Spherical Cathode Research Articles

An Engineering Porous Spherical Carbon Cathode for High-Energy Sodium-Ion Capacitor.

Sodium-ion hybrid capacitors (SICs) are emerging as promising devices that can balance energy and power output. However, the lack of a high-capacity cathode that can match the anode has limited its further application. In this work, we develop an efficient method to prepare spherical porous carbons (SPCs) with great specific surface area and narrow pore size distribution from coal-based humic acid via spray drying and a subsequent chemical activation process. Thanks to this unique porous structure, the SPC cathode has a superb capacity of 223 F g-1 at 0.05 A g-1, as well as splendid rate performance and cycling stability. SICs constructed by an SPC cathode and hard carbon anode can exhibit a high energy density of 179.8 Wh kg-1 at 155 W kg-1 and achieved 89.4% capacity retention after 10 000 cycles at 0.5 A g-1. This outcome presents a viable approach to attaining high-capacity cathodes for constructing outstanding performance hybrid capacitors.

Prilling and Coating Strategy to Synthesize High-Performance Spherical NaNi0.4Fe0.2Mn0.4O2 Cathode Materials for Sodium Ion Batteries.

Low-cost sodium ion batteries are of great significance in large-scale energy storage applications. With its high energy density and simple synthesis process, layered transition-metal oxides have become one of the most likely sodium ion battery cathode materials to replace lithium ion batteries in the energy storage market. Here, we report a prilling and MoS2 coating strategy to prepare the spherical cathode material. The spherical micronano particles shorten the diffusion path of Na+, restrain the complexity phase transitions, and enhance the tap density of the materials. In addition, the MoS2 coating improves the electrical conductivity of the material and the structural stability of the cathode material in air. The initial specific discharge capacity is 148.4 mA h g-1 at 0.1 C, which can be maintained at 128.9 mA h g-1 after exposure to air for 10 days. This method dramatically improves the energy density and structural stability of the cathode material, which provides a new scheme for preparing high-performance sodium ion batteries.

Perspectives of a single-anode cylindrical chamber operating in ionization mode and high gas pressure

As part of the R2D2 (Rare Decays with Radial Detector) R &D, the use of a gas detector with a spherical or cylindrical cathode, equipped with a single anode and operating at high pressure, was studied for the search of rare phenomena such as neutrinoless double-beta decay. The presented measurements were obtained with a cylindrical detector, covering gas pressures ranging from 1 to 10 bar in argon and 1 to 6 bar in xenon, using both a point-like source of 210\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{210} $$\\end{document}Po (5.3 MeV α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}) and a diffuse source of 222\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{222}$$\\end{document}Rn (5.5 MeV α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document}). Analysis and interpretation of the data were developed using the anodic current waveform. Similar detection performances were achieved with both gases, and comparable energy resolutions were measured with both sources. As long as the purity of the gas was sufficient, no significant degradation of the measured energy was observed by increasing the pressure. At the highest operating pressure, an energy resolution better than 1.5% full-width at half-maximum (FWHM) was obtained for both gaseous media, although optimal noise conditions were not reached.

Constructing a Size-Controllable Spherical P2-Type Layered Oxides Cathode That Achieves Practicable Sodium-Ion Batteries.

P2-type layered metal oxides are regarded as promising cathode materials for sodium-ion batteries due to their high voltage platform and rapid Na+ diffusion kinetics. However, limited capacity and unfavorable cycling stability resulting from inevitable phase transformation and detrimental structure collapse hinder their future application. Herein, based on P2-type Na0.67Ni0.18Mn0.67Cu0.1Zn0.05O2, we synthesized a series of secondary spherical morphology cathodes with different radii derived from controlling precursors prepared by a coprecipitation method, which can be promoted to large-scale production. Consequently, the synthesized materials possessed a high tap density of 1.52 g cm-3 and a compacted density of 3.2 g cm-3. The half cells exhibited a specific capacity of 111.8 mAh g-1 at a current density of 0.1 C as well as an 82.64% capacity retention with a high initial capacity of 85.80 mAh g-1 after 1000 cycles under a rate of 5 C. Notably, in situ X-ray diffraction revealed a reversible P2-OP4 phase transition and displayed a tiny volume change of 6.96% during the charge/discharge process, indicating an outstanding cycling stability of the modified cathode. Commendably, the cylindrical cell achieved a capacity of 4.7 Ah with almost no change during 1000 cycles at 2 C, suggesting excellent potential for future applications.

Directional guiding of mass and charge transfer via vertically aligned graphite nanosheets for high-rate and ultralong lifespan Dual-ion batteries

Cathode materials based on graphite for dual-ion batteries (DIBs) demonstrate multifarious merits, such as abundant resources and high anion interaction potential etc. However, the traditional irregular spherical graphite cathodes suffer from uneven anion migration through the highly tortuous pathways and the inductive anisotropic electric fields, leading to mass transfer non-uniformity and sluggish reaction kinetics. Simultaneously, large-sized anions and solvent co-intercalation restrict the anion intercalation behavior and cause severe intercalation volume expansion. To address these challenges, the vertical graphite nanosheets (VGNs) were designed to guide the anion transport directionally for the first time. The perpendicular open structures of VGNs regulate the uniform ion gradient and electric field for rapid anion diffusion by the directional and shortened ion channels with low electrode tortuosity. Meanwhile, the ordered tunnels buffer the intercalation volume expansion, enhancing the structural stability. Consequently, the DIBs with the VGNs as cathodes deliver an impressive discharge specific capacity of ∼ 220 mAh/g at 300 mA g−1, superior rate capability of up to 2000 mA g−1, and excellent cycling stability without obvious degradation after 2000 cycles, which surpasses those of reported DIBs based on anion intercalation cathodes significantly. This investigation on vertically aligned graphite nanosheets provides insights for the development of highly efficient nanomaterials for energy storage systems.

Improvement of electrochemical performance of spherical spinel LiMn2O4 cathode material coated with Al-doped ZnO (AZO) for Li-ion battery

Improvement of electrochemical performance of spherical spinel LiMn2O4 cathode material coated with Al-doped ZnO (AZO) for Li-ion battery

Short-Process Regeneration of Highly Stable Spherical LiCoO2 Cathode Materials from Spent Lithium-Ion Batteries through Carbonate Precipitation.

High-efficacy recycling of spent lithium cobalt oxide (LiCoO2 ) batteries is one of the key tasks in realizing a global resource security strategy due to the rareness of lithium (Li) and cobalt (Co) resources. However, it is of great significance to develop the innovative recycle methods for spent LiCoO2 , simultaneously realizing the efficient recovery of valuable elements and the regeneration of high-performance LiCoO2 . Herein, a novel strategy of regenerating LiCoO2 cathode is proposed, which involves the preparation of micro-spherical aluminum (Al)-doped lithium-lacked precursor (Li2x Co1-x-y Al2/3y CO3, remarked as "PLCAC") via ammonium bicarbonate coprecipitation. The comprehensive conditions affecting particle growth kinetics, morphology and particle size the has been investigated in detail by physical characterizations and electrochemical measurements. And the optimized Al-doped LiCoO2 materials with high-density sphericity (LiCo1-z Alz O2 , remarked as "LCAO") shows a high initial specific capacity of 161 mAh g-1 at 0.1 C and excellent capacity retention of 99.5 % within 100 cycles at 1 C in the voltage range of 2.8 to 4.3 V. Our work provides valuable insights into the featured design of LiCoO2 precursors and cathode materials from spent LiCoO2 batteries, potentially guaranteeing the high-efficacy recycling and utilization of strategic resources.

Kinetically controlled synthesis of low-strain disordered micro-nano high voltage spinel cathodes with exposed {111} facets.

High-voltage LiNi0.5Mn1.5O4 (LNMO) is one of the most promising cathode candidates for rechargeable lithium-ion batteries (LIBs) but suffers from deteriorated cycling stability due to severe interfacial side reactions and manganese dissolution. Herein, a micro-nano porous spherical LNMO cathode was designed for high-performance LIBs. The disordered structure and the preferred exposure of the {111} facets can be controlled by the release of lattice oxygen in the high-temperature calcination process. The unique configuration of this material could enhance the structural stability and play a crucial role in inhibiting manganese dissolution, promoting the rapid transport of Li+, and reducing the volume strain during the charge/discharge process. The designed cathode exhibits a remarkable discharge capacity of 136.7 mA h g-1 at 0.5C, corresponding to an energy density of up to 636.4 W h kg-1, unprecedented cycling stability (capacity retention of 90.6% after 500 cycles) and superior rate capability (78.9% of initial capacity at 10C). The structurally controllable preparation strategy demonstrated in this work provides new insights into the structural design of cathode materials for LIBs.

Improving Structural and Chemical Stability of O3-Type Sodium Layered Oxide Cathode Via Fluorination

A spherical O3-type layered oxide cathode, composed of compactly‐packed nanosized primary particles, is synthesized by the coprecipitation method so that the high tap density of the cathode ensures increased volumetric energy density for energy storage applications. However, drastic volume changes in the deeply charged states contribute to structural degradation, by inducing mechanical stress and the eventual disintegration of the cathode particles by the formation of microcrack. The microcrack traversing the entire secondary particle compromise the mechanical integrity of the cathode and accelerate electrolyte infiltration into the particle interior, causing the subsequent degradation of the exposed internal surfaces. In this study, we suggested a promising fluorination strategy to extend the cycle life of the O3‐type Na[Ni0.5Mn0.5]O2 cathode by improving their mechanical integrity and protecting their surfaces against electrolyte attack. Fluorination not only inhibits the microcracking of cathode secondary particles but also suppresses surface degradation, i.e., the formation of an electrochemically inactive NiO-like rock salt phase and dissolution of transition metals into electrolyte solution.

How to Consider the Interfacial Phenomenon in All‐Solid‐State Batteries? – Quantitative Analysis using µ‐Cavity Electrode

AbstractUnderstanding the intrinsic properties of cathode active particles is required to understand how they depend on the charge transfer resistance at solid–liquid or solid‐solid interfaces. Depth‐of‐discharge (DOD)‐dependent charge transport occurs when lithium ions move from the bulk electrolyte to the cathode active particles. However, composite electrodes consist of unevenly distributed active material, conductive additives, and polymeric binder, which complicates the electron/ion conduction path; hence, estimating the DOD‐dependent charge transfer resistance is difficult. However, micro‐sized spherical cathode active particles can be arranged into a cylindrical cavity trap on a microelectrode to evaluate the interfacial behavior of LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode active particles in liquid and solid electrolyte systems. The electrochemical parameters calculated from the resultant Tafel plot can encourage meaningful discussions and demonstrate the reliability of the measurement technique.

Spherical Sulfur-Infiltrated Carbon Cathode with a Tunable Poly(3,4-ethylenedioxythiophene) Layer for Lithium-Sulfur Batteries.

Li-S batteries have received significant attention owing to their high energy density, nontoxicity, low cost, and eco-friendliness. However, the dissolution of lithium polysulfide during the charge/discharge process and its extremely low electron conductivity hinder practical applications of Li-S batteries. Herein, we report a sulfur-infiltrated carbon cathode material with a spherical morphology and conductive polymer coating. The material was produced via a facile polymerization process that forms a robust nanostructured layer and physically prevents the dissolution of lithium polysulfide. The thin double layer composed of carbon and poly(3,4-ethylenedioxythiophene) provides sufficient space for sulfur storage and effectively prevents the elution of polysulfide during continuous cycling, thereby playing an essential role in increasing the sulfur utilization rate and significantly improving the electrochemical performance of the battery. Sulfur-infiltrated hollow carbon spheres with a conductive polymer layer demonstrate a stable cycle life and reduced internal resistance. The as-fabricated battery demonstrated an excellent capacity of 970 mA h g-1 at 0.5 C and a stable cycle performance, exhibiting ∼78% of the initial discharge capacity after 50 cycles. This study provides a promising approach to significantly improve the electrochemical performance of Li-S batteries and render them as valuable and safe energy devices for large-scale energy storage systems.

Effect of SiO2 Coating on Microstructure and Electrochemical Properties of LiNi0.5Mn1.5O4 Cathode Material

Abstract We present a simple method for producing SiO2-modified LiNi0.5Mn1.5O4 (LNMO) cathode materials. Manganese carbonate was directly mixed with nickel nitrate and lithium hydroxide, and a spherical structure LNMO cathode material was prepared by two-step calcination, then ethyl orthosilicate and LNMO powder were simply mixed in solid and liquid phases to prepare SiO2-coated LNMO material. The effect of SiO2 coating on the structure of LNMO was studied by diffraction of X-rays, scanning electron microscope (SEM), transmission electron microscope (TEM), and thermogravimetric analysis and differential scanning calorimetry. An amorphous SiO2 coating layer developed on the surface of the LNMO particles in the modification and this could alleviate the strike of hydrogen fluoride (HF) caused by electrolyte decomposition as well as the development of a solid electrolyte interphase. The electrochemical performance of the coated material was as follows: when the amount of SiO2 was 0 wt%, 1 wt%, 2 wt%, and 3 wt%, the initial discharge capacity of the sample was 98.2, 84.1, 101.3, and 89.8mAh/g, respectively. After 50 charge−discharge cycles, the capacity retention rates are 92.7%, 66.8%, 97.9%, and 93.8%, respectively. The cyclic stability of the samples can be significantly improved when the SiO2 coating amount is 2 wt% and 3 wt%, indicating that SiO2 coating can not only improve the discharge-specific capacity of the material but also improve its cyclic stability.

Optimized synthesis conditions and electrochemical performances for novel quaternary cobalt-free spherical cathodes

Optimized synthesis conditions and electrochemical performances for novel quaternary cobalt-free spherical cathodes

A large-format streak tube for compressed ultrafast photography

Streak cameras are powerful imaging instruments for studying ultrafast dynamics with the temporal resolution ranging from picosecond to attosecond. However, the confined detection area limits the information capacity of streak cameras, preventing them from fulfilling their potential in lidar, compressed ultrafast photography, etc. Here, we designed and manufactured a large-format streak tube with a large-size round-aperture gate, a spherical cathode, and a spherical screen, leading to an expanded detection area and a high spatial resolution. The simulation results show that the physical temporal resolution of the streak tube is better than 45ps and the spatial resolutions are higher than 14 lp/mm in the whole area of 24 × 28mm2 on the cathode. The experiments demonstrate the streak tube's application potential in weak light imaging benefiting from the imaging magnification of 0.79, a photocathode radiance sensitivity of 37 mA/W, a radiant emitting gain of 11.6 at the wavelength of 500nm, and a dynamic range higher than 512:1. Most importantly, in the photocathode area of Φ35mm, the static spatial resolutions at the center and the edge along the slit (R = 16mm) reach 32 and 28 lp/mm, respectively, and are higher than 10 lp/mm in the whole area of 24 × 28mm2 on the cathode, allowing for a considerable capacity for spatial information.

Enhanced structural and cycling stability of O3-type NaNi1/3Mn1/3Fe1/3O2 cathode by Al replacement of Mn studied in half cell/full sodium-ion batteries

This study uses ball-milling spray drying to prepare a hollow spherical cathode material by doping non-electrochemically active Al into O3-NaNi1/3Mn1/3Fe1/3O2 (NMF) cathode material. The effects of modification on the material's properties were analysed, and the optimum-doped ratio of NaNi1/3Mn(1/3−x)Fe1/3AlxO2 (x = 0.005, NMFA 0.005) was determined. For half-batteries, NMFA 0.005 exhibits a good initial discharge capacity of 115.1 mAh g⁻1 at 1 C and capacity retention of 87.8 % after 200 cycles, which is 16.1 % higher than that of NMF samples. Furthermore, at a high rate (5 C), the initial capacity was 92.3 mAh g−1 and the capacity decline rate was 16.14 %. However, the initial discharge capacity at high voltage was still 136.9 mAh g⁻1. For full batteries, NMFA 0.005 delivered a discharge capacity of 81.1 mAh g⁻1 with a capacity retention of 82.2 % after 100 cycles. Capacity retention was reinforced by approximately 37 % compared with the matrix. Ex situ X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) failure analysis results put together show that an appropriate amount of Al doping could successfully alleviate the Jahn–Teller effect caused by Mn3+, decrease the oxygen loss and increase the stability of the layered structure, all of which result in an excellent electrochemical performance.

What Is Important? Effect of Primary and Secondary Particle Size

High nickel layered oxides are attractive cathode materials that can achieve high energy density in lithium-ion batteries (LIBs). Many researchers have strived to improve the cycling stability and energy density of LiNiO2 (LNO) through another metal mixing, dopping, or coating method. However, the particle size effect of pure LNO during the charging/discharging system has not been fully understood yet. Many computing research results revealed that smaller-particle materials with highly connective interfaces and reduced diffusion paths exhibit higher rate performance and good cycling stability than bulk counterparts. However, our study revealed that the different particle size of LNO has a very different trend in contrast to the computation results because they overlooked the influence of primary particles. In this study, we focus on the impact of the particle size distribution of spherical cathode material on positive electrodes in LIBs. We designed four different particle sizes of Ni(OH)2 by controlling pH, time, and agitation speed. When the other conditions were the same except for the particle size, we were able to explore how the grain size, Li off-stoichiometry (Li1-zNi1+zO2), and activation energy affect the battery performance. Through size comparison, a better understanding of the influence of particle size distribution was obtained, which would be an important basis to engineer electrodes for higher C-rate capability, higher performance, and better stability during battery cycling.

Macroporous vanadium dioxide–reduced graphene oxide microspheres: Cathode material with enhanced electrochemical kinetics for aqueous zinc-ion batteries

Aqueous zinc-ion batteries are being extensively investigated owing to their safe operating conditions. Therefore, the search for cathode materials with optimum composition and nanostructure that enable high zinc-ion storage performance is underway. This study introduces a procedure for the formation of vanadium dioxide-nanoflake-reduced graphene oxide composite (P-VO2@rGO) microspheres with open pores through spray pyrolysis. Spherical cathode materials are formed by spray pyrolysis through the addition of polystyrene nanobeads and graphene oxide nanosheets in the spray solution. This enabled the formation of porous and crumpled graphene oxide microspheres, wherein thin VO2 nanoflakes are anchored. As a cathode for zinc-ion batteries, P-VO2@rGO exhibits a high rate capability (159 mA h g−1; current density = 5.0 A g−1) and stable cycle performance for the 300 cycles at 1.0 A g−1. To discern the synergistic effect of the reduced graphene oxide (rGO) and 3D-porous structure with a small crystal size on the zinc-ion storage, control samples (VO2-rGO composite and porous VO2 microspheres) are synthesized and tested as cathodes for zinc-ion batteries. The synergistic effect of compositing rGO and introducing porous structure with small crystal size enables high reversible capacity and enhances electrochemical kinetics of the electrode.

Electrochemical performance of spherical Li-rich LMNCO cathode materials prepared using a two-step spray-drying method

In this study we synthesized Li-rich Li1.2Ni0.13Mn0.54Co0.13O2 (LMNCO) as a composite cathode material through a two-step spray-drying method, using transition metal (TM) acetates and citric acid (CA, as a chelating agent) at various molar ratios and then calcining at various temperatures for various periods of time. This two-step spray-drying method created hierarchical nano/micro-sphere structures of the LMNCO cathode material. The LMNCO cathode exhibited the best electrochemical performance when synthesized with a TM:CA ratio of 3:2, a calcination temperature of 900 °C, and a calcination time of 5 h. This as-prepared LMNCO composite was then modified with polyimide (PI) at various weight ratios (PI/LMNCO = 0.5, 1.0, and 1.5 wt%) to improve its electrochemical properties. Among the various structures, the LMNCO cathode material coated with 1.0 wt% of PI at a layer thickness of approximately 1.88 nm achieved the best initial discharge capacities. This modified electrode also displayed enhanced cycle stability, with over 93.3 and 87.9% of the capacity retained after 30 cycles at 0.1C and 100 cycles at 1C, respectively. In comparison, the capacity retention of the unmodified LMNCO electrode measured under the same conditions was no more than 91.3% at 0.1C and 70.1% at 1C. Thus, surface modification with PI was an effective method for improving the coulombic efficiency, discharge capacity, and long-term cycling performance of the LMNCO cathode. Such PI-coated LMNCO composite cathode materials appear to be potential candidates for use in next-generation high-performance lithium-ion batteries.

Cathode shape prediction for uniform electrochemical dissolution of array tools for ECDM applications

ABSTRACT The effect of various cathode shapes, i.e., flat-plate, conical, and spherical-shaped cathodes, on the electrochemical dissolution (ECD) behavior of the 3 × 3 area-array tool electrode is presented. The allowed variation in all tip heights is less than 30 μm. Initially, the finite element method (FEM) was used to predicts the reduction in size and heights of the 3 × 3 tips. The spherical shape cathode exhibited uniform current density distribution around the tips, resulting in the consistent dissolution for a longer time than other cathode shapes. Detailed experiments were also performed to predict the dissolution behavior. Experimental results confirmed a similar dissolution behavior. The flat-plate electrode was not suitable in the ECD of array tool electrodes as the difference between the outermost and central tip heights was more than 130 µm, while the difference was less than 30 µm with a spherical-shaped cathode. Electrochemical discharge machining (ECDM) was carried out using the area-array electrodes made by the spherical and flat plate cathodes. The energy channelized by the uniform tips during the ECDM resulted in uniform material removal beneath all the tips, resulting in consistent crater formation. In contrast, a single crater was formed when the non-uniform tips were used.

The Capacity Fading Mechanism of O3-Type Layered Oxide Cathode for Sodium-Ion Batteries

A spherical O3-type layered oxide cathode, composed of compactly‐packed nanosized primary particles, is synthesized by the coprecipitation method so that the high tap density of the cathode ensures increased volumetric energy density for energy storage applications. However, drastic volume changes in the deeply charged states contribute to structural degradation, by inducing mechanical stress and the eventual disintegration of the cathode particles by the formation of microcrack. The microcrack traversing the entire secondary particle compromise the mechanical integrity of the cathode and accelerate electrolyte infiltration into the particle interior, causing the subsequent degradation of the exposed internal surfaces. In this study, we investigated the capacity fading mechanisms related to microcracks for the O3‐type Na[Ni0.5Mn0.5]O2 cathode which is one of the most widely studied materials for SIBs. The electrochemical performance cycled at different upper cut‐off voltages demonstrate that the P3′ to O3′ phase transition above 3.6 V is primarily responsible for the loss of the structural stability of the O3‐type Na[Ni0.5Mn0.5]O2 cathode. References S. Komaba, N. Yabuuchi, T. Nakayama, A. Ogata, T. Ishikawa, I. Nakai, Chem., 2012, 51, 6211. H.-H Ryu, K.-J. Park, C. S. Yoon Y.-K. Sun, Chem. Mater. 2018, 30, 1155.