High energy and power density lithium iron phosphate was studied for hybrid electric vehicle applications. This work addresses the effects of porosity in a composite electrode using a four-point probe resistivity analyzer, galvanostatic cycling, and electrochemical impedance spectroscopy (EIS). The four-point probe result indicates that the porosity of composite electrode affects the electronic conductivity significantly. This effect is also observed from the cell's pulse current discharge performance. Compared to the direct current (dc) methods used, the EIS data are more sensitive to electrode porosity, especially for electrodes with low porosity values.

In the spirit of the theoretical evolution from the Helmholtz model to the Gouy–Chapman–Stern model for electric double-layer capacitors, we explored the effect of a diffuse layer on the capacitance of mesoporous carbon supercapacitors by solving the Poisson–Boltzmann (PB) equation in mesopores of diameters from 2 to 20 nm. To evaluate the effect of pore shape, both slit and cylindrical pores were considered. We found that the diffuse layer does not affect the capacitance significantly. For slit pores, the area-normalized capacitance is nearly independent of pore size, which is not experimentally observed for template carbons. In comparison, for cylindrical pores, PB simulations produce a trend of slightly increasing area-normalized capacitance with pore size, similar to that depicted by the electric double-cylinder capacitor model proposed earlier. These results indicate that it is appropriate to approximate the pore shape of mesoporous carbons as being cylindrical and the electric double-cylinder capacitor model should be used for mesoporous carbons as a replacement of the traditional Helmholtz model.

Graphite nanosheets (GNs) were introduced into polyvinylidene fluoride (PVDF) via the solution mixing technique. The nanocomposites were then subjected to compression molding for electrical measurements. Solution mixing enabled homogeneous dispersion of GN within the PVDF matrix. The electrical transport behavior of such nanocomposites was studied by means of the impedance spectroscopy in a wide frequency range from 102 to 107 Hz. The results showed that the permittivity and conductivity of the composites are frequency dependent and well obeyed with the scaling law (ε′ ∝ ωu and σ′ ∝ ω−v) in the vicinity of percolation threshold (Φc ≈ 2.5 wt%). A large dielectric constant of 173 was observed in the PVDF/GN 2.5 wt% composites at 1 kHz.

Strong interest in energy generation and storage has yielded excellent progress on organic based solar cells, and there is also a strong desire for equivalent advancement in polymer-based charge storage devices such as batteries and super-capacitors. Despite extensive research on electronically conducting polymers including polypyrrole, polythiophene, and polyaniline, limitations to the maximum doping density and chemical stability had been considered a significant restriction on the development of polymer batteries. Recent work appears to show a meaningful increase in the upper bound of the maximum density from 0.5 to 1.0 electrons per monomer depending on the structure, processing, and ionic species used in charging and discharging of the polymers. Several recent examples have also implied that more stable, reversible charge-discharge cycling is being observed in n-doped polymers. These observations suggest that the performance metrics of this class of electronically conducting polymer may ultimately reach the levels required for practical battery applications. Further efforts are essential to perfect practical large-scale electrode fabrication to move toward greater compatibility in the methods used for solar cells and those used in producing batteries. A better understanding must also be developed to elucidate the effects of molecular structure and polymer architecture on these materials.

SnO2@carbon nanofibers were synthesized by a combination of electrospinning and subsequent thermal treatments in air and then in argon to demonstrate their potential use as an anode material in lithium ion battery applications. The as-prepared SnO2@carbon nanofibers consist of SnO2 nanoparticles/nanocrystals encapsulated in a carbon matrix and contain many mesopores. Because of the charge pathways, both for the electrons and the lithium ions, and the buffering function provided by both the carbon encapsulating the SnO2 nanoparticles and the mesopores, which tends to alleviate the volumetric effects during the charge/discharge cycles, the nanofibers display a greatly improved reversible capacity of 420 mAh/g after 100 cycles at a constant current of 100 mA/g, and a sharply enhanced reversible capacity at higher rates (0.5, 1, and 2 C) compared with pure SnO2 nanofibers, which makes it a promising anode material for lithium ion batteries.

A simple and environmentally benign three-step hydrothermal method was developed for growing oriented single-crystalline TiO2-B and/or anatase TiO2 nanowire arrays on titanium foil over large areas. These nanowire arrays are suitable for use as the anode in lithium ion batteries; they exhibit specific capacities ranging from 200–250 mAh/g at charge-discharge rates of 0.3 C where 1 C is based on the theoretical capacity of 168 mAh/g. Batteries retain this capacity over as many as 200 charge-discharge cycles. Even at high charge-discharge rates of 0.9 C and 1.8 C, the specific capacities were 150 mAh/g and 120 mAh/g, respectively. These promising properties are attributed to both the nanometer size of the nanowires and their oriented alignment. The comparable electrochemical performance to existing technology, improved safety, and the ability to roll titanium foils into compact three-dimensional structures without additional substrates, binders, or additives suggest that these TiO2 nanowires on titanium foil are promising anode materials for large-scale energy storage.

The mammalian physiology represents a level of sophistication in materials design, assembly, and function that has yet to be replicated by the modern tools of materials science. Although, the building blocks of our body (pluripotent stem and progenitor cells) are still available within our tissues, the absence of the biological and structural cues that drove the development process early on, in an adult, limits our ability to regenerate after an injury. The goal of regenerative medicine is therefore to recapitulate embryonic events within an artificially defined materials space (i.e., the niche) so that the repair processes can be triggered using our reservoir of stem cells. This engineering of the regenerative niche will require an interdisciplinary exercise involving materials scientists, biologists, and clinicians. The success of this exercise will hinge on our ability to develop materials that incorporate principles of wound healing, lessons from immunology and developmental biology, and knowledge of cellular mechanics and molecular biology such that they can mimic the cellular environment, instruct cells to make fate decisions, and direct the hierarchical organization of tissues. This article presents the current state of this challenge in the implementation of regenerative therapies.

Glassy carbon plates were thermochemically gas phase oxidized to obtain monolithic sandwichlike electrode assemblies with high surface area porous films for electrochemical energy storage applications. Film thicknesses were varied by variation of oxidation parameters time, temperature, and oxygen concentration and measured with electron microscopy. The mass density of the porous carbon film material was estimated by fitting a geometrical model to experimental gravimetric data. Optical Raman spectroscopy line scans suggest that the porosity has a gradient between the surface and the film/bulk interface, which is supported by pore-size distribution data obtained from small-angle x-ray scattering (SAXS) on slightly oxidized and fully oxidized samples. Detailed inspection of the power law behavior of SAXS data suggests that the internal surface area of well-oxidized glassy carbon (GC) is compact and extends over the entire probed volume and thus has optimal pore connectivity. This effect goes along with pore enlargement and a relative decrease of internal surface area per volume. Slightly oxidized carbon has no pore space with a compact, high connectivity internal surface area. The corresponding SAXS power law and the x-ray density suggest that this high volumetric surface area must be interpreted as a result of surface roughness, rather than true geometric or volumetric surface area. In consequence, is this surface area of limited use for electrochemical energy storage?

All-solid-state Li–In/Li4Ti5O12 cells using Li2S–P2S5 solid electrolytes were assembled to investigate their electrochemical properties in the wide voltage range of 0–3 V (versus Li). The Li/Li4Ti5O12 cells using 1 M LiPF6 in ethylene carbonate and diethyl carbonate were fabricated for comparison with the all-solid-state cells. The capacity of the all-solid-state cell using the 70Li2S·27P2S5·3P2O5 (mol%) solid electrolyte decreased with an increase in the current density as well as the cell using the liquid electrolyte. However, the all-solid-state cell was charged and discharged even at a high current density of 10 mA/cm2. The all-solid-state cell was cycled at 1.3 mA/cm2 and retained 90% of the first reversible capacity of about 120 mAh/g after 500 cycles. The all-solid-state cell cycling at 100 °C showed the small overpotential and reversible capacity of about 120 mAh/g at 13 mA/cm2.

Porous SnO2/multiwalled carbon nanotube (CNT) thin film composites as anode material for Li-ion batteries were prepared using the electrostatic spray deposition (ESD) technique. The morphologies of the samples were found to be affected mainly by deposition temperatures. Electrochemical test cells were assembled using the as-prepared samples without any conductive additive or binder. The influence of deposition temperature and CNT content on the electrochemical performance of the anodes was investigated. Compared to pure tin oxide and pure CNT, the composite anode materials showed better discharge capacity and cyclability. Among the composites, the sample deposited at 250 °C with 30 wt% CNT content was found to show better energy capacity. This can be ascribed to the porous nature of the anodes and the improvement in the conductivity by the addition of CNTs.

The effect of chemical treatment on the capacitance of carbon electrodes prepared from waste coffee grounds was investigated. Coffee grounds were impregnated with FeCl3 and MgCl2 and then treated at 900 °C. The resultant carbons were compared with activated coffee ground carbons prepared by ZnCl2 treatment. The carbon treatment processes of FeCl3 and MgCl2 were studied using thermal gravimetric analysis. Raman spectroscopy, x-ray photoelectron spectroscopy, and N2 and CO2 adsorption were used to characterize the activated carbons. Activation with ZnCl2 and FeCl3 produced carbons with higher surface areas (977 and 846 m2/g, respectively) than treatment with MgCl2 (123 m2/g). Electrochemical double-layer capacitances of the carbons were evaluated in 1 M H2SO4 using two-electrode cells. The system with FeCl3-treated carbon electrodes provided a specific cell capacitance of 57 F/g.