Solid Cathode Research Articles

Application of a One-Dimensional Transient Electrorefiner Model to Predict Partitioning of Plutonium from Curium in a Pyrochemical Spent Fuel Treatment Process

It has previously been proposed by safeguards experts that curium will track plutonium through a spent fuel pyroprocessing facility, enabling nondestructive assaying of plutonium via counting neutron emissions from 244Cm. This is a critical assumption for the neutron balance approach to safeguards. If Cm and Pu were to behave chemically the same, counting neutrons could be used to estimate Pu concentrations. In this study, plutonium tracking with curium has been investigated using Enhanced REFIN with Anodic Dissolution (ERAD), a one-dimensional transient electrorefiner model based on fundamental electrochemical equations. The model was used to simulate simultaneous deposition of uranium, plutonium, and curium onto a solid metal cathode. Chemical/physical properties used by the model were either obtained from the literature or assumed. The standard exchange current density of curium was estimated by analyzing published cyclic voltammetry data for LiCl-KCl-CmCl3. The focus of the ERAD calculations was on verifying that Pu and Cm could codeposit onto the cathode along with U and to determine if the Pu/Cm ratio would be the same between the salt pool and cathode deposit. It was determined that Cm largely resists cathode deposition, while Pu can be driven to codeposit at sufficiently high current densities. The expected concentration of Cm in the salt would not support any deposition of Cm onto the cathode. It would need to be raised to ~1 wt% before small gram quantities of Cm will deposit onto the cathode. Even then, the Pu/Cm ratio of the cathode was found to be three orders of magnitude higher than the ratio in the salt. It is, thus, concluded that the neutron balance approach would be ineffective at safeguarding a nuclear fuel pyroprocessing facility.

Hα line Doppler broadening in a glow discharge cathode region in the argon-hydrogen mixture

Spectral measurements of Doppler profiles of the hydrogen Hα spectral line in a glow direct current discharge in a mixture of 1% hydrogen in argon at pressures of 60, 120 and 180 Pa were performed. Solid and mesh cathodes were used. It is brought out that the line shapes are Gaussian with the width corresponding to the effective temperature of the excited atoms of 35-60 eV for emission from the cathode region. The line width does not change with the pressure and the distance from cathode in the region of negative glowing and increases slightly with the distance from the mesh cathode outside of the discharge gap.

An X-band high-impedance relativistic klystron amplifier with an annular explosive cathode

The feasibility of employing an annular beam instead of a solid one in the X-band high-impedance relativistic klystron amplifier (RKA) is investigated in theory and simulation. Small-signal theory analysis indicates that the optimum bunching distance, fundamental current modulation depth, beam-coupling coefficient, and beam-loaded quality factor of annular beams are all larger than the corresponding parameters of solid beams at the same beam voltage and current. An annular beam RKA and a solid beam RKA with almost the same geometric parameters are compared in particle-in-cell simulation. Output microwave power of 100 MW, gain of 50 dB, and power conversion efficiency of 42% are obtained in an annular beam RKA. The annular beam needs a 15% lower uniform guiding magnetic field than the solid beam. Our investigations demonstrate that we are able to use a simple annular explosive cathode immersed in a lower uniform magnetic field instead of a solid thermionic cathode in a complicated partially shielding magnetic field for designing high-impedance RKA, which avoids high temperature requirement, complicated electron-optical system, large area convergence, high current density, and emission uniformity for the solid beam. An equivalent method for the annular beam and the solid beam on bunching features is proposed and agrees with the simulation. The annular beam has the primary advantages over the solid beam that it can employ the immersing uniform magnetic field avoiding the complicated shielding magnetic field system and needs a lower optimum guiding field due to the smaller space charge effect.

Thermal treatment process for the recovery of valuable metals from spent lithium-ion batteries

In this paper, a process based on reducing thermal treatment before acid leaching for the recovery of valuable materials from spent lithium-ion batteries is developed. The thermodynamic behavior of the active cathode materials is investigated through analyzing the gases evolved from the thermal treatment with a thermogravimetric–mass spectrometry (TG–MS) instrument. Scanning electron microscopy (SEM) with energy dispersive x-ray (EDX) spectroscopy analyses are also performed on the solid cathode and anode materials to determine their physicochemical changes from the thermal treatment. The results show that the thermal treatment significantly improves the clean separation of the active materials from the current collectors and the complete removal of the binder and carbonaceous conductor. It also alters the molecular structures of, and partially reduces the transition metals in, the active cathode materials, which increases the leaching efficiency of the transition metals in the subsequent leaching step. After thermal treatment, the leaching efficiency of nickel, cobalt and manganese from the active cathode materials has reached over 98%, 99% and 84%, respectively.

High‐Performance Lithium Solid‐State Batteries Operating at Elevated Temperature

A facile and inexpensive solid-state battery system (Li/LiBH4-LiI/lithiated TiS2) that exhibits excellent performance at elevated temperature (120 °C) is presented. The preformation of solid electrolyte interphase by chemical reaction is demonstrated to prohibit self-discharge and successfully address the interfacial issue between the solid electrolyte and cathode at high temperatures. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Synthesis and electrochemical properties of Li1.2Mn0.54Ni0.13Co0.13O2 cathode material for lithium-ion battery

The layered Li1.2Mn0.54Ni0.13Co0.13O2 lithium-rich manganese-based solid solution cathode material has been synthesized by a simple solid-state method. The as-prepared material has a typical layered structure with R-3m and C2/m space group. The synthesized Li1.2Mn0.54Ni0.13Co0.13O2 has an irregular shape with the size range from 200 to 500 nm, and the primary particle of Li1.2Mn0.54Ni0.13Co0.13O2 has regular sphere morphology with a diameter of 320 nm. Electrochemical performances also have been investigated. The results show that the cathode material Li1.2Mn0.54Ni0.13Co0.13O2 prepared at 900 °C for 12 h has a good electrochemical performance, which can deliver a high initial discharge capacity of 233.5, 214.2, 199.3, and 168.1 mAh g−1 at 0.1, 0.2, 0.5, and 1 C, respectively. After 50 cycles, the capacity retains 178.0, 166.3, 162.1, and 155.9 mAh g−1 at 0.1, 0.2, 0.5, and 1 C, respectively. The results indicate that the simple method has a great potential in synthesizing manganese-based cathode materials for Li-ion batteries.

Electrochemical synthesis of 1-isonicotinoyl-2-isopropylhydrazine on stationary solid electrodes

The possibility of preparing isonicotinoylisopropylhydrazine by electrochemical reduction of the corresponding hydrazone on stationary solid electrodes (titanium, zirconium, nickel, iron, iron-based alloys) was demonstrated. The electrolysis is performed in the cathodic space of the electrolyzer on solid cathodes in aqueous-alcoholic solutions, with glassy carbon used as anode. The hydrazone electroreduction is performed at the cathodic current density of 0.1–0.5 A dm–2 in the temperature interval 40–70°С for 2–5 h. On electrodes with low overvoltage of hydrogen evolution, the C=N double bonds in isonicotinoylisopropylidenehydrazine relatively readily undergo electrohydrogenation with atomic hydrogen.

Actinides recovery from irradiated metallic fuel in LiCl–KCl melts

Electrorefining of irradiated metallic fuels was successfully demonstrated: Actinides (U, Pu, Np, Am and Cm) in the fuels were dissolved in LiCl–KCl melts with high dissolution ratios, while U was selectively deposited on a solid cathode and the simultaneous recovery of actinides in a liquid Cd cathode was confirmed. The behavior of actinides, the fuel matrix stabilizer Zr and fission products such as lanthanide, alkaline, alkaline earth and noble metal, at the electrorefining is discussed based on the ICP-MS analysis of the samples taken from molten salt electrolyte, anode fuel residues and cathode deposits.

Engineering of Hollow Core-Shell Interlinked Carbon Spheres for Highly Stable Lithium-Sulfur Batteries.

We report engineered hollow core-shell interlinked carbon spheres that consist of a mesoporous shell, a hollow void, and an anchored carbon core and are expected to be ideal sulfur hosts for overcoming the shortage of Li-S batteries. The hollow core-shell interlinked carbon spheres were obtained through solution synthesis of polymer spheres followed by a pyrolysis process that occurred in the hermetical silica shell. During the pyrolysis, the polymer sphere was transformed into the carbon core and the carbonaceous volatiles were self-deposited on the silica shell due to the blocking effect of the hermetical silica shell. The gravitational force and the natural driving force of lowering the surface energy tend to interlink the carbon core and carbon/silica shell, resulting in a core-shell interlinked structure. After the SiO2 shell was etched, the mesoporous carbon shell was generated. When used as the sulfur host for Li-S batteries, such a hierarchical structure provides access to Li(+) ingress/egress for reactivity with the sulfur and, meanwhile, can overcome the limitations of low sulfur loading and a severe shuttle effect in solid carbon-supported sulfur cathodes. Transmission electron microscopy and scanning transmission electron microscopy images provide visible evidence that sulfur is well-encapsulated in the hollow void. Importantly, such anchored-core carbon nanostructures can simultaneously serve as a physical buffer and an electronically connecting matrix, which helps to realize the full potential of the active materials. Based on the many merits, carbon-sulfur cathodes show a high utilization of sulfur with a sulfur loading of 70 wt % and exhibit excellent cycling stability (i.e., 960 mA h g(-1) after 200 cycles at a current density of 0.5 C).

Liquid Catholyte Investigations for Safer Storage of a Li Primary Battery

The close proximity of the electrode materials is a design risk for commercial off the shelf (COTS) Li batteries. COTS Li batteries can off gas and ignite if the electroactive materials are inadvertently mixed by events such as thermal abuse, crush, penetration, and shock. Crew safety on US Navy ships and submarines critically depends on minimizing the probability of exposure to toxic gases and fire. The Naval Undersea Warfare Center (NUWC) is investigating a primary Li battery design for undersea applications that is, in principle, safer to store and transport than COTS batteries. In this approach a liquid catholyte is stored separately from a Li metal anode. The catholyte is added to the anode housing immediately prior to off board deployment of the energy section. With this configuration the electroactive materials can be stored separately and more safely than in COTS batteries. NUWC has recently begun investigating slurry catholytes1 comprised of solid redox active cathode materials and electronically conductive carbon powders dispersed in a nonaqueous electrolyte. Our goals are high volumetric charge capacity, high voltage, good power density and a “pumpable” rheology. These properties are significantly affected by the formulation of the slurry such as the choice of redox active material, the volumetric solids concentration of the redox active and carbon materials, the interaction between the particles, and the particle size distributions. This talk will discuss NUWC’s separated anode / catholyte battery concept, the tradeoffs of various electroactive cathode materials, and the results of catholyte investigations and their expected impact on the performance of a Li-slurry catholyte primary battery. 1) M.Duduta., B.Ho, V.C. Wood, P. Limthongkul, V. E. Brunini, W. C. Carter, and Y-M Chiang, Semi-Solid Lithium Rechargeable Flow Battery , Adv. Energy Mater. 2011, 1, 511–516

Change of Average and Local Crystal Structure and Electronic Structure of Li-Rich Solid Solution Cathode Material 0.4Li2MnO3-0.6LiMn1/3Ni1/3Co1/3O2 during Charge-Discharge Process Using First-Principles Calculations and Neutron Beam and Synchrotron X-Ray Sources

In recent years, lithium-ion battery has been expected in order to meet the requirement for the electric vehicles and electric power. The solid solutions of Li2MnO3 and LiMO2 (M = Mn, Ni, Co, etc.) have attracted attention over the last 10 years because they deliver high discharge capacity[1]. On the other hand, it was reported as the one of the problems that discharge voltage of this material decreases by repeating charge and discharge process. But the mechanism of the voltage fade is not clear. To commercialize the solid solution materials, it is necessary to solve the problem. In this study, we focused on the above problem. Our previous report described a transition metal rearrangement that occurs between 4.6 and 3.3 V during the initial discharge process[2]. We synthesized the 0.4Li2MnO3-0.6LiMn1/3Ni1/3Co1/3O2 by coprecipitation method, and its average crystal structure was discussed by Rietveld analysis using powder neutron diffraction measurements(BL20, J-PARC) and synchrotron X-ray diffraction measurements(BL02B2, SPring-8). In addition, we carried out first-principle calculation (VASP-code, WIEN2k-code) in order to discuss the electronic state theoretically. Also, we used Pair Distribution Function (PDF) analysis using synchrotron X-ray total scattering(BL04B2, SPring-8) and neutron total scattering(BL21, J-PARC) in order to discuss the detailed local structure. To discuss the structural changes associated with the repeating charge and discharge process, we carried out X-ray absorption spectroscopy in addition to VASP-code and PDF analysis using synchrotron X-ray total scattering. First, the average and local crystal structures, and the electronic structure of 0.4Li2MnO3-0.6LiMn1/3Ni1/3Co1/3O2 were investigated using a combination of a pair distribution function (PDF) analysis and first-principles calculations. The results of a Rietveld analysis using neutron diffraction data showed that 0.4Li2MnO3-0.6LiMn1/3Ni1/3Co1/3O2 belonged to space group C2/m. Based on the site occupancy results, Mn was localized at 4g sites, and Ni and Co were present at both 4g and 2b sites. Both the maximum entropy method using synchrotron X-ray diffraction data, and calculations using WIEN2k, showed that the covalencies between Mn at 2b sites and O at8j sites in the transition metal layer, and between 2c and 8j sites in the lithium layer, were relatively low. A PDF analysis using both synchrotron X-ray and neutron total scattering data produced good fits to the observed data, and identified local differences in the average structure, such as the precise locations of Li and O. Although some distortion existed, the refined structure contained Mn-O6, Ni-O6, and Co-O6 tetrahedra. The bond lengths corresponded to the ionic radii, so that the valence of Mn, Ni and Co in this material before charging was tetravalent, between divalent and trivalent, and trivalent, respectively. These results were consistent with the valence obtained from the density of states calculated by the WIEN2k code, thus confirming that the local structural model was appropriate. Second, the structural changes associated with the repeating charge and discharge using after first discharge and after fifth discharge were investigated. By the comparison of this material before charge, after first discharge and after fifth discharge using PDF analysis, it was indicated that Li deviated from the plane of Li layer associated with the repeating charge and discharge. While the bond distance of Mn-O and Co-O was longer, that of Ni-O was shorter. From the results, the both the valences of Mn and Ni approached to trivalent. These local structural changes related to the decrease of discharge voltage by repeating charge and discharge. Acknowledgement This work was supported in part by JSPS KAKENHI Grant Number 25420718. [1] M.M. Thackeray, et al., J. Mater. Chem. 15, 2257 (2005). [2] Y. Idemoto et al, Electroch imica Acta, , 153, 399(2015).

Modeling the Molten Salt Electrorefining Process for Spent Metal Fuel Using COMSOL

Molten salt electrorefining process is one of the key steps of the pyrochemical reprocessing flow sheet for the spent metallic fuel from fast reactors. The electrorefining process is simulated using COMSOL Multiphysics. This involves solving multiple equations corresponding to electrochemical reactions at the electrode surfaces, mass transfer of metal ions in the electrolyte, potential distribution in the electrolyte, and overall material balance of metal ions in a coupled manner. The model is validated using the data of laboratory scale electrorefining experiments from literature. The results show a good agreement with the present experimental data, the variation being less than 10% for the U and Pu concentration changes in liquid Cd anode and molten salt, and U deposit on solid cathode.

A Single-Use Paper-Shaped Microbial Fuel Cell for Rapid Aqueous Biosensing.

The traditional chamber-based microbial fuel cell (MFC) often has the disadvantages of high ohmic resistance, large volume requirements, and delayed start-up. In this study, paper-shaped MFCs utilizing a porous carbon anode, a solid Ag2 O-coated carbon cathode, and a micrometer-thin porous polyvinylidene fluoride (PVDF) separator are investigated to address the classical MFC issues. The Ag2 O-coated cathode has a low overpotential of 0.06 V at a reducing current of 1 mA compared to a Pt-air cathode. Rapid inoculation by filtration results in an instantaneous power density of 92 mW m(-2) with an internal resistance of 162 Ω. Integrated current over the first 30 min of operation has a linear relation with microbial concentration.

Understanding the electrochemical superiority of 0.6Li[Li1/3Mn2/3]O2-0.4Li[Ni1/3Co1/3Mn1/3]O2 nanofibers as cathode material for lithium ion batteries

Solid solution cathode materials 0.6Li[Li1/3Mn2/3]O2-0.4Li[Ni1/3Co1/3Mn1/3]O2 with different morphologies were synthesized by electrospinning and coprecipitation method respectively. The field-emission scanning electron microscope images verified the successful formation of nanofibers for electrospinning and nanoparticles for coprecipitation and the nanofibers showed larger specific surface area according to the Brurauer Emmerr Teller procedure. The X-ray powder diffraction patterns and the corresponding lattice parameter refinements showed that both samples can be indexed to hexagonal α-NaFeO2 layered structure with space group of R-3m. And the material prepared by electrostatic spinning method has a tight atomic arrangement in the layer yet the different dimensions do not influence the intercalation and deintercalation of lithium ion through the interlayer. The discharge capacity of nanofibers electrode is 302.3mAhg−1 at 0.05C and the initial columbic efficiency is 76.2%, which are higher than 282.7mAhg−1 and 68.2% of the nanoparticles electrode. The nanofibers electrode also presented better cycleability and rate capability, especially performed capacity of 126.6mAhg−1 at 5C, much higher than that of 109.4mAhg−1 for nanoparticles electrode. The step-by-step cyclic voltammetry revealed that the nanofibers electrode performs higher discharge voltage platform and enhanced discharge energy density. The excellent electrochemical performance of nanofibers electrode is ascribed to the better conductivity and superior lithium ion diffusion ability according to the electrochemical impedance spectrum measurement.

Novel Approach to Extracting Transuranic Elements in Molten Salt Electrorefining

A novel approach to extracting transuranic elements (TRUs) from molten salt into liquid Cd using U metal as a reductant was investigated for the molten salt electrorefining process. We considered two methods of adding U metal: direct extraction (DE) and electrochemical extraction (EE). In the DE method, U metal added to Cd is dissolved and exchanged for TRU ions in the salt. The EE method is based on the principle of a concentration cell. When U metal and Cd separately placed in the salt are electrically connected, the U metal is anodically dissolved in the salt, and U and TRU ions are reduced at the Cd. The advantages of these methods over the conventional electrolytic method are as follows: The container for Cd can be made of steel, dendritic U metal does not form on the surface of the Cd or the crucible, and the operation is simple and stable. It was experimentally demonstrated that Pu and Am could be extracted from LiCl-KCl melt into liquid Cd by both the DE and EE methods when U metal collected at the solid cathode was used as a reductant. Crucibles made of steel could be used as containers for Cd, and a total of ∼3 wt% of U, Pu, and Am in the Cd was collected in 10 h. In the EE tests, the separation factors among U, Pu, and Am were always equal to the values at equilibrium. The rate-determining step for the extraction was not the mass transfer in the Cd or salt phase but the electron transfer at the Cd-salt interface. Then, a concept high-performance electrorefiner equipped with two anode–solid cathode modules and an EE or DE module was preliminarily designed.

Microwave Power and Phase Measurements on a Recirculating Planar Magnetron

Calibrated microwave power and phase measurements are presented for the first recirculating planar magnetron prototype consisting of two coupled six-cavity 1-GHz planar cavity arrays. The results are presented for a solid cathode and two mode-control cathodes (MCCs) with aluminum or velvet electron emitters. The measurements were conducted using a prototype coaxial microwave power extraction scheme. The experimental operating parameters included: pulsed cathode voltages between -250 and -300 kV, voltage pulselengths of 200-600 μs, axial magnetic fields of 0.1-0.32 T, and entrance currents of 1-10 kA. The results showed improved oscillator frequency locking for the MCCs and increases in power and efficiency using the velvet electron emitter.

A Dual-Phase Cathode and a Si/SiOx Anode for Li-Sulfur Batteries

The lithium-sulfur battery is one of the most promising high-energy-density electrochemical energy storage systems for emerging applications such as power storage systems for renewable energy plants and the powering of sustainable electric vehicles.1 The natural abundance and low cost of sulfur, coupled with the high theoretical energy density of sulfur-based cathodes, namely, 1675 mAh g-1 and 3500 Wh kg-1, are the major advantages of this sulfur battery.2 However, the insulating nature of sulfur, leads to low active material utilization, and sulfur electrodes have low stability, arising from the formation of soluble lithium polysulfide during cell operation; these problems, have so far limited the commercialization of this battery.3 There has been consistent progress recently toward optimizing the sulfur electrode.4 Recently, several research groups have reported that the addition of lithium polysulfide to the electrolyte could improve the performance of the Li/S battery in terms of cycle performance and energy density.5 Another major concern regarding the lithium-sulfur battery system is its use of a lithium metal anode, which is well known to have some critical problems including chemical reactivity in commonly used organic electrolytes and dendritic growth of lithium during cycling, leading to poor cycle performance and safety problems. In addition, when coupled with a sulfur cathode, the lithium metal anode reacts with lithium polysulfide to form an insoluble Li2S phase on the lithium surface, leading to the loss of lithium metal and eventually causing poor cycle performance of the system. It should be also noted that an excess amount of lithium metal is needed to construct the full cell to secure its long cycle life, which might lead to degradation of both the energy density and the safety of the full cell. Herein, we demonstrated a lithium-ion sulfur cell configuration using a newly designed dual-type sulfur cathode and a lithiate Si/SiOx nanosphere anode with optimized liquid electrolyte. Our dual-type sulfur cathode system delivered maximum capacity on the order of 1,300 mAh g-1as referred to the mass of the overall sulfur content; that is to say, the mass of sulfur both in the solid cathode and in the dissolved lithium polysulfide. The lithiated Si/SiOx nanosphere anode used showed highly stable cycling behavior over 100 cycles, with a capacity as high as 800 mAh g-1and cycling efficiency approaching 100%. The full lithium-ion sulfur cell presented herein delivered a capacity on the order of about 750mAhg-1. We believe that these results might advance the practical development of the lithium-ion sulfur battery, particularly for use in emerging markets including electric vehicles and large-scale power storage systems for use with renewable energy systems.

Nanoporous-Carbon As an Intercalation Host Material to Enable Multivalent Ion Electrochemical Energy Storage

We study the use of nanoporous-carbon (NPC) as an electrically conductive host material for Mg2+ intercalation. Negligible progress for multivalent energy storage via intercalation into existing carbonaceous materials has been made due to insufficient interstitial/interplanar spacing within the crystallographic structures to host the larger sizes of partially-solvated multivalent ions. However, NPC has high surface area with open and accessible porosity, controllable via mass density, which can minimize the diffusional resistance. Here, we grow NPC directly on stainless-steel disks, which are used as anodes to fabricate coin cells with solid Mg cathodes and a Grinard-based electrolye. NPC mass density is controlled during growth, ranging from 0.06 – 1.0 g/cm3, and correlates directly with electrochemical characterizations. In particular, cyclic voltammetry (CV) scans for NPC with density ~ 0.5 g/cm3 are consistent with the reversible intercalation of Mg ions. Higher density NPC yields capacitive behavior, most likely resulting from the smaller interplanar spacings between graphene sheet fragments and tighter domain boundaries; lower density NPC results in asymmetrical CV scans, consistent with possible structural degradation resulting from mass transport through such a soft carbon material. Briefly, NPC grows via pulsed-laser deposition with controllable mass densities ranging from ~ 0.05 to 2.0 g/cm3. The internal structure of NPC self-assembles during growth and consists of nano-fragments of aligned graphene sheet stacks with interplanar spacings expanded by as much as 55% compared to crystalline graphite. Indeed, typical crystalline domain sizes are only 1 – 2 nm in length, as determined by high-resolution transmission electron microscopy; hence, NPC consists of randomly-oriented graphene nano-crystallites with expanded interplanar spacings, and with a plethora of grain boundaries to enable rapid diffusion of species into an entire volume. Ionic intercalation into graphite is well known. Reducing the mass density of NPC increases the interplanar spacings. Therefore, the advantages of using NPC to study Mg2+intercalation include the tunability of the interplanar spacings and the ability to deposit it onto any substrate material without using binder materials, both increasing the fraction of available carbon surface atoms and simplifying the interpretation of measurements. This suggests the potential to successfully develop NPC as an intercalation host for multivalent energy storage. This work is supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Enhanced electrochemical performances of layered cathode material Li1.5Ni0.25Mn0.75O2.5 by coating with LiAlO2

Layered solid solution cathode Li1.5Ni0.25Mn0.75O2.5 has been synthesized and coated by composite oxides LiAlO2 with varying amounts (1, 3, 5 and 8wt%) in this paper. The effect of coated LiAlO2 on the physical and electrochemical properties of the material has been discussed through the characterizations of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), discharge, cyclic performance, rate capability and electrochemical impedance spectroscopy (EIS). The discharge capacity and coulombic efficiency of Li1.5Ni0.25Mn0.75O2.5 in the first cycle have been improved after LiAlO2 coating. And the 5wt% LiAlO2 coated Li1.5Ni0.25Mn0.75O2.5 shows the best discharge capacity (257.6mAhg−1), capacity retention (101.6% for 50 cycles) and rate capability (88.3mAhg−1 at 10C). Electrochemical impedance spectroscopy (EIS) results show that the Rct of Li1.5Ni0.25Mn0.75O2.5 electrode decreases after LiAlO2 coating, which is due to high lithium ion diffusion coefficient of LiAlO2, is responsible for superior rate capability.

Note: design and development of improved indirectly heated cathode based strip electron gun.

An improved design of indirectly heated solid cathode based electron gun (200 kW, 45 kV, 270° bent strip type electron gun) has been presented. The solid cathode is made of thoriated tungsten, which acts as an improved source of electron at lower temperature. So, high power operation is possible without affecting structural integrity of the electron gun. The design issues are addressed based on the uniformity of temperature on the solid cathode and the single long filament based design. The design approach consists of simulation followed by extensive experimentation. In the design, the effort has been put to tailor the non-uniformity of the heat flux from the filament to the solid cathode to obtain better uniformity of temperature on the solid cathode. Trial beam experiments have been carried out and it is seen that the modified design achieves one to one correspondence of the solid cathode length and the electron beam length.