Nanostructured Carbon Electrodes Research Articles

Tailoring a hierarchical porous carbon electrode from carbon black via 3D diatomite morphology control for enhanced electrochemical performance.

Carbon black, a nano-porous material usually derived from the pyrolysis of waste tyres possesses varied particle sizes and morphology making it a viable material for several engineering applications. However, the high tendency for CB to agglomerate remains a challenge. To address this, bio-templating has been employed to produce a nanostructured porous carbon electrode material for supercapacitor applications using diatomite as a template. Diatomite-synthesized activated carbon (DSAC) was fabricated through a three-step process involving acid treatment of diatomite, thermal activation of carbon black, and bio-template synthesis. The resulting material was thoroughly characterized using XRD, Raman spectroscopy, BET analysis, and SEM imaging. Its electrochemical properties were assessed through cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The DSAC material exhibited a high specific surface area of 266.867 m2 g-1, pore volume of 0.6606 cm3 g-1, and mean pore radius of 1.8943 nm. The electrochemical evaluation revealed that DSAC demonstrates excellent electrochemical performance, achieving a high specific capacitance of 630.18 F g-1 and retaining 94.29% capacitance after 5000 cycles at 1 A g-1. The DSAC electrode is eco-friendly and a promising candidate for supercapacitor applications.

Structure and Dynamics of Adsorbed Dopamine on Solvated Carbon Nanotubes and in a CNT Groove.

Advanced carbon microelectrodes, including many carbon-nanotube (CNT)-based electrodes, are being developed for the in vivo detection of neurotransmitters such as dopamine (DA). Our prior simulations of DA and dopamine-o-quinone (DOQ) on pristine, flat graphene showed rapid surface diffusion for all adsorbed species, but it is not known how CNT surfaces affect dopamine adsorption and surface diffusivity. In this work, we use molecular dynamics simulations to investigate the adsorbed structures and surface diffusion dynamics of DA and DOQ on CNTs of varying curvature and helicity. In addition, we study DA dynamics in a groove between two aligned CNTs to model the spatial constraints at the junctions within CNT assemblies. We find that the adsorbate diffusion on a solvated CNT surface depends upon curvature. However, this effect cannot be attributed to changes in the surface energy roughness because the lateral distributions of the molecular adsorbates are similar across curvatures, diffusivities on zigzag and armchair CNTs are indistinguishable, and the curvature dependence disappears in the absence of solvent. Instead, adsorbate diffusivities correlate with the vertical placement of the adsorbate’s moieties, its tilt angle, its orientation along the CNT axis, and the number of waters in its first hydration shell, all of which will influence its effective hydrodynamic radius. Finally, DA diffuses into and remains in the groove between a pair of aligned and solvated CNTs, enhancing diffusivity along the CNT axis. These first studies of surface diffusion on a CNT electrode surface are important for understanding the changes in diffusion dynamics of dopamine on nanostructured carbon electrode surfaces.

High-performance nanostructured bio-based carbon electrodes for energy storage applications.

Polyacrylonitrile (PAN)-based carbon precursor is a well-established and researched material for electrodes in energy storage applications due to its good physical properties and excellent electrochemical performance. However, in the fight of preserving the environment and pioneering renewable energy sources, environmentally sustainable carbon precursors with superior electrochemical performance are needed. Therefore, bio-based materials are excellent candidates to replace PAN as a carbon precursor. Depending on the design requirement (e.g. carbon morphology, doping level, specific surface area, pore size and volume, and electrochemical performance), the appropriate selection of carbon precursors can be made from a variety of biomass and biowaste materials. This review provides a summary and discussion on the preparation and characterization of the emerging and recent bio-based carbon precursors that can be used as electrodes in energy storage applications. The review is outlined based on the morphology of nanostructures and the precursor’s type. Furthermore, the review discusses and summarizes the excellent electrochemical performance of these recent carbon precursors in storage energy applications. Finally, a summary and outlook are also given. All this together portrays the promising role of bio-based carbon electrodes in energy storage applications.Graphic abstract

Cost-efficient nickel-based thermo-electrochemical cells for utilizing low-grade thermal energy

Utilizing low-grade waste heat by thermo-electrochemical cells (TECs) has recently attracted considerable attention. TECs are easily maintained and exhibit simple structures and flexibility; therefore, they have been proposed as an alternative to thermoelectric devices for utilizing thermal energy harvesting. Nonetheless, TECs use costly platinum (Pt) or nanostructured carbon electrodes, which limits their widespread applications. In this study, a cost-effective nickel-based TEC is developed by controlling the pH of an electrolyte in the immunity or passivation window of nickel (Ni). Notably, our Ni-based TECs have displayed similar performance comparable to that of a Pt electrode. Moreover, the performance and corrosion tolerance of the Ni-based TEC system is higher than that of a carbon electrode. Considering economic aspects, Ni ($15 per kg) costs January 2000 of Pt ($29,700 per kg) and 1/10 of multiwalled nanotubes (MWNTs). The cost per power of the Ni-based TEC ($0.36 W−1) is calculated nearly 1/3500 of that of the state-of-the-art carbon nanotube aerogel sheet electrode. We demonstrate that Ni electrodes operating under alkaline conditions is proposed as a promising alternative to Pt or nanostructured carbon electrodes, possibly facilitating to the commercialization of TECs.

Pyrolytic carbon nanograss electrodes for electrochemical detection of dopamine

Carbon microelectrodes are being used extensively in numerous applications due to their intriguing and promising material properties. Here, we present the optimized fabrication of carbon nanograss (CNG) electrodes with a single-step UV lithography with SU-8 photoresist followed by maskless reactive-ion etching and pyrolysis. This simple method provides nanostructured carbon electrodes with high surface area suitable for electrochemical applications such as biosensing or electrochemical monitoring of cells. The effects of the initial SU-8 film thickness and the etching time on the electrochemical response of the electrodes was investigated using cyclic voltammetry and electrochemical impedance spectroscopy. Finally, the CNG electrodes were tested for electrochemical detection of dopamine and compared with 2D pyrolytic carbon electrodes without nanograss. The carbon electrodes with the highest CNG displayed an approximately 2-fold increase in electrochemical signals compared to the 2D electrodes due to the increase in electrode surface area.

Development of a MnO₂-Modified Screen-Printed Electrode for Phenol Monitoring

In this article, the electrochemical monitoring of phenol (Ph) in water by using a nanostructured MnO2-modified screen-printed carbon electrode (MnO2-SPCE) is reported. MnO2 nanoparticles were synthesized by the redox-precipitation method. Morphological, textural, and microstructural characteristics were investigated by scanning electron microscopy (SEM), X-ray diffraction, Raman, Brunauer–Emmett–Teller (BET) surface area, and pore volume analyses. Electrochemical properties of the modified MnO2-SPCE electrode have been investigated by cyclic voltammetry and linear sweep voltammetry. The detection of Ph in water by the developed sensor was exploited using square wave voltammetry and chronoamperometry. The sensor showed good characteristics, such as simple fabrication, low cost, good sensitivity, stability, reproducibility, and selectivity, against inorganic analytes and other phenolic compounds. The reported results demonstrated the great potential of nanostructured MnO2 in developing high performances electrochemical sensors to be utilized in the field of environmental pollution monitoring.

Carbon screen-printed electrodes modified with composite films based on silica for H2O2 determination

In this study, a nanostructured screen-printed carbon electrode (nanoSPCE) was modified with silica-based composite films containing metal oxides (MnO2 or CuO) without and with graphene oxide (GO). According to scanning electron microscopy results, uniform thin films with encapsulated metal oxides and GO were formed on the surface of nanoSPCEs. The electrochemical parameters of the modified electrodes were measured by cyclic voltammetry for the non-enzymatic determination of H2O2. Because of the combined action of GO and metal oxides, the modified electrodes have improved electrocatalytic performance for the determination of H2O2 in phosphate buffer solutions. NanoSPCE/MnO2/GO/SiO2 and nanoSPCE/CuO/GO/SiO2 exhibited stable current-voltage responses and good sensing for H2O2 with a wide linear detection range of 0.005–0.5 mM and 0.05–0.3 mM, respectively.

Bamboo-like N/S-codoped carbon nanotube aerogels for high-power and high-energy supercapacitors

Three-dimensional carbon aerogels with high surface area, low cost and excellent structural stability, have shown extraordinary promise for supercapacitors (SCs). Pore-forming and heteroatom-doping have been reported to play an important role in improving the power and energy densities of nanostructured carbon electrodes. We propose novel bamboo-like N/S-codoped carbon nanotube aerogels (NS–CNAs) facilely fabricated through MnO2-templated polymerization, freeze-drying and calcination. The cryptomelane-type MnO2 nanowires are served as self-sacrificing templates and oxidative initiators for polymerization of pyrrole in acidic environment. XPS analysis can confirm the N content of 4.09% and the S content of 0.66%, which are mainly derived from PPy with nitrogen-containing skeletons and PSS with sulfonic acid groups respectively. Based on porous structure and N/S codoping, the assembled NS-CNA SC can provide high supercapacitive performances, such as a specific capacitance of 328 F g−1 (at 1 A g−1), the rate capability of 66.5% (from 1 A g−1 to 10 A g−1), an energy density of 45.6 Wh kg−1 (at 0.5 kW kg−1) and the capacity retention of 97.4% (after 10,000 cycles), opening up a highly-efficient approach to developing high-performance supercapacitors.

Heteroatom‐Doped and Oxygen‐Functionalized Nanocarbons for High‐Performance Supercapacitors

AbstractElectrochemical capacitors (best known as supercapacitors) are high‐performance energy storage devices featuring higher capacity than conventional capacitors and higher power densities than batteries, and are among the key enabling technologies of the clean energy future. This review focuses on performance enhancement of carbon‐based supercapacitors by doping other elements (heteroatoms) into the nanostructured carbon electrodes. The nanocarbon materials currently exist in all dimensionalities (from 0D quantum dots to 3D bulk materials) and show good stability and other properties in diverse electrode architectures. However, relatively low energy density and high manufacturing cost impede widespread commercial applications of nanocarbon‐based supercapacitors. Heteroatom doping into the carbon matrix is one of the most promising and versatile ways to enhance the device performance, yet the mechanisms of the doping effects still remain poorly understood. Here the effects of heteroatom doping by boron, nitrogen, sulfur, phosphorus, fluorine, chlorine, silicon, and functionalizing with oxygen on the elemental composition, structure, property, and performance relationships of nanocarbon electrodes are critically examined. The limitations of doping approaches are further discussed and guidelines for reporting the performance of heteroatom doped nanocarbon electrode‐based electrochemical capacitors are proposed. The current challenges and promising future directions for clean energy applications are discussed as well.

Electron Transfer Kinetics at Graphene Quantum Dot Assembly Electrodes.

Electrochemical performance of nanostructured carbon electrodes was evaluated using cyclic voltammetry and a simple simulation model. The electrodes were prepared from soluble precursors by anodic electrodeposition of two sizes of graphene quantum dot assemblies (hexabenzocoronene (HBC) and carbon quantum dot (CQD)) onto a conductive support. Experimental and simulated voltammograms enabled the extraction of the following electrode parameters: conductivity of the electrodes (a combination of ionic and electronic contributions), density of available electrode states at different potentials, and tunneling rate constant (Marcus-Gerischer model) for interfacial charge transfer to ferrocene/ferrocenium (Fc/Fc+) couple. The parameters indicate that HBC and CQD have significant density of electronic states at potentials more positive than -0.5 V versus Ag/Ag+. Enabled by these large densities, the electron transfer rates at the Fc/Fc+ thermodynamic potential are several orders of magnitude slower than those commonly observed on other carbon electrodes. This study is expected to accelerate the discovery of improved synthetic carbon electrodes by providing fast screening methodology of their electrochemical behavior.

Biomass-Derived Carbon: A Value-Added Journey Towards Constructing High-Energy Supercapacitors in an Asymmetric Fashion.

Currently, asymmetric supercapacitors (ASCs) produced from supercapacitors (SCs) offer more benefits for energy-storage applications because they display a high operational voltage in aqueous-based electrolytes that may enhance grid storage and zero-power transportation with high energy density in the future. At the same time, the realization of low-cost energy devices through the construction of cheap electrode materials deserves a permanent place in the market once the goals of high energy, extra power, and long cycling stability are achieved. Biomass-derived carbon retrieved from sources such as plants has attracted considerable attention because of the rich abundance, low cost, and environmentally friendliness. In addition, the utilization of porous hierarchical structures has achieved enhanced electrochemical performance with excellent capacitance, outstanding stability, and praiseworthy rate capability. However, issues still persist in procedures used to obtain biomass-derived carbon materials with a high yield and a high degree of carbonization/graphitization, surface functionality, and porous characteristics, wherein the materials are used as electrodes in ASC devices. The present review briefly addresses the need for biomass-derived carbon materials in ASCs, comprehensively categorizes SCs in the context of their historical background, and elucidates the SC mechanism. In addition, influencing factors, such as the pore size distribution, role of surface functional groups, surface area, active-material loading, heteroatom doping, and activation techniques used in the preparation of biomass-derived carbon, have been discussed in detail. Moreover, this review assesses other nanostructured carbon electrodes used in ASCs and advances made in the fabrication of ASCs by using biomass-derived carbon in aqueous electrolytes. Finally, existing challenges and mandatory solutions toward developing cost-effective and high-performance ASCs by using environmentally friendly biomass-derived carbon materials are discussed in detail.

Potential-Dependent Double Layer Capacitance at Room Temperature Ionic Liquids - Carbon Electrode Interfaces Studied By Electrochemical Impedance Spectroscopy

The electrochemical double layer (EDL) at the electrode-electrolyte interface is the near-surface region which governs the electrochemical phenomena (e.g., electrodeposition, corrosion, and heterogeneous catalysis). Energy storage technologies (e.g., supercapacitors, batteries, solar cells etc.) rely on the structural and electrical organization of the interface for the storage capabilities. Improvement in performance and efficiency of these devices seeks a comprehensive understanding of how electrode properties (e.g., its bulk electrical properties, microstructure, surface functional groups) and the type and structure of electrolyte affect the interfacial organization. Room temperature ionic liquids (RTILs) are a unique class of electrolytes that are significantly different from conventional organic and aqueous electrolytes. RTILs have no solvent (i.e. are solely made up of ions) and exist in the liquid state at room temperature. This unique physical, chemical and molecular make-up results in remarkable properties like wide potential window (> 4 V), environmentally-benign characteristics, and excellent thermal and electrochemical stability. To optimally harness these properties and engineer RTIL-based devices, a fundamental understanding of their electrochemical behavior is critical. This critical knowledge gap is impeding the systematic progress toward innovative and more efficient energy storage technologies. Addressing this longstanding challenge requires a systematic study of structure, distal extent, and dynamics of the interfacial organization. The shape of capacitance-potential (C-E) trend can suggest the broad molecular architecture of interfacial organization. Traditional models of interfacial organization that are based on dilute-solution approximation cannot be applied to RTILs because of absence of solvent, high concentration (3-7 M), asymmetric charge distribution, and strong inter-ionic interactions. Theoretical studies based on mean-field theories predict a bell- or a camel-shaped C-E curvature depending on the nature of the RTIL. However, experimental capacitive studies exhibit a wide range of C-E trends such as a U-shaped, bell-shaped, or relatively featureless. Rigorous justification of these seemingly contradictory observations remains a challenge due to difficulties in reconciling theoretical and experimental data. In this presentation, capacitance of carbon electrode-RTIL interface will be discussed as a function of the applied potential, RTIL type, carbon electrode bulk material (sp2-, sp3- and hybrid sp2/sp3-bonded carbon), and the surface functional groups (hydrogen- and oxygen-terminated). Cyclic voltammetry and broadband electrochemical impedance spectroscopy were employed to investigate the C-E trends for nanostructured carbon electrodes in 1-alkyl-3-methylimidazolium-based RTILs. Comparison measurements were made using a planar gold electrode in the same RTILs. Two approaches for analyzing the impedance data were compared by fitting a) an electrical equivalent circuit in Nyquist plane b) complex capacitance using Cole-Cole function to deconvolute the effect of two relaxation processes observed over different timeframes. In addition, several ‘user-defined’ variables (such as potential window probed, potential scan direction, impedance data analyses methods etc.) will be discussed which can affect the resultant C-E trends. This work provides insights into the structure and dynamics of RTILs-electrode interfaces, the role of experimental variables, and impedance analyses methods for such electrochemical measurements.

Miniature Nanostructured Power Sources on the Basis of Direct Nuclear Energy Conversion

Tiny nanostructured high-energy power sources based on the direct conversion of nuclear energy to electricity are developed for power supply of microelectronic and micromechanical devices, as well as remote objects. The role of energy converters in such power sources is played by metal–insulator–metal (MIM) structures with a characteristic layer thickness of 10–100 nm, and highly thermodynamically stable and radiation resistant asymmetric supercapacitors comprising a nanostructured carbon electrode and an inorganic electrolyte possessing high thermodynamic and radiation resistance are applied for energy accumulation. The predicted autonomous operation time of the power sources is not less than 20 years, specific energy is 103 kWh/kg, and capacity is not less than 1 kWh/kg.

Nanostructured Carbon Electrodes for Increased Power Density in Flow Thermo-Electrochemical Generator Heat Sinks

Heat is a by-product of all energy conversion mechanisms. Efforts to utilize and dissipate heat remain a challenge for further development and optimization of energy conversion devices. Stationary thermo-electrochemical cell is a low cost method to harvest heat; however, it suffers from low power density. Flow thermo-electrochemical cell (fTEC) heat sink presents itself as a unique solution as it can simultaneously scavenge and remove heat to maintain devices in the operating range. In this work, multiwalled nanotube (MWNT) electrodes have been used and electrode configuration has been changed to maximize the temperature difference over a small interelectrode separation. As a result, power per unit area of fTEC heat sink has been improved by more than seven-fold to 0.36 W/m2.

Nanostructured carbon electrode modified with N-doped graphene quantum dots-chitosan nanocomposite: a sensitive electrochemical dopamine sensor.

A highly selective and sensitive dopamine electrochemical sensor based on nitrogen-doped graphene quantum dots–chitosan nanocomposite-modified nanostructured screen printed carbon electrode is presented, for the first time. Graphene quantum dots were prepared via microwave-assisted hydrothermal reaction of glucose, and nitrogen doping was realized by introducing ammonia in the reaction mixture. Chitosan incorporation played a significant role towards the selectivity of the prepared sensor by hindering the ascorbic acid interference and enlarging the peak potential separation between dopamine and uric acid. The proposed sensor's performance was shown to be superior to several recently reported investigations. The as-prepared CS/N,GQDs@SPCE exhibited a high sensitivity (i.e. ca. 418 µA mM cm−2), a wide linear range i.e. (1–100 µM) and (100–200 µM) with excellent correlations (i.e. R2 = 0.999 and R2 = 1.000, respectively) and very low limit of detection (LOD = 0.145 µM) and limit of quantification (LOQ = 0.482 µM) based on S/N = 3 and 10, respectively. The applicability of the prepared sensor for real sample analysis was tested by the determination of dopamine in human urine in pH 7.0 PBS showing an approximately 100% recovery with RSD < 2% inferring both the practicability and reliability of CS/N,GQDs@SPCE. The proposed sensor is endowed with high reproducibility (i.e. RSD = ca. 3.61%), excellent repeatability (i.e. ca. 0.91% current change) and a long-term stability (i.e. ca. 94.5% retained activity).

Stability and catalytic properties of nanostructured carbons in electrochemical environments

This work reports a study of the electrocatalytic properties and stability of nanostructured carbon electrodes by on-line differential electrochemical mass spectrometry (DEMS). A wide electrochemical characterization in 0.1 M NaHCO3 involving anodic (carbon corrosion and oxygen evolution reaction, OER) and cathodic (CO2 reduction and hydrogen evolution reaction, HER) key reactions in energy-conversion devices was performed. DEMS studies showed that the faradaic current from 1.3 to 1.6 V vs. RHE of carbons was only associated to CO2 formation by corrosion and not to OER, the stability being improved by the graphitic character of carbon. H2 evolution was also enhanced with graphitic carbon nanofilaments, even though metal traces might positively influence their catalytic activity. By comparison of the faradaic currents and the H2 formation signals, in the absence and presence of CO2, a high inhibition of the HER was established for all carbon electrodes due to the species adsorption from CO2 reduction.

Processing nanoparticle\u2013nanocarbon composites as binder-free electrodes for lithium-based batteries

The processing of battery materials into functional electrodes traditionally requires the preparation of slurries using binders, organic solvents, and additives, all of which present economic and environmental challenges. These are amplified in the production of nanostructured carbon electrodes which are often more difficult to disperse in slurries and require more energy-intensive and longer processing. In this study we demonstrate a new process for preparing binder-free nanocarbon/nanoparticle (Fe–C) composite electrodes and study the effect of processing on the nanocomposite’s cycling performance in lithium cells. The binder-free electrodes were prepared by a two-step method: pulsed-electrodeposition of iron-based catalyst followed by chemical vapor deposition of a carbon film. SEM and TEM of the Fe–C showed that the active materials have a fibrous and tortuous morphology with disordered nanocrystalline domains characteristic of an amorphous carbon. The Fe–C electrodes showed good mechanical stability and an excellent cycle performance with an average stable capacity of 221 mAhg−1, and 85% capacity retention for up to 50 cycles. By reducing the number of processing steps and eliminating the use of binders and other chemicals this new method offers a “greener” alternative than current processing methods.Graphical abstractSynopsis: gains in sustainability can be achieved by eliminating use of binders, chemicals, and the number of electrode’s processing steps in this new method.

A Simple and Direct Preparation of a Substrate-Free Interconnected Nanostructured Carbon Electrode from Date Palm Leaflets for Detecting Hydroquinone

A Simple and Direct Preparation of a Substrate-Free Interconnected Nanostructured Carbon Electrode from Date Palm Leaflets for Detecting Hydroquinone

Supersonic cluster beam printing of carbon microsupercapacitors on paper

Paper is a cheap, lightweight and renewable material with increasing applicative interest as a substrate for disposable and flexible electronics. The integration of planar energy storage devices on paper is a necessary and challenging step for the development of smart and autonomous flexible electronic platforms. Here we report the one-step, room temperature, fabrication of planar microsupercapacitors where nanostructured current collectors and carbon electrodes are deposited by supersonic cluster beam deposition (SCBD) on plain paper sheets and 1-Ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide ([Emim][NTf2]) is used as ionic liquid electrolyte. As-prepared microsupercapacitors showed a high capacitance density of about 7 F cm−3 and good capacity retention upon prolonged cycling. The encapsulation of SCBD-made microsupercapacitors by means of a polydimethylsiloxane layer and their usability in driving a low power temperature sensor are demonstrated.

Carbon-Based Electrodes for High Energy Electrochemical Capacitors

Electrochemical capacitors (ECs) have been considered as one of the most promising electrochemical energy storage devices owing to their several advantages such as high power density and long cycle life. In ECs, charges are stored on the surface of porous electrodes, therefore, the available energy density strongly depends on the microstructure and surface chemistry of the electrodes. However, state-of-the-art ECs only exhibit an energy density of 4–5 Wh/kg by using the electric double layer capacitance, which is still considerably lower than that of Li-ion batteries. In this presentation, we will show our recent results on enhancing the energy density of carbon-based electrodes for capacitive energy storage. Firstly, for replacing the conventional activated carbon in ECs, we developed high surface area carbons with a surface area of 3550 m2/g from polyacrylonitrile via a low-cost and scalable process.1 The high surface area carbon exhibited a capacitance of 150 F/g in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) and 210 F/g in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC). The composite electrodes consisting of high surface area carbon and carbon nanotubes delivered a high capacitance of~ 170 F/g in symmetric configurations, and a high capacity of~ 150 mAh/g in asymmetric configurations against lithium metal with excellent rate-performance at practical mass loading and bulk densities. Improving volumetric performance has been one of the major challenges in nanostructured carbon electrodes for capacitive energy storage. Recently, we developed a simple hydrothermal oxidation method for functionalizing carbon nanotube films using dilute nitric acid.2 This method shows high efficiency in densifying as-assembled single-walled carbon nanotubes (SWNT) films from 0.63 g/cm3 to 1.02 g/cm3, as well as introducing a considerable amount of redox-active oxygen functional groups on the surface of the SWNTs. The functionalized SWNT electrodes deliver high volumetric as well as gravimetric capacities, 154 Ah/L and 152 mAh/g, respectively, owing to the surface redox reactions between the introduced oxygen functional groups and Li ions. In addition, the functionalized electrodes also exhibit a remarkable rate capability by retaining its high capacity of 94 Ah/L (92 mAh/g) at a high discharge rate of 10 A/g.