Three-Dimensional Porous Particles Composed of Curved, Two-Dimensional, Nano-Sized Layers for Li-Ion Batteries

Thin Si films coated on porous 3D particles composed of curved 2D graphene sheets have been synthesized utilizing techniques that allow for tunable properties. Since graphene exhibits specific surface area up to 100 times higher than carbon black or graphite, the deposition of the same mass of Si on graphene is much faster in comparison -- a factor which is important for practical applications. In addition, the distance between graphene layers is tunable and variation in the thickness of the deposited Si film is feasible. Both of these characteristics allow for optimization of the energy and power characteristics. Thicker films will allow higher capacity, but slower rate capabilities. Thinner films will allow more rapid charging, or higher power performance. In this innovation, uniform deposition of Si and C layers on high-surface area graphene produced granules with specific surface area (SSA) of 5 sq. m/g

Silicon-based anode and method for manufacturing the same

A silicon-based anode comprising silicon, a carbon coating that coats the surface of the silicon, a polyvinyl acid that binds to at least a portion of the silicon, and vinylene carbonate that seals the interface between the silicon and the polyvinyl acid. Because of its properties, polyvinyl acid binders offer improved anode stability, tunable properties, and many other attractive attributes for silicon-based anodes, which enable the anode to withstand silicon cycles of expansion and contraction during charging and discharging

Alginate-containing compositions for use in battery applications

A silicon-based anode comprises an alginate-containing binder. The many carboxy groups of alginate bind to a surface of silicon, creating strong, rigid hydrogen bonds that withstand battery cycling. The alginate-containing binder provides good performance to the anode by (1) improving the capacity of the anode in comparison to other commercially-available binders, (2) improving Columbonic efficiency during charging and discharging cycles, and (3) improving stability during charging and discharging cycles

Alginate-containing compositions for use in battery applications

A silicon-based anode comprises an alginate-containing binder. The many carboxy groups of alginate bind to a surface of silicon, creating strong, rigid hydrogen bonds that withstand battery cycling. The alginate-containing binder provides good performance to the anode by (1) improving the capacity of the anode in comparison to other commercially-available binders, (2) improving Columbonic efficiency during charging and discharging cycles, and (3) improving stability during charging and discharging cycles

Carbide-Derived Carbons: Effect of Pore Size on Hydrogen Uptake and Heat of Adsorption

Cryoadsorption is a promising method of enhancing gravimetric and volumetric onboard H2 storage capacity for future transportation needs. Inexpensive carbide-derived carbons (CDCs), produced by chlorination of metal carbides, have up to 80 % open-pore volume with tunable pore size and specific surface area (SSA). Tuning the carbon structure and pore size with high sensitivity by using different starting carbides and chlorination temperatures allows rational design of carbon materials with enhanced C-H2 interaction and thus increased H2 storage capacity. A systematic experimental investigation of a large number of CDCs with controlled pore size distributions and SSAs shows how smaller pores increase both the heat of adsorption and the total volume of adsorbed H2. It has been demonstrated that increasing the average heat of H2 adsorption above 6.6 kJ mol-1 substantially enhances H2 uptake at 1 atm (1 atm = 101 325 Pa) and -196 °C. The heats of adsorption up to 11 kJ mol-1 exceed values reported for metal-organic framework compounds and carbon nanotubes

Phonon Confinement Effects in the Raman Spectrum of Nanodiamond

Nanodiamonds (ND) exhibit unique properties due to their small size and high surface-to-volume ratio compared to bulk diamonds. A reduction in crystal size also affects ND Raman spectra. The confinement of optical phonons in nanocrystals (\u3c10 nm) results in asymmetrically broadened Raman lines, which are shifted toward lower wavenumbers. The phonon confinement model (PCM) relates the observed changes in the Raman spectra to the crystal size and can be used for size characterization at the nanoscale. While the PCM was successfully applied to a variety of materials including Si and BN, results remained unsatisfactory in the case of ND. In order to improve the agreement between the predictions of the model and experimental Raman spectra of ND, effects such as crystal size distribution, lattice defects, and the energy dispersion of the phonon modes were taken into consideration and incorporated into the PCM. This work has shown that phonon wave vectors from small vibrational domains lead to a broad shoulder peak at ~1250 cm-1, that is often observed in the Raman spectrum of ND

Formation of porous SiC ceramics by pyrolysis of wood impregnated with silica

International Journal of Applied Ceramic Technology, 3(6): pp. 485-490.Biomorphous β-SiC ceramics were produced at 1400°C from pine wood impregnated with silica. This one-step carbothermal reduction process decreases the cost of manufacturing of SiC ceramics compared to siliconization of carbonized wood in silicon vapor. The synthesized sample exhibits 14 m2/g surface area and has a hybrid pore structure with large 5- 20 μm tubular macropores and small (< 50 nm) slit shaped mesopores. SiC whiskers of 20- 400 nm in diameter and 5-20 μm in length formed within the tubular pores. These whiskers are expected to improve the filtration by removing dust particles that could otherwise penetrate through large pores. After ultrasonic milling, the powdered sample showed an average particle size of ~30 nm. The SiC nanopowder produced in this process may be used for manufacturing SiC ceramics for structural, tribological, and other applications

Electrodeposition of Nanostructured Magnesium Coatings

In this work, we report on the electroplating of ultrafine and uniform magnesium (Mg) films on copper (Cu) and carbon nanotube (CNT) paper substrates. By controlling the process parameters and utilizing the pulsed deposition method, the average grain size of Mg was reduced to nanodimensions. Surface pretreatment of the substrates by depositing a seed layer was found to be an efficient strategy for reducing the energy barrier for nucleation, thus improving nucleation density and the uniformity of deposited coatings. This work provides important guidance for the fabrication of smooth nanostructured Mg films on different substrates for a wide variety of applications

Carbide-derived carbons designed for efficient hydrogen storage

Carbide-derived carbons (CDCs) with specific surface area (SSA) ~ 2000 m2/g and open pore volume up to 80% are produced by chlorine etching of metal carbides. Tuning the pore size distribution by carbide precursor selection and etching temperature yields enhanced hydrogen storage capacity at both ambient and elevated pressure. Our goal is to establish the fundamental relation between capacity and SSA, pore size and pore volume

Titanium Carbide Derived Nanoporous Carbon for Energy-Related Applications

High surface area nanoporous carbon has been prepared by thermo-chemical etching of titanium carbide TiC in chlorine in the temperature range 200–1200 °C. Structural analysis showed that this carbide-derived carbon (CDC) was highly disordered at all synthesis temperatures. Higher temperature resulted in increasing ordering and formation of bent graphene sheets or thin graphitic ribbons. Soft X-ray absorption near-edge structure spectroscopy demonstrated that CDC consisted mostly of sp2 bonded carbon. Small-angle X-ray scattering and argon sorption measurements showed that the uniform carbon-carbon distance in cubic TiC resulted in the formation of small pores with a narrow size distribution at low synthesis temperatures; synthesis temperatures above 800 °C resulted in larger pores. CDC produced at 600–800 °C show great potential for energy-related applications. Hydrogen sorption experiments at −195.8 °C and atmospheric pressure showed a maximum gravimetric capacity of ∼ 330 cm3/g (3.0 wt.%). Methane sorption at 25 °C demonstrated a maximum capacity above 46 cm3/g (45 vol/vol or 3.1 wt.%) at atmospheric pressure. When tested as electrodes for supercapacitors with an organic electrolyte, the hydrogen-treated CDC showed specific capacitance up to 130 F/g with no degradation after 10 000 cycles