Charge storage in metal-silicon nitride-silicon capacitors.
Metal-silicon nitride-silicon /MNS/ capacitor charge storage variation with temperature and time
TIME FUNCTION↗
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Selective Ion Enrichment and Charge Storage through Transport Hysteresis in Conical Nanopipettes
Greater selectivity and controls in the ion transport dynamics are essential in fields such as charge storage, separation, energy storage and conversion, neuromorphic computing and learning, electrochemistry, to name a few. Mechanistic insights into the intriguing hysteresis effects in the rectified electrokinetic transport through single conical nanopipettes are unveiled by combining time-resolved electroanalytical experiments with numeric simulation. Cations as counterions for surface charges are found to dominate not just the through-nanopore flux but also the hysteresis charges, that is, the net enriched or expelled charges during the transport process. Built on our earlier report on the through-nanopore ion flux dominated by counterions for surface charges, the “trapped ions” or hysteresis charges are analyzed herein. Cation selectivity is almost 100% in the hysteresis charges during the potential scans in low conductivity states driven by the combined applied and intrinsic surface electrical fields. Surprisingly, the cation selectivity in the total hysteresis charges remains high at 70–80% over a wide bulk concentration range in the high conductivity (HC) states, where higher ionic strength due to ion enrichment would decrease electrostatistic effects and thus ion selectivity. The retained high selectivity at HC is explained by the competition effects of electroosmotic flow against the co-ion migration. Furthermore, the respective cation and anion portions in the total hysteresis charges over a wide range of ionic strength and measurement conditions provide generalizable strategies for improvements in both transport throughput and selectivity.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Differential imaging using charge-coupled device (CCD) imagers with on-chip charge storage
A CCD technique is described which allows long integration periods between readouts together with moderate chopping rates. During each phase of a differential chopping cycle, one set of charge images is shifted to the center of the chip, which is light sensitive. At the same time, the other set of charge images is shifted under one of two masked areas which serve as charge-storage sites. Since the vertical shifting between phases can be accomplished in much less time than the typical exposure per phase, there is negligible image smearing. For a given light level and chopping rate the performance of this technique is limited primarily by the readout noise and the vertical charge transfer inefficiency. If many transfer cycles are required between readouts, the charge transfer inefficiency will diffuse the accumulated charge images along the vertical columns. Laboratory and astronomical data obtained with this technique using a CCD camera and the 2.3 m telescope on Kitt Peak are presented.
Stockman, H. S.↗
Phase transformation and electrochemical charge storage properties of vanadium oxide/carbon composite electrodes synthesized via integration with dopamine
Abstract Chemically preintercalated dopamine (DOPA) molecules were used as both a reducing agent and a carbon precursor to prepare δ‐V 2 O 5 · n H 2 O/C, H 2 V 3 O 8 /C, VO 2 (B)/C, and V 2 O 3 /C nanocomposites via hydrothermal treatment or hydrothermal treatment followed by annealing under Ar flow. We found that the phase composition and morphology of the produced composites are influenced by the DOPA:V 2 O 5 ratio used to synthesize (DOPA) x V 2 O 5 precursors through DOPA diffusion into the interlayer region of the δ‐V 2 O 5 · n H 2 O framework. The increase of DOPA concentration in the reaction mixture led to a more pronounced reduction of vanadium and a higher fraction of carbon in the composites’ structure, as evidenced by X‐ray photoelectron spectroscopy and Raman spectroscopy measurements. The electrochemical charge storage properties of the synthesized nanocomposites were evaluated in Li‐ion cells with nonaqueous electrolytes. δ‐V 2 O 5 · n H 2 O/C, H 2 V 3 O 8 /C, VO 2 (B)/C, and V 2 O 3 /C electrodes delivered high initial capacities of 214, 252, 279, and 637 mAh g –1 , respectively. The insights provided by this investigation open up the possibility of creating new nanocomposite oxide/carbon electrodes for a variety of applications, such as energy storage, sensing, and electrochromic devices.
Materials Science↗
Effects of interlayer confinement and hydration on capacitive charge storage in birnessite
Nanostructured birnessite exhibits high specific capacitance and nearly ideal capacitive behaviour in aqueous electrolytes, rendering it an important electrode material for low-cost, high-power energy storage devices. The mechanism of electrochemical capacitance in birnessite has been described as both Faradaic (involving redox) and non-Faradaic (involving only electrostatic interactions). To clarify the capacitive mechanism, we characterized birnessite’s response to applied potential using ex situ X-ray diffraction, electrochemical quartz crystal microbalance, in situ Raman spectroscopy and operando atomic force microscope dilatometry to provide a holistic understanding of its structural, gravimetric and mechanical responses. These observations are supported by atomic-scale simulations using density functional theory for the cation-intercalated structure of birnessite, ReaxFF reactive force field-based molecular dynamics and ReaxFF-based grand canonical Monte Carlo simulations on the dynamics at the birnessite–water–electrolyte interface. We show that capacitive charge storage in birnessite is governed by interlayer cation intercalation. We conclude that the intercalation appears capacitive due to the presence of nanoconfined interlayer structural water, which mediates the interaction between the intercalated cation and the birnessite host and leads to minimal structural changes.
36 MATERIALS SCIENCE↗
Probing the In Situ Pseudocapacitive Charge Storage in Ti 3 C 2 MXene Thin Films with X-ray Reflectivity
MXenes are a large family of two-dimensional materials that are attractive for energy storage due to their high-rate charging capabilities as well as for electrochemical actuators, water purification, and many other technologies. Ion intercalation during electrochemically driven charge and discharge processes is the fundamental process associated with MXene functionality, which we have characterized here using in situ and operando X-ray reflectivity (XRR). Experiments performed at the Advanced Photon Source at Argonne National Laboratory monitored the changes in the structure of a Ti 3 C 2 MXene film on a platinum current collector as a function of static applied potential between 0.3 and –0.7 V vs Ag/AgCl in an aqueous 0.1 M Li 2 SO 4 electrolyte. Negative potential sweeps lead to a contraction of 1.2 Å in the interlayer spacing and a loss of electron density between the layers, likely due to Li + ion insertion and water removal. The change in lattice spacing includes a continuous variation vs potential as well as an additional discrete contraction that occurs near –0.35 V that has the characteristics of a first-order transition. The continuous change in the MXene interlayer spacing is associated with the capacitive charge, while the discrete change in structure correlated to the weak feature in the cyclic voltammogram at –0.35 V can be interpreted as either a pseudocapacitive charging process or a potential-dependent change in capacity.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Structuring, stochastic behavior, and charge storage capacity of redox-active microemulsions formulated with mixtures of toluene and ionic liquid as oil phase
Oil/water microemulsions (µEs) are promising electrolytes for redox flow batteries (RFBs) as they simultaneously improve charge capacity and ionic conductivity. Here, we report the successful formulation of bicontinuous µEs where the oil phase is a solution of trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)amide ionic liquid in toluene with redox-active ferrocene. We examined the effect of supporting electrolyte anion (NO 3 – , Cl – , ClO 4 – ) on the structure, reactivity, transport, and electrolytic performance of redox-active µEs. Neutron scattering and nuclear magnetic resonance showed that the domain size increased as Cl – > NO 3 – > ClO 4 – while the ferrocene diffusion coefficient increased as NO 3 – > Cl – > ClO 4 – . Scanning electrochemical microscopy indicated anion-dependent current fluctuations during electrolysis, with ClO 4 – exhibiting the least high-frequency oscillations, which correlate to the highest charge and discharge capacity and reversibility. All ionic liquid containing systems improved the performance of toluene-based µEs, highlighting new design principles for these electrolytes.
diffusion↗
Improved solid state electron-charge-storage device
Storage device is applicable in memory systems and in high-resolution arrays for light-responsive image sensing. The device offers high yield in multiple arrays and allows charge release with light striking only the edge of a metal electrode.
Kuper, A. B.↗
Pseudocapacitive Charge Storage in Electrochromic Transition-Metal Oxide Thin Films
Electrochromic pseudocapacitive transition-metal oxide materials, such as tungsten oxide, which combine fast response, high energy density, and optical effects, can play a significant role as energy storage materials. Here we investigate the electrochemical kinetics of thin films of tungsten oxide, which turn transparent to sky-blue color in the lithiated state due to the reduction of W 6+ to W 5+ . In this study, we investigated the charge density, charge transfer, ion diffusion, and interfacial behavior upon Li + insertion/de-insertion in WO 3 . The electrochromic thin film's pseudocapacitive and electrical double layer mechanism was differentiated based on the power-law. Faradaic diffusion-controlled process dominates over the surface capacitive behavior at scan rates below 40 mV s –1 . These films exhibit an areal charge density of around 100 mC cm –2 and a capacitance of 80 mF cm –2 , superior to most comparable electrochromic materials and supercapacitors. This work combines electrochromics and energy storage properties and provides a fundamental understanding of pseudocapacitive and electrochromic mechanisms in WO 3 .
25 ENERGY STORAGE↗
Transit time and charge storage measurements in heavily doped emitters
A first direct measurement of the minority-carrier transit time in a transparent heavily doped emitter layer is reported. The value was obtained by a high-frequency conductance method recently developed and used for low-doped Si. The transit time coupled with the steady-state current enables the determination of the quasi-static charge stored in the emitter and the quasi-static emitter capacitance. Using a transport model, from the measured transit time, the value for the minority-carrier diffusion coefficient and mobility is estimated. The measurements were done using a heavily doped emitter of the Si p(+)-n-p bipolar transistor. The new result indicates that the position-averaged minority-carrier diffusion coefficients may be much smaller than the corresponding majority-carrier values for emitters having a concentration ranging from about 3 x 10 to the 19th per cu cm to 10 to the 20th per cu cm.
Neugroschel, A.↗
Na-Ion Intercalation and Charge Storage Mechanism in 2D Vanadium Carbide
Explore the source record for details and available documents.
99 GENERAL AND MISCELLANEOUS↗
Operando leaching of pre-incorporated Al and mechanism in transition-metal hybrids on carbon substrates for enhanced charge storage
Insufficient exposure and utilization of active sites often induces an inferior reactivity for transition-metal-based two-dimensional (2D) materials. In response, we for the first time propose a universal "nano-tailoring" strategy to incorporate abundant defects and active sites into low-crystallinity nanosheets by electrochemically leaching of Al species. With MnAl layered double hydroxides (LDHs) as a representative example, potassium-birnessite MnO 2 (AK-MnO 2 ) with oxygen vacancies and abundant edge sites is successfully produced. The oxygen vacancies are shown to help optimize the electron-transfer and ion-adsorption capability. These integrated advantages endow the AK-MnO 2 with a high capacitance value of 239 F g –1 at 100 A g –1 . By further combining with soft X-ray absorption spectroscopy techniques, we unravel that the reducibility of M 2+ in M 2+ Al-LDH serves as the key descriptor for the reconstruction rate. Here, this "nano-tailoring" strategy can provide some important implications and clues to manipulating 2D materials for efficient energy storage and conversion.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Switchable Charge Storage Mechanism via in Situ Activation of MXene Enables High Capacitance and Stability in Aqueous Electrolytes
The need for reliable renewable energy storage devices has become increasingly important. However, the performance of current electrochemical energy storage devices is limited by either low energy or power densities and short lifespans. Herein, we report the synthesis and characterization of multilayer Ti 4 N 3 T x MXene in various aqueous electrolytes. We demonstrate that Ti 4 N 3 T x can be electrochemically activated through continuous cation intercalation over a 10 day period using cyclic voltammetry. A wide operating window of 2 V is maintained throughout activation. After activation, capacitance at 2 mV s -1 increases by 300%, 140%, and 500% in 1 M H2SO4, 1 M MgSO4, and 1 M KOH, respectively, while maintaining ~600 F g -1 at 2 mV s–1 after 50000 cycles in 1 M H 2 SO 4 . This activation process is possibly attributed to the unique morphology of the multilayered material, allowing cation intercalation to increase access to redox-active sites between layers. This work adds to the growing repository of electrochemically stable MXenes reported for aqueous energy storage applications. These findings offer a reliable option for reliable energy storage devices with potential applications in large-scale grid storage and electric vehicles.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Continuous transition from double-layer to Faradaic charge storage in confined electrolytes
Not provided.
Energy & Fuels↗
A Parallel Kinetic Model for Surface and Bulk Charge Storage in ε -MnO 2 Pseudocapacitors
Pseudocapacitive materials such as manganese dioxide (MnO 2 ) are attractive for energy storage applications due to their ability to combine the fast kinetics of capacitors with the higher energy density of battery-type systems. However, the electrochemical behavior of MnO 2 remains difficult to interpret mechanistically, in part because existing models often fail to distinguish between surface-based redox processes and bulk intercalation mechanisms. In this work, we develop a physics-based model that represents MnO 2 pseudocapacitance as a linear combination of two independent, parallel electrochemical processes: (i) the surface or near-surface redox storage and (ii) lithium ion intercalation into the bulk material. These two processes are treated with distinct kinetic and thermodynamic parameters and are assumed to proceed independently. The total measured current is assumed to be the sum of these two partial currents. We validate the model using rate-dependent cyclic voltammetry experiments, demonstrating that it captures key trends and provides physically interpretable parameters reflecting the relative contributions of surface and bulk processes. By enabling a clear separation between these mechanisms, the model offers a useful framework for analyzing pseudocapacitive materials and can guide the rational design of high-performance energy storage electrodes.
Energy - Storage↗
Camera tubes employing electron-imaging charge-storage targets
Secondary electron conduction camera tube evolution
Goetze, G. W.↗