Search

This proceedings article presents actionable research targets on the basis of the presentations and discussions at the 2nd Curing Coma National Institutes of Health (NIH) symposium held from May 3 to May 5, 2021. Here, we summarize the background, research priorities, panel discussions, and deliverables discussed during the symposium across six major domains related to disorders of consciousness. The six domains include (1) Biology of Coma, (2) Coma Database, (3) Neuroprognostication, (4) Care of Comatose Patients, (5) Early Clinical Trials, and (6) Long-term Recovery. Following the 1st Curing Coma NIH virtual symposium held on September 9 to September 10, 2020, six workgroups, each consisting of field experts in respective domains, were formed and tasked with identifying gaps and developing key priorities and deliverables to advance the mission of the Curing Coma Campaign. The highly interactive and inspiring presentations and panel discussions during the 3-day virtual NIH symposium identified several action items for the Curing Coma Campaign mission, which we summarize in this article.

This study reports a high-performance tin (Sn)-coated vertically aligned carbon nanofiber array anode for lithium-ion batteries. The array electrodes have been prepared by coaxial sputter-coating of tin (Sn) shells on vertically aligned carbon nanofiber (VACNF) cores. The robust brush-like highly conductive VACNFs effectively connect high-capacity Sn shells for lithium-ion storage. A high specific capacity of 815 mAh g-1 of Sn was obtained at C/20 rate, reaching toward the maximum value of Sn. However, the electrode shows poor cycling performance with conventional LiPF6 based organic electrolyte. The addition of fluoroethylene carbonate (FEC) improve the performance significantly and the Sn-coated VACNFs anode shows stable cycling performance. The Sn-coated VACNF array anodes exhibit outstanding capacity retention in the half-cell tests with electrolyte containing 10 wt.% FEC and could deliver a reversible capacity of 480 mAh g-1 after 50 cycles at C/3 rate.

This study reports an approach to achieving stable 2 and 3 Li+ insertion, respectively, into vanadium pentoxide (V2O5) as lithium-ion battery (LIB) cathode materials using a core-shell structure based on a self-standing carbon nanofiber (CNF) membrane fabricated by an electrospinning process. Uniform coaxial V2O5 shells are coated onto continuous CNF cores via a pulsed electrodeposition. The materials analyses confirm that the V2O5 shell after 4 h of thermal annealing at 300 °C forms a partially hydrated amorphous structure. SEM and TEM images indicate that the uniform 30–50 nm thick V2O5 shell forms an intimate interface with the CNF core. Lithium insertion capacities up to 291 and 429 mAh g−1 are achieved in the voltage ranges of 4.0–2.0 V and 4.0–1.5 V, respectively, which are in good agreement with the theoretical values of 294 mAh g−1 for 2 Li+/V2O5 insertion and 441 mAh g−1 for 3 Li+/V2O5 insertion into crystalline V2O5 materials. Moreover, after 100 cycles, remarkable retention rates of 97% and 70% are obtained for 2 Li+/V2O5 and 3 Li+/V2O5 insertion, respectively. These results reveal that it is potentially feasible to fabricate the core-shell structure with electrospinning and electrodeposition processes to break the intrinsic limits of V2O5 and enabling this high-capacity cathode materials for future LIBs.

The influence of temperature on the energy storage behavior of relaxor-ferroelectric epitaxial Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) thin film capacitors fabricated using pulsed laser deposition was evaluated using cyclic current-voltage measurements from 25 °C to 225 °C in order to elucidate ferroelectric and dielectric contributions across the Curie temperature (Tc). In the film thickness range of 125 nm to 500 nm, it has been found that the leakage current through the capacitors increases monotonically with increasing temperature and the effect is more prominent at smaller film thickness, primarily due to a more efficient movement of ferroelectric domains. While these effects prevent thinner PLZT films from maintaining adequate energy storage efficiencies at temperatures above ~ 100 °C, thicker films show promising energy storage properties in a wide temperature range. Specifically, the 500 nm thick PLZT film capacitors have a nearly constant energy storage efficiency above ~ 70% in the temperature range of 25 °C to 175 °C, with a peak efficiency of 78% at 175 °C due to the large dielectric constant exceeding ~ 2000 as the temperature approaches the PLZT Tc of 200 °C. By quantifying the three contributions of the electric conductivity, dielectric capacitance, and relaxor-ferroelectric domain switching polarization to temperature dependent energy storage properties of relaxor-ferroelectric capacitors, this study reveals that the dielectric contribution dominates in the PLZT capacitors with smaller thickness, while even contributions from all three components are present in films of larger thickness. These results suggest that the PLZT relaxor-ferroelectric thin film capacitors are promising for energy storage applications and further improvement of performance may be achieved by optimization of the film/electrode interface.

Mesoporous hybrids of V2O5 nanoparticles anchored on reduced graphene oxide (rGO) have been synthesized by slow hydrolysis of vanadium oxytriisopropoxide using a two-step solvothermal method followed by vacuum annealing. The hybrid material possesses a hierarchical structure with 20-30 nm V2O5 nanoparticles uniformly grown on rGO nanosheets, leading to a high surface area with mesoscale porosity. Such hybrid materials present significantly improved electronic conductivity and fast electrolyte ion diffusion, which synergistically enhance the electrical energy storage performance. Symmetrical electrochemical capacitors with two rGO-V2O5 hybrid electrodes show excellent cycling stability, good rate capability, and a high specific capacitance up to ∼466 F g(-1) (regarding the total mass of V2O5) in a neutral aqueous electrolyte (1.0 M Na2SO4). When used as the cathode in lithium-ion batteries, the rGO-V2O5 hybrid demonstrates excellent cycling stability and power capability, able to deliver a specific capacity of 295, 220, and 132 mAh g(-1) (regarding the mass of V2O5) at a rate of C/9, 1C, and 10C, respectively. The value at C/9 rate matches the full theoretical capacity of V2O5 for reversible 2 Li(+) insertion/extraction between 4.0 and 2.0 V (vs Li/Li(+)). It retains ∼83% of the discharge capacity after 150 cycles at 1C rate, with only 0.12% decrease per cycle. The enhanced performance in electrical energy storage reveals the effectiveness of rGO as the structure template and more conductive electron pathway in the hybrid material to overcome the intrinsic limits of single-phase V2O5 materials.

Metallic aerogels have attracted intense attention due to their superior properties, such as high electrical conductivity, ultralow densities, and large specific surface area. The preparation of metal aerogels with high efficiency and controllability remains challenge. A 3D freeze assembling printing technique integrated with drop-on-demand inkjet printing and freeze casting are proposed for metallic aerogels preparation. This technique enables tailoring both the macrostructure and microstructure of silver nanowire aerogels (SNWAs) by integrating programmable 3D printing and freeze casting, respectively. The density of the printed SNWAs is controllable, which can be down to 1.3 mg cm−3. The ultralight SNWAs reach high electrical conductivity of 1.3 S cm−1 and exhibit excellent compressive resilience under 50% compressive strain. Remarkably, the printing methodology also enables tuning aerogel architectures with designed Poisson's ratio (from negative to positive). Moreover, these aerogel architechtures with tunable Poisson's ratio present highly electromechanical stability under high compressive and tensile strain (both strain up to 20% with fully recovery).

The energy storage properties of Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) films grown via pulsed laser deposition were evaluated at variable film thickness of 125, 250, 500, and 1000 nm. These films show high dielectric permittivity up to ∼1200. Cyclic I-V measurements were used to evaluate the dielectric properties of these thin films, which not only provide the total electric displacement, but also separate contributions from each of the relevant components including electric conductivity (D1), dielectric capacitance (D2), and relaxor-ferroelectric domain switching polarization (P). The results show that, as the film thickness increases, the material transits from a linear dielectric to nonlinear relaxor-ferroelectric. While the energy storage per volume increases with the film thickness, the energy storage efficiency drops from ∼80% to ∼30%. The PLZT films can be optimized for different energy storage applications by tuning the film thickness to optimize between the linear and nonlinear dielectric properties and energy storage efficiency.

High-aspect-ratio, vertically aligned carbon nanofibers (VACNFs) were conformally coated with aluminum oxide (Al2O3) and aluminum-doped zinc oxide (AZO) using atomic layer deposition (ALD) in order to produce a three-dimensional array of metal-insulator-metal core-shell nanostructures. Prefunctionalization before ALD, as required for initiating covalent bonding on a carbon nanotube surface, was eliminated on VACNFs due to the graphitic edges along the surface of each CNF. The graphitic edges provided ideal nucleation sites under sequential exposures of H2O and trimethylaluminum to form an Al2O3 coating up to 20 nm in thickness. High-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy images confirmed the conformal core-shell AZO/Al2O3/CNF structures while energy-dispersive X-ray spectroscopy verified the elemental composition of the different layers. HRTEM selected area electron diffraction revealed that the as-made Al2O3 by ALD at 200 °C was amorphous, and then, after annealing in air at 450 °C for 30 min, was converted to polycrystalline form. Nevertheless, comparable dielectric constants of 9.3 were obtained in both cases by cyclic voltammetry at a scan rate of 1000 V/s. The conformal core-shell AZO/Al2O3/VACNF array structure demonstrated in this work provides a promising three-dimensional architecture toward applications of solid-state capacitors with large surface area having a thin, leak-free dielectric.

This study reports a 3D freeze-printing method that integrates inkjet printing and freeze casting to control both the microstructure and macroporosity via formation of ice microcrystals during printing. A viscous aqueous ink consisting of a molecular MoS2 precursor (ammonium thiomolybdate) mixed with graphene oxide (GO) nanosheets is used in the printing process. Post-treatments by freeze-drying and reductive thermal annealing convert the printed intermediate mixture into a hybrid structure consisting of MoS2 nanoparticles anchored on the surface of 2D rGO nanosheets in a macroporous framework, which is fully characterized with FESEM, TEM, XRD, Raman spectroscopy and TGA. The resulting hybrid MoS2-rGO aerogels are studied as anodes for sodium ion batteries. They present a high initial specific capacity over 429 mAh/g at C/3.3 rate in the potential range of 2.5–0.10 V (vs Na+/Na). The process involves both reversible 2 Na+ insertion and slow irreversible conversion of MoS2 to metallic Mo. At higher rates, the conversion reaction is suppressed and the electrode is dominated by fast Na+ intercalation with good stability. This demonstrates that the 3D printing technology can be used as a processing technique to control the materials properties for energy storage. Keywords: 3D printing, Hybrid MoS2/graphene aerogel, Freeze-casting, Sodium ion battery, Porous electrode materials

A transition in source-drain current vs. back gate voltage (ID-VBG) characteristics from extrinsic polar molecule dominant hysteresis to anti-hysteresis induced by an oxygen deficient surface layer that is intrinsic to the ferroelectric thin films has been observed on graphene field-effect transistors on Pb0.92La0.08Zr0.52Ti0.48O3 gates (GFET/PLZT-Gate) during a vacuum annealing process developed to systematically remove the polar molecules adsorbed on the GFET channel surface. This allows the extrinsic and intrinsic hysteresis on GFET/PLZT-gate devices to detangle and the detection of the dynamic switch of electric dipoles using GFETs, taking advantage of their high gating efficiency on ferroelectric gate. A model of the charge trapping and pinning mechanism is proposed to successfully explain the transition. In response to pulsed VBG trains of positive, negative, as well as alternating polarities, respectively, the source-drain current ID variation is instantaneous with the response amplitude following the ID-VBG loops measured by DC VBG with consideration of the remnant polarization after a given VBG pulse when the gate electric field exceeds the coercive field of the PLZT. A detection sensitivity of around 212 dipole per μm(2) has been demonstrated at room temperature, suggesting the GFET/ferroelectric-gate devices provide a promising high-sensitivity scheme for uncooled detection of electrical dipole dynamic switch.

Here the authors demonstrate an approach to achieving stable 3 Li+ insertion into vanadium pentoxide (V2O5) by implementing a 3D core–shell structure consisting of coaxial V2O5 shells sputter-coated on vertically aligned carbon nanofiber cores. The hydrated amorphous microporous structure in the “as-deposited” V2O5 shells and the particulated nanocrystalline V2O5 structure formed by thermal annealing are compared. The former provides remarkably high capacities of 360 and 547 mAh g−1 in the voltage range of 4.0–2.0 and 4.0–1.5 V, respectively, far exceeding values in current oxide-based lithium ion battery cathodes and even the corresponding theoretical values of 294 mAh g−1 for 2 Li+/V2O5 insertion and 441 mAh g−1 for 3 Li+/V2O5 insertion into crystalline V2O5 materials. This is attributed to the additional reactions with the hydrated amorphous structure. After 100 cycles of 3 Li+/V2O5 insertion/extraction at 0.20 A g−1 (≈C/3), ≈84% of the initial capacity is retained. After thermal annealing, the core–shell structure presents a capacity of 294 and 390 mAh g−1, matching well with the theoretical values for 2 and 3 Li+/V2O5 insertion. The annealed sample shows further improved stability, with a remarkable capacity retention of ≈100% and ≈88% for 100 cycles of 2 and 3 Li+/V2O5 insertion/extraction.