Solid-state Cathode Research Articles

A flexible NASICON-type composite electrolyte for lithium-oxygen/air battery

Lithium-air/oxygen battery has raised widespread interest due to its extraordinary theoretical energy density (up to 3500 Wh kg−1). In this study, a flexible free-standing NASICON (Na-super ionic conductor)-type hybrid solid-state polymer electrolyte (HSPE) based on PVDF-HFP (poly(vinylidene fluoride-hexafluoropropylene)) copolymer and NASICON LATP (Li1.3Al0.3Ti1.7(PO4)3) was prepared and investigated. The HSPE membranes exhibited an ionic conductivity of 1.02 × 10−4 S cm−1 at room temperature along with a electrochemical window from 2 to 4.5 V. Using the HSPE, a lithium-oxygen/air battery with an inorganic solid-state cathode was fabricated. High initial discharge capacities of 4654 and 5564.3 mAh g−1 were reached under pure O2 and ambient air, respectively. Compared to conventional porous polypropylene (PP) separator, the HSPE membrane alleviated the corrosion of the lithium anode, thus improving the cyclability of the cells. The results presented in this study suggest the great potential application of NASICON-type HSPE membrane in solid-state rechargeable lithium-air/oxygen batteries.

Flexible and stretchable microbial fuel cells with modified conductive and hydrophilic textile

We built a flexible, stretchable microbial fuel cell (MFC) by laminating two functional components: a bioanode textile with a conductive and hydrophilic polymer coating and a solid-state cathode textile loaded with silver oxide. The textile MFC used Pseudomonas aeruginosa PAO1 as a biocatalyst to generate the maximum power and current density of 1.0µW/cm2 and 6.3µA/cm2, respectively, which are comparable with or even higher than other flexible MFCs such as paper-based devices (~ a few µW/cm2). Additionally, the textile MFC generated consistent power even with repeated 70 cycles of 50% stretching. A simple batch fabrication method simultaneously produced 20 individual 2cm × 2cm devices by using brushing, spraying, ironing, and computerized sewing, a process that will revolutionize the mass production of textile MFCs. This achievement is scientifically meaningful because developing textile MFCs requires integration of both electronic and fluidic components into the textile three-dimensionally. This flexible and stretchable energy harvesting device is expected to be easily integrated with the next generation stretchable electronics for realizing low-power, stand-alone, self-sustainable systems.

Carbon black as an alternative cathode material for electrical energy recovery and transfer in a microbial battery

Rather than the conventional concept of viewing conductive carbon black (CB) to be chemically inert in microbial electrochemical cells (MECs), here we confirmed the redox activity of CB for its feasibility as an electron sink in the microbial battery (MB). Acting as the cathode of a MB, the solid-state CB electrode showed the highest electron capacity equivalent of 18.58 ± 0.46 C/g for the unsintered one and the lowest capacity of 2.29 ± 0.48 C/g for the one sintered under 100% N2 atmosphere. The capacity vibrations of CBs were strongly in coincidence with the abundances of C=O moiety caused by different pretreatments and it implied one plausible mechanism based on CB’s surface functionality for its electron capturing. Once subjected to electron saturation, CB could be completely regenerated by different strategies in terms of electrochemical discharging or donating electrons to biologically-catalyzed nitrate reduction. Surface characterization also revealed that CB’s regeneration fully depended on the reversible shift of C=O moiety, further confirming the functionality-based mechanism for CB’s feasibility as the role of MB’s cathode. Moreover, resilience tests demonstrated that CB cathode was robust for the multi-cycles charging-discharging operations. These results imply that CB is a promising alternative material for the solid-state cathode in MBs.

Effect of XRD relative intensities of the Li (002) on surface, optical and electrochemical impedance spectroscopy analyses of the deposited LiCoO2 thin film

In this paper, the effect of RF power on LiCoO2 thin films was investigated using X-ray diffractometer (XRD), atomic force microscopy, UV–Vis spectrophotometer, and potentiostat. The microstructural, surface, optical and electrochemical impedance measurements were performed to LiCoO2 thin films, are used to for the fully solid-state battery cathode material. According to obtained results, the relative intensities of the Li (002) crystal phase in XRD patterns of deposited LiCoO2 thin films were increased by increasing applied RF power, for the first time. The intensity of the LiCoO2 (104) plane is nearly invariant. The relative intensities of the LiCoO2 (113) plane were decreased by increasing RF power. The peak locations of the Li (002) and LiCoO2 (104) were not changed. It was found that Li (002) relative intensities affect the all investigated parameters for the LiCoO2 thin films. Especially, transmittance value increased about 20%. The band gap of the deposited film was changed 100–300 meV drastically. Deposited samples are shown high transparency in the visible region. Randles circuit was used for the equivalent circuit model. Nyquist plots, fitting parameters values and value of the circuit elements were estimated by ZSim software.

Rechargeable membraneless glucose biobattery: Towards solid-state cathodes for implantable enzymatic devices

Enzymatic biobatteries can be implanted in living organisms to exploit the chemical energy stored in physiological fluids. Generally, commonly-used electron donors (such as sugars) are ubiquitous in physiological environments, while electron acceptors such as oxygen are limited due to many factors including solubility, temperature, and pressure. The wide range of solid-state cathodes, however, may replace the need for oxygen breathing electrodes and serve in enzymatic biobatteries for implantable devices. Here, we have fabricated a glucose biobattery suitable for in vivo applications employing a glucose oxidase (GOx) anode coupled to a solid-state Prussian Blue (PB) thin-film cathode. PB is a non-toxic material and its electrochemistry enables fast regeneration if used in a secondary cell. This novel biobattery can effectively operate in a membraneless architecture as PB can reduce the peroxide produced by some oxidase enzymes. The resulting biobattery delivers a maximum power and current density of 44 μW cm−2 and 0.9 mA cm−2, respectively, which is ca. 37% and 180% higher than an equivalent enzymatic fuel cell equipped with a bilirubin oxidase cathode. Moreover, the biobattery demonstrated a stable performance over 20 cycles of charging and discharging periods with only ca. 3% loss of operating voltage.

Chemically Regenerative Redox Fuel Cells Using Iron Redox Couples as a Liquid Catalyst with Cocatalysts

Chemically regenerative redox fuel cells (CRRFCs) using liquid catalysts as an alternative to solid-state cathode catalysts have been intensively studied. Here, we studied Fe2+/Fe3+ as a liquid catalyst with Fe-macrocycles as a cocatalyst in CRRFCs. The Fe2+-oxidation rate was enhanced in the presence of Fe-Phthanolocyanine. The single cell having the cathode supplied by the liquid catalyst with Fe-Pc showed a maximum power density of ∼249 mW cm–2.

Carbon Nanohorn and Ionic Liquid Mixture: Towards High Performance Organic Catholyte for Rechargeable Lithium Metal Battery

Recenlty, several novel prototypes of lithium metal battery that use lithium metal as anode and soluble halogen redox couple (such as Br2/Br- and I2/I-) as catholyte have been developed.1-3 These emerging prototypes have several advantages compared with existing lithium-oxygen (Li-O2) and lithium-sulfur (Li-S) batteries. The high solubility of redox couple circumvents the deposition of insoluble and electrical-insulating product on the carbon anode that has caused large overpotential for Li-O2 batteries. And the cell potentials of these prototypes are much larger than those of Li-S batteries, because of the high redox potential (vs Li+/Li) of the halogen redox couples: 3.6 V for I2/I- and 4.1 V for Br2/Br-, compared with 2-2.4 V for polysulfide. Probably the most distinct feature of these new lithium metal battery is the use of an aqueous solution as cathode that provides much higher ion conductivity and thus better power performance than solid-state cathodes. However, the aqueous electrolyte also poses several challenges to other components of the battery. First, a strictly water-tight ion exchange membrane is needed to protect the lithium metal anode from the catholyte and any water leakage will cause safety issues considering the violent reaction between lithium and water. Secondly, corrosive I2 or Br2 has to be added to the electrolyte to ensure reversible redox reactions. Finally, the small electrochemical window of water limit the further improvement on cell potential. To address these issues with existing aqueous catholyte, this paper proposes an organic catholyte with acetonitrile as solvent, I2-free ionic liquid as redox active species, and carbon nanohorn as additives. Compared with aqueous electrolyte, organic electrolyte has much higher voltage window and poses less safety threat to the lithium metal anode, but unfortunately, it also has lower ion conductivity. The carbon nanohorn additives mitigate the low conductivity problems by forming a percolating nanoscale conductive network inside the organic electrolyte.4 This network extend the reaction site from the surface of the carbon current collector into the bulk of the organic catholyte, hence it reduces the I- ion diffusion length to compensate for the lower ion conductivity of organic electrolyte. The good electrical conductivity of the carbon nanohorn also reduce the internal resistance of the battery to improve power formances. Last but not the least, the carbon nanohorn has catalytic effect towards the reduction of I2 to I-. As a result, even without adding corrosive I2 to the electrolyte, the I- to I2 reduction reaction can still proceed with low overpotential. Based on the aforementioned analysis, we developed a novel organic catholyte by mixing carbon nanohorn (CNH) into 37 mg/ml acetonitrile solution of 1-ethyl-3-methylimidazolium iodide ([EMIM]I) ionic liquid. The weight ratio between CNH and [EMIM]I is 1:1. The CNH is from Graphene Laboratories Inc. Calverton, NY, USA and the [EMIM]I (97%) and acetonitrile (anhydrous, 99.8%) are from Sigma Aldrich, Milwaukee, WI, USA. All materials and chemicals are used without further processing or purification. To elucidate the effect of CNH additives, 37 mg/ml [EMIM]I in acetonitrile solution are used as a reference catholyte. These two catholyte systems are studied inside a glovebox using a three-electrode beaker cell with glassy carbon of 7.07 mm2 area as working electrode, silver wire as non-aqueous reference electrode, and platinum mesh as counter electrode. In cyclic voltammetry study, the cell using CNH-added electrolyte has higher cathodic current (corresponding to reduction of I2 to I-) than that of CNH-free cell, demonstrating that this reduction reaction is more facile in the CNH-added cell. Electrochemical impedance spectroscopy of CNH-added electrolyte at 0.1Hz-100kHz demonstrates lower impedance at high frequency region and lower charge transfer resistance in mid-frequency region, which proves that the CNH can reduce the internal resistance of the cell and facilitate the I-/I2 redox reaction as expected. Ongoing work is to assemble the CNH-added electrolyte with lithium metal anode and evaluate the lithium metal battery performance. Reference Lu, Yuhao, John B. Goodenough, and Youngsik Kim. "Aqueous cathode for next-generation alkali-ion batteries." Journal of the American Chemical Society 133.15 (2011): 5756-5759.Zhao, Yu, et al. "A reversible Br 2/Br− redox couple in the aqueous phase as a high-performance catholyte for alkali-ion batteries." Energy & Environmental Science 7.6 (2014): 1990-1995.Zhao, Yu, Lina Wang, and Hye Ryung Byon. "High-performance rechargeable lithium-iodine batteries using triiodide/iodide redox couples in an aqueous cathode." Nature communications 4 (2013): 1896.Fan, Frank Y., William H. Woodford, Zheng Li, Nir Baram, Kyle C. Smith, Ahmed Helal, Gareth H. McKinley, W. Craig Carter, and Yet-Ming Chiang. "Polysulfide flow batteries enabled by percolating nanoscale conductor networks." Nano letters 14, no. 4 (2014): 2210-2218.

Solid state cathode materials for secondary magnesium-ion batteries that are compatible with magnesium metal anodes in water-free electrolyte

With high elemental abundance, large volumetric capacity, and dendrite-free metal deposition, magnesium metal anodes offer promise in beyond-lithium-ion batteries. However, the increased charge density associated with the divalent magnesium-ion (Mg2+), relative to lithium-ion (Li+) hinders the ion-insertion and extraction processes within many materials and structures known for lithium-ion cathodes. As a result, many recent investigations incorporate known amounts of water within the electrolyte to provide temporary solvation of the Mg2+, improving diffusion kinetics. Unfortunately with the addition of water, compatibility with magnesium metal anodes disappears due to forming an ion-insulating passivating layer. In this short review, recent advances in solid state cathode materials for rechargeable magnesium-ion batteries are highlighted, with a focus on cathode materials that do not require water contaminated electrolyte solutions for ion insertion and extraction processes.

A miniature origami biofuel cell based on a consumed cathode.

Considerable interest has been focused on miniature biofuel cells (BFCs) because of their portability and possibility to be implantable. Origami devices with hollow channels will provide novel insight into the assembly methods of miniature BFCs. Herein a miniature origami BFC has been fabricated from a MnO2-graphite flake consumed solid-state cathode. For further practical applications, miniature origami BFCs can directly generate energy from soft drinks.

Relative contribution of set cathode potential and external mass transport on TCE dechlorination in a continuous-flow bioelectrochemical reactor

Microbial bioelectrochemical systems, which use solid-state cathodes to drive the reductive degradation of contaminants such as the chlorinated hydrocarbons, are recently attracting considerable attention for bioremediation applications. So far, most of the published research has focused on analyzing the influence of key (bio)electrochemical factors influencing contaminant degradation, such as the cathode potential, whereas only few studies have examined the potential impact of mass transport phenomena on process performance. Here we analyzed the performance of a flow-through bioelectrochemical reactor, continuously fed with a synthetic groundwater containing trichloroethene at three different linear fluid velocities (from 0.3m d−1 to 1.7m d−1) and three different set cathode potentials (from −250mV to −450mV vs. the standard hydrogen electrode). The obtained results demonstrated that, in the range of fluid velocities which are characteristics for natural groundwater systems, mass transport phenomena may strongly influence the rate and extent of reductive dechlorination. Nonetheless, the relative importance of mass transport largely depends on the applied cathode potential which, in turn, controls the intrinsic kinetics of biological reactions and the underlying electron transfer mechanisms.

A Li-O₂/air battery using an inorganic solid-state air cathode.

The "(-) lithium (Li) anode|organic anolyte + inorganic catholyte|solid-state cathode (+)" Li-O2/air battery based on an inorganic solid-state air cathode was fabricated with a simple method. The electrochemical performance and reaction products of the Li-O2/air batteries under pure O2 and ambient air were investigated, respectively. The inorganic Li-ion conductive solid-state electrolyte Li1.3Al0.3Ti1.7(PO4)3 was stable during cycling and avoided the decomposition and volatilization problems that conventional organic electrolytes faced. Moreover, the porous air cathode provided a sufficient gas-phase O2-transport channel, facilitating the achievement of a high capacity of 14192 or 7869 mA h g(-1) under pure O2 or ambient air, respectively. Our results demonstrate that the Li-O2/air battery using an inorganic porous air cathode has a great potential for practical application.

Gyrotron and power supply development for upgrading the electron cyclotron heating system on DIII-D

An upgrade of the electron cyclotron heating system on DIII-D to almost 15MW is being planned which will expand it from a system with six 1MW 110GHz gyrotrons to one with ten gyrotrons. A depressed collector 1.2MW 110GHz gyrotron is being commissioned as the seventh gyrotron. A new 117.5GHz 1.5MW depressed collector gyrotron has been designed, and the first article will be the eighth gyrotron. Two more are planned, increasing the system to ten total gyrotrons, and the existing 1MW gyrotrons will subsequently be replaced with 1.5MW gyrotrons.Communications and Power Industries completed the design of the 117.5GHz gyrotron, and are now fabricating the first article. The design was optimized for a nominal 1.5MW at a beam voltage of 105kV, collector potential depression of 30kV, and beam current of 50A, but can achieve 1.8MW at 60A. The design of the collector permits modulation above 100Hz by either the body or the cathode power supply, or both, while modulation below 100Hz must use only the cathode power supply.General Atomics is developing solid-state power supplies for this upgrade: a solid-state modulator for the cathode power supply and a linear high voltage amplifier for the body power supply. The solid-state modulator has series-connected insulated-gate bipolar transistors that are switched at a fixed frequency by a pulse-width modulation regulator to control the output voltage. The design of the linear high voltage amplifier has series-connected transistors to control the output voltage, which was successfully demonstrated in a proof-of-principle test at 2kV. The designs of complete power supplies are progressing.The design features of the 117.5GHz 1.5MW gyrotron and the solid-state cathode and body power supplies will be described and the current status and plans are presented.

A study of binary iron/lithium organometallic complexes as single source precursors to solid state cathode materials for potential Li ion battery application

Solid state and solution phase decomposition of organometallic half sandwich and sandwich complexes of type [CpFeCODLi × DME] 1, [CpFeCODLi × TMEDA] 2 and [(Cp) 2FeLi 2 × 2 TMEDA] 3 (Cp = cyclopentadienyl, COD = 1,5-cyclooctadiene, DME = dimethoxyethane, TMEDA = tetramethylethylenediamine) derived from ferrocene, yield different kinds of lithium ferrites under oxidative and inert conditions. Thermogravimetry (TG) and TG coupled mass spectrometry of these compounds indicate that the decomposition begins above 170 °C for 1, 185 °C for 2 and 190 °C for 3 with removal of all the organic ligands. In the absence of oxygen, compounds 1, 2 and 3 decompose to a mixture of Fe, Fe 3C and Li 2O/Li 2CO 3 at temperatures above 200 °C. Amorphous α-LiFeO 2 is formed in the temperature range of 200–400 °C in the presence of oxygen. Crystalline α-LiFeO 2 is formed only above 400 °C using 1. Elemental analysis of the LiFeO 2 obtained from 1 indicates a drastic decrease in the carbon and hydrogen content with the increase in the oxidation temperature. XRD reveals the presence of Li 2CO 3 as second phase formed for precursors 1, 2, and 3 under oxidative conditions. Solution phase decomposition of 2 and 3 in the absence of oxygen followed by annealing at 600 °C yields Li 2Fe 3O 5, Li 5FeO 4 and Fe 3C depending on the solvent to precursor ratio in contrast to the α-LiFeO 2 phase formed under pure solid state decomposition conditions. However, all lithium ferrites (Li 2Fe 3O 5, Li 5FeO 4) are converted to α-LiFeO 2 when oxidized above 500 °C. The α-LiFeO 2 products were further characterized by IR, XPS, and TEM. Electrochemical analysis of the α-LiFeO 2 was performed, showing a moderate initial capacity of 13 mAh/g.

On relationship between the field at an autoemitter top, anode voltage and cathode geometry

Currently a lot of electron emission experiments both in carbon nanotubes with top curvature radius <1nm, and in emitters as short as 103nm with top curvature radius of some tens nanometer are carried out. Experimental results can be explained by a tunnel emission through potential barrier in vacuum near the solid-state cathode border making use of Fowler–Nordheim law. However, in case of cathodes with radius of top curvature less than 100nm this law is not valid.To proof this statement, the potential of an autoemission diode consisting of a tip cathode located on a flat metal base and flat anode, its dependence on the shape, height of the tip as well as voltage drop on it were calculated in this paper. It has been shown that with cathode tip height and its radius of curvature decreasing (⩽100nm) the transparency of the potential barrier depends non-linearly on the anode voltage in the Fowler–Nordheim coordinates when the cathode tip height decreases from 1000 down to 150nm. To obtain a measurable autoemission current, work function must not exceed the uniform field’s potential drop between cathode top and its base. Deduced is the analytic formula for the electric field potential that extends approximation features for real cathodes shapes and enables more accurate electric field modeling at the surface.

Ultracold Electron Source for Single-Shot, Ultrafast Electron Diffraction

Ultrafast electron diffraction (UED) enables studies of structural dynamics at atomic length and timescales, i.e., 0.1 nm and 0.1 ps, in single-shot mode. At present UED experiments are based on femtosecond laser photoemission from solid state cathodes. These photoemission sources perform excellently, but are not sufficiently bright for single-shot studies of, for example, biomolecular samples. We propose a new type of electron source, based on near-threshold photoionization of a laser-cooled and trapped atomic gas. The electron temperature of these sources can be as low as 10 K, implying an increase in brightness by orders of magnitude. We investigate a setup consisting of an ultracold electron source and standard radio-frequency acceleration techniques by GPT tracking simulations. The simulations use realistic fields and include all pairwise Coulomb interactions. We show that in this setup 120 keV, 0.1 pC electron bunches can be produced with a longitudinal emittance sufficiently small for enabling sub-100 fs bunch lengths at 1% relative energy spread. A transverse root-mean-square normalized emittance of epsilon(x) = 10 nm is obtained, significantly better than from photoemission sources. Correlations in transverse phase-space indicate that the transverse emittance can be improved even further, enabling single-shot studies of biomolecular samples.

Fabrication of all solid-state lithium-ion batteries with three-dimensionally ordered composite electrode consisting of Li 0.35La 0.55TiO 3 and LiMn 2O 4

A composite electrode between three-dimensionally ordered macroporous (3DOM) Li 0.35La 0.55TiO 3 (LLT) and LiMn 2O 4 was fabricated by colloidal crystal templating method and sol–gel process. A close-packed PS beads with the opal structure was prepared by filtration of a suspension containing PS beads. Li–La–Ti–O sol was injected by vacuum impregnation process into the voids between PS beads, and then was heated to form 3DOM-LLT. Three-dimensionally ordered composite material consisting of LiMn 2O 4 and LLT was prepared by sol–gel process. The prepared composite was characterized with SEM and XRD. All solid-state Li-ion battery was fabricated with the LLT–LiMn 2O 4 composite electrode as a cathode, dry polymer electrolyte and Li metal anode. The prepared all solid-state cathode exhibited a volumetric discharge capacity of 220 mAh cm −3.

Synthesis and Electrochemistry of Acicular Silver Vanadium Oxide Nanofibers

AbstractSilver vanadium oxide (SVO, Ag2V4O11) has demonstrated commercial success as a solid-state cathode material in power sources for implantable biomedical devices. This report describes the synthesis of SVO via a hydrothermal method. This novel synthetic approach allows low temperature production of acicular SVO nanofibers with a high surface area. This material was investigated as a cathode material in primary lithium batteries for high rate pulse applications.

A solid-state cathode ray tube

A solid-state cathode ray tube

Features of explosive electron emission from a multipoint liquid-metal emitter

A multipoint liquid-metal (MLM) emitter operating in the explosive regime is characterized by a significantly greater working capacity than solid-state explosive cathodes. The MLM emitter described is capable of producing a series of blow-up emission pulses with a repetition period from 25 μs to 1 ms controlled by external circuit parameters. The high stability of the MLM emitter operation is explained by the explosive emission taking place simultaneously from several hundreds of emitting points.

Behaviour of porous cathodes in high temperature fuel cells

The applicability of classical liquid electrochemical concepts to porous cathode structures used in high temperature fuel cells is discussed. It does appear that the performance of molten carbonate fuel cell cathodes can be satisfactorily interpreted in terms of conventional electrochemical engineering invoking thin films of molten electrolyte distributed in the partially flooded porous cathode structure. In contrast, the behaviour of porous oxide cathodes deposited on ceramic oxide electrolytes is dominated by interfacial oxygen surface exchange reactions and diffusive processes. The importance of the characteristic length term, L c ( D ∗ k ) , which indicates the change-over from surface to bulk control is emphasised. It is suggested that for porous oxide cathode structures, in which the grain size is usually around 1 μm, the oxygen reduction process will invariably be dominated by the interfacial oxygen exchange process. For mixed conducting cathodes, chemical processes such as changes in the oxide stoichiometry, can contribute significantly to the overpotential within the electrode. This can lead to erroneous interpretations if the I– V characteristics are analysed in terms of conventional electrochemical expressions. Finally the design of optimised solid state cathodes is discussed and the need for oxygen surface diffusion data is emphasised.