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.