Hollow Anode Research Articles

Instability analysis of Li-ion battery electrode particles induced by chemomechanical growth using incremental deformation theory

Volumetric swelling due to lithiation into active battery materials is a well-known phenomenon. A chemo-mechanical framework can suitably explain the deformations of the electrode and the generation of diffusion-induced stresses (DIS). Various experimental works have shown that the effects of DIS further cause the active material to lose its structural stability. However, relatively few frameworks exist that can investigate such phenomena in a comprehensive manner. These are mainly based on the Euler–Bernoulli beam theory and the von-Karman plate theory. In the present work we present a generalized three-dimensional instability framework incorporating the theory of incremental deformation. We use this theory on a widely used chemo-mechanical framework. Notably, similar existing instability investigations on negative electrode materials are based only on incompressible material behaviour. As opposed to it, in this work we have considered a compressible material. Also, we account for the spatial and temporal nature of growth, which is a significant departure from the existing instability frameworks. Therefore, this current work brings the investigation of structural instability of electrode material closer to physical reality. In our study, we use the compound matrix method to find the critical lithiation parameter. Then we consider three sets of problems, each with a particular combination of boundary conditions applied on the inner and outer cylindrical surfaces of hollow cylindrical anode particles. These are free-free, fixed-free, and free-fixed, where each combination represents a particular type of interaction between an electrode particle and its surroundings. Most importantly, we find that the free-free and fixed-free conditions show only a pure axial and mixed mode of instability, and do not show the pure circumferential mode. The free-fixed conditions, however, shows all three modes of instability. Additionally, the presence of mode crossover makes the instability pattern of such electrode particles significant.

The cobalt-based metal organic frameworks array derived CoFeNi-layered double hydroxides anode and CoP/FeNi2P heterojunction cathode for ampere-level seawater overall splitting

The seawater electrolysis technology powered by renewable energy is recognized as the promising “green hydrogen” production method to solve serious energy and environmental problems. The lack of low-cost and ampere-level current OER (oxygen evolution reaction) and HER (hydrogen evolution reaction) catalysis limits their industrial application. In this work, a unique tri-metal (Co/Fe/Ni) layered double hydroxide hollow array anode catalyst (CFN-LDH/NF) and the CoP/FeNi2P heterojunction hollow array cathode are successfully prepared via one in-situ growth of Co-MOF on nickel foam (Co-MOF/NF) precursor, which exhibits excellent catalytic performance. The η1000 values of 352 and 392 mV are achieved for CFN-LDH/NF (OER catalyst) in 1.0 M KOH and alkaline seawater solution, respectively. The CFNP/NF with a low overpotential of 281 mV is required to reach 1000 mA cm−2 current density for HER in 1.0 M KOH solution, while the η1000 in alkaline seawater solution is 312 mV. The CFN-LDH/NF||CFNP/NF electrolyzer exhibits excellent long-term durability over 100 h, achieving current density of 500 mA cm−2 at 1.825 V in 1.0 M KOH solution. The construction of hollow tri-metal LDH and phosphides heterostructures may open a new and relatively unexplored path for fabricating high performance seawater splitting catalysis.

Intergrating Hollow Multishelled Structure and High Entropy Engineering toward Enhanced Mechano-Electrochemical Properties in Lithium Battery.

Hollow multishelled structures (HoMSs) are attracting great interest in lithium-ion batteries as the conversion anodes, owing to their superior buffering effect and mechanical stability. Given the synthetic challenges, especially elemental diffusion barrier in the multimetal combinations, this complex structure design has been realized in low- and medium-entropy compounds so far. It means that poor reaction reversibility and low intrinsic conductivity remain largely unresolved. Here, a hollow multishelled (LiFeZnNiCoMn)3O4 high entropy oxide (HEO) is developed through integrating molecule and microstructure engineering. As expected, the HoMS design exhibits significant targeting functionality, yielding satisfactory structure and cycling stability. Meanwhile, the abundant oxygen defects and optimized electronic structure of HEO accelerate the lithiation kinetics, while the retention of the parent lattice matrix enables reversible lithium storage, which is validated by rigorous in situ tests and theoretical simulations. Benefiting from these combined properties, such hollow multishelled HEO anode can deliver a specific capacity of 967 mAh g-1 (89% capacity retention) after 500 cycles at 0.5 A g-1. The synergistic lattice and volume stability showcased in this work holds great promise in guiding the material innovations for the next-generation energy storage devices.

Graphene encapsulated NiO-Co3O4 open-ended hollow nanocube anode with enhanced performance for lithium/sodium ion batteries

The development of innovative anode materials with distinctive structures that ensure high specific capacity and extended cycling stability is necessary to enhance the performance of lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Herein, graphene-encapsulated NiO-Co3O4 open-ended hollow nanocube (NiO-Co3O4@rGO) anodes are synthesized by a hydrothermal reduction method. The composite materials effectively solve some of the problems faced by transition metal oxides, such as low capacity due to volume expansion, poor electrical conductivity, etc. The NiO-Co3O4 @rGO composites exhibit fantastic lithium-storage performance, including considerable specific capacity (804.5 mAh g−1 at 100 mA g−1 after 100 cycles) and favorable long-term cycling stability (434.1 mAh g−1 at 1000 mA g−1 after 500 cycles), thanks to the special structure and the introduction of rGO. Additionally, the hollow NiO-Co3O4@rGO composites show a strong sodium-storage capability, with a reversible discharge capacity of 269.2 mAh g−1 after 100 cycles at 100 mA g−1. This practical synthesis strategy demonstrates its promising potential as a high-performance anode material for LIBs and SIBs.

A graphene-like hollow sphere anode for lithium-ion batteries.

We report a flash Joule heating method for the rapid preparation of graphene-like materials. The L-GHS exhibited a uniform diameter of 200 nm and an ideal specific surface area of 670 m2 g-1. Meanwhile, the specific capacity of L-GHS remained at 942 mA h g-1 after 600 cycles (1 A g-1), which shows excellent electrochemical performance.

Simultaneously enabling superior ICE and high rate/cycling stability with a hollow carbon nanosphere anode for sodium-ion storage

Hollow carbon nanosphere anode materials were manipulated by a pyrolysis temperature-mediated microstructure strategy to simultaneously achieve high ICE and superior rate/cycling stability.

Fabrication of Hollow and Hierarchical CuO Micro-Nano Cubes Wrapped by Reduced Graphene Oxide as a Prospective Anode for SIBs.

In this study, hollow and hierarchical CuO micro-nano cubes wrapped by reduced graphene oxide (H-CuO MNCs@rGO) were designed and successfully fabricated via a novel three-step wet-chemical method. Benefiting from its unique hollow and hierarchical micro-nano structures, H-CuO MNCs@rGO exhibited significantly enhanced electrochemical Na+ storage performance when utilized as anode material for sodium-ion batteries (SIBs). Specifically, H-CuO MNCs@rGO demonstrated a specific capacity of 380.9 mAh g-1 in the initial reversible cycle and a capacity retention of 218.9 mAh g-1 after 150 cycles at a current density of 300 mA g-1. Furthermore, through the dominant pseudocapacitive behavior, an optimized rate capability of 221.2 mAh g-1 at 800 mA g-1 can be obtained for H-CuO MNCs@rGO. The comprehensive Na+ storage properties of H-CuO MNCs@rGO obviously exceeded those of hollow CuO cubes (H-CuO MNCs) and bulk CuO anodes. Such enhanced Na+ storage performances of H-CuO MNCs@rGO can be attributed to its reasonable hollow and hierarchical micro-nano structures, which provide abundant redox active sites, shorten Na+ migration pathway, buffer volume expansion, and improve electronic/ionic conductivity during sodiation/desodiation process. Our strategy provides a facile and innovative approach for the design of CuO with rational micro-nano structure as a high-performance anode for SIBs, which would also be a guiding way for tailoring transition metal oxides in other scalable and functional applications.

Study of trigger mechanisms of a pseudospark switch configuration with a steady-state auxiliary glow discharge

This paper presents data on investigation of the pseudospark switch whose trigger unit uses a low-current auxiliary glow discharge with hollow cathode and hollow anode. The electrode system of this unit communicates with the main high-voltage gap of the switch due to the aperture in the flat part of one of the trigger electrodes. It is shown that when the electrode with the aperture plays of role of the hollow cathode of the auxiliary discharge, a low parasitic current through the aperture is provided by the ion flow. This ion current does not practically influence on the static breakdown voltage of the main gap. Applying the trigger pulse between the trigger electrodes leads to the pulsed trigger discharge with an enhanced current. At a negative polarity of the trigger pulse, the cavity with aperture turns out into the hollow anode so that the current is able to be intercepted through the aperture to the grounded cavity of the main gap. The plasma is generated in the cavity and the switch is triggered. With the proper selection of the geometry of the trigger electrodes, the delay time to trigger at a level of several tens of nanoseconds is achievable.

(Invited) Zirconia-Based Hollow Anode Development for Molten Regolith Electrolysis

Molten regolith electrolysis (MRE) is a promising in-situ resource utilization technique for producing oxygen and molten metal alloys from lunar regolith. However, MRE requires operating temperatures at or above 1600°C to melt lunar regolith and dissociate the molten oxides to enable electrolysis. Anode degradation in this corrosive and oxidizing environment is a major concern for long-term operation on the lunar surface and can be mitigated by a novel hollow anode design with a solid electrolyte shell and porous metallic core as proposed here. The metallic anode will be shielded from the regolith melt by an oxygen ion-conducting zirconia-based ceramic, allowing electron transfer to occur in the interior of the shell. Additionally, bubble formation at a traditional anode surface is avoided, thereby eliminating the concerns of molten regolith splatter and increased ohmic resistance. This work focuses on corrosion studies of dense stabilized zirconia in contact with molten lunar mare and highlands regolith simulants at 1600°C to support hollow anode development. The interactions between zirconia and molten regolith are characterized using SEM/EDS, with an emphasis on elemental analysis to assess reactivity and degradation of zirconia.

Generation of pulsed proton beams in a vacuum diode with a passive anode

The paper presents the results of a study of a pulsed proton beam generated of in a diode with a metal anode (stainless steel, titanium, and copper) operating in bipolar-pulse mode. The experiments were carried out on the TEMP-6 accelerator (250–300 kV, 120 ns) with a focusing diode geometry in a mode of self-magnetic insulation of electrons. For analysis of the ion beam parameters, we used the infrared imaging diagnostics of the beam energy density (spatial resolution of 2 mm) and the time-of-flight diagnostics of the beam compositions (time resolution 1 ns). It was found that with continuous supply of hydrogen into a hollow anode (with holes on the working surface) and a hydrogen pressure in the diode chamber of 30–80 mPa, the proton content in the beam exceeds 80%. An increase in the first pulse duration leads to an increase in the ion current density up to 100 A/cm2 and the energy density at the focus up to 3 J/cm2. We analyzed various mechanisms of proton beam generation: ions acceleration from the gas plasma in the plasma erosion mode; ions acceleration from the explosive emission plasma of a metal anode the near-surface layer of which is saturated with metal hydrides (anode material). It was found that hydrogen embrittlement of the near-surface layer of the anode occurs during the injection of hydrogen, and during the explosive emission of electrons, part of the material is sprayed in the form of finely dispersed clusters.

Preparing a graphene/carbon nanotube coated hollow nickel phosphides microsphere anode with high stability for high-performance lithium/sodium battery

Transition metal phosphides as anode materials for energy storage batteries have attracted great attention due to their high specific capacity and safety. However, it is difficult to maintain the structural stability of the electrode material during the repeated Li+/Na+ insertion/ deintercalation process, especially at a high rate and long-life cycle. Herein, the graphene/carbon nanotubes coated Ni2P (h-Ni2P-G/CNTs) microspheres composite with hollow structure has been successfully prepared by one-step phosphorous heat treatment of Ni-MOF precursor microspheres and applied in the lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) anode. When the h-Ni2P-G/CNTs is used as an anode for LIBs, it delivers high reversible capacities of 506 mAh/g after 200 cycles at 0.2 A/g. As an anode for SIBs, the electrode provides 430 mAh/g capacity at 0.1 A/g after 180 cycles. The excellent performances can be attributed to the synergistically structural and electronic modulations between h-Ni2P, Ni, and G/CNTs, which provide more space to alleviate the volume effect on cycling and shortens the ion/charge diffusion path to speed up the reaction kinetics.

Development and characteristics study of compact Penning ion source

A compact-size Penning ion source with a small discharge volume (1.24 cm3) is developed. It consists of two concentric cylinders of different heights that act as cathodes and one hollow cylindrical anode. A homogeneous magnetic field is achieved within the discharge volume with geometrical optimization of the ion source. As a result, dense plasma is generated at low discharge power. The dynamics of the pulse mode discharge at low pulse width and frequency of anode voltage are studied. A high discharge (hundreds of amperes) current pulse with low delay time and fast rise time is recorded. The ion source is equally efficient to operate in continuous as well as pulse modes of ionization for various gases. It is operated in a wide range of low pressure at low anode voltage. An extraction system is designed to extract ions efficiently in the axial direction at a variable extraction voltage. The beam current of 200 µA in continuous mode and 6 A fast pulse in the pulsed mode of discharge have been measured. Variable beam current can be extracted with variable extraction voltage for any potential application.

Effect of filler wire on structure and properties of joints of 1565chM alloy sheets made by plasma welding

The results of the effect of filler wire on the structure and mechanical properties of the butt joints of 1565chM alloy sheets with a thickness of 7 mm made by plasma hollow anode welding are presented. It is shown that the introduction of 0.17...0.25 % scandium into the filler wire containing 5.6...6.2 % magnesium contributes to a decrease in the cracking coefficient and a significant increase of the critical deformation rate of the sample during MVTU sample welding, increase of the ultimate strength of the weld metal and its impact strength. There is a significant decrease in the size of the grain in the weld metal.

Sulfur doped hollow carbon nanofiber anodes for fast-charging potassium-ion storage

Sulfur doping can bridge durable active sites to induce CS electron coupling to produce unparalleled Faraday conversion, breaking the limitations of ion storage capacitance, and therefore it is an effective way to design carbon materials with improved electrochemical performance. However, sulfur doping methods, especially how to design S-rich by atomic transition among carbon membered-ring structure of anodes remains a confusing topic. Herein, the linear relationship between sulfur and nitrogen content is found, and the tendency of sulfur to replace pyrrolic nitrogen is demonstrated. The sulfur replaces part of nitrogen atoms and form CS bonds with binds covalently to carbon skeleton, where S-rich hollow carbon nanofibers (NHCFs-S) are synthesized. The introduction of high sulfur doping in carbon results to the improvement of conductivity, Faraday reaction activity and pseudocapacitive adsorption behavior. For potassium-ion batteries, the fabricated NHCFs-S material delivers a 369 mAh/g high capacity at 1.0 A/g after 100 cycles with 80 % initial coulombic efficiency and a desirable rate capability of 261 mAh/g even at 5.0 A/g. This work provides a selection for high-performance anodes design and a reference for the future research of high sulfur doped in carbon materials.

Revealing pre-breakdown processes of a single-gap pseudospark switch triggered from the anode side

Pseudospark switch is a special kind of low-pressure (typically 1–100 Pa) high-voltage pulsed discharge switch with the hollow electrode configuration. This paper experimentally investigates the pre-breakdown processes of a single-gap pseudospark switch triggered from the anode side. The species and contents of impurities on copper electrode surface are firstly analyzed, which mainly include C, N and O. Then, at the same conditions, the trigger delay and jitter of triggering from the anode side are significantly higher than the cathode side, as well as the minimum voltage and pressure that the switch can be triggered. The evolution of the discharge region of the pseudospark switch triggered from the anode side is observed by the ICCD camera for the first time in the literature. The time-resolved images show that the luminescence firstly appears in the hollow anode where the trigger discharge happens and then in the hollow cathode, the cathode hole, the main gap and the anode hole successively, which is completely different from triggering from the cathode side. Finally, a model considering the migration and collisions of ions and fast atoms is established, and it points out that the ion flux from the hollow anode plays an important role in triggering from the anode side. The key processes also include the formations of the positive space charge column inside the hollow cathode and the intense secondary electron emission as an electron source for the main gap.

A preliminary study on the hollow anode of a 450 kV rod-pinch diode

This paper proposes a hollow rod as the anode of a rod-pinch diode (RPD) at about 450 kV voltage. Two kinds of hollow rod anodes that may enhance the central radiation dose are obtained through PIC and Monte Carlo simulations. The experimental results show that the hollow anode made by Electrical Discharge Machining (EDM) can effectively enhance the forward central dose of the 450 kV rod-pinch diode, which helps to improve the radiation imaging definition.

Measurements and interpretation of EEDF in a discharge with a hollow cathode in helium: effect of the measuring probe and the anode on the form of the distribution function

Experimental and theoretical studies of the electron energy distribution function in hollow cathode discharge plasma have been carried out. The discharge was ignited in helium at a pressure of 0.75 Torr, and the distance between the rectangular hollow cathode and anode was 3 cm. The measurements were performed using the probe method at various distances from the anode. The obtained distribution functions turned out to be strongly depleted in low-energy electrons. As applied to the experimental conditions, the role of two effects that can lead to such depletion was analyzed: instrumental distortions of the distribution function due to the electron sink on the probe and the absorption of electrons by the anode. According to the calculations, under the considered conditions, the main contribution to the depletion of the measured distribution functions by the slow electrons comes from the second effect.

Synthesis of Porous Hollow Spheres Co@TiO2−x-Carbon Composites for Highly Efficient Lithium-Ion Batteries

The hollow TiO2 anode material has received great attention for next-generation LIBs because of its excellent stability, environmental friendly, and low volume change during lithiation/delithiation. However, there are some problems associated with the current anatase TiO2 anode materials in practical application owing to low lithium-ion diffusivity and poor reversible theoretical capacities. The introduction of defects has been turned out to be a significant and effective method to improve electronic conductivity, especially oxygen vacancies. In this paper, a facile hydrothermal reaction and subsequent chemical vapor deposition method were successfully used to fabricate Co@TiO2−x-carbon hollow nanospheres. These results suggest that the synthesized product exhibits good rate performance and superior cycling stability.

Pulsed Non-Self-Sustained Arc Discharge in Extended Hollow Anode

Pulsed Non-Self-Sustained Arc Discharge in Extended Hollow Anode

Coiled Conformation Hollow Carbon Nanosphere Cathode and Anode for High Energy Density and Ultrafast Chargeable Hybrid Energy Storage.

Lithium-ion batteries and pseudocapacitors are nowadays popular electrochemical energy storage for many applications, but their cathodes and anodes are still limited to accommodate rich redox ions not only for high energy density but also sluggish ion diffusivity and poor electron conductivity, hindering fast recharge. Here, we report a strategy to realize high-capacity/high-rate cathode and anode as a solution to this challenge. Multiporous conductive hollow carbon (HC) nanospheres with microporous shells for high capacity and hollow cores/mesoporous shells for rapid ion transfer are synthesized as cathode materials using quinoid:benzenoid (Q:B) unit resins of coiled conformation, leading to ∼5-fold higher capacities than benzenoid:benzenoid resins of linear conformation. Also, Ge-embedded Q:B HC nanospheres are derived as anode materials. The atomic configuration and energy storage mechanism elucidate the existence of mononuclear GeOx units giving ∼7-fold higher ion diffusivity than bulk Ge while suppressing volume changes during long ion-insertion/desertion cycles. Moreover, hybrid energy storage with a Q:B HC cathode and Ge-Q:B HC anode exploit the advantages of capacitor-type cathode and battery-type anode electrodes, as exhibited by battery-compatible high energy density (up to 285 Wh kg-1) and capacitor-compatible ultrafast rechargeable power density (up to 22 600 W kg-1), affording recharge within a minute.