COVID-19 pandemic highlights need for US policies that increase supply chain resilience.

Shortages of masks, personal protective equipment (PPE), and ventilators characterized the early days of the COVID-19 pandemic crisis in the United States. As supply deficiencies strained healthcare systems across the country, national attention focused on the Strategic National Stockpile (SNS), overseen by the US Department of Health & Human Services-specifically, its inability to significantly alleviate rapidly deteriorating conditions in hospitals. While nominally a "stockpile," the SNS does not possess, operate, or restock a vast system of federally owned warehouses filled with enough medical equipment to weather a crisis. Instead, as summarized in a June 2020 RAND Corporation report and testimony to the US Congress, the program is primarily a logistics service that coordinates the flow of materials between state and local entities, and its own small stockpile was quickly overwhelmed by the demands of the pandemic.

COVID-19 disrupts battery materials and manufacture supply chains, but outlook remains strong.

The effects of the coronavirus global pandemic have rippled through many lives and have upended aspects of health care, transportation, and the economy in virtually every country. The energy materials and renewable generation and conversion market, which includes battery-powered electric vehicles, grid storage, and personal electronic devices, is no exception.

Effect of Metal Ion Intercalation on the Structure of MXene and Water Dynamics on its Internal Surfaces.

MXenes are a recently discovered class of 2D materials with an excellent potential for energy storage applications. Because MXene surfaces are hydrophilic and attractive interaction forces between the layers are relatively weak, water molecules can spontaneously intercalate at ambient humidity and significantly influence the key properties of this 2D material. Using complementary X-ray and neutron scattering techniques, we demonstrate that intercalation with potassium cations significantly improves structural homogeneity and water stability in MXenes. In agreement with molecular dynamics simulations, intercalated potassium ions reduce the water self-diffusion coefficient by 2 orders of magnitude, suggesting greater stability of hydrated MXene against changing environmental conditions.

Synthesis of carbon/sulfur nanolaminates by electrochemical extraction of titanium from Ti2SC.

Herein we electrochemically and selectively extract Ti from the MAX phase Ti2SC to form carbon/sulfur (C/S) nanolaminates at room temperature. The products are composed of multi-layers of C/S flakes, with predominantly amorphous and some graphene-like structures. Covalent bonding between C and S is observed in the nanolaminates, which render the latter promising candidates as electrode materials for Li-S batteries. We also show that it is possible to extract Ti from other MAX phases, such as Ti3AlC2, Ti3SnC2, and Ti2GeC, suggesting that electrochemical etching can be a powerful method to selectively extract the "M" elements from the MAX phases, to produce "AX" layered structures, that cannot be made otherwise. The latter hold promise for a variety of applications, such as energy storage, catalysis, etc.

Effects of structural disorder and surface chemistry on electric conductivity and capacitance of porous carbon electrodes.

This article reports on changes in electric double layer charge storage capacity as a function of surface chemistry and graphitic structure of porous carbon electrodes. By subjecting 20 nm to 2.0 µm sized carbide-derived carbons (CDCs) synthesized at 800 °C to high-temperature vacuum annealing at 700-1800 °C, we produce three-dimensional internal surface architectures with similar pore sizes and volumes but divergent surface chemistry and wall graphitization. Annealing increases carbon ordering and selectively removes functional groups, and both transformations affect conductivity and wettability. Contrary to an expected increase in gravimetric capacitance, we demonstrate no increases in charge storage despite increased conductivity and pore accessibility. At the same time, annealing improves the charge/discharge rates in EMIm-TFSI ionic liquid electrolyte. The annealing process eliminates faradaic reactions that limit the voltage window, but potentially accelerates catalytic breakdown of the ions themselves. We therefore corroborate the theory that surface groups and defects in the graphitic structure act as dopants that allow facile movement of ions into pores, improve screening in the superionic state, and affect the quantum capacitance contribution from the carbon structure.

One-step synthesis of nanocrystalline transition metal oxides on thin sheets of disordered graphitic carbon by oxidation of MXenes.

Herein we show that heating 2D Ti3C2 in air results in TiO2 nanocrystals enmeshed in thin sheets of disordered graphitic carbon structures that can handle extremely high cycling rates when tested as anodes in lithium ion batteries. Oxidation of 2D Ti3C2 in either CO2 or pressurized water also resulted in TiO2-C hybrid structures. Similarly, other hybrids can be produced, as we show here for Nb2O5/C from 2D Nb2C.

Room-temperature carbide-derived carbon synthesis by electrochemical etching of MAX phases.

Porous carbons are widely used in energy storage and gas separation applications, but their synthesis always involves high temperatures. Herein we electrochemically selectively extract, at ambient temperature, the metal atoms from the ternary layered carbides, Ti3 AlC2 , Ti2 AlC and Ti3 SiC2 (MAX phases). The result is a predominantly amorphous carbide-derived carbon, with a narrow distribution of micropores. The latter is produced by placing the carbides in HF, HCl or NaCl solutions and applying anodic potentials. The pores that form when Ti3 AlC2 is etched in dilute HF are around 0.5 nm in diameter. This approach forgoes energy-intensive thermal treatments and presents a novel method for developing carbons with finely tuned pores for a variety of applications, such as supercapacitor, battery electrodes or CO2 capture.

Development of a green supercapacitor composed entirely of environmentally friendly materials.

Owing to recent power- and energy-density advances, higher efficiencies, and almost unlimited lifetimes, electrical double-layer capacitors (EDLCs, also known as supercapacitors) are now used in a wide range of energy harvesting and storage systems, which include portable power and grid applications. Despite offering key performance advantages, many device components pose significant environmental hazards once disposed. They often contain fluorine, sulfur, and cyanide groups, which are harmful if discarded by using conventional landfill or incineration methods, and they are constructed by using multiple metallic parts, which contribute to a high ash content. We explore designs for a fully operational supercapacitor that incorporates materials completely safe to dispose of and easy to incinerate. The components, which include material alternatives for the current collector, electrolyte, separator, particle binder, and packaging, are all mutually compatible, and most of them exhibit better performance than commonly used materials. We selected a graphite foil as current collector, sodium acetate as electrolyte, an ester as porous membrane based on acetate cellulose, and polymers based on polyvinyl alcohol as environmentally benign solutions for device components. The presented materials all originate from simple and inexpensive source compounds, which decreases the environmental impact of their manufacture and renders them more viable for integration into commercial devices for large-scale stationary and transportation energy storage applications.

Ion dynamics in porous carbon electrodes in supercapacitors using in situ infrared spectroelectrochemistry.

Electrochemical double layer capacitors (EDLCs), or supercapacitors, rely on electrosorption of ions by porous carbon electrodes and offer a higher power and a longer cyclic lifetime compared to batteries. Ionic liquid (IL) electrolytes can broaden the operating voltage window and increase the energy density of EDLCs. Herein, we present direct measurements of the ion dynamics of 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide in an operating EDLC with electrodes composed of porous nanosized carbide-derived carbons (CDCs) and nonporous onion-like carbons (OLCs) with the use of in situ infrared spectroelectrochemistry. For CDC electrodes, IL ions (both cations and anions) were directly observed entering and exiting CDC nanopores during charging and discharging of the EDLC. Conversely, for OLC electrodes, IL ions were observed in close proximity to the OLC surface without any change in the bulk electrolyte concentration during charging and discharging of the EDLC. This provides experimental evidence that charge is stored on the surface of OLCs in OLC EDLCs without long-range ion transport through the bulk electrode. In addition, for CDC EDLCs with mixed electrolytes of IL and propylene carbonate (PC), the IL ions were observed entering and exiting CDC nanopores, while PC entrance into the nanopores was IL concentration dependent. This work provides direct experimental confirmation of EDLC charging mechanisms that previously were restricted to computational simulations and theories. The experimental measurements presented here also provide deep insights into the molecular level transport of IL ions in EDLC electrodes that will impact the design of the electrode materials' structure for electrical energy storage.

Polymer single crystal-decorated superhydrophobic buckypaper with controlled wetting and conductivity.

Herein we report fabrication of uniform, free-standing nanohybrid buckypaper with high carbon nanotube (CNT) contents (13-70%) using polymer single crystal-decorated CNTs as the precursor. Polyethylene single crystals were periodically grown on CNT surfaces, forming a nanohybrid shish kebab (NHSK) structure. Vacuum filtering a NHSK suspension led to polymer single crystal-decorated buckypaper (named as NHSK paper) with a wide range of CNT contents and uniform CNT dispersion. Porosity, surface roughness, and conductivity of NHSK paper can be controlled by tuning the polymer single crystal size. Because of the hierarchical roughness created by intra- and inter-NHSK nanostructure, NHSK paper with controlled kebab size exhibits both superhydrophobicity and high surface water adhesion, which mimics the rose petal effect. We anticipate that this unique NHSK paper can find applications in sensors, electrochemical devices, and coatings.