Synthesis of nanocrystals with exposed high-energy facets is a well-known challenge in many fields of science and technology. The higher reactivity of these facets simultaneously makes them desirable catalysts for sluggish chemical reactions and leads to their small populations in an equilibrated crystal. Using anatase TiO 2 as an example, we demonstrate a facile approach for creating high surface area, stable nanosheets comprised of nearly 100% exposed (001) facets. Our approach relies on spontaneous assembly of the nanosheets into three-dimensional, hierarchical spheres that stabilizes them from collapse. We show that the high surface density of exposed TiO 2 (001) facets leads to fast lithium insertion/deinsertion processes in batteries that mimic features seen in high power electrochemical capacitors.2

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Novel, porous NiCo2O4 nanotubes (NCO-NTs) are prepared by a single-spinneret electrospinning technique followed by calcination in air. The obtained NCO-NTs display a one-dimensional architecture with a porous structure and hollow interiors. The effect of precursor concentration on the morphologies of the products is investigated. Due to their unique structure, the prepared NCO-NT electrode exhibits a high specific capacitance (1647 F g(-1) at 1 A g(-1)), excellent rate capability (77.3 % capacity retention at 25 A g(-1)), and outstanding cycling stability (6.4 % loss after 3000 cycles), which indicates it has great potential for high-performance electrochemical capacitors. The desirable enhanced capacitive performance of NCO-NTs can be attributed to the relatively large specific surface area of these porous and hollow one-dimensional nanostructures.

Uniform α-MoO3 nanorods are synthesized with controlled aspect ratios through a fast hydrothermal route. The control over the aspect ratio of these as-prepared nanorods is realized by applying different reaction times of 2−20 h. Specifically, the nanorods prepared with a reaction time of 2 h are, on average, much shorter in length and slightly smaller in width compared with those obtained with a longer reaction time of 20 h. The products are thoroughly characterized by FESEM/TEM/XRD/BET techniques. The electrochemical properties of the samples are analyzed using cyclic voltammetry and charge−discharge cycling. These studies reveal that the as-prepared nanorods with a smaller aspect ratio exhibit a higher initial discharge capacity, a lower irreversible loss, and better rate behavior at different charge−discharge rates. When compared to α-MoO3 submicrometer particles prepared through direct thermal decomposition, these as-prepared nanorods show much better lihtium storage properties, demonstrating that enhanced physical and/or chemical properties can be obained from proper nanostructuring of the material.

We demonstrate a facile route for the scalable synthesis of SnO2 nanoparticles with controlled carbon nanocoating for use as high-capacity anode materials for next-generation lithium-ion batteries. SnO2 nanoparticles with size in the range of 6 −10 nm are produced via a simple hydrothermal method with high yield, which are then encapsulated by a carbon layer through a modified method. The weight fraction of carbon present in the final product can be readily tuned by varying the concentration of glucose used during the hydrothermal coating process. A systematic study has been carried out to examine the effect of carbon content upon lithium-ion battery performance. It is found that the optimized SnO2@carbon nanoparticles manifest excellent lithium storage properties. As an example, SnO2@carbon with 8 wt % carbon can deliver a capacity as high as 631 mA h g−1 even after 100 charge/discharge cycles at a current drain of 400 mA g−1.

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We report a simple approach for synthesizing uniform hollow spheres assembled from anatase TiO 2 nanosheets with large amount of exposed (001) facets. These hierarchical TiO 2 hollow spheres possessing a high specific surface area of 134.9 m 2 g À1 manifest a high Coulombic efficiency for lithium extraction, excellent capacity retention, and superior rate behaviour owing to the hollow structure and unique crystal faceting of the building blocks.Titania (TiO 2 ) is of great importance for both fundamental studies and technological applications such as energy storage 1-5 and photocatalysis. 6,7 Among titania polymorphs, anatase TiO 2 is most widely studied. 8 The surface energies of (001) and (101) facets of anatase TiO 2 have been calculated to be 0.90 and 0.44 J m À2 , respectively. 9 Therefore, anatase nanocrystals are dominantly bound by energetically favored (101) facets. Those high-energy (001) facets are more likely to form during the earliest stages of crystal growth; however, they are quickly eliminated during further growth. 10 Thus, growth of nano/microanatase TiO 2 crystals with exposed (001) facets is highly challenging. Recently, Yang et al. reported the pioneering work on anatase TiO 2 microcrystals with 47% exposed (001) facets. 11 Following that a series of research works on synthesis of sheet-like anatase TiO 2 single-crystals with as high as 89% exposed (001) facets have been reported. 6,12-14 Despite the high percentages of (001) facets, the specific surface area of these TiO 2 nano/microcrystals is generally low because of the relatively large crystal size along the [001] direction. The absolute amount of (001) facets is more relevant for practical applications, for example, photocatalysis. How to get high surface area nano/microanatase TiO 2 crystals with exposed (001) facets is the second challenge. By reducing the thickness in the [001] direction and increasing the two-dimensional lateral size of the (001) planes, Wu et al. synthesized anatase TiO 2 nanosheets (NSs) with thickness of less than 1 nm by employing a facile nonaqueous route. 15

A simple electrospinning technique is employed for the preparation of high‐performance V2O5 nanofibers. The fibers thus prepared are subjected to heat treatment under the optimized conditions at 400 °C in air to achieve a single phase. The powder X‐ray diffraction pattern confirms the formation of an orthorhombic structure with Pmmn space group. Morphological studies conducted by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM), clearly reveal the presence of a highly interconnected network of fibers with the diameter ranging from approximately 500–800 nm. After the heat treatment, translation of smooth fibrous morphology into porous fibers with embedded nanocrystals of V2O5 is noticed from the SEM measurements. The sintered V2O5 nanofibers are used to fabricate a hybrid electrochemical capacitor (HEC) and it is coupled with a substrate‐free single‐walled carbon nanotube (SWCNT) network (called “Bucky paper”) in a conventional organic electrolyte solution. Supercapacitive behavior of HEC is studied in both potentiostatic and galvanostatic modes at room temperature. The HEC demonstrated very stable and excellent cycling behavior during 3500 cycles of galvanostatic charge and discharge tests. This hybrid system is also well established during the rate capability studies from the applied current density of 30 to 210 mA g−1 and delivered maximum energy and power densities of 18 Wh kg−1 and 315 W kg−1, respectively.