Capacitance Of Electrode Research Articles

Operando Nanomechanical Mapping of Amorphous Silicon Thin Film Electrodes in All-Solid-State Lithium-Ion Battery Configuration during Electrochemical Lithiation and Delithiation.

An operando bimodal atomic force microscopy system was constructed to perform nanomechanical mapping of an amorphous Si thin film electrode deposited on a Li6.6La3Zr1.6Ta0.4O12 solid electrolyte sheet during electrochemical lithiation/delithiation. The evolution of Young's modulus maps of the Si electrode was successfully tracked as a function of apparent Li content x in lithium silicide (LixSi) simultaneously with real-time surface topography observation. At the initial stage of lithiation, the average modulus steeply decreased due to the generation of LixSi from intrinsic Si, followed by a moderate modulus reduction until the electrode capacity reached 3300 mAh g-1 (Li content x = 3.46). In the following delithiation, the gradual recovery of the average modulus of LixSi was observed up to 1467 mAh g-1 (Li content x = 1.54) at which delithiation stopped due to the significant volume change induced by phase transformation of LixSi.

High-performance supercapacitors based on self-supporting thick carbon electrodes from renewable biomass wood

It is expected that supercapacitors will be used for next generation emerging energy storage devices. The electrode is the most important component of supercapacitors, and thick carbon electrode is promising for supercapacitors, while maintaining a high specific capacitance and cycle life is still a fundamental challenge for thick electrodes. Herein, we reasonably designed a low cost, green, porous and high-quality loaded (40 mg cm−2) self-supporting thick carbon electrode (800 μm), and systematically studied effect of section pore structure on its electrochemical performance. The thick carbon electrode retained the natural pore structure of paulownia combined with mesopores and micropores formed by KOH etching, which increased the transport kinetics of electrolyte ions. The specific capacitance of the ultra-thick self-supported electrode reaches 7120.7 mF cm−2 (257.5 F g−1 and 89.1 F cm−3). The assemble symmetric supercapacitor (SSC) displayed a high-energy density of 2.55 mWh cm−3 at a power density of 3308 mW cm−3, and capacity retention rate of 87.75% atter 5000 cycles. The work provides a new ultra-thick electrode design strategy towards high performance energy storage devices.

3D interconnected porous graphene architecture as a high-performance capacitive deionization electrode

Capacitive deionization (CDI) is a promising technology for brackish water desalination because of its high efficiency, no secondary pollution and low cost. However, the ion removal capacity of CDI system for brackish water desalination is still insufficient. Herein, a new in-situ porous Cu template method is used to prepare a unique open three-dimensional mesoporous graphene foam (3DMG) with high CDI performance. The developed 3DMG material has rich mesoporous structure, interconnected pore structure, high specific surface area, good hydrophilicity and excellent electrical conductivity, which can achieve effective solution/pore contact, rapid ion migration and high electrosorption capacity. Therefore, the specific capacitance of 3DMG as high as 141.37F/g at 1 M NaCl and 10 mV/s, and the maximum salt adsorption capacity is as high as 32.08 mg/g (1000 mg/L, 1.2 V), which is significantly higher than that of graphene-based electrode materials reported in most literatures. It also shows excellent regeneration performance and stability after repeated electrosorption-desorption cycles. The developed 3DMG undoubtedly provides a promising electrode material platform for CDI devices, effectively solving the urgent problem of freshwater resource shortage.

Graphene Nanocomposite Materials for Supercapacitor Electrodes

Graphene and related materials (graphene oxide, reduced graphene oxide) as a subclass of carbon materials and their composites have been examined in various functions as materials in supercapacitor electrodes. They have been suggested as active masses for electrodes in electrochemical double-layer capacitors, tested as conducting additives for redox-active materials showing only poor electronic conductivity, and their use as a coating of active materials for corrosion and dissolution protection has been suggested. They have also been examined as a corrosion-protection coating of metallic current collectors; paper-like materials prepared from them have been proposed as mechanical support and as a current collector of supercapacitor electrodes. This entry provides an overview with representative examples. It outlines advantages, challenges, and future directions.

Zinc-copper dual-ion electrolytes to suppress dendritic growth and increase anode utilization in zinc ion capacitors.

The main bottlenecks that hinder the performance of rechargeable zinc electrochemical cells are their limited cycle lifetime and energy density. To overcome these limitations, this work studied the mechanism of a dual-ion Zn-Cu electrolyte to suppress dendritic formation and extend the device cycle life while concurrently enhancing the utilization ratio of zinc and thereby increasing the energy density of zinc ion capacitors (ZICs). The ZICs achieved a best-in-class energy density of 41 watt hour per kilogram with a negative-to-positive (n/p) electrode capacity ratio of 3.10. At the n/p ratio of 5.93, the device showed a remarkable cycle life of 22,000 full charge-discharge cycles, which was equivalent to 557 hours of discharge. The cumulative capacity reached ~581 ampere hour per gram, surpassing the benchmarks of lithium and sodium ion capacitors and highlighting the promise of the dual-ion electrolyte for delivering high-performance, low-maintenance electrochemical energy supplies.

Three-dimensional dual-layered conductive binder enables stable and high performance of SiOx/C anodes

Among practical anode materials for next-generation lithium-ion batteries (LIBs), SiOx has garnered substantial attention owing to its relatively low volumetric variation and high theoretical capacity. Nevertheless, the volumetric change of micro-SiOx remains a formidable challenge for existing adhesives. Here, we propose an innovative design strategy that amalgamates both rigidity and flexibility, in which rigid anion gum Arabic (GA), flexible acrylic random copolymer (ARC), and carbon nanotubes (CNTs) interwoven into a 3D network with strong interfacial adhesion and excellent mechanical properties. These attributes effectively restrict SiOx particles and favor a stable solid electrolyte interphase (SEI) layer formed on SiOx. Here, GA plays a pivotal role in dispersing CNTs and maintaining their consistent proximity to SiOx, thereby establishing stable electron conduction networks. The SiOx electrode still sustains a specific capacity of 760 mAh g−1 after 350 cycles under a high current of 1C. Additionally, at 0.2C, the SiOx electrode attains a notably high capacity of 1105 mAh g−1 with a capacity retention of 72.9 % at the 300th cycle, while exhibiting an excellent areal capacity of 1.4 mAh cm−2 even after 400 cycles. This work develops a straightforward yet highly efficacious approach for fabricating high areal capacity electrodes and offers promising prospects for improving the stableness of Si-based anodes.

Polyaniline packed activated carbon as pseudocapacitive negative electrodes

Hybrid supercapacitors (HSCs) are attracting more attentions due to their potential high power and energy density. To exploring high capacity negative electrode materials, especially the capacitive materials, is more critical for further enhancing the energy density of HSC in comparing with more reported advanced battery-type positive materials. For perfect combination of electrochemical double layer and pseudocapacitive capacitance in negative electrode, the method of evenly filling polyaniline on nanopores of activated carbon is developed herein with keeping large surface area, the suitable ion-diffusion structure of activated carbon and further obtaining rich surface redox-active sites. The polyaniline packed activated carbons exhibit high specific capacitance (437.9 F g−1 at 0.5 A g−1) in negative voltage window (0 to −1.0 V), superior rate performance (378.0 F g−1 at 30 A g−1), and excellent capacitance retention even at a high mass loading and a high current density (326.5 F g−1 at 10 mg cm−2 and 20 A g−1). Additionally, an aqueous HSC based on the polyaniline packed activated carbon negative electrode and Ni-Co-LDH positive electrode presents higher energy density of 44.6 Wh kg−1 at a power density of 377.1 W kg−1. The present study presents novel method and materials for developing high performance capacitive negative electrode materials.

Novel design of high elastic solid polymer electrolyte for stable lithium metal batteries

Li metal anodes have high specific capacity and low electrode potential, and have always been considered as one of the most promising anode materials. However, the growth of Li dendrites, unstable solid electrolyte interface layer (SEI), severe side reactions at the Li/electrolyte interface, and infinite volume expansion of the Li anode seriously hinder the practical application of solid-state Li metal batteries (LMBs). Herein, we report a polyurethane elastomer (TPU) material with high elasticity and interfacial stability as a solid polymer electrolyte (SPE) for LMBs. The synergistic effects of its designed soft chain forging (PEO) and hard chain segments (IPDI) can enhance Li ion conductivity, elastic modulus and flexibility of the SPE to settle the challenges of the Li metal anodes. Moreover, Li2S, as a solid-state electrolyte additive, is able to effectively inhibit the occurrence of side reactions at the interface between Li metal and SPE, promote the decomposition of N(CF3SO2)2− and in-situ generation of LiF with low Li+ diffusion barrier and excellent electronic insulation, achieving rapid Li ion transport and uniform Li deposition. As a result, stable cycle of up to 1400 h has been achieved for a Li||TPU-Li2S||Li battery at 0.1 mA/cm2 at 50 ℃, accompanied with a stable cycling performance of 350 h at a higher current density of 0.5 mA/cm2. Finally, the LiFePO4||TPU-Li2S||Li full battery exhibits an excellent cycling performance with a capacity retention rate of 80 % after 500 cycles at 1C. This simple and low-cost strategy provides novel design thoughts for practical application of high-performance SPEs in stable and long-life LMBs.

Asymmetric Solvents Regulated Crystallization-Limited Electrolytes for All-Climate Lithium Metal Batteries.

Electrolytes that can keep liquid state are one of the most important physical metrics to ensure the ions transfer with stable operation of rechargeable lithium-based batteries at a wide temperature window. It is generally accepted that strong polar solvents with high melting points favor the safe operation of batteries above room temperatures but are susceptible to crystallization at low temperatures (≤-40 °C). Here, a crystallization limitation strategy was proposed to handle this issue. We demonstrate that, although the high melting points of ethylene sulfite (ES, -17 °C) and fluoroethylene carbonate (FEC, ≈23 °C), their mixtures can avoid crystallization at low temperatures, which can be attributed to low intermolecular interactions and altered molecular motion dynamics. A suitable ES/FEC ratio (10 % FEC) can balance the bulk and interface transport of ions, enabling LiNi0.8 Mn0.1 Co0.1 O2 ||lithium (NCM811||Li) full cells to deliver excellent temperature resilience and cycling stability over a wide temperature range from -50 °C to +70 °C. More than 66 % of the capacity retention was achieved at -50 °C compared to room temperature. The NCM811||Li pouch cells exhibit high cycling stability under realistic conditions (electrolyte weight to cathode capacity ratio (E/C)≤3.5 g Ah-1 , negative to positive electrode capacity ratio (N/P)≤1.09) at different temperatures.

Asymmetric Solvents Regulated Crystallization‐Limited Electrolytes for All‐Climate Lithium Metal Batteries

AbstractElectrolytes that can keep liquid state are one of the most important physical metrics to ensure the ions transfer with stable operation of rechargeable lithium‐based batteries at a wide temperature window. It is generally accepted that strong polar solvents with high melting points favor the safe operation of batteries above room temperatures but are susceptible to crystallization at low temperatures (≤−40 °C). Here, a crystallization limitation strategy was proposed to handle this issue. We demonstrate that, although the high melting points of ethylene sulfite (ES, −17 °C) and fluoroethylene carbonate (FEC, ≈23 °C), their mixtures can avoid crystallization at low temperatures, which can be attributed to low intermolecular interactions and altered molecular motion dynamics. A suitable ES/FEC ratio (10 % FEC) can balance the bulk and interface transport of ions, enabling LiNi0.8Mn0.1Co0.1O2||lithium (NCM811||Li) full cells to deliver excellent temperature resilience and cycling stability over a wide temperature range from −50 °C to +70 °C. More than 66 % of the capacity retention was achieved at −50 °C compared to room temperature. The NCM811||Li pouch cells exhibit high cycling stability under realistic conditions (electrolyte weight to cathode capacity ratio (E/C)≤3.5 g Ah−1, negative to positive electrode capacity ratio (N/P)≤1.09) at different temperatures.

Harnessing laser technology to create stable metal halide perovskite-rGO conjugates as promising electrodes for Zn-ion capacitors.

We report that the direct conjugation of metal halide perovskite nanocrystals on rGO sheets can provide high performance and stable electrodes for Zn-ion capacitors. It is the first time that metal halide nanocrystals have been used to enhance the energy storage of 2D materials in capacitors by introducing an additional pseudocapacitance mechanism. In particular, we present a simple, rapid and room temperature laser-induced method to anchor CsPbBr3 nanocrystals on rGO sheets without affecting the initial morphology and crystal structure of the two components. The flexible and high surface area of the rGO sheets enables the conjugation of individual metal halide perovskite nanocrystals, giving rise to new synergetic functionalities. As a result, the specific capacitance of the perovskite-rGO conjugated electrodes can be enhanced by 178- and 152-times compared to those of the plain rGO and perovskite electrodes respectively.

Development and application of a CNT-Ag-Cu-Al/PS-based paper electrode for detecting diverse analytes in complex matrices.

Electrochemical sensors play a crucial role in the detection of different analytes in complex matrices, and their performance is highly dependent on the electrode capacity. However, most of the available electrodes can only be used for single-component detection, so it is urgent to develop electrodes with high sensitivity and selectivity for different components. Herein, we report an amphiprotic amino-bonded carbon nanotube-Ag/Cu/Al nanoparticle/polystyrene-coated paper electrode (CNT-Ag-Cu-Al/PS electrode), which can be used for the measurement of glucose (Glc), oxytetracycline (OTC), and hydroquinone (HQ), respectively. The results showed that the analytical sensitivity and selectivity of the CNT-Ag-Cu-Al/PS electrode were comparable to those of single metal-coated paper substrate. The developed electrode also exhibited excellent linear responses for Glc, OTC, and HQ in the ranges of 1.0-1000.0 μM, 1.0 × 10-2 to 10.0 μM, and 5.0 × 10-3 to 50.0 μM, and the limits of detection (LODs) were 0.2055 μM (Glc), 0.0074 μM (OTC), and 0.0048 μM (HQ). Owing to the characteristics of good selectivity, anti-interference, stability, and reproducibility, the CNT-Ag-Cu-Al/PS paper electrode has been successfully applied to the detection of these analytes in complex human body fluids, food, and environmental waters. The paper electrode is promising for the detection of target compounds in complex matrices.

Are SAXS and SANS suitable to extract information on the role of water for electric-double-layer formation at the carbon-aqueous-electrolyte interface?

This study reports on the applicability of X-ray transmission (XRT), small- and wide-angle X-ray scattering (SAXS/WAXS) and small-angle neutron scattering (SANS) for investigating fundamental processes taking place in the working electrode of an electric double-layer capacitor with 1 M RbBr aqueous electrolyte at different applied potentials. XRT and incoherent neutron scattering are employed to determine global ion- and water-concentration changes and associated charge-balancing mechanisms. We showcase the suitability of SAXS and SANS, respectively, to get complementary information on local ion and solvent rearrangement in nanoconfinement, but also underscore the limitations of simple qualitative models, asking for more quantitative descriptions of water-water and ion-water interactions via detailed atomistic modelling approaches.

Synthesis and performance of binder-free porous carbon electrodes in electrochemical capacitors.

Porous binder-free carbon electrodes were obtained by impregnating cellulose filter papers with phenolic resin through soft-salt template synthesis and thermal pyrolysis. These self-standing electrodes were used directly in a supercapacitor device. To understand the impacts of filter paper (FP) thickness on carbon filter paper (CFP) morphology, porosity, and surface functionalities, five different materials were examined. The CFP electrode thickness was adjusted linearly with the FP thickness to produce electrodes ranging from 100 to ∼800 μm. As the thickness of the CFP increased, there was an increase in the specific surface area and oxygen-based functionalities. Electrochemical testing in a 1 M KOH aqueous electrolyte demonstrated that electrode thickness played a key role in electrochemical capacitor (EC) performance, i.e., capacitance enhances linearly when the electrode becomes thinner. For low thicknesses (<280 μm), the capacitance and rate capability decreased slightly with increasing thickness; for high thicknesses, the performance drastically degraded despite the high specific surface area and oxygen surface functionalities. This effect was amplified at high regimes, indicating that high electrode thicknesses and fiber diameters limited electrolyte diffusion in the applied synthesis conditions. Thus, the high material porosity was inaccessible to ion adsorption. Consequently, thinner electrodes showed the highest capacitance (197 F g-1 at 0.1 A g-1) and rate capability (81%) values, exceeding those of their traditional binder-electrode counterparts prepared under similar conditions. Finally, for alkali metal hydroxide solutions, 1 M KOH exhibited a cation match with the salt template (KCl), while CsOH achieved additional capacitance retention (88% at 10 A g-1). Complex ion adsorption mechanisms were observed through a quartz crystal microbalance.

An ammonium vanadate/MXene nanocomposite for high-performance ammonium ion storage

We developed an NH4V4O10-MXene (NVO@MX) nanocomposite as promising positive electrode for advanced ammonium ion hybrid capacitors.

Impact of gate electrode on free chlorine sensing performance in solution-gated graphene field-effect transistors.

Free chlorine is widely used to disinfect water used for drinking and food processing. This requires highly sensitive, simple, and capable continuous-measurement sensors to enable the concentration of free chlorine in water to be monitored and controlled. Free chlorine sensors based on solution-gated graphene field-effect transistors (GFETs) are a suitable platform for highly sensitive and continuous measurements. However, their sensing mechanisms require further elucidation to improve their performance. In this study, we focused on the gate electrode and investigated its influence on the sensing performance. Using the free chlorine sensor based on the solution-gate GFET, we showed that the Dirac point voltage in the transfer curve changed significantly as the free chlorine concentration changed, and the electric double-layer capacitance of the gate electrode decreased. Furthermore, we demonstrated that a solution-gated GFET using graphene or boron-doped diamond as the gate electrode could be used to detect changes in the free chlorine concentration in the concentration range of tap water. The sensing performance in the low concentration range benefits from the wide potential window of carbon-based electrodes, which do not have electrochemically active sites. Using these carbon-based materials as gate electrodes, GFETs have the potential to be used as durable sensors that are resistant to surface fouling and oxidation.

Supramolecular design as a route to high-performing organic electrodes.

Organic electrodes may someday replace transition metals oxides, the current standard in electrochemical energy storage, including those with severe issues of availability, cost, and recyclability. To realize this more sustainable future, a thorough understanding of structure-property relationships and design rules for organic electrodes must be developed. Further, it is imperative that supramolecular interactions between organic species, which are often overlooked, be included in organic electrode design. In this review, we showcase how molecular and polymeric electrodes that host non-covalent interactions outperform materials without these features. Using select examples from the literature, we emphasize how dispersion forces, hydrogen-bonding, and radical pairing can be leveraged to improve the stability, capacity, and energy density of organic electrodes. Throughout this review, we identify potential next-generation designs and opportunities for continued investigation. We hope that this review will serve as a catalyst for collaboration between synthetic chemists and the energy storage community, which we view as a prerequisite to achieving high-performing supramolecular electrode materials.

Rational electrolyte design and electrode regulation for boosting high-capacity Zn-iodine fiber-shaped batteries with four-electron redox reactions.

Aqueous Zn ion-based fiber-shaped batteries (AZFBs) with the merits of high flexibility and safety have received much attention for powering wearable electronic devices. However, the relatively low specific capacity provided by cathode materials limits their practical application. Herein, we first propose a simple strategy for fabricating high-capacity Zn-iodine fiber-shaped batteries with a high concentration electrolyte and a reduced graphene oxide fiber (GF) cathode. It was found that oxygen functional groups in the graphene sheet demonstrate strong interaction with polyiodides but hinder electron conductivity; thus, the optimal balance between the specific capacity and coulombic efficiency of the GF electrode can be a function of the surface properties at different hydrothermal temperatures. Besides, the regulated high concentration electrolyte effectively suppresses the diffusion of polyiodides, which is attributed to the constrained freedom of water. More importantly, a four-electron redox mechanism was experimentally revealed through in situ Raman spectra. As a result, this fiber-shaped battery delivers a superior high reversible capacity of 390 mA h cm-3 at 1 A cm-3, an excellent rate performance of 125.7 mA h cm-3 at a high current density of 8 A cm-3 and outstanding cycling life with 82% capacitance retention after 2500 cycles.

Water-soluble densely functionalized poly(hydroxycarbonylmethylene) binder for higher-performance hard carbon anode-based sodium-ion batteries

A high-density carboxylic acid containing water-soluble polymer binder, poly(hydroxycarbonylmethylene), enhances the specific capacity, rate capability and initial coulombic efficiency of hard carbon electrode in sodium-ion batteries.

Heterointerface regulation of covalent organic framework-anchored graphene via a solvent-free strategy for high-performance supercapacitor and hybrid capacitive deionization electrodes.

Covalent organic frameworks (COFs) with customizable geometry and redox centers are an ideal candidate for supercapacitors and hybrid capacitive deionization (HCDI). However, their poor intrinsic conductivity and micropore-dominated pore structures severely impair their electrochemical performance, and the synthesis process using organic solvents brings serious environmental and cost issues. Herein, a 2D redox-active pyrazine-based COF (BAHC-COF) was anchored on the surface of graphene in a solvent-free strategy for heterointerface regulation. The as-prepared BAHC-COF/graphene (BAHCGO) nanohybrid materials possess high-speed charge transport offered by the graphene carrier and accelerated electrolyte ion migration within the BAHC-COF, allowing ions to effectively occupy ion storage sites inside BAHC. As a result, the BAHCGO//activated carbon asymmetric supercapacitor achieves a high energy output of 61.2 W h kg-1 and a satisfactory long-term cycling life. More importantly, BAHCGO-based HCDI possesses a high salt adsorption capacity (SAC) of 67.5 mg g-1 and excellent long-term desalination/regeneration stability. This work accelerates the application of COF-based materials in the fields of energy storage and water treatment.