Charge Storage Devices Research Articles

The mechanism underlying silicon oxide based resistive random-access memory (ReRAM)

In this work, we have inspected the theoretical resistive switching properties of two ReRAM models based on heterojunction structures of Cu/SiOx nanoparticles (NPs)/Si and Si/SiOx NPs/Si, in which dielectric layers of the silica nanoparticles present dislocations at bicrystal interfaces. To validate the theoretical model, a charge storage device with the structure Cu/SiOx/Si was fabricated and its ReRAM properties were studied. Our examinations on the electrical, thermal and structural aspects of resistive switching uncovered the switching behavior relies upon the material properties and electrical characteristics of the switching layers, as well as the metal electrodes and the interfacial structure of grains within the dielectric materials. We also determined that the application of an external electric field at Grain Boundaries (GB) is crucial to resistive switching behavior. Moreover, we have demonstrated that the switching behavior is influenced by variations in the atomic structure and electronic properties, at the atomic length scale and picosecond timescale. Our findings furnish a useful reference for the future development and optimization of materials used in this technology.

Ternary nanostructured MZnCo oxides (M=Al, Mg, Cu, Fe, Ni) prepared by hydrothermal method as excellent charge storage devices

Electrochemical properties of the spinel groups of MZnCo oxides (M=Al, Mg, Cu, Fe, Ni) as the active electrode materials are studied and compared in this investigation. Different morphologies (nano-sheets and nano-wires) of such transition metal oxides were hydrothermally synthesized at 150 °C for 5 h on a Ni foam as substrate. Their capacitive behavior is analyzed with cyclic voltammetry, chrono-potentiometry, and electrochemical impedance spectroscopy to compare their performance as the charge storage devices. The charge storage capacity of ZnCo2O4, AlZnCo, MgZnCo, CuZnCo, FeZnCo, and NiZnCo oxides was found to be 917, 995, 886, 702, 682, 462 C g−1, respectively, at 50 mV s−1 scan rate. Among them, the highest specific capacity was found to be for AlZnCo oxide (at below 50 mV s−1 scan rates) and also for MgZnCo oxide (at higher 50 mV s−1 scan rates). The obtained results represent that the specific capacity of CuZnCo, FeZnCo, and NiZnCo oxide electrodes is lower than ZnCo2O4 oxide in all the scan rates. The cyclic life of all the electrodes shows excellent life performance after 5000 cycles. According to the obtained results, MZnCo oxide with multiple oxidation states showed superior electrochemical properties for electrochemical applications as a result of the rapid ion/electron transfer.

RDNA-01. TUBULIN AND MICROTUBULES AS MOLECULAR TARGETS FOR TTFIELD THERAPY

Abstract TTField (Tumor-treating field) therapy utilizes low intensity intermediate frequency AC electric fields to reduce the spread of cancer. While it has attained FDA approval for the treatment of recurrent glioblastoma multiforme, the exact molecular targets of TTField therapy are not well understood. Microtubules are pipe-like polymers of the highly charged (–31 e) and strongly dipolar (dipole moment 1666 D) protein, α, β- tubulin. Studies on the electrical properties of microtubules have recently gained interest, with them being modelled as molecular targets of TTFields. Here, we experimentally show that while tubulin polymerized into microtubules leads to an increase in solution capacitance, unpolymerized tubulin has no appreciable effect. To the best of our knowledge, we present the first experimental quantification of the capacitance of a 20 μm-long microtubule. Using these results, we calculate the resonant frequency of a microtubule meshwork in a cell-like environment to be in the TTField regime. Our results utilize high ionic strength solutions and cell-like concentrations of tubulin to show the potential of microtubules as the targets of TTField action and as intracellular charge-storage devices. We conclude with a hypothesis of an electrically-tunable cell, where the dielectric properties of the cytoskeleton alter local and global charge storage and transport.

Influence of carboxymethyl cellulose content on structures and electrochemical behaviors of reduced graphene oxide films

Film-like charge-storage devices have attracted considerable attention owing to the emergence of flexible, bendable and wearable devices. Reduced graphene oxide (rGO), which is similar to graphene, is a promising deformable electrode for charge storage. However, film-like rGO has a densely stacked structure and poor wettability to the electrolyte, which are challenging issues. In this study, carboxymethyl cellulose/graphene oxide (CG) films with different amounts of carboxymethyl cellulose (CMC) were prepared. CMC, which is a derivative of cellulose and a water-soluble polymer, functioned as an activation agent. The CG films were converted into reduced CG (rCG), which had enhanced electrochemical properties because of the increase in the accessible areas to the electrolyte ions and the pseudocapacitance due to the thermal reduction process. The CG films possessed bending property and were retained after reduction. However, the bending property decreased after reduction when the CMC was added in excess. The thickness of the rCG films increased as vacancies were formed between stacked rGO layers, and basic oxygen functional groups capable of electrochemically performing a Faradaic redox reaction were created by CMC activation. The areal specific capacitance of the rCG films increased by a factor of 30 compared with the rGO film before cycling. With increasing charging/discharging cycles, the specific capacitance of the rCG films drastically increased owing to synergistic effects of electro-activation and pseudocapacitance.

Design & Implementation of Power Bank using Supercapacitor

Portable power banks are comprised of battery in a case with a circuit to control power flow. Power banks are becoming increasingly popular because the battery life of phones, tablets and portable media players is exceeded by the number of time gadgets used in aday. In this paper, the design and implementation of power bank using supercapacitors as a charge storage device is presented. Existing power banks use batteries to store charges and it takes a long time to charge completely. In this work, batteries are replaced with supercapacitors to take advantage of its quick charging and slow discharging feature. Supercapacitors are charged using charging and regulation circuit. An output regulator circuit delivers the necessary power for charging portable devices. A display is also implemented using a PIC microcontroller for monitoring.

Electrochemical study of perlite-barium ferrite/conductive polymer nano composite for super capacitor applications

Polyaniline/perlite-barium ferrite nanoparticles (PANI/PBF-NPs) composite electrodes were studied in here for super capacitor applications. The PBF-NPs synthesized using hydrothermal technique and then the composite electrode was fabricated electrochemically by cyclic voltammetry (CV) technique. Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller nitrogen adsorption/desorption (BET) and fast Fourier transform infrared spectroscopy (FTIR) were employed to study the morphological and structural properties of the prepared electrodes. Furthermore, various electrochemical techniques were used such as CV, Galvano static charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) to investigate their electrochemical performance as well. SEM graphs show uniform distribution of 60-nm PBF-NPs in the PANI filaments. The specific capacitance of PANI and composite electrodes was obtained to be 225 and 330 F/g, respectively. In addition, inclusion of PBF-NPs in the structure of PANI electrode had significantly increased the conductivity of composite electrodes. Continuous charge-discharge cycles test illustrated the good capability of this nano composite material for use as a charge storage device.

Behavior Modeling for Charge Storage in Single-Poly Floating Gate Device.

Single-poly floating gate is an efficient device for charge storage due to low power program, and implemented in a standard CMOS process. In floating gate, charges are injected and removed through the thin gate oxide. Among the gate leakage current mechanisms, FN tunneling is significant in the high electric field, while PF emission in the low electric field. We extracted FN and PF components from the measured current and built an accurate model which include fringing field effect induced by the 3-dimensional structure. This model helps engineers reflect exact behaviors of charge storage device in their circuit design.

“Induced Electron Transfer” in Silk Cocoon Derived N-Doped Reduced Graphene Oxide-Mo-Li-S Electrode

Developing 'carbon lithium sulfide composite (C-Li2S)' cathode is a promising strategy for Li-S battery. Quite interestingly, when Li and S are caged in a heavily nitrogen-doped reduced graphene oxide (NDRGO) matrix derived from Tassar silk cocoon, the composite (NDRGO-Li-S) electrode behaves like a supercapacitor. In this work, we first optimized the concentrations of sulfur and then introduced molybdenum in the NDRGO matrix to develop a stable NDRGO-Mo-Li-2S (where 2 stands for 2M) composite electrode. The electrode design process utilized the concepts of ‘embedded redox couples' and ‘induced electron transfer’; a putative strategy to alter internal electron-shuttling kinetics for applications in various charge storage devices; where a time of electron-shuttling is the key. In NDRGO-Mo-Li-2S composite the charge transport occurs via ‘induced electron transfer’, where Li+, is an external oxidant, provoking the inter atom electron transfer between Mo(VI), the internal oxidant, and S(-II), the internal reductant in Mo-S redox couple. This redox reaction is reversed using NDRGO, an external reductant inducing inter atom electron flow across (Mo(V)–(S2)) to complete the starting to product and back cycle. Such a redox cycle is competent for the flow of electrons in a lasting charge storage material through this unique bio-inorganic hybrid approach.

All-printed, interdigitated, freestanding serpentine interconnects based flexible solid state supercapacitor for self powered wearable electronics

While the textile based stretchable supercapacitors have been demonstrated as efficient charge storage devices, challenges in developing self powered wearable devices still exist. The present work describes a screen printed flexible and stretchable supercapacitor that can act as an energy buffering element for powering wearable fitness monitoring devices. The supercapacitor possesses interdigitated shaped intrinsically stretchable electrodes with free-standing serpentine interconnects. The symmetric supercapacitor relies on carbon nanotube and poly(aniline) as active materials and polyurethane as a stretch enduring binder. Such in-plane supercapacitors are realized by initially printing on a paper substrate, pre-coated with a water soluble layer, and then transferred onto a pre-strained elastomeric substrate. The supercapacitor showed excellent mechanical resiliency even though subjected to intense mechanical deformations. The electrode possessed highest areal capacitance of 167 mF/cm2 at a current density of 0.4 mA/cm2 and showed appreciable areal energy and power density of 14.9 μWh/cm2 and 0.29 mW/cm2, respectively. The supercapacitor showed conformal integration with the stretchable sweat band and which (3 devices, in series) can independently power a red light emitting diode. In combination with a flexible solar cell and a custom-made low power booster, the supercapacitor can continuously powers the wearable pulse rate sensor even in the presence of poor sunlight intensity.

Electrochemically Generated γ-Lix V2 O5 as Insertion Host for High-Energy Li-Ion Capacitors.

In this study, we explored the feasibility of using electrochemically generated γ-Lix V2 O5 as an insertion-type anode in the lithium-ion capacitor (LIC) with activated carbon (AC) as a cathode. Along with the native form of V2 O5 , their carbon composites are also used as the electrode material which is prepared by high-energy ball milling. The electrochemical pre-lithiation strategy is used to generate the desired γ-phase of V2 O5 (γ-Lix V2 O5 ). Under the optimized mass loading conditions, the LICs are assembled with γ-Lix V2 O5 as anode and AC as a cathode in the organic medium. Among the different LICs fabricated, AC/γ-Lix V2 O5 -BM50 configuration delivered an energy density of 33.91 Wh kg-1 @ 0.22 kW kg-1 with excellent capacity retention characteristics. However, a dramatic increase in energy density (43.98 Wh kg-1 @0.28 kW kg-1 ) is noted after the electrolyte modification with fluoroethylene carbonate. The high temperature performance of the assembled LIC is also studied and found that γ-Lix V2 O5 phase can be used as a potential battery-type component to construct high-performance hybrid charge storage devices.

Colossal Dielectric Response of PVDF-HFP Amalgamated Ultra-Low-Density Metal-Derived Nanoparticles: Frontier of an Excellent Charge Separator

As a high-dielectric separator, a wide variety of polymers like poly(vinylidene fluoride) (PVDF) and its co-polymer such as poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) are commonly employed due to having modifiable electrical properties with impregnating suitable dopants in the fabrication of a high-performance charge storage device. In this report, improvement of efficiency has been studied by tuning the doping concentration of triturated material like ultra-low-density copper sulphate (ULDCS) within PVDF-HFP matrix and found a massive increment in β phase (β%), dielectric constant (er) and ac conductivity (σac) with ∼ 2.3, ∼ 56 and ∼ 21 fold (at 100-Hz frequency), respectively, at a critical percentage of 10-ml doping compared to the pristine polymer matrix. One crucial factor like dielectric leakage has been taken into account intensely with reduction of ∼ 2.6 times at 100-Hz frequency with respect to the pristine one to obtain excellent behaviour of the separator. These extremely desirable properties can make the sample a very promising candidate to be used as a high-dielectric separator of an extraordinary charge storage device. In this context, a super-charge storage device has been fabricated using our synthesized high-dielectric material as a separator, and the device performance is amplified to a greater extent. Generation of high potential up to 3.77 V with high rate of retentivity (∼ 88.86%) is the key function of our device, and the efficiency of the device has also been verified by lighting up to 25 light-emitting diodes (LEDs) for 10 min.

Biomass-Derived Carbon Materials as Prospective Electrodes for High-Energy Lithium- and Sodium-Ion Capacitors.

Biomass-derived carbon materials have received special attention as efficient, low-cost, active materials for charge-storage devices, regardless of the power system, such as supercapacitors and rechargeable batteries. In this Minireview, we discuss the influence of biomass-derived carbonaceous materials as positive or negative electrodes (or both) in high-energy hybrid lithium-ion configurations with an organic electrolyte. In such hybrid configurations, the electrochemical activity is completely different to conventional electrical double-layer capacitors; that is, one of the electrodes undergoes a Faradaic reaction, whilst the counter electrode undergoes a non-Faradaic reaction, to achieve high energy density. The use of a variety of biomass precursors with different properties, such as surface functionality, the presence of inherent heteroatoms, tailored meso-/microporosity, high specific surface area, various degrees of crystallization, calcination temperature, and atmosphere, are described in detail. Sodium-ion capacitors are also discussed, because they are an important alternative to lithium-ion capacitors, owing to the low abundance and high cost of lithium. The electrochemical performance of carbonaceous electrodes in supercapacitors and rechargeable batteries are not discussed.

Biomimetic Solid-State Zn2+ Electrolyte for Corrugated Structural Batteries.

Batteries based on divalent metals, such as the Zn/Zn2+ pair, represent attractive alternatives to lithium-ion chemistry due to their high safety, reliability, earth-abundance, and energy density. However, archetypal Zn batteries are bulky, inflexible, non-rechargeable, and contain a corrosive electrolyte. Suppression of the anodic growth of Zn dendrites is essential for resolution of these problems and requires materials with nanoscale mechanics sufficient to withstand mechanical deformation from stiff Zn dendrites. Such materials must also support rapid transport Zn2+ ions necessary for high Coulombic efficiency and energy density, which makes the structural design of such materials a difficult fundamental problem. Here, we show that it is possible to engineer a solid Zn2+ electrolyte as a composite of branched aramid nanofibers (BANFs) and poly(ethylene oxide) by using the nanoscale organization of articular cartilage as a blueprint for its design. The high stiffness of the BANF network combined with the high ionic conductivity of soft poly(ethylene oxide) enable effective suppression of dendrites and fast Zn2+ transport. The cartilage-inspired composite displays the ionic conductance 10× higher than the original polymer. The batteries constructed using the nanocomposite electrolyte are rechargeable and have Coulombic efficiency of 96-100% after 50-100 charge-discharge cycles. Furthermore, the biomimetic solid-state electrolyte enables the batteries to withstand not only elastic deformation during bending but also plastic deformation. This capability make them resilient to different type of damage and enables shape modification of the assembled battery to improve the ability of the battery stack to carry a structural load. The corrugated batteries can be integrated into body elements of unmanned aerial vehicles as auxiliary charge-storage devices. This functionality was demonstrated by replacing the covers of several small drones with corrugated Zn/BANF/MnO2 cells, resulting in the extension of the total flight time. These findings open a pathway to the design and utilization of corrugated structural batteries in the future transportation industry and other fields of use.

Structural and Electronic Properties of PPy-DBSA/Zirconium Oxide Composites

The composites of doped polypyrrole (PPy) with dodecylbenzenesulfonic acid (DBSA) and zirconium oxide (ZrO2) nanoparticles have been prepared by in-situ polymerization method. The structural properties of synthesized polypyrrole and PPy-DBSA-ZrO2 were studied by X-ray diffraction (XRD) analysis. XRD pattern show that PPy-DBSA is intercalated into the layers of ZrO2 successfully and thus the degree of crystallinity increases due to crystalline nature of ZrO2. FTIR analysis indicated that there is a strong interaction between PPy-DBSA and ZrO2 nanoparticles. Electronic properties (dielectric and conductivity) of PPy and PPy-DBSA-ZrO2 composite have been investigated between frequency ranges from 20 Hz to 1M Hz. Higher dielectric constants and dielectric losses of PPy-DBSA-ZrO2 composites than those of synthesized PPy and PPy-DBSA were found. As the content of ZrO2 increased, the dielectric constant and loss also increased. The value of dielectric constant for all samples is very high at low frequency but decreases with increase in frequency. Synthesis of PPy-DBSA-ZrO2 composite materials with a large dielectric constant is essential for the improvement of a novel generation dynamic RAM and in charge storage devices.

Electrode engineering starting from live biomass: a ‘smart’ way to construct smart pregnant hybrids for sustainable charge storage devices

Electrode engineering beginning from live biomass is confirmed as a ‘smart’ way to construct smart hybrids for sustained charge storage.

Electrical double layer supercapacitors based on graphene nanoplatelets electrodes in organic and aqueous electrolytes: Effect of binders and scalable performance

The effect of some commercial binders, carboxymethyl cellulose, polyvinylidene fluoride, modified styrene-butadiene copolymer and vinylidene fluoride-hexafluoropropene copolymer on the capacitive performance of symmetric Graphene nanoplatelets (GnP) electrodes has been investigated in both organic and aqueous electrolytes. Surface area, pore size distribution, resistance and wetting behaviour of the electrodes have been measured and the effects of these factors have been studied to rationalise their electrical double layer capacitor (EDLC) performances. The most homogeneous distribution and lowest aggregation of the GnP electrode is obtained with CMC binder. Among the electrodes, it has also shown better capacitive behaviour in both aqueous and organic electrolyte due to its higher surface area, and higher mesoporous and microporous distributions than the other electrodes. To investigate scalable performance of the GnP electrodes, CMC binder electrodes have been scaled up from coin cell to pouch cell size. The coin cell electrodes showed higher capacitance than the pouch cell up to current densities of 50 A g−1. The pouch cell has exhibited the higher capacitance at 50 A g−1 and better capacitance retention, which shows that the pouch cell is a better charge storage device than coin cell at high current densities.

Mesoporous Mn3O4 coated reduced graphene oxide for high-performance supercapacitor applications

We report the facile synthesis of mesoporous Mn3O4 coated reduced graphene oxide (rGO) nanocomposite using a simple low temperature wet chemical process and demonstrated the nanocomposite material as high-performance electrodes for electrochemical supercapacitor. The nanocomposite structure is unique as it consists of an ultra-thin, mesoporous (pore size ∼1.9–2.6 nm) with oriented pore size of Mn3O4 layer deposited on the surface of rGO. The structure and the orientation of nanopores in the Mn3O4 layer were further confirmed using HRTEM, while structural and morphological analysis were carried out using XRD, Raman spectroscopy, SEM, TEM, and SAED. The pore size and the pore distributions were verified using BET surface area technique, which demonstrated the nanocomposite exhibits uniform distribution of pores of dimension ∼1.9–2.6 nm throughout. The electrocatalytic behavior of the nanocomposite was found to be ideal for their use as supercapacitor electrodes as high-performance charge storage devices. Finally, we demonstrate the supercapacitor electrode using Mn3O4-rGO nanocomposite followed by their electrochemical characterizations for electrocatalytic activity for charge storage. The hybrid material shows best capacitance value of 221 F g−1 at current density 0.15 A g−1 with good cycling stability. We believe that our investigations will pave a pathway towards various new applications, including, electrochemical catalysis, sensing, energy harvesting and storage and many more.

High power Na-ion capacitor with TiS2 as insertion host

High power capability of the hybrid charge storage device Na-ion capacitor (NIC) is fabricated using battery type TiS2 as an insertion host with the double layer forming activated carbon (AC) as supercapacitor component. Earlier, it is presumed that Na/TiS2 system is considered as impractical energy storage system. TiS2 single crystals are synthesized and exhibit the reversible insertion of ~0.62 mol. Na. AC/TiS2 assembly is delivering the maximum energy density of ~38 Wh kg−1. One of the important aspects of this NIC is high power capability, which outperformed its analogue Li-ion capacitor fabricated under similar circumstances.

Enhanced photocatalytic activity and enormous dielectricity of α-Fe2O3/reduced graphene oxide nanocomposites

Nanocomposites of single-phase iron oxide (α-Fe2O3) and reduced graphene oxide (rGO) with different volume fractions have been prepared by chemical route. Structural, morphological and spectroscopic characterizations have been performed by XRD, FESEM, TEM, XPS and Raman studies. Photocatalytic activity of these composites has been investigated by the degradation of methylene blue dye under visible light irradiation. The activity is found to depend on the percentage of volume fraction (vf) of rGO in the composite. At \( v_{\text{f}} = 10.3, \) the photocatalytic activity becomes maximum and the degree of degradation of MB is found to be ~ eight times to that of pure α-Fe2O3. The enhanced photocatalytic activity may be attributed to the prolonged lifetime of electron–hole pair produced in α-Fe2O3. The stability and reusability of photocatalyst during photocatalytic reaction, which is a crucial factor for the practical applications, is also verified. At this particular volume fraction of rGO, i.e., vf = 10.3, the nanocomposite exhibits huge dielectric constant ~ 2950 times to that of pure α-Fe2O3 along with moderate dielectric loss enabling it a potential candidate for charge storage device.

Nitrogen ion implanted ultrananocrystalline diamond films: A better electrostatic charge storage medium

Atomic force microscopy (AFM) is used to induce electrostatically charged areas on nitrogen-ion-implanted ultrananocrystalline diamond (UNCD) films by applying a bias voltage to the AFM tip during the tapping mode scan. For local and intentional electrostatic charging, both positive and negative charges can be stored on pristine as well as nitrogen-ion-implanted UNCD films, as detected by Kelvin probe force microscopy. Interestingly, the charge storage capacity of pristine UNCD increases with the N-ion implantation dose. The potential amplitude and spatial distribution of the trapped charges can be controlled by the bias and load applied to the tip. The enhanced charge storage properties with doping are attributed to the formation of impurities, various defects, and the induction of an enhanced graphitic sp2 phase because of the high N-ion implantation dose, where all act as trapping centres for extra charge. The formation of various defect states and conducting sp2 nanographitic phases facilitate enhanced charge storage in N-ion-implanted UNCD films. This study underscores the potential importance of doping-dependent charge storage and the role of defects and nanographitic phases as a strategy for enhancing the electrostatic charge storage capability of diamond-based charge storage devices.