. [ABSTRACT FROM AUTHOR]

Abstract The 3D printing technique offers huge opportunities for customized thick‐electrode designs with high loading densities to enhance the area capacity in a limited space. However, key challenges remain in formulating 3D printable inks with exceptional rheological performance and facilitating electronic/ion transport in thick bulk electrodes. Herein, a hybrid ink consisting of woody‐derived cellulose nanofibers (CNFs), multiwalled carbon nanotubes (MWCNTs), and urea is formulated for the 3D printing nitrogen‐doped thick electrodes, in which CNFs serve as both dispersing and thickening agents for MWCNTs, whereas urea acts as a doping agent. By systematically tailoring the concentration‐dependent rheological performance and 3D printing process of the ink, a variety of gel architectures with high geometric accuracy and superior shape fidelity are successfully printed. The as‐printed gel architecture is then transformed into a nitrogen‐doped carbon block with a hierarchical porous structure and superior electrochemical performance after freeze‐drying and annealing treatments. Furthermore, a quasi‐solid‐state symmetric supercapacitor assembled with two interdigitated carbon blocks obtained by a 3D printing technique combined with a nitrogen‐doping strategy delivers an energy density of 0.10 mWh cm−2 at 0.56 mW cm−2. This work provides guidance for the formulation of the printable ink used for 3D printing of high‐performance thick carbon electrodes.

Abstract Understanding the configuration and properties of the simplest lithium‐ion crystal, the Li‐Cl crystal, is essential for developing Li‐based electrochemical energy storage and conversion devices. Under ambient conditions, LiCl in a 1:1 stoichiometry is the only known stable form of the Li‐Cl crystal, and the corresponding crystals are insulating. Here, using cryo‐electron microscopy (cryo‐EM) and X‐ray photoelectron spectroscopy (XPS), this work reports a novel abnormal 2D Li2Cl crystal in ultra‐thin reduced graphene oxide (rGO) membranes by simply soaking the rGO membrane in unsaturated LiCl solution under ambient conditions and showed its high‐resolution image. Unexpectedly, such Li2Cl crystal presents metallic properties rather than insulating properties. Using vacuum filtration of the unsaturated LiCl solution through rGO membranes, this work prepares the rGO membranes with high content Li2Cl, displaying a high areal capacitance of 220 mF cm−2. Remarkably, the Li2Cl‐rGO membranes also exhibit heterostructure property and piezoelectricity. For the excess Li and unique electrical characteristics, these Li2Cl‐rGO membranes can be used as a humidity sensor. These findings point to possibilities for creating new Li‐based materials and fabricating novel high‐performance electronic devices, transistors, and sensors.

Simpler methods for fabricating electrodes for charge storage applications are required because electrode materials have appreciable significance to enhance the electrochemical performance of charge/energy storage devices. Fractal porous silicon (pSi) substrate, prepared using a simple metal-assisted chemical etching (MACE) technique, has been studied here for possible application for charge storage. Electrochemical investigations have been carried out on the fabricated pSi electrodes, duly characterized using electron microscopy and Raman spectroscopy. The electrochemical performance of the prepared pSi electrode was studied using cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) in a three-electrode system. A comparative electrochemical measurement indicates more capacitive current flow in the pSi electrodes whereas c-Si shows an ohmic behavior. The equivalent circuit of the electrode-electrolyte system for pSi and c-Si was also drawn by the curve fitting of the Nyquist plot. The areal capacitance of the prepared pSi was also calculated at different scan rates and a moderate areal capacitance values were obtained which suggests that the pSi can be a possible candidate for the energy/charge storage electrodes. [ABSTRACT FROM AUTHOR]

In the field of construction, structural supercapacitors (SSCs) have been widely noticed due to their simultaneous functions of load-bearing and energy storage. Unfortunately, the currently available electrodes for SSCs are still aimed at application scenarios such as electronics and electric vehicles, and while their performance is good, they are not applicable to the construction sector, which is massive in scale and extremely cost-sensitive industry. Herein, after trade-off between cost and electrochemical performance, a novel low-cost 3D nanomaterial was designed through a facile approach aimed at increasing the areal energy density of SSCs. By growing Mg-Co double hydroxide nanomaterials directly on nickel foam, we achieved a large areal capacitance of 2577 mF/cm2 at 5 mA/cm2 (1136.7 F/g at 2.2 A/g). It also exhibits good cycling stability with a capacitance retention of 82.4 % after 10,000 cycles. In addition, SSCs using magnesium-cobalt double hydroxides achieves a high energy density of 285.6 μWh/cm3 at a power density of 6.31 mW/cm3, which is superior to previously reported structural devices. This demonstrates that Mg-Co double hydroxide electrode has good suitability with SSCs and effectively improves the areal energy density of SSCs. Our proposed method also provides a faster and more reliable pathway for low-cost electrode preparation in SSCs, which may lead to the development of a new generation of SSCs. • Preparation of Mg-Co double hydroxide electrode by one-step hydrothermal method. • The Mg-Co double hydroxide electrode have good electrochemical properties. • SSCs using Mg-Co double hydroxide electrode provide excellent energy density. [ABSTRACT FROM AUTHOR]

[Display omitted] • Energy-storage performance of CuFe(P 2 O 7) was optimized by tuning the ionic ratio. • CFP-4 electrodes' uneven porous structures are driven by abundant metal ions. • Optimized CFP-4 electrodes deliver excellent C A of 1609 mF cm−2 at 3 mA cm−2. • CuFe(P 2 O 7) exhibited good long-term durability of 70 % over 5000 GCD cycles. • CFP// AC asymmetric device yields an ED of 20.62 µWh kg−1 and a PD of 3750 µW kg−1. In this study effects of different precursor concentrations on the microstructural and electrochemical properties of hydrothermally deposited CuFe(P 2 O 7) electrodes are investigated. The X-ray diffraction observations confirm the formation of the CuFe(P 2 O 7) phase. The optimum CuFe(P 2 O 7) electrode displays an excellent capacitance of 1609 mF cm−2 (192.84 F g−1) at 3 mA cm−2 with excellent energy and power densities. Moreover, the best electrode exhibits a high diffusion coefficient of 4.527 × cm3 S−1 × 10−7 with b-value of 0.62 and sustains 70 % stability over 5000 cycles. Constructed asymmetric supercapacitor device yields an energy density of 20.62 µWh kg−1 and power density of 3750 µW kg−1 with noteworthy retention of 67 % over long-term 10,000 cycles. The encouraging electrochemical activity of CuFe(P 2 O 7) can be correlated with alterations in chemical states, and high electrochemical active surface area which offer more accessible sites with enhanced electrical conductivity, efficient electron transportation. [ABSTRACT FROM AUTHOR]

A well‐designed pore structure and optimized interface will improve specific capacitances of carbon‐based supercapacitor electrodes significantly. Herein, a simple strategy is used to prepare the hierarchically porous 3D‐printed carbon aerogel (CA) electrodes via combining direct ink writing, freezing drying, carbonization, and polypyrrole (PPy) posttreatment. The 3D‐printed CA electrodes without PPy present a quasi‐proportional increase in areal capacitance as thickness, achieving an extremely high areal capacitance of 6875 mF cm–2 under a thickness of 2.2 mm. Additionally, PPy posttreated 3D‐printed CA (PPy@CA) electrode has improved wettability and contact conductivity, which shows a further significant increase of areal capacitance to 8126 mF cm–2. After 10 000 continuous cycles, the PPy@CA electrode exhibits an excellent cyclic stability similar to that of 3D‐printed CA electrode by maintaining 91% of its original capacitance. This simple strategy may provide a novel insight to dramatically boost the energy storage properties of supercapacitor electrodes and their functionalization. [ABSTRACT FROM AUTHOR]

A well‐designed pore structure and optimized interface will improve specific capacitances of carbon‐based supercapacitor electrodes significantly. Herein, a simple strategy is used to prepare the hierarchically porous 3D‐printed carbon aerogel (CA) electrodes via combining direct ink writing, freezing drying, carbonization, and polypyrrole (PPy) posttreatment. The 3D‐printed CA electrodes without PPy present a quasi‐proportional increase in areal capacitance as thickness, achieving an extremely high areal capacitance of 6875 mF cm–2 under a thickness of 2.2 mm. Additionally, PPy posttreated 3D‐printed CA (PPy@CA) electrode has improved wettability and contact conductivity, which shows a further significant increase of areal capacitance to 8126 mF cm–2. After 10 000 continuous cycles, the PPy@CA electrode exhibits an excellent cyclic stability similar to that of 3D‐printed CA electrode by maintaining 91% of its original capacitance. This simple strategy may provide a novel insight to dramatically boost the energy storage properties of supercapacitor electrodes and their functionalization. [ABSTRACT FROM AUTHOR]

Preparing sustainable and highly efficient biochars as electrodes remains a challenge for building green energy storage devices. In this study, efficient carbon electrodes for supercapacitors were prepared via a facile and sustainable single-step pyrolysis method using spruce bark as a biomass precursor. Herein, biochars activated by KOH and ZnCl2 are explored as templates to be applied to prepare electrodes for supercapacitors. The physical and chemical properties of biochars for application as supercapacitors electrodes were strongly affected by factors such as the nature of the activators and the meso/microporosity, which is a critical condition that affects the internal resistance and diffusive conditions for the charge accumulation process in a real supercapacitor. Results confirmed a lower internal resistance and higher phase angle for devices prepared with ZnCl2 in association with a higher mesoporosity degree and distribution of Zn residues into the matrix. The ZnCl2-activated biochar electrodes' areal capacitance reached values of 342 mF cm−2 due to the interaction of electrical double-layer capacitance/pseudocapacitance mechanisms in a matrix that favors hydrophilic interactions and the permeation of electrolytes into the pores. The results obtained in this work strongly suggest that the spruce bark can be considered a high-efficiency precursor for biobased electrode preparation to be employed in SCs. [ABSTRACT FROM AUTHOR]

Abstract Vanadium sulfide (VS2) nanomaterials have been deposited on surface-modified stainless steel mesh (SMSSM) by facial hydrothermal method and subsequent effects of acidic etching on surface morphology and supercapacitive performance of the electrode were studied. The acid etching process improves the coupling interaction between the stainless steel mesh and active materials. The optimized 1% etched SMSSM with VS2 (1%/VS2) loaded electrode reveals the porous fine nanoparticles composed surface nanostructure. The prepared 1%/VS2 electrode exhibited an excellent areal capacitance of 45.83 mF/cm2, which is two times higher than that of a non-etched VS2 loaded electrode. These results showed that the acidic etching process significantly improved the surface nanostructure of the VS2 material that improved the capacitance of the SMSSM substrate.

Abstract Functional carbonaceous materials for supercapacitors (SCs) without using acid for post-treatment remain a substantial challenge. In this paper, we present a less harmful strategy for preparing three-dimensional (3D) N,O-codoped egg-box-like carbons (EBCs). The as-prepared EBCs with opened pores provide plentiful channels for ion fast transport, ensure the effective contact of EBCs electrodes and electrolytes, and enhance the electron conduction. The nitrogen and oxygen atoms doped in EBCs improve the surface wettability of EBC electrodes and provide the pseudocapacitance. Consequently, the EBCs display a prominent areal capacitance of 39.8 μF cm−2 (340 F g−1) at 0.106 mA cm−2 in 6 M KOH electrolyte. The EBC-based symmetric SC manifests a high areal capacitance to 27.6 μF cm−2 (236 F g−1) at 0.1075 mA cm−2, a good rate capability of 18.8 μF cm−2 (160 F g−1) at 215 mA cm−2 and a long-term cycle stability with only 1.9% decay after 50,000 cycles in aqueous electrolyte. Impressively, even in all-solid-state SC, EBC electrode shows a high areal capacitance of 25.0 μF cm−2 (214 F g−1) and energy density of 0.0233 mWh cm−2. This work provides an acid-free process to prepare electrode materials from industrial by-products for advanced energy storage devices.

Self-supporting electrode materials with the advantages of a simple operation process and the avoidance of the use any binders are promising candidates for supercapacitors. In this work, carbon-based self-supporting electrode materials with nanosheets grown on Al foil were prepared by combining hydrothermal reaction and the one-step chemical vapor deposition method. The effect of the concentration of the reaction solution on the structures as well as the electrochemical performance of the prepared samples were studied. With the increase in concentration, the nanosheets of the samples became dense and compact. The CNS-120 obtained from a 120 mmol zinc nitrate aqueous solution exhibited excellent electrochemical performance. The CNS-120 displayed the highest areal capacitance of 6.82 mF cm−2 at the current density of 0.01 mA cm−2. Moreover, the CNS-120 exhibited outstanding rate performance with an areal capacitance of 3.07 mF cm−2 at 2 mA cm−2 and good cyclic stability with a capacitance retention of 96.35% after 5000 cycles. Besides, the CNS-120 possessed an energy density of 5.9 μWh cm−2 at a power density of 25 μW cm−2 and still achieved 0.3 μWh cm−2 at 4204 μW cm−2. This work provides simple methods to prepared carbon-based self-supporting materials with low-cost Al foil and demonstrates their potential for realistic application of supercapacitors.

Miniaturized electronics require integrated unit configuration in very limited space, where energy storage per unit area is thus extremely critical. Micro‐supercapacitors (MSCs), mainly established on planar substrates, are superior but still suffer from limited areal capacitance. Herein, a novel strategy is introduced to construct high cross‐section MSCs using 3D fabrics as the porous skeleton. Interdigitated poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) is patterned on 3D fabrics to achieve continuous conductive networks, while MnO2 microspheres epitaxially grown on PEDOT:PSS are fully exposed to electrolyte with the support of fabric fibers. The unique architecture can utilize more active sites of thick electrodes and the high conductivity of interpenetrating fiber networks. The resulting fabric‐based MSCs demonstrate ultra‐high areal capacitance of 135.4 mF cm−2, which is 3.5 times that of devices on polyethylene terephthalate substrates and is among the highest values for planar‐based MSCs using the same interdigital geometry. Moreover, the flexible fabrics endow MSCs with extremely high bending stability with 94% capacitance retention even after 3000 cycles. These figures‐of‐merit enable fabric‐based MSCs promising to be used in the next‐generation of wearable electronics. [ABSTRACT FROM AUTHOR]

Summary: MXenes have potential applications in the field of supercapacitors. As a two‐dimensional material, how its structure, properties, and surface chemistry facilitate energy storage is discussed. A detailed analysis of the synthesis of MXenes and factors affecting energy storage in supercapacitor grounds is explained in detail. Possibilities of anode architecture to improve supercapacitor performance on industrial standards are discussed. This review will aid in planning better MXene hybrid anodes to assemble supercapacitors with desired electrochemical performance. Ways to improve capacitance, energy density, and voltage window of electrodes are explained based on literature reports. Electrochemical performance is evaluated by the effect of hierarchical structures, heterostructures, transition metal oxides, carbon compounds, polymers, and so on. Anode fabrication methods for modern micro‐supercapacitors are also incorporated in this study. A good selection of electrolytes and fabrication techniques adapted for MXene‐based anode fabrication is emphasized. This review will help in future options of supercapacitor anode designing. [ABSTRACT FROM AUTHOR]

Flexible supercapacitors represent an attractive technology for the next generation of wearable consumer electronics as power sources but usually suffer from relatively low energy density. It is highly desired to construct high-performance electrodes for the practical applications of supercapacitors. Here, inspired by the natural structure of the spider web, an elaborate design of binder is reported through a biosynthesis process to construct flexible electrodes with both excellent mechanical properties and electrochemical performance. Through this strategy, a spider-web-inspired 3D structural binder enables large ion-accessible surface area and high packing density of active electrode material as well as efficient ion transport pathways. As a result, a high areal capacitance of 4.62 F cm-2 and a high areal energy density of 0.18 mW h cm-2 is achieved in the composite electrodes and symmetric supercapacitors, respectively, demonstrating a promising potential to construct flexible energy storage devices for diverse practical applications. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate the fabrication of vertically aligned carbon nanowalls (CNW) enrobed with porous molybdenum sulfide (MoSx) as electrode for electrochemical capacitors with large areal capacitance that can be used for micro-supercapacitors. The deposition of MoSx onto the CNW electrode was performed using hydrothermal technique allowing a good coverage of the deposit along the CNW. The electrode can deliver an areal capacitance as high as 366 mF cm−2 (which is one of the highest reposted in the case of MoSx). Our strategy allows using hydrothermal technique to deposit different transition metal sulfides onto porous template in order to obtain materials with high specific capacitance and highlight CNW as promising template to deposit different materials for high-performance energy storage systems. [ABSTRACT FROM AUTHOR]

Si-based micro-supercapacitors are considered to be promising in energy storage due to their compatibility to modern electronics and high energy densities. However, the capacitance and cycle stability of the electrode remains to be further improved. In this work, we fabricated high-crystalline graphene/SiC (G/SiC) nano-matrix on the surface of planar Si and Si nanowires (SiNWs) array by laser chemical vapor deposition. The surface of SiNWs was fully covered with the G/SiC passivation layers, which composed of highly <001>−orientated 3C–SiC with graphene distributed in the films and the outermost layer. Compared to the SiNWs and planar G/SiC/Si structures, the G/SiC/SiNWs nano-matrix exhibited a low charge transfer resistance of 3.1 Ω, and a high areal capacitance value of ∼3.2 mF/cm2 achieved at a CV scan rate of 50 mV/s, nearly 10 times and 75 times higher than those of SiNWs and G/SiC/Si, respectively. The capacitance of the G/SiC/SiNWs nano-matrix was increased by 115% after 10,000 cyclic voltammetry cycles at 100 mV/s, showing excellent cyclic stability. This type of G/SiC/SiNWs nano-matrix heterostructure electrode paves the way for Si-based electrochemical applications. Image 1 [ABSTRACT FROM AUTHOR]

Preparing sustainable and highly efficient biochars as electrodes remains a challenge for building green energy storage devices. In this study, efficient carbon electrodes for supercapacitors were prepared via a facile and sustainable single-step pyrolysis method using spruce bark as a biomass precursor. Herein, biochars activated by KOH and ZnCl2 are explored as templates to be applied to prepare electrodes for supercapacitors. The physical and chemical properties of biochars for application as supercapacitors electrodes were strongly affected by factors such as the nature of the activators and the meso/microporosity, which is a critical condition that affects the internal resistance and diffusive conditions for the charge accumulation process in a real supercapacitor. Results confirmed a lower internal resistance and higher phase angle for devices prepared with ZnCl2 in association with a higher mesoporosity degree and distribution of Zn residues into the matrix. The ZnCl2-activated biochar electrodes’ areal capacitance reached values of 342 mF cm−2 due to the interaction of electrical double-layer capacitance/pseudocapacitance mechanisms in a matrix that favors hydrophilic interactions and the permeation of electrolytes into the pores. The results obtained in this work strongly suggest that the spruce bark can be considered a high-efficiency precursor for biobased electrode preparation to be employed in SCs.

Abstract Few-layer graphene sheet-passivated porous silicon (PSi) as an outstanding electrochemical double-layer supercapacitor electrode was demonstrated. The PSi matrix was formed by electrochemical etching of a doped silicon wafer and was further surface-passivated with few-layer graphene sheets by a Ni-assisted chemical vapor deposition process where a wide range of porous PSi structures, including mesoporous, macroporous, and hybrid porous structures were created during the graphene growth as temperature increases. The microstructural and graphene-passivation effects on the capacitive performance of the PSi were investigated in detail. The hybrid porous PSi electrode, optimized in terms of capacitive performances, achieves a high areal capacitance of 6.21 mF/cm2 at an ultra-high scan rate of 1000 mV/s and an unusual progressing cyclic stability of 131% at 10,000 cycles. Besides mesopores and macropores, micropores were introduced onto the surfaces of the passivating few-layer graphene sheets with a KOH activation process to further increase the functioning surface area of the hierarchical porous PSi electrode, leading to a boost in the areal capacitance by 31.4% up to 8.16 mF/cm2. The present designed hierarchical porous PSi-based supercapacitor proves to be a robust energy storage device for microelectronic applications that require stable high rate capability.

Flexible electrodes have important potential applications in energy storage of multi‐functional portable electronic devices because of their powerful structural properties. Here, fibrous and flexible electrodes comprising hierarchical nanostructure graphene for use in advanced supercapacitors have been fabricated with an electrochemical deposition method in one step. Excellent electrochemical performance of the fibrous and flexible nanostructure material was achieved, with the areal capacitance of 48.83 mF cm−2, according to the galvanostatic charge/discharge analysis at a current density of 0.199 mA cm−2. The electrodes also showed a good cycle performance, with 91.2% of the original capacity retained after 4000 cycles. Such electrodes may provide new design opportunities for wearable electronics and energy storage applications. [ABSTRACT FROM AUTHOR]

Supercapacitors operating at high frequencies while exhibiting high capacitance have been challenging to fabricate due to high resistance and constrained ion diffusion in the active layers. To overcome these limitations, thin layers of pseudocapacitive materials with high theoretical capacitance can be used. Still, construction of such electrodes exhibiting effective ion diffusion, sufficient electrochemically‐active surface area, and high conductivity has encountered significant difficulties. Here, we integrated nickel atoms into a ruthenium layer through a simple electrochemical deposition method, producing a thin electrode comprising hexagonal nickel ruthenium (NiRu) nanodendrites. Further oxidation of the NiRu alloy generated a thin surface layer of pseudocapacitive RuO2 exhibiting significant areal capacitance. A symmetric device from two NiRu/RuO2 electrodes displayed an energy density of 0.714 μWh cm−2 with a remarkable power density of 1500 mW cm−2, ∼250 W cm−3 for a full device. The NiRu/RuO2 supercapacitor outperforms commercial capacitors in both energy and power densities and may replace bulky capacitors in microelectronic devices. [ABSTRACT FROM AUTHOR]

Flexible and foldable microcomponents are highly desirable for energy devices. In this work, flexible asymmetric micro‐capacitor (AMC) is fabricated by using uniform Ag/Bi2S3 (or Bi2S3) nanoflowers, active carbon and carbon fibres are used as positive material, negative material and current collector, respectively. On one hand, the areal capacitance of Ag/Bi2S3 electrode has increased by more than 6 times than Bi2S3, and 86 and 68% of capacitances are retained for Ag/Bi2S3 and Bi2S3 electrodes after 4000 cycles, respectively. On the other hand, Ag/Bi2S3‐based AMC has an energy density of (0.0134 mWhcm−3) 4.36 times higher than Bi2S3‐based one (0.0025 mWhcm−3); after 4000 cycles, 84 and 33% of capacitances are retained for Ag/Bi2S3‐ and Bi2S3‐based AMCs, respectively. The improved performances are mainly attributed to the enhanced electrical conductance by Ag loading (Bi2S3: 21.898 Ω; Ag/Bi2S3: 4.5643 Ω). Most importantly, the AMC is flexible and foldable, which is promising to conveniently apply in complicated energy devices, production for practical applications. [ABSTRACT FROM AUTHOR]

Vanadium sulfide (VS2) nanomaterials have been deposited on surface-modified stainless steel mesh (SMSSM) by facial hydrothermal method and subsequent effects of acidic etching on surface morphology and supercapacitive performance of the electrode were studied. The acid etching process improves the coupling interaction between the stainless steel mesh and active materials. The optimized 1% etched SMSSM with VS2 (1%/VS2) loaded electrode reveals the porous fine nanoparticles composed surface nanostructure. The prepared 1%/VS2 electrode exhibited an excellent areal capacitance of 45.83 mF/cm2, which is two times higher than that of a non-etched VS2 loaded electrode. These results showed that the acidic etching process significantly improved the surface nanostructure of the VS2 material that improved the capacitance of the SMSSM substrate. [ABSTRACT FROM AUTHOR]

Hierarchical porous carbon has become one of the most competitive electrode materials for supercapacitor. The biomass-derived carbon materials are taken for candidate due to their renewability, sustainability, abundance, and low cost. However, the areal capacitance of carbonized biomass needs to be further improved. Herein, we developed a facile and eco-friendly method for the synthesis of porous carbon from agricultural straw, using carbonizing lignocellulose foams and then KOH activation. The obtained biomass foams were controllably carbonized to form all-carbon material for making the electrode for supercapacitor. The results showed that the as-prepared biomass-derived hierarchical porous carbon (BHPC) materials had a high specific surface area of 772 m2 g−1 after KOH activation, and contained the microporous (1.05–1.74 nm) matching with the electrolyte 6 M KOH. The high porosity and the interconnected three-dimensional nanostructure provided efficient migration of the ions in electrolyte, thus the BHPC displayed an outstanding electrochemical performance of supercapacitors. The specific capacitances attained 226.2 F g−1 (specific surface-area capacitance was 29.3 μF cm−2) at a current density of 0.5 A g−1 within a potential window of −1.0 to 0 V in a three-electrode system. This work provides a promising approach to realizing the waste straws into a high-valued energy storage material. • Lignocellulosic foam through dissolving, gelation, and drying using wheat straw. • Porous carbon was prepared from pyrolysis and activation of lignocellulosic foam. • It had high specific surface area (1063 m2 g−1) as well as abundant micropores. • The high areal capacitance of 29.3 μF cm−2 was obtained (0.5 A g−1). [ABSTRACT FROM AUTHOR]

Electric double layer capacitors (EDLCs) have been known as energy storage device and different materials have been used as EDLC electrode materials. Recently, graphene has been considered as one of the most promising materials for use in EDLC structure. In this research, a theoretical study on bilayer graphene (as an EDLC with vacuum dielectric) in two symmetries (D2h and D6h) with different distances and applied voltages is done, where the charge separation among a bilayer graphene structure is calculated by electron deformation orbital theory. Although it was found that capacitance is almost independent of applied voltage in constant distances, the relationship between capacitance and inverse of distance was nonlinear in the cases of constant voltages. The structure change from D2h to D6h did not affect the specific capacitances, significantly, although the areal capacitance of D2h structure was greater than that of D6h structure. [ABSTRACT FROM AUTHOR]

Herein, we presented the fabrication of α-MnO 2 thin film pseudocapacitive electrodes with enhanced optical transparency and areal capacitance. The optimized electrodes were achieved through a low-energy, binder-free, hexamethylenetetramine-assisted electrodeposition. Before this, attempts to increase the optical transparency of MnO 2 electrodes had only been successful by reducing its mass load and thickness, which compromised its storage capacity. In this study, analysis of the optical dispersion properties of MnO 2 was combined with the electrochemical investigation to demonstrate a nexus between nano-morphology, transparency and storage capacity. [Display omitted] • MnO 2 thin films were electrodeposited on a transparent substrate. • Morphological structures of MnO 2 thin film were tuned by hexamethylenetetramine. • Successful blue-shifting of the absorption edge of MnO 2 thin films was achieved. • HMTA-assisted electrodeposited MnO 2 films exhibited improved storage capacity and transparency. [ABSTRACT FROM AUTHOR]

Article Highlights: A green low-cost route without the acid washing step is used to prepare the N,O-codoped egg-box-like carbons. The obtained carbons possess moderate N, O contents and tuned transfer channels with three-dimensional (3D) egg-box-like structures. The fabricated electrode exhibits high areal capacitance and long-term cycle stability.Functional carbonaceous materials for supercapacitors (SCs) without using acid for post-treatment remain a substantial challenge. In this paper, we present a less harmful strategy for preparing three-dimensional (3D) N,O-codoped egg-box-like carbons (EBCs). The as-prepared EBCs with opened pores provide plentiful channels for ion fast transport, ensure the effective contact of EBCs electrodes and electrolytes, and enhance the electron conduction. The nitrogen and oxygen atoms doped in EBCs improve the surface wettability of EBC electrodes and provide the pseudocapacitance. Consequently, the EBCs display a prominent areal capacitance of 39.8 μF cm−2 (340 F g−1) at 0.106 mA cm−2 in 6 M KOH electrolyte. The EBC-based symmetric SC manifests a high areal capacitance to 27.6 μF cm−2 (236 F g−1) at 0.1075 mA cm−2, a good rate capability of 18.8 μF cm−2 (160 F g−1) at 215 mA cm−2 and a long-term cycle stability with only 1.9% decay after 50,000 cycles in aqueous electrolyte. Impressively, even in all-solid-state SC, EBC electrode shows a high areal capacitance of 25.0 μF cm−2 (214 F g−1) and energy density of 0.0233 mWh cm−2. This work provides an acid-free process to prepare electrode materials from industrial by-products for advanced energy storage devices. [ABSTRACT FROM AUTHOR]

Silicon nanowire arrays (SiNWs) were fabricated by one-step metal-assisted chemical etching process and modified with MnO2 nanoparticles by a chemical electroless method. Scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), secondary ion mass spectroscopy (SIMS), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to characterize the MnO2-modified SiNWs. It was noted that the amount of deposited MnO2 increases with increasing deposition time. Moreover, it was found that the deposition of MnO2 on the SiNWs electrode surface leads to an increase of charge and discharge capacitive current and capacitance. Indeed, MnO2–modified SiNWs presents the largest areal capacitance of 21.296 mF/cm2 which is 14 times larger than that of SiNWs/Si (1.55 mF/cm2) and an energy density of 1.66375 mWh/cm2 for a scan rate of 10 mV/s. Therefore, MnO2@SiNWs/Si nanocomposite is a promising material for the micro-supercapacitor technology. [ABSTRACT FROM AUTHOR]

To improve dielectric properties and areal capacitance according to percolation theory, 0 to 50 wt% of Cu was used as a metal filler in a BaTiO 3 (BT) matrix. BT–Cu composite films with a thickness of approximately 2 μm were fabricated using aerosol deposition at room temperature for application in embedded-film capacitors. The flow conditions of the carrier gas were varied to fabricate very compact composite thin films without surface craters and internal pores to obtain a high dielectric constant, low dielectric loss, and low leakage current. The BT–Cu composite films displayed highly dense microstructures and smooth surfaces, and good dielectric properties were observed when the carrier gas was supplied at 10 L/min. The dielectric constant of the composite films increased with the increase in Cu content. Although the dielectric loss and leakage current also increased with the increase in Cu content, they were within the allowable limits until the Cu concentration reached 40 wt% in the composite film, and the 40 wt% of Cu contained films showed high areal capacitances that were approximately five times the values reported in previous studies. In addition, a percolation threshold was observed in the composite film with 45 wt% Cu. Despite the appearance of this percolation threshold, the BT–Cu composite films all revealed low frequency dependence because the formation of micro-capacitor structures dominated their interiors. [ABSTRACT FROM AUTHOR]