Enhanced ion transport in Li2O and Li2S films.

Films of Li2O and Li2S grown by sputter deposition exhibit Li+ conductivity values at room temperature which are enhanced by 3-4 orders of magnitude relative to bulk samples. Possible mechanisms are discussed. The results may help explain the ion transport pathway through passivation layers containing these chalcogenides in batteries.

3D Honeycomb Architecture Enables a High-Rate and Long-Life Iron (III) Fluoride-Lithium Battery.

Metal fluoride-lithium batteries with potentially high energy densities, even higher than lithium-sulfur batteries, are viewed as very promising candidates for next-generation lightweight and low-cost rechargeable batteries. However, so far, metal fluoride cathodes have suffered from poor electronic conductivity, sluggish reaction kinetics and side reactions causing high voltage hysteresis, poor rate capability, and rapid capacity degradation upon cycling. Herein, it is reported that an FeF3 @C composite having a 3D honeycomb architecture synthesized by a simple method may overcome these issues. The FeF3 nanoparticles (10-50 nm) are uniformly embedded in the 3D honeycomb carbon framework where the honeycomb walls and hexagonal-like channels provide sufficient pathways for the fast electron and Li-ion diffusion, respectively. As a result, the as-produced 3D honeycomb FeF3 @C composite cathodes even with high areal FeF3 loadings of 2.2 and 5.3 mg cm-2 offer unprecedented rate capability up to 100 C and remarkable cycle stability within 1000 cycles, displaying capacity retentions of 95%-100% within 200 cycles at various C rates, and ≈85% at 2C within 1000 cycles. The reported results demonstrate that the 3D honeycomb architecture is a powerful composite design for conversion-type metal fluorides to achieve excellent electrochemical performance in metal fluoride-lithium batteries.

From Serendipity to Rational Design: Tuning the Blue Trigonal Bipyramidal Mn3+ Chromophore to Violet and Purple through Application of Chemical Pressure.

We recently reported that an allowed d-d transition of trigonal bipyramidal (TBP) Mn3+ is responsible for the bright blue color in the YIn1-xMnxO3 solid solution. The crystal field splitting between a'(dz2) and e'(dx2-y2, dxy) energy levels is very sensitive to the apical Mn-O distance. We therefore applied chemical pressure to compress the apical Mn-O distance in YIn1-xMnxO3, move the allowed d-d transition to higher energy, and thereby tune the color from blue to violet/purple. This was accomplished by substituting smaller cations such as Ti4+/Zn2+ and Al3+ onto the TBP In/Mn site, which yielded novel violet/purple phases. The general formula is YIn1-x-2y-zMnxTiyZnyAlzO3 (x = 0.005-0.2, y = 0.1-0.4, and z ≤ 0.1), where the color darkens with the increasing amount of Mn. Higher y or small additions of Al provide a more reddish hue to the resulting purple colors. Substituting other rare earth cations for Y has little impact on color. Crystal structure analysis by neutron powder diffraction confirms a shorter apical Mn-O distance compared with that in the blue YIn1-xMnxO3. Magnetic susceptibility measurements verify the 3+ oxidation state for Mn. Diffuse reflection spectra were obtained over the wavelength region 200-2500 nm. All samples show excellent near-infrared reflectance comparable to that of commercial TiO2, making them ideal for cool pigment applications such as energy efficient roofs of buildings and cars where reducing solar heat to save energy is desired. In a comparison with commercial purple pigments, such as Co3(PO4)2, our pigments are much more thermally stable and chemically inert, and are neither toxic nor carcinogenic.

Facile synthesis of one-dimensional peapod-like Sb@C submicron-structures.

We demonstrate a novel synthetic route to fabricate a one-dimensional peapod-like Sb@C structure with disperse Sb submicron-particles encapsulated in carbon submicron-tubes. The synthetic route may well serve as a general methodology for fabricating carbon/metallic fine structures by thermally reducing their carbon-coated metal oxide composites.