High Capacitance Density Research Articles

Enhancing Comprehensive Energy Storage Properties in Tungsten Bronze Sr0.53Ba0.47Nb2O6-Based Lead-free Ceramics by B-Site Doping and Relaxor Tuning.

Dielectric ceramics with relaxor characteristics are promising candidates to meet the demand for capacitors of next-generation pulse devices. Herein, a lead-free Sb-modified (Sr0.515Ba0.47Gd0.01) (Nb1.9-xTa0.1Sbx)O6 (SBGNT-based) tungsten bronze ceramic is designed and fabricated for high-density energy storage capacitors. Using a B-site engineering strategy to enhance the relaxor characteristics, Sb incorporation could induce the structural distortion of the polar unit BO6 and order-disorder distribution of B-site cations as well as the modulation of polarization in the SBGNT-based tungsten bronze ceramic. More importantly, benefiting from the effective inhibition of abnormal growth of non-equiaxed grains, Sb introduction into SBGNT-based ceramics could effectively suppress the conductivity and leakage current density, enhancing the breakdown strength, as proved by the electrical impedance spectra. Consequently, a remarkable comprehensive performance via balancing recoverable energy density (∼3.26 J/cm3) and efficiency (91.95%) is realized simultaneously at 380 kV/cm, which surpasses that of the pristine sample without the Sb dopant (2.75 J/cm3 and 80.5%, respectively). The corresponding ceramics display superior stability in terms of fatigue (105 cycles), frequency (1∼200 Hz), and temperature (20∼140 °C). Further charge-discharge analysis indicates that a high power density (89.57 MW/cm3) and an impressive current density (1194.27 A/cm2) at 150 kV/cm are achieved simultaneously. All of the results demonstrate that the tungsten bronze relaxors are indeed gratifying lead-free candidate materials for dielectric energy storage applications.

Tunable Capacitive Behavior in Metallopolymer-based Electrochromic Thin Film Supercapacitors.

Volumetric capacitance is a more critical performance parameter for rechargeable power supply in lightweight and microelectronic devices as compared to gravimetric capacitance in larger devices. To this end, we report three electrochromic metallopolymer-based electrode materials containing Fe2+ as the coordinating metal ion with high volumetric capacitance and energy densities in a symmetric two-electrode supercapacitor setup. These metallopolymers exhibited volumetric capacitance up to 866.2 F cm-3 at a constant current density of 0.25 A g-1. The volumetric capacitance (poly-Fe-L2: 544.6 F cm-3 > poly-Fe-L1: 313.8 F cm-3 > poly-Fe-L3: 230.8 F cm-3 at 1 A g-1) and energy densities (poly-Fe-L2: 75.5 mWh cm-3 > poly-Fe-L1: 43.6 mWh cm-3 > poly-Fe-L3: 31.2 mWh cm-3) followed the order of the electrical conductivity of the metallopolymers and are among the best values reported for metal-organic systems. The variation in the ligand structure was key toward achieving different electrical conductivities in these metallopolymers with excellent operational stability under continuous cycling. High volumetric capacitances and energy densities combined with tunable electro-optical properties and electrochromic behavior of these metallopolymers are expected to contribute to high performance and compact microenergy storage systems. We envision that the integration of smart functionalities with thin film supercapacitors would warrant the surge of miniaturized on-chip microsupercapacitors integrated in-plane with other microelectronic devices for wearable applications.

Organic field-effect transistors with low-temperature curable high-k hybrid gate dielectrics

We report a low-voltage-operated organic field-effect transistor that uses a hybrid gate insulator that has a high dielectric constant k. The gate insulator consists of a high-k polymer cyanoetylated pullulan (CEP) that can be efficiently cross-linked by glycidoxypropyltrimethoxysilane (GOPTMS) at low temperature (∼110 °C). The very low curing temperature is below the glass transition temperature T g of conventional plastic substrates for plastic electronics, and is therefore compatible with many plastic substrates for plastic electronics. The cross-linking is very efficient in that only 1/10 (w:w) GOPTMS: CEP produced densely cross-linked thin films with a smooth surface, good insulating property, high capacitance density and high k. The devices functioned at low voltage, and exhibited charge carrier mobility ∼1.83 cm2 V−1 s−1, and steep substheshold swing ∼88 mV dec−1. These results imply that high quality polymer gate insulators are achievable at low temperature with a very small fraction of blended crosslinking agents; this characteristic offers a method to achieve portable all-plastic flexible electronics that function at low voltage.

Application of Solution Method to Prepare High Performance Multicomponent Oxide Thin Films.

Capacitors play an increasingly important role in hybrid integrated circuits, while the MIM capacitors with high capacitance density and small thickness can meet the needs of high integration. Generally speaking, the films prepared with a single metal oxide dielectric often achieve a breakthrough in one aspect of performance, but dielectric layers are required to be improved to get better performance in leakage current, capacitance density, and transmittance simultaneously in modern electronic devices. Therefore, we optimized the performance of the dielectric layers by using multiple metal oxides. We combined zirconia, yttria, magnesium oxide, alumina, and hafnium oxide with the solution method to find the best combination of these five metal oxides. The physical properties of the multi-component films were measured by atomic force microscopy (AFM), ultraviolet-visible spectrophotometer, and other instruments. The results show that the films prepared by multi-component metal oxides have good transmittance and low roughness. The thicknesses of all films in our experiment are less than 100 nm. Then, metal–insulator–metal (MIM) devices were fabricated. In addition, we characterized the electrical properties of MIM devices. We find that multi-component oxide films can achieve good performances in several aspects. The aluminum-magnesium-yttrium-zirconium-oxide (AMYZOx) group of 0.6 M has the lowest leakage current density, which is 5.03 × 10−8 A/cm2 @ 1.0 MV/cm. The hafnium-magnesium-yttrium-zirconium-oxide (HMYZOx) group of 0.8 M has a maximum capacitance density of 208 nF/cm2. The films with a small thickness and a high capacitance density are very conducive to high integration. Therefore, we believe that multi-component films have potential in the process of dielectric layers and great application prospects in highly integrated electronic devices.

Enhanced electrochemical properties of zinc and manganese co-doped NiO nanostructures for its high-performance supercapacitor applications

In electrochemical energy storage devices, improving the availability of ions in the electrodes for charge storage and rate performance is a challenging task in the present era. So, in this report, an attempt was made to prepare Zn and Mn co-doped NiO nanostructures with improved electrochemical performance. The structural study revealed pure, and co-doped NiO nanostructures crystallize into face-centred cubic geometry with space group Fm3m. A prominent decrease in grain size was noticed with the increase in Mn concentration, showing an inverse relation with the optical bandgap. The room temperature ferromagnetism was improved by Mn doping. The electrochemical study proves the pseudocapacitive nature, with enhanced specific capacitance (846.71 Fg−1) in Ni0.9Zn0.04Mn0.06O nanoparticles. The galvanostatic charge–discharge study revealed a power density of 8900 W/kg at an energy density of 12.47 Wh/kg in Ni0.9Zn0.04Mn0.06O nanostructures. The improved specific capacitance, fascinating charging-discharging ability, and high-power density of Ni0.9Zn0.04Mn0.06O nanostructures makes it a special candidate for high-performance supercapacitor.

Dielectric Properties Investigation of Metal-Insulator-Metal (MIM) Capacitors.

This study presents the construction and dielectric properties investigation of atomic-layer-deposition Al2O3/TiO2/HfO2 dielectric-film-based metal–insulator–metal (MIM) capacitors. The influence of the dielectric layer material and thickness on the performance of MIM capacitors are also systematically investigated. The morphology and surface roughness of dielectric films for different materials and thicknesses are analyzed via atomic force microscopy (AFM). Among them, the 25 nm Al2O3-based dielectric capacitor exhibits superior comprehensive electrical performance, including a high capacitance density of 7.89 fF·µm−2, desirable breakdown voltage and leakage current of about 12 V and 1.4 × 10−10 A·cm−2, and quadratic voltage coefficient of 303.6 ppm·V−2. Simultaneously, the fabricated capacitor indicates desirable stability in terms of frequency and bias voltage (at 1 MHz), with the corresponding slight capacitance density variation of about 0.52 fF·µm−2 and 0.25 fF·µm−2. Furthermore, the mechanism of the variation in capacitance density and leakage current might be attributed to the Poole–Frenkel emission and charge-trapping effect of the high-k materials. All these results indicate potential applications in integrated passive devices.

A high energy density supercapacitor fabricated with aqueous polymer electrolyte based on soybean protein isolate grafted by polyacrylic acid

Soybean protein isolate (SPI) has good reactivity, hydrophilicity and film-forming properties, but its electrochemical performance is poor when used as a polymer electrolyte matrix. The graft-modification of the SPI using polyacrylic acid (PAA) allows the introduction of strong hydrophilic carboxyl groups into the SPI molecular chains. This enables the SPI to effectively absorb electrolytes in the subsequent electrolyte adsorption process, resulting in a modified polymer electrolyte. The resulting constructed supercapacitor can operate stably in a voltage window of 0–2 V and exhibit excellent electrochemical behavior with a high single electrode specific capacitance up to 293.08 F g−1 and an energy density of 38.76 W h kg−1 at a power density of 734.38 W kg−1, which is much better than SPI-based supercapacitor. This simple, low-cost and environmentally friendly approach has a great potential for the development of high-performance supercapacitor with high voltage window, high specific capacitance and high energy density.

Boosting Low-Temperature Resistance of Energy Storage Devices by Photothermal Conversion Effects.

While flexible supercapacitors with high capacitance and energy density is highly desired for outdoor wearable electronics, their application under low-temperature environments, like other energy storage devices, remains an urgent challenge. Solar thermal energy converts solar light into heat and has been extensively applied for solar desalination and power generation. In the present work, to address the failure problem of energy storage devices in a cold environment, solar thermal energy was used to improve flexible supercapacitor performance at low temperature. As a proof of concept presented here, a typical all-solid-state supercapacitor composed of activated carbon electrodes and gel polymer electrolyte was coated by a carbonized melamine sponge. Due to the ability of photothermal conversion of carbonized melamine sponge, the capacitance of the supercapacitor was greatly enhanced, which could be further improved by adding surface plasmonic nanomaterials, for example, Ag nanowires. Compared with the device without photothermal conversion layers, the specific capacitance increased 3.48 times at -20 °C and retained 87% capacitance at room temperature and the specific capacitance increased 6.69 times at -50 °C and retained 73% capacitance at room temperature. The present work may provide new insights on the application of solar energy and the design of energy storage devices with excellent low-temperature resistance.

Construction of a porous carbon skeleton in wood tracheids to enhance charge storage for high-performance supercapacitors

Wood with vertically aligned tracheids has many potential applications in energy storage. Carbonized wood inherits the previous tracheid structure and has good electrical conductivity, which provides favorable conditions for its application in self-supporting electrodes of supercapacitors. However, problems such as low specific surface area, low space utilization, and hydrophobicity limit the development of wood-derived carbon (WC) as an electrode material. Here, to improve the specific surface area and tracheid space utilization of WC, a porous carbon skeleton (PCS) was simply and efficiently constructed in its interior by using glucose and sodium chloride templates, and then potassium hydroxide etching treatment was used to further improve the specific surface area and hydrophilicity of the PCS, resulting in an etched porous carbon skeleton (E-PCS). The prepared E-PCS@WC electrode had an excellent area/volumetric specific capacitance of 7.29 F cm−2/145.8 F cm−3, and the supercapacitor exhibited a high volumetric capacitance and volumetric energy density of 34.99 F cm−3 and 4.86 mWh cm−3 at a power density of 2.5 mW cm−2. The supercapacitor constructed from this electrode exhibited good cycling stability with a retention rate of 98.5% over 20,000 cycles at a current density of 50 mA cm−3. This research will provide new ideas and a scientific basis for the design, construction and application of new green energy storage devices.

Elastic polyaniline nanoarrays/MXene textiles for all-solid-state supercapacitors and anisotropic strain sensors

Wearable electronics have attracted much attention in recent years, and textiles have been considered as the desirable substrate. However, it remains a critical challenge to fabricate electronic textiles that are multifunctional, breathable, highly conductive, and elastic. Herein, we develop a novel chemical polymerization and coating strategy to construct interconnected networks of polyaniline (PANI) nanoarrays and MXene on the fiber surface. The fabricated PANI nanoarrays/MXene modified rib knitting fabric exhibit low electrical resistance and good elasticity. The all-solid-state PANI/MXene fabric-based supercapacitors show a high specific capacitance and energy density of 647 mF/cm2 and 8.08 μWh/cm2, respectively, which is higher than most MXene-based textiles. Moreover, the PANI/MXene fabrics demonstrate anisotropic yet exceptional strain sensing performance, including high sensitivity (gauge factor, 435.0), linearity (>0.9), and wide range (0–40.8%), which enables them as wearable sensors to detect large human motions accurately. This work provides a new approach to accomplishing high-performance textile-based wearable electronics.

Tough and redox-mediated alkaline gel polymer electrolyte membrane for flexible supercapacitor with high energy density and low temperature resistance

To meet the practical application requirements of the flexible supercapacitors, the improvements of the toughness and energy density attract more and more attention. Herein, a physically cross-linked double network alkaline gel polymer electrolyte (AGPE) membrane based on PVA and kappa-carrageenan is developed. In this AGPE membrane, KOH plays a dual role including carrier donator and ion cross-linker, which makes the AGPE membrane show the unique improvement of ionic conductivity (0.31 S/cm) and mechanical properties (tensile strength of 1.62 MPa and tensile elongation of 670%) at the same time. In order to improve energy density, the redox-active mediator p-phenylene diamine has been introduced in the AGPE membrane, endowing the fabricated supercapacitor with high electrode specific capacitance (741 F/g) and energy density (18.3 Wh/kg) with a maximum power density of 800 W/kg. Meanwhile, the supercapacitor can exhibit great flexibility and toughness, and maintain stable capacitance performance under bending and stretching state. Moreover, the supercapacitor shows an excellent low temperature resistance and it is able to maintain 82% of its room-temperature capacitance even at -40 °C. This investigation offers a strategy to prepare gel polymer electrolyte membrane with high adaptive ability of deformation and low temperature, which has potential application in various flexible, portable and wearable electronics. • Dual role KOH can improve conductivity and mechanical properties simultaneously. • PPD can signally increase the capacitance and energy density of EDLC supercapacitor. • Supercapacitor shows ideal electrochemical properties under deformation and coldness.

84%-Efficiency Fully Integrated Voltage Regulator for Computing Systems Enabled by 2.5-D High-Density MIM Capacitor

We present a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> -thin-profile power delivery solution including a charge pump with integrated passives. Targeting 1 W/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> or higher power density, a 2.5-D high-density metal-insulator-metal (MIM) capacitor deposited on high aspect ratio (HAR) (up to 5) oxide studs is proposed. With approximately 25-nm-thick HfAlOx dielectric, its measured capacitance density is 25.4 nF/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for a capacitor size ranging from 1/16 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> to 1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . This shows <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.6\times $ </tex-math></inline-formula> density improvement compared with the planar MIM. Theoretically, 86 nF/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> density@1.36-V bias can be obtained if a 10-nm dielectric is deposited. Moreover, the measured leakage current density is within 65 pA/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 1-V bias (negligible for a 1 W/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -power delivery). For a backside (BS) power delivery, this 2.5-D MIM capacitor can be realized by only three BS metal layers. This enables the low-cost and thin-profile delivery system ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim \!\!\mu \text{m}$ </tex-math></inline-formula> thickness), and the whole power delivery efficiency including a 1/2-ratio charge pump is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\eta \,\,=84$ </tex-math></inline-formula> %@1 W/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (>5% boost in the power efficiency).

Facile hydrothermal synthesis of Au-Mn3O4 decorated graphene oxide nanocomposites for solid-state supercapacitor

Nanocomposites of Au-Mn3O4 flowers decorated on graphene oxide have been developed through a hydrothermal technique to improve the efficiency and electrochemical behavior of transition metal oxide (TMO)-based energy materials. The mechanism for the formation of the flower morphology of the nanocomposites has been proposed with the help of time-dependent electron microscopy imaging. The surface properties and chemical composition of the nanocomposites were thoroughly investigated. The optimized nanocomposite has shown a high specific capacitance (475 F g−1) and excellent energy density (55.8 W h kg−1). The charge storage mechanism of the materials was also examined to provide an in-depth understanding of the superior electrochemical performance of the nanocomposites. In addition, the presence of graphitic carbon in the nanocomposites has resulted in better cycle stability of Au-Mn3O4//GO in an acidic electrolyte.

Highly Deformable, Conductive Double-Network Hydrogel Electrolytes for Durable and Flexible Supercapacitors.

Developing flexible energy storage devices with the ability to retain capacitance under extreme deformation is promising but remains challenging. Here, we report the development of a durable supercapacitor with remarkable capacitance retention under mechanical deformation by utilizing a physical double-network (DN) hydrogel as an electrolyte. The first network is hydrophobically associating polyacrylamide cross-linked by nanoparticles, and the second network is Zn2+ cross-linked alginate. Through soaking such a DN hydrogel into a high concentration of ZnSO4 solution, a highly deformable electrolyte with good conductivity is fabricated, which also shows adhesion to diverse surfaces. Directly attaching the hydrogel electrolyte to two pieces of an active carbon cloth facilely produces a flexible supercapacitor with a high specific capacitance and theoretical energy density. Remarkable capacitance retention under tension, compression, and bending is observed for the supercapacitor, which can also maintain above 87% of the initial capacitance after 4000 charge-discharge cycles. This study provides a simple way to fabricate hydrogel electrolytes for deformable yet durable supercapacitors, which is expected to inspire the development of next-generation flexible energy storage devices.

Sr-doped urchin-like NiCo hydroxide and Sr-doped flower-like NiCo hydroxide@O-doped layered porous carbon for high-performance asymmetric supercapacitors with gel electrolyte

In order to improve the engineering practicability and cyclic stability of electrode material, the biomass-based porous carbon is designed as the solid substrate to load the mixed metal hydroxide. O-doped layered porous carbon is prepared from bagasse pith by chemical activation. Its flat and broad surface is ideal for loading metal hydroxide. A simple strategy is devised to synthesize Sr-doped urchin-like NiCo hydroxide (U-SrNiCo-OH) and Sr-doped flower-like NiCo hydroxide@O-doped layered porous carbon (F-SrNiCo-OH@OLPC). The U-SrNiCo-OH electrode shows high specific capacity (616.69Cg−1 at 1Ag−1 and 425.00Cg−1 at 50Ag−1) and excellent rate performance (68.92% retention from 1Ag−1 to 50Ag−1). Compared with the U-SrNiCo-OH electrode, the F-SrNiCo-OH@OLPC-40 electrode exhibits close specific capacity (584.16Cg−1 at 1Ag−1 and 341.66Cg−1 at 50Ag−1) and higher cyclic stability (63.59% retention after 5000 cycles). When used as the positive material, F-SrNiCo-OH@OLPC-60 performs best. In the gel electrolyte, the asymmetric supercapacitor based on F-SrNiCo-OH@OLPC-60 delivers high specific capacitance (93.60Fg−1 at 0.5Ag−1 and 47.00Fg−1 at 10Ag−1) and high energy density (29.12Whkg−1 at 374.14Wkg−1). Based on the molecular dynamics (MD) simulations, the OLPC configuration with microporous structure similar to that of OLPC is constructed, and the charging dynamics of asymmetric supercapacitor is studied. F-SrNiCo-OH@OLPC, with low cost and excellent electrochemical performance, has great application potential in energy storage/conversion. The MD simulations provide a new perspective for understanding the energy storage process of asymmetric supercapacitor.

Flexible, ultralight, and high-energy density electrochemical capacitors using sustainable materials

Development of flexible, ultralight, scalable and non-leaking energy storage devices such as electrochemical capacitors that are on par with commercial standards and offer compliances while retaining safety remain a significant challenge for the realization of wearable devices. Generally, the bottleneck to the improvement of such devices is the need to use ecofriendly electrode and electrolyte materials with desirable surface, electrochemical and mechanical properties. Thus, this study provides a new platform for development of flexible, ultralight, freestanding electrochemical capacitor using a composite of cellulose/SWCNTs (CL/CNTs) electrode films and a new cellulose/NaHSO4 hydrogel electrolyte. Herein, we took advantage of the renewability and flexibility of cellulose in combination with the high conductivity and storage capacity of SWCNTs to create a high specific capacitance, energy and power density. Moreover, the new cellulose/NaHSO4 hydrogel electrolyte provided stable cycling, leading to non-leakage device exhibiting ∼100% capacitance retention after 3000 cycles.

Carbon hollow fibers with tunable hierarchical structure as self-standing supercapacitor electrode

• A wet-spinning combined with foaming was designed to make PAN hollow porous fiber. • The derived hollow porous carbon fiber showed hierarchical micro/meso/macro-pores. • Self-standing fiber-shape electrode had high capacitance and energy density. Hollow porous carbon fibers (HPCF) have shown great promise as electrode materials for high-performance supercapacitor due to its light weight and short ion diffusion pathway. However, it remains a challenge to prepare self-standing HPCF with abundant active sites and robust secondary structure via facile processing methods. We have fabricated a HPCF with hierarchical pores by a wet-spinning integrated with chemical foaming strategy and subsequent carbonization-activation. The unique cellular structure combined with hierarchical meso-/micro-pores in HPCF allows exposure of abundant active sites. Especially, interconnected macro-pores facilitates the permeability of liquid electrolyte and mesopores promotes the rate of ions transport. The effect of blowing agents (isocyanate) content on the microstructures and electrochemical properties of HPCF were investigated. The HPCF-10 as self-standing electrode delivered a large specific capacitance as high as 283F/g at 1 A/g and long-term cycle stability (100% capacitance retention after 10,000 cycles). The Mn 3 O 4 doped electrode had a pseudocapacitive behavior and showed an improved specific capacitance of 353F/g at 1A/g. The assembled asymmetric supercapacitor displayed an energy density of 17.8 Wh/kg and power density of 2.5 kW/kg. In addition, it displayed an excellent retention of 90.5% after 10,000 cycles. HPCF-based supercapacitors allow great promises for energy storage devices.

Electrochemical storage mechanism of interstratification-assembled Ti3C2Tx MXene/NiCo-LDHs electrode in alkaline, acid and neutral electrolytes

Different kinds of two-dimensional hybrid electrodes have high theoretical capacitance and energy density. However, the origin of the electrochemical storage mechanism still remains elusive in alkaline, acid and neutral electrolytes. Herein, the interstratification-assembled Ti 3 C 2 T x MXene/NiCo-LDHs electrodes were successfully prepared and studied in different electrolytes by in-situ Raman spectroscopy. The results show that H 2 O molecules in neutral electrolyte combine with –OH at the end of Ti 3 C 2 T x MXene during charging, and debonding occurs during discharge. Similarly, this reaction also occurs in the discharge process with NiCo-LDHs and provides smaller pseudocapacitance characteristics. Although this pseudocapacitance reaction also occurs in acidic and alkaline electrolytes, however, the difference is that the hydrogen ions will promote the electrochemical performance of Ti 3 C 2 T x MXene and has a certain corrosion consumption effect on NiCo-LDHs, but generally improve the electrochemical performance of Ti 3 C 2 T x MXene/NiCo-LDHs. Interestingly, the OH − in alkaline electrolyte can promote the electrochemical performance of NiCo-LDHs, and produce a new electrochemical reaction with –F between the layers of Ti 3 C 2 T x MXene, which greatly improves the overall electrochemical performance of this hybrid electrodes. As a result, Ti 3 C 2 T x MXene/NiCo-LDHs electrodes have the best electrochemical performance in alkaline electrolyte with capacitance of 283 F g −1 , energy density of 14.2 Wh kg −1 and power density of 3007.1 W kg −1 . This work lays a foundation for the preparation of high-performance two-dimensional hybrid electrochemical energy storage devices.

Pyrazine-based organic electrode material for high-performance supercapacitor applications

Pseudocapacitors (PCs) exhibit high capacitance and high energy density, which renders incredible execution in energy storage gadgets. PCs bridge the gap between batteries and electrostatic double-layer capacitors (EDLCs). Herein, we designed novel electrode material i.e. naphtho[2,3-h]naphtho[2′,3′:5,6]quinoxalino[2,3-a]naphtho[2′,3′:5,6]quinoxaline [2,3-c]phenazine-5,12,17,22, 27,30-hexaone (Pyz-ANQ) composed of hexaketocyclohexane (HKCH) and 2,3-diaminoanthraquione (ANQ) subunits. The Pyz-ANQ electrode has been fabricated on a Toray carbon paper (CP) and used as a pseudocapacitor electrode which showed efficient pseudocapacitor performance in a three-electrode configuration. The specific capacitance (Csp) by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) analysis are 85.2 F g−1 at a scan rate of 5 mV s−1 and 43.1 F g−1 at current density 0.5 A g−1 in 1 M H2SO4, respectively. The PCs behavior is attributed to the reversible redox chemistry of Pyz-ANQ. Furthermore, we fused the material into a symmetric solid-state two-electrode supercapacitor (SSSC) device for practical demonstration of its potential in future energy storage applications and it shows the Csp value by two methods CV and GCD such as 52.5 F g−1 @ 5 mV s−1 and 36.6 F g−1 @ 0.5 A g−1, as well as it shows excellent cyclic performance in three-electrode and two-electrode system in the percentage of 78.8% and 75.9% for 2000 GCD cycles. Significantly, Pyz-ANQ/CP electrode has an energy density of 2.6 Wh kg−1 at 4.7 kW kg−1 of power density, respectively. In this way, by utilizing HKCH and ANQ in the redox system, Pyz-ANQ/CP results in pseudocapacitive energy storage, bringing a new dimension to improve the chemistry of organic supercapacitors.

Synergistically modified WS2@PANI binary nanocomposite-based all-solid-state symmetric supercapacitor with high energy density

WS2@PANI nanocomposite prepared by hydrothermal and physical blending method shows remarkably high specific capacitance and energy density while retaining excellent cyclic stability.