Capacitance Of Electrode Research Articles

Enhancing the Electrochemical Performances of Disordered Li1.23Ni0.3Nb0.3Fe0.16O0.85F0.15 Cathode Material for Lithium-Ion Batteries by LiNbOx Coating.

For the next generation of lithium-ion batteries (LIBs), it is primary to seek high capacity and long-lifetime electrode materials. Li-excess disordered rock-salt structure (DRS) cathodes have gained much attention due to their high specific capacity. However, Li-excess can lead to a decrease in the structural stability of an electrode material. A new Li-rich DRS oxyfluorides, Li1.23Ni0.3Nb0.3Fe0.16O0.85F0.15 (F0.15) with a series amounts of LiNbOx (LN) coating (0, 5, 10, and 15 wt % denoted as F0.15-LN0, F0.15-LN5, F0.15-LN10, and F0.15-LN15, respectively), are successfully synthesized and evaluated as cathode materials in LIBs. Among them, F0.15-LN10 exhibits the highest initial discharge specific capacity of 296.1 mAh g-1 (at a current density of 20 mA g-1) with the capacity retention rate of 14% higher than that of the uncoated F0.15 after 80 cycles. Even at 300 mA g-1, F0.15-LN10 still delivers the highest discharge specific capacity of 130 mAh g-1. After 20 cycles, the charge-transfer impedance of F0.15-LN10 remained the smallest. The characterizations indicate that LN coating reduces the surface polarization of the cathode materials, slows the interfacial side reactions between the electrolyte and the electrode, and speeds up the Li+ diffusion. These results demonstrate that LN coating is an effective strategy to improve the electrochemical performance.

Behavior of NO3−-Based Electrolyte Additive in Lithium Metal Batteries

While lithium metal is highly desired as a next-generation battery material due to its theoretically highest capacity and lowest electrode potential, its practical application has been impeded by stability issues such as dendrite formation and short cycle life. Ongoing research aims to enhance the stability of lithium metal batteries for commercialization. Among the studies, research on N-based electrolyte additives, which can stabilize the solid electrolyte interface (SEI) layer and provide stability to the lithium metal surface, holds great promise. The NO3− anion in the N-based electrolyte additive causes the SEI layer on the lithium metal surface to contain compounds such as Li3N and Li2O, which not only facilitates the conduction of Li+ ions in the SEI layer but also increases its mechanical strength. However, due to challenges with the solubility of N-based electrolyte additives in carbonate-based electrolytes, extensive research has been conducted on electrolytes based on ethers. Nonetheless, the low oxidative stability of ether-based electrolytes hinders their practical application. Hence, a strategy is needed to incorporate N-based electrolyte additives into carbonate-based electrolytes. In this review, we address the challenges of lithium metal batteries and propose practical approaches for the application and development of N-based electrolyte additives.

Scalable slot-die coated flexible supercapacitors from upcycled PET face shields.

Upcycling Covid19 plastic waste into valuable carbonaceous materials for energy storage applications is a sustainable and green approach to minimize the burden of waste plastic on the environment. Herein, we developed a facile single step activation technique for producing activated carbon consisting of spherical flower like carbon nanosheets and amorphous porous flakes from used PET [poly(ethylene terephthalate)] face shields for supercapacitor applications. The as-obtained activated carbon exhibited a high specific surface area of 1571 m2 g-1 and pore volume of 1.64 cm3 g-1. The specific capacitance of these carbon nanostructure-coated stainless steel electrodes reached 228.2 F g-1 at 1 A g-1 current density with excellent charge transport features and good rate capability in 1 M Na2SO4 aqueous electrolyte. We explored the slot-die coating technique for large-area coatings of flexible high-performance activated carbon electrodes with special emphasis on optimizing binder concentration. Significant improvement in electrochemical performance was achieved for the electrodes with 15 wt% Nafion concentration. The flexible supercapacitors fabricated using these electrodes showed high energy and power density of 21.8 W h kg-1 and 20 600 W kg-1 respectively, and retained 96.2% of the initial capacitance after 10 000 cycles at 2 A g-1 current density. The present study provides a promising sustainable approach for upcycling PET plastic waste for large area printable supercapacitors.

Boron enriched edge-nitrogen defective carbon network toward high-capacity capacitive deionization

Nitrogen doping is an effective strategy to enhance the salt adsorption capacity (SAC) of carbon electrodes for capacitive deionization (CDI) via generating abundant active adsorption sites. However, the uncontrolled interior doping and the undesired defective sites usually restrict the further enhancement in SAC. Herein, the additional boron element is introduced into the carbon matrix to not only create the porous architectures but also modulate the types of doping species. It is observed that the introduction of B selectively converts the inert graphitic N into active pyrrolic N species with enhanced adsorption capacity in the carbon skeleton. Specifically, the optimized B enriched edge-N defective carbon network (ENC-X) exhibits a high edged N doping content of 85.8 %. Benefitting from the integrative modulation in surface functionalities, the optimized samples demonstrate a significantly higher SAC value of 84.6 mg g−1 in 500 mg L−1 NaCl solution at 1.2 V, comparable to that of the most carbonaceous materials reported so far. Additionally, density functional theory calculations uncover the synergistic effect between B and N doping, further facilitating the capacitive adsorption of sodium ions. Overall, this study highlights the advantages of regulating heteroatom species and co-doping, offering a new perspective for the application of heteroatom-doped carbon in CDI field.

MnO2-based capacitive system enhances ozone inactivation of bacteria by disrupting cell membrane

The application of ozone (O3) disinfection has been hindered by its low solubility in water and the formation of disinfection by-products (DBPs). In this study, capacitive disinfection is applied as a pre-treatment for O3 oxidation, in which manganese dioxide with a rambutan-like hollow spherical structure is used as the electrode to increase the charge density on the electrode surface. When a voltage is applied, the negative-charged microbes are attracted to the electrodes and killed by electrical interactions. The contact between microbes and capacitive electrodes leads to changes in cell permeability and burst of reactive oxygen species, thereby promoting the diffusion of O3 into the cells. After O3 penetrates the cell membrane, it can directly attack the cytoplasmic constituents, accelerating fatal and irreversible damage to pathogens. As a result, the performance of the capacitance-O3 process is proved better than the direct sum of the two individual process efficiencies. The design of capacitance-O3 system is beneficial to reduce the ozone dosage and DBPs with a broader inactivation spectrum, which is conducive to the application of ozone in primary water disinfection.

Facile synthesis of MgO-carbon nanocomposites for advanced capacitive electrode materials

Facile synthesis of MgO-carbon nanocomposites for advanced capacitive electrode materials

Co-assisted strategy of sacrificial salt-template and nitrogen-doping to promote lithium storage performance of NiO-Ni/N-C frameworks

Tailoring the omnidirectional conductivity networks in nickel oxide-based electrodes is important for ensuring their long lifespan, stability, high capacity, and high-rate capability. In this study, nickel metal nanoparticles and a three-dimensional nitrogen-doped carbon matrix were used to embellish the nickel oxide composite NiO–Ni/N–C via simplified hard templating. When a porous nitrogen-doped carbon matrix is present, a rapid pathway would be established for charging and discharging the electrons and lithium ions in a lithium-ion battery, thereby alleviating the volumetric expansion of the NiO nanoparticles during the operation of the battery. Moreover, the Ni0 ions added to serve as active sites to improve the capacity of the NiO-based electrodes and strengthen their conductivities. The multielement-effects of the optimal NiO–Ni/N–C electrode leads it to exhibit a capacity of 1310.8 mAh g-1 at 0.1 A g-1 for 120 loops and a rate capability of 441.5 mAh g-1 at 20.0 A g-1. Kinetic analysis of the prepared electrodes proved their ultrafast ionic and electronic conductivities. This strategy of hard templating reduces the number of routes required for preparing different types of electrodes, including NiO-based electrodes, and improves their electrochemical performance to enable their use in energy storage applications.

Capacitive deionization electrode fabrication using activated carbon derived from agriculture by-products toward industry application: A review

Capacitive deionization (CDI), membrane capacitive deionization (MCDI), and flow capacitive deionization (FCDI) are emerging technologies applied to remove ions from brackish water or saline wastewater based on electrode double layer (EDL) mechanisms. The electrode itself can be seen as the most important factor that determines the deionization efficiency of the CDI system. Electrode fabrication using activated carbon derived from agriculture byproducts is a useful solution to decrease cost, restrict environmental pollution, and enable agriculture waste recovery. In this review, the primary parameter's impact on activated carbon (AC) and the electrode fabrication process from the agriculture byproducts is detailed in a discussion to find the most optimal conditions. With excellent characteristics for the activated carbon such as a surface area of up to 2500 m2/g, it can be used to fabricate electrodes that have a high adsorption capacity of approximately 25 mg/g, able to be advanced to 40 mg/g with a modified AC. It can achieve a cycle performance of 95–97 %. The deionization efficiency of the CDI, MCDI, and FCDI systems can be up to 90 % with an input salt concentration from 2000 to 3000 mg/L where the water recovery ratio achieved is 50–90 %, alongside a salt rejection rate of about 7–75 %. AC can be modified to increase its special properties such as surface area, conductivity, and ion selectivity using different methods. The drawbacks and challenges of the CDI technology are also mentioned along with useful solutions such as electrode coating techniques using an anilox roller and a spray, for use in industry applications.

Impact of typology and density of point defects on capacitance of graphene-based electrodes

The influence of defects on graphene quantum capacitance has been widely studied using various modeling approaches and in particular the fixed-band approximation (FBA). However, computational models do not yield results in agreement with experiments and can rarely account for the effect of the metallic substrate. They typically predict capacitance values an order of magnitude higher than experiment. In this paper we assess the capacity of the recently developed interfacial capacitance model (ICM) based on density functional theory (DFT) calculations, to investigate the impact of three point-like defects on graphene capacitance. The modeled defects are single-vacancy, double-vacancy, and Stone-Wales; all defective graphene structures are modeled on Cu(111) substrate. The impact of the density of single-vacancy defects on the capacitance was carefully analyzed. The computations demonstrate that the ICM can predict capacitance of graphene on a metallic substrate in agreement with experiment even in the case of the existence of defect. This suggests that ICM can be generalized for assessing graphene capacitance and interfacial capacitance regardless of morphology of the surface. The results ranged from 1.692 μF cm−2 to 1.872 μF cm−2 for defective models, compared with 1.73 μF cm−2 of pristine model which is in agreement with experiment. Various defective cases were analyzed using density of states, projected density of states, electrons isosurfaces, and structural parameters. The charge separation triggered by defects can be correlated with the increase in capacitance as long as no chemical bonding is triggered by the defect between copper and graphene.

Elucidating the Role of Electrochemically Formed LiF in Discharge and Aging of Li-CFx Batteries.

Fifty years after its introduction, the lithium-carbon monofluoride (Li-CFx) battery still has the highest cell-level specific energy demonstrated in a practical cell format. However, few studies have analyzed how the main electrochemical discharge product, LiF, evolves during the discharge and cell rest periods. To fill this gap in understanding, we investigated molecular-level and interfacial changes in CFx electrodes upon the discharge and aging of Li-CFx cells, revealing the role of LiF beyond that of a simple discharge product. We reveal that electrochemically formed LiF deposits on the surface of the CFx electrode and subsequently partially disperses into the electrolyte to form a colloidal suspension during cell aging, as determined from galvanostatic electrochemical impedance spectroscopy (EIS), solid-state 19F nuclear magnetic resonance (NMR), dynamic light scattering (DLS), and operando optical light microscopy measurements. Electrochemical LiF formation and LiF dispersion into the electrolyte are distinct competing rate processes that each affect the cell impedance differently. Using knowledge of LiF dispersion and saturation, an in-line EIS method was developed to compute the depth of discharge of CFx cells beyond coulomb counting. Solid-state 19F NMR measurements quantitatively revealed how LiF and CF moieties evolved with discharge. Covalent CF bonds react first, followed by a combination of covalent and ionic CF bonds. Quantitively correlating NMR and electrochemical measurements reveals not only how LiF formation affects cell impedance but also that CF bonds with the most ionic character remain unreacted, which limits realization of the full theoretical specific capacity of the CFx electrode. The results reveal new insights into the electrochemical discharge mechanism of Li-CFx cells and the unique role of LiF in cell discharge and aging, which suggest pretreatment strategies and methods to improve and measure the performance of Li-CFx batteries.

Retraction Note: Graphene-Based Important Carbon Structures and Nanomaterials for Energy Storage Applications as Chemical Capacitors and Supercapacitor Electrodes: a Review

Retraction Note: Graphene-Based Important Carbon Structures and Nanomaterials for Energy Storage Applications as Chemical Capacitors and Supercapacitor Electrodes: a Review

On the Interaction between PEDOT:PSS Dispersions and Aluminium Electrodes for Solid State Electrolytic Capacitors

The use of conductive polymers in aluminium electrolytic capacitors prevents leakage and enlarges the temperature use range when compared with their liquid counterparts. PEDOT:PSS is an outstanding candidate due to its tunable properties, i.e., electronic conductivity (10−5 to 103 S/cm), and its high thermal stability. As a result of their synthesis, PEDOT:PSS dispersions are characterized by a low pH value, which can influence pH sensitive materials such as aluminium. However, no work to date has studied the interaction between PEDOT:PSS dispersions and aluminium oxide substrates. In this work, the interface and interaction between PEDOT:PSS and an aluminium electrode were studied for the first time via odd random phase electrochemical impedance spectroscopy and analysed post mortem by SEM and AFM characterization. PEDOT:PSS dispersions at different pH values (1.9, 4.9, 5.8) were applied in a layered manner onto a non-etched aluminium substrate with a grown oxide layer on top, which provided a model system for the analysis of the interface. The analysis showed that the acidic PEDOT:PSS dispersions attacked the aluminium substrate, forming pores on the surface, but had a positive impact on the capacitance of the aluminium oxide/PEDOT:PSS systems. On the other hand, neutral dispersions did not affect the aluminium electrode, but showed poor layer formation properties, and the electrochemical analysis displayed a dispersion of results ranging from capacitive to resistive behaviour.

One-step Solid-State Synthesis of V1.13Se2/V2O3 Heterostructure as a High Pseudocapacitance Anode for Fast-Charging Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) offer several benefits, including cost-efficiency and fast-charging characteristics, positioning them as attractive substitutes for lithium-ion batteries in energy storage applications. However, the inferior capacity and cycling stability of electrodes in SIBs necessitate further enhancement due to sluggish reaction kinetics. In this respect, the utilization of heterostructures, which can provide an inherent electric field and abundant active sites on the surface, has emerged as a promising strategy for augmenting the cycling stability and rate features of the electrodes. This work delves into the utilization of V1.13Se2/V2O3 heterostructure materials as anodes, initially fabricated via a simplified one-step solid-state sintering technique. The high pseudocapacitance and low characteristic relaxation time constant give the V1.13Se2/V2O3 heterostructure impressive properties, such as a high capacity of 328.5 mAh g-1 even after 1500 cycles at a high current density of 2 A g-1 and rate capability of 278.9 mAh g-1 at 5 A g-1. Moreover, the assembled sodium-ion full battery delivers a capacity of 118.5 mAh g-1 after 1000 cycles at 1 A g-1. These findings provide novel insight and guidance for the rapid synthesis of heterojunction materials and the advancement of SIBs.

Template-free efficacious morphology of electrosynthesized polyaniline/β-cyclodextrin host-guest complex on Au/rGO modified electrode for removal and recovery of rare-earth and heavy elements from seawater

Global water pollution and scarcity of water resources are turning increasingly into serious threats to the survival of all living organisms on Earth. This study offers an influent strategy for the electrosynthesis of reduced graphene oxide/polyaniline/β-cyclodextrin (rGO/PAni/βCD) nanocomposite and its application to the removal/recovery of heavy elements (HEs) and rare-earth elements (REEs). Besides physicochemical and electrochemical studies, the surface morphological and statistical properties of fabricated nanocomposite electrode were examined. The textural and morphological characteristics of nanocomposite electrode were investigated via AFM data based on statistical, stereometric, and fractal theory. The cohesive, porous, and well-developed morphology of fabricated nanocomposite electrode has enabled the electrodeposition technique to achieve significant simultaneous removal/recovery efficiency of HE and REE ions such as Pb(II), Cu(II), Cd(II), Hg(II), Ce(IV), and Nb(V). Therefore, using rGO/PAni/βCD, considerable removal of HEs and REEs was achieved under optimized pH, 0.1 M KNO3, and 35 mg L−1 metal ion initial concentration during 20 min. Removal capacity of the nanocomposite electrode is preserved subsequent to 10 cycles of electrodeposition/desorption, according to the desorption investigation through eluted adsorbent at time intervals in deionized water and adjusted acidic pH values. Then, using rGO/PAni/CD nanocomposite, simulated seawater remediation was accomplished successfully. This interdisciplinary approach reveals that the removal/recovery efficiency enhance linearly along with the improvement of well-developed morphology for electrosynthesized composites. Thus, these results suggest how the morphological features of the polymer composites could improve remediation of water resources.

The impact of carbon material microstructure on li-ion storage behaviors of Si in Si/C anodes

Due to the demand for high mass loading in industrial application, micron-sized Si/C composites are preferred compared to nanoparticles. Utilizing Al-Si alloy as the raw material, an ant's nest-like porous Si/C composite material was successfully constructed through carbon coating and acid etching techniques, leading to an improvement in the cyclic stability of micron-sized Si/C composites under high mass loading. Furthermore, notable observations were made regarding the influence of carbon material type on the independent charge–discharge behavior of Si within the Si/C composite material, especially during the plateau region of Si-Li conversion processes. In-situ XRD test revealed transitions of Si between crystalline and amorphous states in the Si/C composite material during charge and discharge processes. Additionally, in Si/C composite materials fabricated using hard carbon, the increased lithium-ion transport rate attributed to the highly disordered structure of hard carbon promotes the acquisition of charges during delithiation process. As a result, this decelerates the lithium de-alloying process in Si-Li alloys, leading to an improved conversion depth of amorphous Si-Li alloys and a reduction in electrode capacity decay. This study provides valuable insights into Si conversion processes within Si/C composite materials and offers rational strategies for future material optimization.

Preparation of Ordered Fe3O4 Nanohoneycombs and Their Application in Capacitors

Fe substrates with a depression pattern were anodized to obtain Fe oxide films with a nanohoneycomb structure and orderly arranged cylindrical pores of uniform size. Crystalline Fe oxide films could be obtained by the heat treatment of amorphous samples obtained by the anodization of Fe substrates, but the atmosphere during heat treatment had a significant effect on the surface structure and crystallinity of the resulting samples. The heat treatment of the anodized samples in air produced a crystalline Fe oxide film consisting of Fe2O3 and Fe3O4, but the nanohoneycomb structure could not be maintained above 400 °C because the Fe substrate was oxidized during the heat treatment, and its surface structure changed significantly. On the other hand, the heat treatment of the anodized samples in N2 atmosphere yielded Fe3O4 nanohoneycombs, which retained their regular honeycomb structure after heat treatment. The evaluation of the capacitor properties of the heat-treated samples showed that the properties differed markedly owing to the effects of the surface structure and crystallinity, with the sample heat-treated at 400 °C in N2 atmosphere with the largest specific capacitance. The Fe3O4 nanohoneycombs obtained in this study are expected to be useful as electrodes for high-capacity capacitors.

Characteristics of evolution and collapse in spark-induced cavitation bubbles

Numerous scientists have thoroughly researched cavitation bubble dynamics using experimental methods such as tube arrest, underwater discharge, ultrasound, and laser focusing. In this study, with the aid of high-speed photography, the formation mechanism of the electrode-contact spark-induced cavitation bubble is discovered, i.e., electrolysis results in non-condensable gases wrapping the small inter-electrode gaps, and the non-condensable gases are broken down by discharge to form plasma, which then induces the cavitation bubble. Since the cavitation bubbles already contain a certain amount of non-condensable gases during the discharge process, the differences in the spatiotemporal evolution and collapse characteristics of the cavitation bubbles with varying amounts of non-condensable gases are further analyzed. The results show that underwater electrode-contact discharge system has an optimal voltage if the capacitance and discharge electrode size remain constant, and the cavitation bubbles generated under the optimal voltage condition are not only morphologically closest to the laser-induced cavitation bubbles, but also the change in radius over time during collapse is quite consistent with the Rayleigh bubble. Furthermore, compared to cavitation bubbles generated under varying voltages, those induced by the optimal voltage have a lower amount of non-condensable gases. This leads to the minimum first contraction radius and the maximum rebound radius being close to the corresponding values of the laser-induced cavitation bubbles. These new findings are of great significance for the improvement of experimental technology in the study of cavitation bubble dynamics, obtaining precise and dependable experimental data, and validating numerical simulations.

Analysis of CNT and rGO Mediation for an Efficient Super-Capacitive Response in Cr-Doped Co3O4 Based Composites

The synthesis of novel and high capacitance electrode materials has attracted much attention over the last few decades to meet the needs of electrode materials in supercapacitors. Cobalt oxide, one of several vanadium oxides, has recently gained popularity due to its unique layered structure, phase transition, and applications in supercapacitors. Here, we present structural, morphological, and electrochemical analysis of Cr-doped Co3O4 nanostructures and their carbon nanotubes/reduced graphene oxide (CNT/rGO) based composites. Hydrothermal and solvothermal routes are followed to prepare the samples. The active material is developed via a polymer-based binder and is used as the electrode in a three-electrode electrochemical system. X-ray diffraction confirms the spinel-type cubic crystal structure, while the stoichiometric elemental contents are verified via an energy dispersive X-ray spectroscopy. Well-shaped layered growth of the nanocomposites is revealed by field emission scanning electron microscopy. The electrochemical analysis is performed using a 2 M KOH electrolyte solution and a three-electrode electrochemical setup. The pure and Cr-doped nanocomposite samples reveal a pseudo capacitive behavior in all samples. The systematic capacitive and resistive response of the samples has also been presented in this report. The aforementioned attributes make the synthesized specimen a potential candidate for an electrode material.

High capacity rocking-chair capacitive deionization using highly crystalline sodium cobalt hexacyanoferrate (NaCoHCF) electrodes

Prussian blue analogue (PBA) electrodes are widely used cation-selective electrodes for electrochemical desalination technologies due to their high specific capacity rates and fast kinetic properties. Despite the fact that previous studies of PBAs for electrochemical desalination have shown remarkable desalination capacity levels, they remain insufficient if used to desalt highly concentrated salt water such as seawater. Here, we applied highly crystalline sodium cobalt hexacyanoferrate (NaCoHCF) electrodes, a type of PBA that can utilize two redox active sites, to a rocking-chair capacitive deionization (RCDI) process. The specific capacity of the NaCoHCF electrode using two redox active sites was 88 mAh g-1 (active material: 110 mAh g-1), confirmed to be 1.5 times higher than that of PBA electrode that use one redox active site. As a result of desalination tests, this system achieved a high desalination capacity of 123 mg g-1 (active material: 154 mg g-1) with 88% ion removal in a 500 mM NaCl solution. The results of this study present a considerable increase in the desalination capacity through the introduction of NaCoHCF electrodes that utilize two redox active sites in the RCDI system.

Regulating lithium nucleation and deposition on carbon cloth decorated with vertically aligned Ag-doped MnO2 nanosheet arrays for dendrite-free lithium metal anode

Metallic Li with high specific capacity and low electrode potential is considered as the most promising anode material. The main obstacles to its application are uncontrollable Li dendrites growth and infinite volume changes. Herein, we design a modified carbon cloth (CC) by vertically aligned MnO2 nanosheet arrays embedded with tiny Ag (Ag/MnO2@CC) through hydrothermal approach. Density functional theory (DFT) calculations indicate that MnO2 and Ag show a more negative adsorption energy (−4.31 and −2.34 eV) than C (−1.65 eV), implying their better lithiophilicity. Finite element simulations demonstrate that the Ag-doped MnO2 nanosheet arrays reduce local current density and redistribute Li-ion flux. Moreover, the channels assembled by vertical-aligned MnO2 nanosheets and 3D CC can offer sufficient spaces to buffer volume fluctuation during cycling. Accordingly, the Ag/MnO2@CC is employed as a lithiophilic host to supervise homogenous Li nucleation and deposition. The Ag/MnO2@CC electrodeposited with Li exhibits dendrite-free feature and a high Coulombic efficiency of 99.9% during 300 cycles. The symmetric cell shows an ultra-low polarization voltage of 14 mV over 1300 h at 1 mA cm−2 with the capacity of 1 mAh cm−1. The full cell paired with LiFePO4 exhibits excellent capacity of 105.5 mAh g−1 after 400 cycles at 1 C.