High-power Discharge Research Articles

Polymer Matrix Nanocomposites with 1D Ceramic Nanofillers for Energy Storage Capacitor Applications.

Recent developments in various technologies, such as hybrid electric vehicles and pulsed power systems, have challenged researchers to discover affordable, compact, and super-functioning electric energy storage devices. Among the existing energy storage devices, polymer nanocomposite film capacitors are a preferred choice due to their high power density, fast charge and discharge speed, high operation voltage, and long service lifetime. In the past several years, they have been extensively researched worldwide, with 0D, 1D, and 2D nanofillers being incorporated into various polymer matrixes. However, 1D nanofillers appeared to be the most effective in producing large dipole moments, which leads to a considerably enhanced dielectric permittivity and energy density of the nanocomposite. As such, this Review focuses on recent advances in polymer matrix nanocomposites using various types of 1D nanofillers, i.e., linear, ferroelectric, paraelectric, and relaxor-ferroelectric for energy storage applications. Correspondingly, the latest developments in the nanocomposite dielectrics with highly oriented, surface-coated, and surface-decorated 1D nanofillers are presented. Special attention has been paid to identifying the underlying mechanisms of maximizing dielectric displacement, increasing dielectric breakdown strength, and enhancing the energy density. This Review also presents some suggestions for future research in low-loss, high energy storage devices.

Hydrated hybrid vanadium oxide nanowires as the superior cathode for aqueous Zn battery

Zinc batteries are at the forefront of aqueous energy storage due to their intrinsic safety and low cost. Various vanadium oxides stand out among the few cathode candidates. Herein, we demonstrate a new heterogeneous vanadium oxide nanowire with V2O5·nH2O shell and V3O7·H2O core, named h-VOW, as a promising cathode candidate for Zn batteries. Thanks to the synergies of multivalent states of vanadium elements associated with inherent high conductivity, in an aqueous electrolyte, h-VOW/Zn battery delivers high discharge capacity (455 mAh g−1 at 0.1 A g−1), energy density (340 Wh kg−1) and power density (9105 W kg−1). Moreover, the gel electrolyte imparts satisfied deformability and weather resistance to the flexible quasi-solid-state battery, allowing it to withstand extremely harsh conditions without catastrophic failure.

2D Nitrogen‐Doped Carbon Nanotubes/Graphene Hybrid as Bifunctional Oxygen Electrocatalyst for Long‐Life Rechargeable Zn–Air Batteries

AbstractThe rational construction of efficient bifunctional oxygen electrocatalysts is of immense significance yet challenging for rechargeable metal–air batteries. Herein, this work reports a metal–organic framework derived 2D nitrogen‐doped carbon nanotubes/graphene hybrid as the efficient bifunctional oxygen electrocatalyst for rechargeable zinc–air batteries. The as‐obtained hybrid exhibits excellent catalytic activity and durability for the oxygen electrochemical reactions due to the synergistic effect by the hierarchical structure and heteroatom doping. The assembled rechargeable zinc–air battery achieves a high power density of 253 mW cm−2 and specific capacity of 801 mAh gZn−1 with excellent cycle stability of over 3000 h at 5 mA cm−2. Moreover, the flexible solid‐state rechargeable zinc–air batteries assembled by this hybrid oxygen electrocatalyst exhibits a high discharge power density of 223 mW cm−2, which can power 45 light‐emitting diodes and charge a cellphone. This work provides valuable insights in designing efficient bifunctional oxygen electrocatalysts for long‐life metal–air batteries and related energy conversion technologies.

Effects of power per pulse on reactive HiPIMS deposition of ZrO2 films: A time-resolved optical emission spectroscopy study

Time-resolved optical emission spectroscopy was carried out during controlled reactive high-power impulse magnetron sputtering of ZrO2 films in argon–oxygen gas mixtures. The effects of increased target power density (up to 3.0 kW cm−2) applied in voltage pulses shortened from 200 to 50 μs were studied at a nearly constant deposition-averaged target power density (close to 50 W cm−2) and a fixed repetition frequency of 500 Hz. The trends in time evolution of the local ground-state densities of Zr, Ar, and O atoms and that of the Zr+, Zr2+, Ar+, and O+ ions during a voltage pulse were deduced from the time evolution of the corresponding excited-state populations and the excitation temperature. It was found that the sputtered Zr atoms are much more ionized (with a high fraction of Zr2+ ions) and the Ar atom density is more decreased near the target during the shorter (50 μs) high-power pulses. These shorter pulses produce a four times higher pulse-averaged target power density oscillating between 1.7 and 2.1 kW cm−2 during deposition. Under these conditions, much higher densities of O atoms and Zr2+ ions were measured in the plasma bulk. The higher backward flux of the Zr+ and Zr2+ ions onto the target during this high-power discharge regime contributed significantly to a 34% decrease in the efficiency of the magnetron sputter deposition of ZrO2 films.

Time-resolved characterization of non-thermal plasma-assisted photocatalytic removal of nitric oxide

We performed time-resolved characterization of plasma-photocatalytic removal of nitric oxide (NO) in a ceramic foam packing double dielectric barrier discharge reactor using mid-infrared laser absorption spectroscopy. Non-thermal plasma (NTP) was generated in the porous ceramic foam coated with mesoporous TiO2 thin film. Real-time NO monitoring was performed using a quantum cascade laser at 5.26 µm combined with a custom-designed multipass gas cell, leading to a sub-ppm detection limit at 0.1 s measurement time. By analyzing the feed gas of 90 ppm NO/1% O2 balanced in N2, the plasma treatment without TiO2 photocatalyst had no effect on NO removal when the discharge power was below 45 W. In comparison, the NTP-TiO2 system achieved an efficiency of 49% for NO removal even at the relatively low discharge power of 18 W. The synergy between NTP and TiO2 photocatalyst effectively promotes the NO removal at low plasma discharge powers. However, we also observed a negative effect of TiO2 photocatalyst on NO removal at a relatively high discharge power of 135 W.

Observation of multiply charged states ions in a high-power pulsed reflex discharge

Time-resolved optical emission spectroscopy studies have been made to investigate the elemental/charge composition of the plasma ionic component at pulsed reflex discharge. The discharge plasma has are registered spectral lines neutral atoms and ions of the working gas Ar, Ar1+, Ar2+, and also of the cathode material: Zr, Zr1+, Zr2+, Zr3+. The presence of zirconium in the spectrum attests to the entry of cathode material into the plasma and its subsequent ionization. The variation of spectral line intensity with time in the early stage of the discharge and in the stage of dense plasma existence (time interval from the onset of the discharge up to 4 ms) correlates with the dynamics of plasma parameters. Characteristic times of appearance of excited atoms and ions in the plasma have been determined. The time of appearance of excited Zr* atoms is by the order of magnitude longer than that of Ar*. The stage of high-voltage mode exhibits the lines of excited Ar*, Zr* atoms and Ar+*, Zr+* ions, with the intensity of which sharply increasing during the transition to the high-current mode. The excited Ar2+*, Zr2+*, Zr3+* ions appear later, when the discharge has already gone into the high-current mode.

Scenario with combined density and heating control to reduce the impact of the bootstrap current in Wendelstein 7-X

Wendelstein 7-X is a low-shear stellarator with an island divertor, formed by natural magnetic islands at the plasma edge and ten modular divertor units for particle and energy exhaust. For the island divertor concept to work properly, the device is optimized for small internal currents. In particular, the bootstrap current is minimized. Previous studies predicted a thermal overload of the targets at a particular location, due to the slow evolution of the toroidal net current in the initial phase of certain otherwise desirable high-power discharges. The present numerical study explores the neoclassical predictions for the bootstrap current in more detail and demonstrates, as a proof of principle, that a path from low density and low heating power to high density and full heating power exists, on which the bootstrap current remains constant. This offers the possibility to reach the predetermined toroidal net current at low heating power, where no overload will occur in the transient phase.

Power Flow Optimization for an Offshore Multi-energy System

Qu, B.; Zhong, M.; Jia, H.; Yan, H.; Zhang, J., and Sun, Y., 2019. Power flow optimization for an offshore multi-energy system. In: Guido-Aldana, P.A. and Mulahasan, S. (eds.), Advances in Water Resources and Exploration. Journal of Coastal Research, Special Issue No. 93, pp. 585–596. Coconut Creek (Florida), ISSN 0749-0208.The increase of offshore PV and wind power installation capacity can increase the uncertainty and randomness of the power system. Therefore, it is necessary to study the offshore multi-energy system. A traditional offshore community with hybrid energy storage system (HESS) installation usually participates in demand response program to improve system economy. However, due to the high price and low discharge power of the HESS, it cannot response to the loads effectively. This paper introduces water electrolysis and on-board hydrogen storage technologies to an offshore multi-energy system, so as to effectively optimize the operation of system. Subsequently, to analyze the impact of climate change on system operation, the concept of loads matching degree is firstly defined. Finally, this paper gives a suggestion for an existed offshore multi-energy system on how to reasonably increase renewable generation system installation capacity. Results show that compared with the traditional offshore multi-energy system, the improved system can significantly reduce system operation costs and carbon emissions by 23.02% and 48.43%, respectively. Additionally, with the increase of loads matching degree, offshore system optimal operation costs, carbon emissions and the amount of hydrogen produced by water electrolysis reduce significantly. Finally, the growth of renewable energy generation capacity can lead to the reduce of emissions and increase of operating costs.

Designing High Power Lithium Ion Cells

Applications like hybrid electric vehicles (HEV) require batteries with high volumetric and gravimetric power densities, in both charge and discharge modes. Lithium ion cells are now being designed with different power : energy ratios, for specific applications. Many cells are rated for high rate discharge (> 10 C), but not for high rate charge (< 2 C). However, even 10 C is not enough. A selection of commercial lithium ion cells, mainly cylindrical 18650 cells, were disassembled and characterised. The cells had a variety of different power : energy ratios, and this was correlated with key design parameters. For example, cells with a high power density had relatively low coat weights and areal capacities, and used active materials with a smaller particle size. However, most of the cells had the same tag arrangement, when high power cells were predicted to use more tags. Having disassembled the cells, the harvested electrodes were tested in coin cell half cells. The tests included resistance measurements, continuous discharge tests at relatively low rates, and pulse charge and discharge tests at high rates. During lithiation pulses, all the anode voltages went negative of zero volts vs. Li/Li+ by around 5 C. However, the reaction still appeared to be under solid state diffusion control, based on the linearity of the voltage vs. time0.5 GITT plots. These and other results will be presented at the meeting.

Investigation of the emission spectra of a high-power impulse gas discharge of a magnetron during reactive sputtering

This paper presents the results of a study of the properties of a gas discharge of a magnetron during sputtering at a direct current (DCMS) and by high-power impulse method (HiPIMS). During the study, the copper target was sputtered in a mixture of argon and oxygen. It was found that, depending on the discharge parameters, sputtering is possible in two modes: oxide, during which deposition of oxide films occurs, and metal, in which deposition of metal structures is possible. As a result of the study, current-voltage characteristics, emission spectra of the gas discharge, as well as the dependence of the pressure in the vacuum chamber on the discharge current were obtained.

Langmuir probe diagnostics of an impulse magnetron discharge with hot Cr target

Impulse magnetron discharge (pulse duration 20 ms) with uncooled Cr target has been investigated with a specially designed Langmuir probe setup in a wide range of parameters (magnetic field and discharge power). The spatial distributions of electron temperature and plasma density have been measured in the gasless self-sputtering mode. It has been shown that in the gasless high-power pulsed discharge with hot Cr target, plasma density is as high as 5 × 1018 m−3 at a pulsed power density of 1430 W/cm2, while the electron temperature drops to values below 1 eV.

Investigation of the influence of the parameters of a pulsed power source on the properties of a magnetron’s high-power gas discharge

The paper presents the results of an experimental study of the emission spectra of a gas discharge during high-power impulse magnetron sputtering. The influence of the repetition frequency and duration of current pulses on the intensity of the spectral lines of various particles is shown. The parameters of the gas-discharge plasma during HiPIMS and at a direct current were also compared.

Next Generation Materials for Lithium-Ion Space Batteries

EaglePicher has been supplying batteries for energy storage for satellites and other space applications since 1958. These batteries have achieved over 2.6 billion hours of cell operations with no failures in orbit. Over the decades the battery chemistry has changed amongst various chemistries with some overlap and some still being used today. Typical space battery chemistries include: silver-zinc, nickel-hydrogen, nickel-cadmium, and then lithium-ion. Even within the lithium-ion chemistry the formulations and packaging has evolved over time and continues to change. Lithium-ion space batteries continue to evolve today. New satellites and space applications are demanding increased energy, more power, and smaller volumes. This has led to improvements in increased energy, wider operating temperatures, more power and smaller packages. Every change in battery performance requires new or modified battery materials. For increased energy the incumbent cathode material for lithium-ion batteries is Lithiated Nickel Cobalt Oxide (NCO). This was changed to the Lithiated Nickel Cobalt Aluminum Oxide to increase the energy and improve cycle life. For wider operating temperatures the electrolyte formulation has evolved with new components and additives. Newer and next generation satellites are carrying state of the art instruments that demand high power or pulses of power. New lithium-ion battery chemistries have been developed to supply very high power discharges to supply the large currents. As small satellites are increasing in popularity, there is a push for smaller battery packs. This has led to a decrease in cell capacity and the introduction of commercial of the shelf (COTS) cells. These are often cylindrical in shape and typically 18650 in size. Transitioning to COTS cells has increased the ability to create modular space batteries, but has brought up new concerns on quality and reliability. Quality and reliability, plus safety, are top concerns for space batteries. Replacement of batteries in space is extremely difficult and expensive. As each of the next generation battery materials are developed, reliability and safety much be eminent. These materials and batteries are often expected to supply power for decades. The continued testing, evaluation and analysis of the new chemistries and designs provides assurances for long-term performance and reliability. As these batteries have the potential to power satellites, landers, rovers, capsules, and habitats, EaglePicher continues to develop, evolve, demonstrate, and produce new battery chemistries and designs to meet the mission requirements. Acknowledgements We would like to thank: NASA JPL, Lockheed Martin and the Unites States Government for supporting some of this effort, and many of the EaglePicher employees who worked on these projects.

Progress in disruption prevention for ITER

Key plasma physics and real-time control elements needed for robustly stable operation of high fusion power discharges in ITER have been demonstrated in recent research worldwide. Recent analysis has identified the current density profile as the main drive for disruptive instabilities in discharges simulating ITER’s baseline scenario with high and low external torque. Ongoing development of model-based profile control and active control of magnetohydrodynamic instabilities is improving the stability of multiple scenarios. Significant advances have been made toward real-time physics-based prediction of instabilities, including path-oriented analysis, active sensing, and machine learning techniques for prediction that are beginning to go beyond simple disruption mitigation trigger applications. Active intervention contributes to prevention of disruptions, including forced rotation of magnetic islands to prevent wall locking, and localized heating/current drive to shrink the islands. Stable discharge rampdowns have been achieved with the fastest ITER-like scaled current ramp rates, while maintaining an X-point configuration. These elements are being integrated into stable operating scenarios and new event-handling systems for off-normal events in order to develop the physics basis and techniques for robust control in ITER.

Exploring deuterium beam operation and the behavior of the co-extracted electron current in a negative-ion-based neutral beam injector

The achievements of the deuterium beam operation of a negative-ion-based neutral beam injector (N-NBI) in the large helical device (LHD) are reported. In beam operation in LHD-NBIs, both hydrogen (H) and deuterium (D) neutral beams were generated by changing the operation gas using the same accelerator. The maximum accelerated deuterium negative-ion current () reaches 46.2 A from two beam sources with the averaged current density being 190 A m−2 for 2 s, and the extracted electron to accelerated ion current ratio () increases to 0.39 using 5.6 V high bias voltage in the first deuterium operation in 2017. An increase of electron density in the vicinity of the plasma grid (PG) surface, which is considered the main reason for the increase of co-extracted electrons in a beam, is confirmed by the half-size research negative-ion source in the neutral beam test stand at the National Institute for Fusion Science (NIFS). The deuterium negative-ion density is also larger than the hydrogen negative-ion density in the vicinity of the PG surface using the same discharge conditions. In the latest experimental campaign in 2018, increases to 55.4 A with the averaged current density being 233 A m−2 for 1.5 s using the shot extraction gap length. The low of 0.31 can be maintained by using high discharge power. The various parameters mentioned above are defined in detail below.

Optimization of discharges with ion cyclotron range of frequencies using local gas injection in EAST

In view of improving ion cyclotron range of frequencies (ICRF) wave coupling in EAST (experimental advanced superconducting tokamak) necessary to obtain high-power discharges, two series of experiments in L-mode were devoted to the use of local gas injection as a tool to increase density in front of the antennas. During the first session, the quantity of deuterium simultaneously puffed from five different poloidal positions on each side of one ICRF antenna was gradually increased. Steady gas puffing on this antenna (~8.1020 e s−1) increased antenna coupling resistance by 100%, but puffing more gas did not provoke any further improvement. Plasma central electron density was not kept constant when using local puff but kept increasing during the discharges. During the second session, the global density was well-controlled and remained constant, the distance between the separatrix and the first wall was increased by 2 cm allowing, the gas to spread better, and puffing more gas this time lead to better wave coupling. The same amount of gas was then puffed from three different locations and changes in SOL (scrape-off layer) parameters were measured from several locations. Extensive analysis of the edge diagnostics made it possible to observe an electron density increase and a temperature decrease caused by the ionization of neutrals in the SOL. Heat loads on the divertor targets were slightly mitigated by gas injection, which is favorable from the perspective of long pulse scenario development. Injection at mid-plane led to the best results with the highest coupling simultaneously achieved for both antennas and smallest heat loads on the divertor target (below 1 MW m−2). As far as wave coupling efficiency is concerned, most experimental trends were also successfully reproduced by antenna modelling with the RAPLICASOL finite element code with experimental density profiles from reflectometry as the main input.

Deuterium retention on the tungsten-coated divertor tiles of JET ITER-like wall in 2015–2016 campaign

Tungsten-coated divertor tiles exposed during the third JET ITER-Like Wall (ILW) campaign in 2015–2016 (ILW-3) were studied with Secondary Ion Mass Spectrometry (SIMS). ILW-3 campaign contained more high-power plasma discharges and longer plasma time than the earlier ILW campaigns. Measurements showed increased beryllium (Be) deposition on the upper inner divertor, whereas on the outer divertor, Be deposition was lower than during the second campaign in 2013–2014 (ILW-2). Increased intensities of nickel, molybdenum and tungsten were observed at the surface layer of the inner divertor Be dominated deposits. These layers are probably formed during the high-power plasma discharge phase near the end of the ILW-3 campaign. Compared to the earlier campaigns, D retention on the upper inner divertor was observed to on a similar level than after ILW-2, whereas at the lower inner divertor and most parts of the outer divertor, D retention was lower for ILW-3 than ILW-2. D retention was increased at lower part of outer divertor Tile 7, where Be deposition was slightly increased. Probable reason for the reduction is the higher surface temperature of the tiles due to higher powers used.

Compound control for energy management of the hybrid ultracapacitor-battery electric drive systems

This paper proposes a compound control framework for energy management of hybrid ultracapacitor-battery electric drive system. It includes a topology and compound controllers. The topology guarantees that the ultracapacitor current and the battery current can be controlled individually. In addition, the control of the hybrid power source is linked with the control of the electric drive system directly. Compound controllers include an active disturbance rejection controller, two current controllers and two operational modes switch controllers. Active disturbance rejection controller is applied in the control of the ultracapacitor in a load-following mode. Current controllers are applied to control the battery current and the charge current of the ultracapacitor. Event trigger based operational modes switch controllers coordinate the active disturbance rejection controller and the current controllers. The advantages of the proposed compound control are that ultracapacitor supplies peak and ripple current while battery supplies smooth and steady current; the control of the hybrid power source is linked with the control of the electric drive system; the high power discharge ability of ultracapacitor is used to reject disturbance. The experimental results validate the performance of the proposed control framework in this work.

Infrared imaging investigation of temperature fluctuation and spatial distribution for a large laminated lithium–ion power battery

The present study investigates the thermal behaviors of a naturally cooled NCM-type LIB (LiNi1−x−yCoxMnyO2 as cathode) from an experimental and systematic approach. The temperature distribution was acquired for different discharge rates and Depth of Discharge (DOD) by the infrared imaging (IR) technology. Two new factors, the temperature variance (Tvar2) and local overheating index (LOH index), were proposed to assess the temperature fluctuation and distribution. Results showed that the heat generation rate was higher on the cathode side than that on the anode side due to the different resistivity of current collectors. For a low-power discharge, the eventual stable high-temperature zone occurred in the center of the battery, while with a high-power discharge, the upper part of the battery was the high–temperature region from the very beginning of discharge. It was found that the temperature variance (Tvar2) and local overheating index (LOH index) were capable of holistically exhibiting the temperature non-uniformity both on numerical fluctuation and spatial distribution with varying discharge rates and DOD. With increasing the discharge rate and DOD, temperature distribution showed an increasingly non-uniform trend, especially at the initial and final stage of high-power discharge, the heat accumulation and concentration area increased rapidly.

2-D rGO impregnated circular-tetragonal-bipyramidal structure of PPY-TiO2-rGO nanocomposite as ETL for OLED and supercapacitor electrode materials

Two dimensional rGO was decorated over circular-bipyramidal structure of PPY-TiO2 by chemical oxidative polymerization of pyrrole monomer. The structural analysis of PPY, GO, TiO2, PPY-TiO2 and PPY-TiO2-rGO nanocomposite was observed by XRD, FESEM and TEM analysis. Inflated non-radiative electron-hole recombination rate and lower value of decay time with better thermal stability were observed for PPY-TiO2-rGO nanocomposite. Enhanced current density (~ 300%), optimized low band gap (~ 1.32 eV), high dielectric constant and high specific surface area were also observed for ternary nanocomposite. The PPY-TiO2-rGO electrode also manifested the high specific capacitance value (~ 1171 F/g) and high discharge time (~ 3450 s) with high electrochemical reduction potential (~ +0.610 V). These increased rates of non-radiative recombination, reduced band gap, enhanced conductivity and thermal stability, high values of dielectric constant, improved electrochemical reduction potential, augmented specific capacitance, high discharge time and power density (~ 799.74 W/kg) with scant loss in energy density at high current density proposed that, PPY-TiO2-rGO nanocomposite can be employed as electron transport layer (ETL) material in OLED devices and supercapacitor electrode material.