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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Electrodes with Electrodeposited Water-excluding Polymer Coating Enable High-Voltage Aqueous Supercapacitors

Aqueous supercapacitors are powerful energy sources, but they are limited by energy density that is much lower than lithium-ion batteries. Since raising the voltage beyond the thermodynamic potential for water splitting (1.23 V) can boost the energy density, there has been much effort on water-stabilizing salvation additives such as Li 2 SO 4 that can provide an aqueous electrolyte capable of withstanding ~1.8 V. Guided by the first-principles calculations that reveal water can promote hydrogen and oxygen evolution reactions, here, we pursue a new strategy of covering the electrode with a dense electroplated polymerized polyacrylic acid, which is an electron insulator but a proton conductor and proton reservoir. The combined effect of salvation and coating expands the electrochemical window throughout pH 3 to pH 10 to 2.4 V for both fast and slow proton-mediated redox reactions. This allows activated carbon to quadruple the energy density, a kilogram of nitrogen-doped graphene to provide 127 Watt-hour, and both to have improved endurance because of suppression of water-mediated corrosion. Therefore, aqueous supercapacitors can now achieve energy densities quite comparable to that of a lithium-ion battery, but at 100 times the charging/discharging speed and cycle durability.

Dong, Wujie↗
NASA NTRS1974

Growth and development in inert non-aqueous liquids

A preview is presented of the survival and growth capabilities of higher plants in non-aqueous, inert liquids. The two media which were used are mineral (white) oil and fluorochemical inert liquid FC-75. Both liquids dissolve oxygen and carbon dioxide readily, but are insoluble in water. Consequently, plants submerged in these liquids are capable of gas exchange with the atmosphere, but possess a water impermeable coating the dimensions of which are determined by the size of the liquid holding container. In a sense, growing plants in a tank of mineral oil imparts on them a cuticle. Plants plus prescribed volumes of water were innoculated into mineral oil. Organisms with minimal water supplied could then be observed. Also, submersed plants covered with an oil slick were shown to be capable of growth in dessicating atmospheres.

Siegel, S. M.↗
NASA NTRS2001

Joint EPA/NASA/USAF Interagency Depainting Study

Environmental regulations such as National Emission Standards for Hazardous Air Pollutants (NESHAPs) are drivers for the implementation of environmentally compliant methodologies in the manufacture of aerospace hardware. In 1995, the Environmental Protection Agency (EPA) promulgated the NESHAP for the Aerospace Manufacture and Rework (Aerospace NESHAP) industry. Affected facilities were to be in compliance by September 1998. Several aerospace manufacturing operations are regulated within the Aerospace NESHAP including Depainting operations. The National Aeronautics and Space Administration (NASA), EPA, and United States Air Force (USAF) combined resources to evaluate the performance of nine alternative depainting processes. The seven alternative depainting processes were: (1) Chemical stripping (non-methylene chloride); (2) Carbon Dioxide Blasting; (3) Xenon Flashlamp; (4) Carbon Dioxide Laser Stripping; (5) Plastic Media Blasting; (6) Sodium Bicarbonate Wet Stripping; and (7) Waterjet Blasting and Wheat Starch Blasting. All epoxy primer and polyurethane top coat system was applied to 2024-T3 clad and non-clad aluminum test specimens. Approximately 200 test specimens were evaluated in this study. Each coupon was subjected to three, four, or five complete depainting cycles. This paper discusses the conclusions from the study including the test protocol, test parameters, and achievable strip rates for the alternative depainting processes. Test data includes immersion corrosion testing, sandwich corrosion testing and hydrogen embrittlement testing for the non-methylene chloride chemical strippers. Additionally, the cumulative effect of the alternative depainting processes on the metallurgical integrity of the test substrate is addressed with the results from tensile and fatigue evaluations.

Clark-Ingram, M.↗
NASA NTRS2004

The Influence of Sizings on the Durability of High-Temperature Polymer Composites

To increase performance and durability of high-temperature composites for potential rocket engine components, it is necessary to optimize wetting and interfacial bonding between high modulus carbon fibers and high-temperature polyimide resins. Sizings commercially supplied on most carbon fibers are not compatible with polyimides. In this study, the chemistry of sizings on two high-modulus carbon fibers (M40J and M60J, Toray) was characterized as was the chemistry of PMR-II-50 fluorinated polyimide resin. The carbon fibers were characterized using single filament wetting, scanning electron microscopy, fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopic measurements. The polyimide matrix resins were coated onto glass filaments for characterization by wetting measurements. Surface energy components were obtained by wetting with nondispersive (methylene iodide), acidic (ethylene glycol), and basic (formamide) probes. A continuous desizing system that uses an environmentally friendly chemical-mechanical process was developed for tow level fiber. Composites were fabricated with fibers containing the manufacturer's sizing, desized, and further treated with a reactive finish. Results of room-temperature tests after thermal aging show that the reactive finish produces a higher strength and more durable interface compared to the manufacturer's sizing. When exposed to moisture blistering tests, however, the better bonded composite displayed a tendency to delaminate, presumably due to trapping of volatiles.

Allred, Ronald E.↗
NASA NTRS2008

NASA Tech Briefs, July 2008

Topics covered include: Torque Sensor Based on Tunnel-Diode Oscillator; Shaft-Angle Sensor Based on Tunnel-Diode Oscillator; Ground Facility for Vicarious Calibration of Skyborne Sensors; Optical Pressure-Temperature Sensor for a Combustion Chamber; Impact-Locator Sensor Panels; Low-Loss Waveguides for Terahertz Frequencies; MEMS/ECD Method for Making Bi(2-x)Sb(x)Te3 Thermoelectric Devices; Low-Temperature Supercapacitors; Making a Back-Illuminated Imager with Back-Side Contact and Alignment Markers; Compact, Single-Stage MMIC InP HEMT Amplifier; Nb(x)Ti(1-x)N Superconducting-Nanowire Single-Photon Detectors; Improved Sand-Compaction Method for Lost-Foam Metal Casting; Improved Probe for Evaluating Compaction of Mold Sand; Polymer-Based Composite Catholytes for Li Thin-Film Cells; Using ALD To Bond CNTs to Substrates and Matrices; Alternating-Composition Layered Ceramic Barrier Coatings; Variable-Structure Control of a Model Glider Airplane; Axial Halbach Magnetic Bearings; Compact, Non-Pneumatic Rock-Powder Samplers; Biochips Containing Arrays of Carbon-Nanotube Electrodes; Nb(x)Ti(1-x)N Superconducting-Nanowire Single-Photon Detectors; Neon as a Buffer Gas for a Mercury-Ion Clock; Miniature Incandescent Lamps as Fiber-Optic Light Sources; Bidirectional Pressure-Regulator System; and Prism Window for Optical Alignment. Single-Grid-Pair Fourier Telescope for Imaging in Hard-X Rays and gamma Rays Range-Gated Metrology with Compact Optical Head Lossless, Multi-Spectral Data Compressor for Improved Compression for Pushbroom-Typetruments.

Source record↗
DOE OSTI2023

Lithium metal negative electrode and method of manufacturing the same

A negative electrode for an electrochemical cell of a secondary lithium metal battery is manufactured by a method in which a precursor solution is applied to a major surface of a lithium metal substrate to form a precursor coating thereon. The precursor solution includes an organophosphate, a nonpolar organic solvent, and a lithium-containing inorganic ionic compound dissolved therein. At least a portion of the nonpolar organic solvent is removed from the precursor coating to form a protective interfacial layer on the major surface of the lithium metal substrate. The protective interfacial layer exhibits a composite structure including a carbon-based matrix component and a lithium-containing dispersed component. The lithium-containing dispersed component is embedded in the carbon-based matrix component and includes a plurality of lithium-containing inorganic ionic compounds, e.g., lithium phosphate (Li3PO4) and lithium nitrate (LiNO3).

Xiao, Xingcheng↗
NASA NTRS1974

Production development of organic nonflammable spacecraft potting, encapsulating and conformal coating compounds. Volume 3: Appendices

Appendices are presented which include: statement of work; material vendor contacts; formulation/processing data sheet; upward propagation test; flammability test conditions/results sheet; odor test; vacuum stability requirements; flammability test facility; determination of offgassing products and carbon monoxide test; and pneumatic and mechanical impact test guidelines.

Lieberman, S. L.↗
DOE OSTI2023

Mastering the synergy between Na 3 V 2 (PO 4 ) 2 F 3 electrode and electrolyte: A must for Na-ion cells

Sodium-ion batteries are emerging as suitable energy storage devices for special applications such as high-power devices with the advantages of being cheaper and more sustainable than the Li-ion equivalents. The sodium ion cells consisting of polyanionic Na 3 V 2 (PO 4 ) 2 F 3 - hard carbon electrodes exhibit high power rate capabilities but limited cycle life, especially at high temperatures. To circumvent this drawback we herein conducted in-depth analyses of the origins of structural degradations occurring in Na 3 V 2 (PO 4 ) 2 F 3 electrodes upon long cycling. Vanadium dissolution with associated parasitic reactions is identified as one of the major reasons for cell failure. Its amount varies depending on the electrolyte, with NaTFSI-based electrolyte showing the least vanadium dissolution as the TFSI - anion decomposes without producing acidic impurities, in contrast to the NaPF 6 -based electrolyte. The dissolved vanadium species undergoes oxidation and reduction processes at the Na 3 V 2 (PO 4 ) 2 F 3 and HC electrodes, respectively, with the electrochemical signature of these processes being used as a fingerprint to identify state of health of the 18650 cells. Here, having found that surface reactivity is the primary cause of vanadium dissolution we provide methods to mitigate it by combining surface coating and optimized electrolyte formulation.

25 ENERGY STORAGE↗
NASA NTRS2016

Corrosion-Activated Micro-Containers for Environmentally Friendly Corrosion Protective Coatings

This work concerns the development of environmentally friendly encapsulation technology, specifically designed to incorporate corrosion indicators, inhibitors, and self-healing agents into a coating, in such a way that the delivery of the indicators and inhibitors is triggered by the corrosion process, and the delivery of self-healing agents is triggered by mechanical damage to the coating. Encapsulation of the active corrosion control ingredients allows the incorporation of desired autonomous corrosion control functions such as: early corrosion detection, hidden corrosion detection, corrosion inhibition, and self-healing of mechanical damage into a coating. The technology offers the versatility needed to include one or several corrosion control functions into the same coating.The development of the encapsulation technology has progressed from the initial proof-of-concept work, in which a corrosion indicator was encapsulated into an oil-core (hydrophobic) microcapsule and shown to be delivered autonomously, under simulated corrosion conditions, to a sophisticated portfolio of micro carriers (organic, inorganic, and hybrid) that can be used to deliver a wide range of active corrosion ingredients at a rate that can be adjusted to offer immediate as well as long-term corrosion control. The micro carriers have been incorporated into different coating formulas to test and optimize the autonomous corrosion detection, inhibition, and self-healing functions of the coatings. This paper provides an overview of progress made to date and highlights recent technical developments, such as improved corrosion detection sensitivity, inhibitor test results in various types of coatings, and highly effective self-healing coatings based on green chemistry. The NASA Kennedy Space Centers Corrosion Technology Lab at the Kennedy Space Center in Florida, U.S.A. has been developing multifunctional smart coatings based on the microencapsulation of environmentally friendly corrosion indicators, inhibitors and self-healing agents. This allows the incorporation of autonomous corrosion control functionalities, such as corrosion detection and inhibition as well as the self-healing of mechanical damage, into coatings. This paper presents technical details on the characterization of inhibitor-containing particles and their corrosion inhibitive effects using electrochemical and mass loss methods.Three organic environmentally friendly corrosion inhibitors were encapsulated in organic microparticles that are compatible with desired coatings. The release of the inhibitors from the microparticles in basic solution was studied. Fast release, for immediate corrosion protection, as well as long-term release for continued protection, was observed.The inhibition efficacy of the inhibitors, incorporated directly and in microparticles, on carbon steel was evaluated. Polarization curves and mass loss measurements showed that, in the case of 2MBT, its corrosion inhibition effectiveness was greater when it was delivered from microparticles.

Corrosion Control↗
DOE OSTI2021

High Flux Microchannel Receiver Development (Final Report)

The opportunity addressed in this project was using microscale heat exchanger technology for improving solar thermal central receiver efficiency. This will result in smaller, less expensive components and reduce the levelized cost of electricity from concentrated solar thermal power. This micro-pin solar receiver (MSR) directly heats high pressure (25 MPa) supercritical carbon dioxide (sCO 2 ) from 550°C to 720°C with an incident flux of at least 120 W/cm 2 at a receiver efficiency of >90% (assuming availability of 95% absorptivity coating), and receiver cost target of less than $\$$150/kWt. Realization of the MSR required an understanding of thermal hydraulic performance of sCO 2 in micro-pin passages, mechanical behavior of high nickel alloys at high temperatures including joints, advanced fabrication methods of high nickel alloys (etching, machining, brazing, welding, diffusion bonding), and the cost implications of these when the concept is scaled to production volumes. The technology can be used with gases (sCO 2 , helium, etc.) or with liquids such as molten salt or liquid metal. Given the high pressure associated with sCO 2 , its use demonstrates a “worst case” scenario, and the successful development of the MSR for this application will result in the development of a technology also applicable to a range of other heat transfer fluids that will enable next generation CSP plants, including support of the Gen3CSP program.

14 SOLAR ENERGY↗
DOE OSTI2026

A MINi Powder INjector (MINPIN) for the SMART tokamak

Here, this article presents the design and performance characterization of a MINi Powder INjector (MINPIN) developed for boron wall conditioning (boronization) in the SMall Aspect Ratio Tokamak (SMART) at the University of Seville, Spain. SMART studies positive and negative triangularity plasmas within the low aspect ratio range of 1.4 < R/a < 3, with a major radius (R) of 0.40–0.60 m and a minor radius (a) of 0.20–0.33 m. MINPIN, in design, will gravitationally deliver boron (B) powder into the plasma, which ablates and transports the injected material. Mounted on the top of the vessel, the MINPIN will drop controlled amounts of powder using a piezoelectric blade driven by a signal generator that vibrates at a set frequency. The B will then be deposited in a layer on SMART’s stainless steel vacuum vessel walls, and this boronization process reduces the influx of intrinsic wall impurities, such as oxygen, carbon, nitrogen, and iron, which radiate power and cool the plasma. In the laboratory, we calibrated the drop rate for 1–10 mg/s, which will enable controlled boronization coating while achieving efficient powder ablation. We propose MINPIN’s operational scenarios based on the calibrated drop rate and estimated drop duration, assuming the distance from MINPIN to SMART’s plasmas.

Boron powder↗
NASA NTRS1996

Friction and Wear Properties of As-Deposited and Carbon Ion-Implanted Diamond Films

Recent work on the friction and wear properties of as-deposited and carbon ion-implanted diamond films was reviewed. Diamond films were produced by the microwave plasma chemical vapor deposition (CVD) technique. Diamond films with various grain sizes and surface roughnesses were implanted with carbon ions at 60 keV ion energy, resulting in a dose of 1.2 x 10(exp 17) carbon ions per cm(exp 2). Various analytical techniques, including Raman spectroscopy, proton recoil analysis, Rutherford backscattering, transmission and scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction, were utilized to characterize the diamond films. Sliding friction experiments were conducted with a polished natural diamond pin in contact with diamond films in the three environments: humid air (40% relative humidity), dry nitrogen (less than 1 percent relative humidity), and ultrahigh vacuum (10(exp -7) Pa). The CVD diamond films indeed have friction and wear properties similar to those of natural diamond in the three environments. The as-deposited, fine-grain diamond films can be effectively used as self-lubricating, wear-resistant coatings that have low coefficients of friction (0.02 to 0.04) and low wear rates (10(exp -7) to lO(exp -8) mm(exp 3) N(exp -1) m(exp -1)) in both humid air and dry nitrogen. However, they have high coefficients of friction (1.5 to 1.7) and a high wear rate (10(exp -4) mm(exp 7) N(exp -1) m(exp -1)) in ultrahigh vacuum. The carbon ion implantation produced a thin surficial layer (less than 0.1 micron thick) of amorphous, non-diamond carbon on the diamond films. In humid air and dry nitrogen, the ion-implanted, fine and coarse-grain diamond films have a low coefficient of friction (around 0.1) and a low wear rate (10(exp -7) mm(exp 3) N(exp -1) m(exp-1)). Even in ultrahigh vacuum, the presence of the non-diamond carbon layer reduced the coefficient of friction of fine-grain diamond films to 0.1 or lower and the wear rate to 10(exp -6) mm(exp 3) N(exp -1) m(exp -1). Thus, the carbon ion-implanted, fine-grain diamond films can be effectively used as wear-resistant, self-lubricating coatings not only in air and dry nitrogen, but also in ultrahigh vacuum.

Miyoshi, Kazuhisa↗
DOE OSTI2025

Constraining Black Carbon Aging in Global Models to Reflect Timescales for Internal Mixing

The radiative effects of black carbon depend critically on its atmospheric lifetime, which is controlled by the rate at which freshly emitted combustion particles become internally mixed with other aerosol components. Global aerosol models strive to represent this process, but the timescale for aerosol mixing is not easily constrained using observations. In this study, we apply a timescale parameterization derived from particle‐resolved simulations to quantify, in a global aerosol model, the timescale for internal mixing. We show that, while highly variable, the average timescale for internal mixing is approximately 3 hr, which is much shorter than the 24‐hr aging timescale traditionally applied in bulk aerosol models. We then use the mixing timescale to constrain the aging criterion in the Modal Aerosol Module. Our analysis reveals that, to best reflect timescales for internal mixing, modal models should assume that particles transition from the hydrophobic (fresh) to the hydrophilic (aged) class once they accumulate a coating thickness equal to four monolayers of sulfuric acid, as opposed to the model's current aging criterion of eight monolayers. We show that, in remote regions like the Arctic and Antarctic, predictions of black carbon loading and its seasonal variation are particularly sensitive to the model representation of aging. By constraining aging in global models to reflect mixing timescales simulated by the particle‐resolved model, we eliminate one of the free parameters governing black carbon's long‐range transport and spatiotemporal distribution.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Alternate Methods for Cleaning Zirconium Plate

The United States High Performance Research Reactor Conversion Program identified the need to transition from highly enriched uranium fuel to lowly enriched uranium fuel for high power research and civil reactors. One of the fuel configurations selected for these reactors was a uranium (U) foil alloyed with 10% molybdenum (Mo). The U-10Mo fuel foil was then covered with a zirconium (Zr) interlayer and pressed into an aluminum cladding. Idaho National Laboratory prescribed a need to remove surface oxidation on the Zr prior to bonding it with U-10Mo fuel foil. To determine the best method of oxidation removal, a variety of polishing methods, including hand polishing with a diamond paste or Scotch-Brite™ pads, mechanically wet-polishing with abrasive belts, and chemical etching with hydrofluoric/nitric acid mixtures, were investigated on pre-polished Zircaloy 702 sheets purchased directly from the manufacturer. No change in surface roughness was detected using any of these methods relative to the as-received material. In fact, scanning electron microscopy detected grit from hand polishing with Amplex Grade 30 waste soluble diamond paste and Scotch-Brite™ pads. Visible staining was found, and fluorine detected via X-ray photoelectron spectroscopy on the flash etching samples. These contaminants were not seen on the as-received material. In addition to the need to remove the oxide layer on the Zr prior to co-rolling, there are concerns that the Neolube debonding agent on the co-rolling can may contaminate the Zr surface after co-rolling. The experimental results found that zirconium in contact with Neolube coated steel plates was easily cleaning with ethanol wiping after heat treated and no carbide inclusions remained on the surface. Overall, all cleaning methods tested did not significantly change the surface roughness of the plates or reduce the oxide layer present on the zirconium. Carbon was found on all the samples, before and after cleaning, except for the flash etch samples which detected fluorine instead. The insignificant changes seen in the cleaned plates relative to the as received plates question the need for cleaning prior to rolling. Further investigation in the requirements for cleaning at this step is recommended. Current methods for cleaning the surface after hot rolling with alcohol appear sufficient. After hot rolling, if Neolube does peel off the can and onto the zirconium coated foil surface, a dry abrasive or diamond paste polish is not recommended due to the chance of abrasive being embedded into the surface. However, the ability of an etchant to lift the lubricant off the zirconium surface indicates that a spot etch method could work to clean specific spots where Neolube is present, if the need arises.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS2016

Nanomaterial Based Sensors for NASA Missions

Nanomaterials such as carbon nanotubes (CNTs), carbon nanofibers (CNFs), graphene and metal nanowires have shown interesting electronic properties and therefore have been pursued for a variety of space applications requiring ultrasensitive and light-weight sensor and electronic devices. We have been pursuing development of chemical and biosensors using carbon nanotubes and carbon nanofibers for the last several years and this talk will present the benefits of nanomaterials these applications. More recently, printing approaches to manufacturing these devices have been explored as a strategy that is compatible to a microgravity environment. Nanomaterials are either grown in house or purchased and processed as electrical inks. Chemical modification or coatings are added to the nanomaterials to tailor the nanomaterial to the exact application. The development of printed chemical sensors and biosensors will be discussed for applications ranging from crew life support to exploration missions.

sensors↗
DOE OSTI2023

Predictive Modeling of Electrodeposition in a Single Pore Flow-Through Electrode: From Electronucleation to Coating Thickness Uniformity

The emergence of advanced manufacturing methods capable of producing porous three-dimensional structures has expanded the design space for next-generation functional components. The ability to fabricate ordered 3D foams for use in electrocatalysis reactors has increased the need for controlled deposition of catalytic metals onto porous support materials, such as carbon. However, there is a lack of clear design guidelines for electrodeposition onto 3D substrates, due to the geometric complexity and multi-scale nature of the problem. Furthermore, electro-nucleation phenomena are often overlooked in macro-scale models of current distribution during deposition. Here, a graphite flow-through electrode (FTE) is used as a model system for copper deposition within a single pore. Potential distributions and electro-nucleation phenomena are coupled in a continuum level model by incorporating nucleation size and density as a function of overpotential, determined experimentally using in situ atomic force microscopy (AFM). The model predictions are validated by measuring the coating uniformity in the pore using micro-computed X-ray tomography (μCT). A scaling analysis comprising dimensionless parameters such as the Wagner number is presented. The simplified scaling relationship framework can guide the electrodeposition process and electrode design to optimize plating of porous substrates under fluid flow conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2015

Characterization of Encapsulated Corrosion Inhibitors for Environmentally Friendly Smart Coatings

The NASA Kennedy Space Center's Corrosion Technology Lab at the Kennedy Space Center in Florida, U.S.A. has been developing multifunctional smart coatings based on the microencapsulation of environmentally friendly corrosion indicators, inhibitors and self-healing agents. This allows the incorporation of autonomous corrosion control functionalities, such as corrosion detection and inhibition as well as the self-healing of mechanical damage, into coatings. This paper presents technical details on the characterization of inhibitor-containing particles and their corrosion inhibitive effects using electrochemical and mass loss methods. Three organic environmentally friendly corrosion inhibitors were encapsulated in organic microparticles that are compatible with desired coatings. The release of the inhibitors from the microparticles in basic solution was studied. Fast release, for immediate corrosion protection, as well as long-term release for continued protection, was observed. The inhibition efficacy of the inhibitors, incorporated directly and in microparticles, on carbon steel was evaluated. Polarization curves and mass loss measurements showed that, in the case of 2MBT, its corrosion inhibition effectiveness was greater when it was delivered from microparticles.

Corrosion↗
DOE OSTI2020

Towards Understanding of Cracking during Drying of Thick Aqueous-Processed LiNi 0.8 Mn 0.1 Co 0.1 O 2 Cathodes

Replacing N-methyl-2-pyrrolidone (NMP) with water for processing of lithium-ion battery (LIB) electrodes has both cost and environmental benefits, which include reduced drying time, lower dryer capital cost, elimination of NMP recovery capital equipment, and no release of volatile organic compounds (VOCs) into the environment. However, aqueous-processed thick cathodes (≳4 mAh/cm 2 ) typically exhibit detrimental cracking during drying that is not observed for the NMP-based counterpart. The reasons for cracking of these water-based thick electrodes are still not well understood due to the complex nature of the colloidal dispersions used in the LIB electrode processing steps. In this work, the contributions of various factors responsible for cracking are discussed. We show that eliminating hydrogen evolution due to corrosion of the aluminum current collector eliminated the majority of the cracks regardless of the coating thickness, identifying the gas evolution as the primary reason for electrode cracking. Some secondary cracks and pinhole-type defects remained after addressing the aluminum current collector corrosion, which are thought to be caused by an inferior binding network formed by carbon black and binder in aqueous-processed cathodes compared to those processed with NMP. The thick aqueous processed cathodes are not able to sufficiently withstand the drying stresses without crack formation. We demonstrate reduction of these secondary defects by either improving the binding network or by reducing the drying stress. The former was achieved by replacing carbon black with vapor grown graphite tubes (VGGTs) that caused a more efficient utilization of the emulsion binder. Here, the latter was achieved by adding a small amount of IPA as a co-solvent that has been shown to reduce capillary stresses.

25 ENERGY STORAGE↗