Rechargeable Li-ion batteries are currently being explored for high-power applications such as electric vehicles. However, in order to deploy Li-ion batteries in next-generation vehicles, it is essential to develop electrodes made from durable, nontoxic, and inexpensive materials with a high charge/discharge rate and a high reversible capacity. Transition metal oxides such as Fe

Lithium-ion batteries are current power sources of choice for portable electronics, offering high energy density and longer lifespan than comparable technologies. Significant improvements in rate and durability for inexpensive, safe and non-toxic electrode materials may enable utilization in hybrid electric or plug-in hybrid electric vehicles (PHEVs). Furthermore, recent efforts for hybrid electric vehicle applications have been focused on new anode materials with slightly more positive insertion voltages with respect to Li/Li þ to minimize any risks of high-surface-area Li plating while charging at high rates, a major safety concern.[1] In hybrid electric vehicles, batteries are cycled with $10% charge/discharge from the point where the cell is at 50% capacity. when cycled in a voltage window of 3.0-0.005 V, but this material suffered from poor cycling stability, with the capacity degrading to 400 mA h g À1 in $100 cycles. [8] By increasing the cut-off potential to 0.2 V and employing a slow rate (discharge and charge at C/15 and C/20, respectively), the cycling was more stable, ranging from 600-400 mA h g À1 in 100 cycles.[8] A tin-doped MoO 3 system was also explored, and the average charge potential was lowered, but at the expense of capacity fading.[9] Here we report on anodes fabricated from crystalline MoO 3 nanoparticles that display both a durable reversible capacity of 630 mA h g À1 and durable high rate capability.The nanoparticle anodes show no capacity degradation for 150 cycles between 3.5 to 0.005 V with both charge and discharge at C/2, compared to micrometer-sized particles where the capacity quickly fades. (Typically both decreased capacity and rapid degradation are observed when deep cycles are employed at higher rates.) Upon cycling, long-range order in the MoO 3 nanostructures is lost. First-principle calculations are employed in order to explain the nanoparticle durability despite the loss of structural order. The crystalline molybdenum oxide nanoparticles are grown at high density by a previously described economical hot-wire chemical vapor deposition (HWCVD) technique.[10] Figure 1a shows a representative transmission electron microscopy (TEM) image of the as-synthesized nanoparticles. Extensive TEM analyses reveal that the bulk powder contains almost exclusively nanospheroids with diameters of 5-20 nm, thus providing a short solid-state Li-ion diffusion path. A highresolution TEM image of a nanoparticle where the lattice fringes are visible is shown in Figure 1b. A simple electrophoresis deposition process [11] is employed to fabricate high-surface area porous nanoparticle films on a stainless steel electrode with a thickness of $2 mm. Figure 1c displays a scanning electron microscopy (SEM) image of an electrophoresis-deposited film. The mass density of the nanoparticle film was found to be $3.3 g cm À3 from mass and thickness data compared to 4.7 g cm À3 for the bulk material. Furthermore, the electrode is comprised of entirely COMMUNICATION

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Zinc oxide (ZnO) is an important material for hybrid inorganic-organic devices in which the characteristics of the interface can dominate both the structural and electronic properties of the system. These characteristics can be modified through chemical functionalization of the ZnO surface. One of the possible strategies involves covalent bonding of the modifier using silane chemistry. Whereas a significant body of work has been published regarding silane attachments to glass and SiO2, there is less information about the efficacy of this method for controlling the surface of metal oxides. Here we report our investigation of molecular layers attached to polycrystalline ZnO through silane bonding, controlled by an amine catalyst. The catalyst enables us to use triethoxysilane precursors and thereby avoid undesirable multilayer formation. The polycrystalline surface is a practical material, grown by sol-gel processing, that is under active exploration for device applications. Our study included terminations with alkyl and phenyl groups. We used water contact angles, infrared spectroscopy, and X-ray photoemission spectroscopy to evaluate the modified surfaces. Alkyltriethoxysilane functionalization of ZnO produced molecular layers with submonolayer coverage and evidence of disorder. Nevertheless, a very stable hydrophobic surface with contact angles approaching 106 degrees resulted. Phenyltriethoxysilane was found to deposit in a similar manner. The resulting surface, however, exhibited significantly different wetting as a result of the nature of the end group. Molecular layers of this type, with a variety of surface terminations that use the same molecular attachment scheme, should enable interface engineering that optimizes the chemical selectivity of ZnO biosensors or the charge-transfer properties of ZnO-polymer interfaces found in oxide-organic electronics.

Optical lithography is used to fabricate LPCMO wires starting from a single (La(5/8-0.3)Pr(0.3))Ca3/8MnO3 (LPCMO) film epitaxially grown on a LaAlO3(100) substrate. As the width of the wires is decreased, the resistivity of the LPCMO wires exhibits giant and ultrasharp steps upon varying temperature and magnetic field in the vicinity of the metal-insulator transition. The origin of the ultrasharp transitions is attributed to the effect of spatial confinement on the percolative transport in manganites.

Electrochromic materials exhibit switchable optical properties that can find applications in various fields, including smart windows, nonemissive displays, and semiconductors. High-performing nickel oxide electrochromic materials have been realized by controlling the material composition and tuning the nanostructural morphology. Post-treatment techniques could represent efficient and cost-effective approaches for performance enhancement. Herein, we report on a post-processing ozone technique that improves the electrochromic performance of an aluminum-containing nickel oxide material in lithium-ion electrolytes. The resulting materials were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy, and X-ray absorption spectroscopy (XAS). It was observed that ozone exposure increased the Ni oxidation state by introducing hole states in the NiO(6) octahedral unit. In addition, ozone exposure gives rise to higher-performing aluminum-containing nickel oxide films, relative to nickel oxide containing both Al and Li, in terms of switching kinetics, bleached-state transparency, and optical modulation. The improved performance is attributed to the decreased crystallinity and increased nickel oxidation state in aluminum-containing nickel oxide electrochromic films. The present study provides an alternative route to improve electrochromic performance for nickel oxide materials.

Large scale phase separation between ferromagnetic metallic and charge-ordered insulating states in La1−x−yPryCaxMnO3 (LPCMO) crystals and thin films is very sensitive to structural and magnetic changes and is responsible for the enhanced magnetoresistance in LPCMO compared to its parent compounds. By epitaxially growing LPCMO thin films on different substrates, the strain on the LPCMO thin films can be changed, thereby controlling the energy balance between the two phases. LPCMO films of several different thicknesses have been grown on NdGaO3 (NGO), SrTiO3 (STO), SrLaGaO4 (SLGO), and LaAlO3 (LAO) substrates. The compressive strain from the LAO and SLGO substrates suppresses the long-range charge ordering in these samples and enhances magnetoresistance and magnetic hystereses. Conversely, the tensile strain from the STO and NGO substrates enhances the long-range charge ordering and reduces the magnetoresistance and magnetic hystereses.

Electrochromic effects of transition metal oxides provide a great platform for studying lithium intercalation chemistry in solids. Herein, we report on an electronically modified nanocomposite nickel oxide (i.e., Li2.34NiZr0.28Ox) that exhibits significantly improved electrochromic performance relative to the state-of-the-art inorganic electrochromic metal oxides in terms of charge/discharge kinetics, bleached-state transparency, and optical modulation. The knowledge obtained from O K-edge X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS) suggests that the internally grown lithium peroxide (i.e., Li2O2) species plays a major role in facilitating charge transfer thus enabling optimal electrochromic performance. This understanding is relevant to recent theoretical studies concerning conductivity in Li2O2 for lithium-air batteries (as cited in the main text). Furthermore, we elucidate the electrochromism in modified nickel oxide in lithium ion electrolyte with the aid of Ni K-edge XAS and Ni L-edge XAS studies. The electrochromism in the nickel oxide materials arises from the reversible formation of hole states on the NiO6 units, which then impacts the Ni oxidation state through the Ni3d-O2p hybridization states. This study sheds light on the lithium intercalation chemistry for general energy storage and semiconductor applications.