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The search for new electrode materials for lithium-ion batteries (LIBs) has been an important way to satisfy the ever-growing demands for better performance with higher energy/power densities, improved safety and longer cycle life. Nanostructured metal oxides exhibit good electrochemical properties, and they are regarded as promising anode materials for high-performance LIBs. In this feature article, we will focus on three different categories of metal oxides with distinct lithium storage mechanisms: tin dioxide (SnO(2)), which utilizes alloying/dealloying processes to reversibly store/release lithium ions during charge/discharge; titanium dioxide (TiO(2)), where lithium ions are inserted/deinserted into/out of the TiO(2) crystal framework; and transition metal oxides including iron oxide and cobalt oxide, which react with lithium ions via an unusual conversion reaction. For all three systems, we will emphasize that creating nanomaterials with unique structures could effectively improve the lithium storage properties of these metal oxides. We will also highlight that the lithium storage capability can be further enhanced through designing advanced nanocomposite materials containing metal oxides and other carbonaceous supports. By providing such a rather systematic survey, we aim to stress the importance of proper nanostructuring and advanced compositing that would result in improved physicochemical properties of metal oxides, thus making them promising negative electrodes for next-generation LIBs.

Porous Co(3)O(4) nanowires with large aspect ratio have been obtained by annealing long Co(CO(3))(0.5)(OH)·0.11H(2)O precursor nanowires synthesized by a facile hydrothermal method. The results show that the amount of the additive (urea) has an important impact on the morphology of the as-synthesized cobalt-carbonate-hydroxide intermediate, where the uniformity and the overall structure can be controlled by changing the urea concentration. After the heat treatment, the as-obtained phase-pure Co(3)O(4) nanowires with a well retained structure are applied as the electrode material for supercapacitors, and the sample exhibits excellent performance with a high specific capacitance of 240 F g(-1) after 2000 charge/discharge cycles, corresponding to a retention of 98% of the initial capacitance., (This journal is © The Royal Society of Chemistry 2012)

In this work, we demonstrate an interesting polystyrene microsphere-assisted synthesis of hierarchical MoS(2) spheres composed of ultrathin nanosheets. The as-prepared sample exhibits promising lithium storage properties with improved cyclic capacity retention and rate capability.

We demonstrate an unusual formation of large 2D nanosheets from nanomosaic building blocks of anatase TiO(2) nanosheets with exposed (001) facets. It is proposed that large PVP molecules adsorbed on the (001) facets serve as the linker that brings building blocks together, at the same time prevents them from stacking along the c-axis., (This journal is © The Royal Society of Chemistry 2011)

We demonstrate a new hydrothermal method to directly grow SnO(2) nanosheets on a graphene oxide support that is subsequently reduced to graphene. This unique SnO(2)/graphene hybrid structure exhibits enhanced lithium storage properties with high reversible capacities and good cycling performance., (This journal is © The Royal Society of Chemistry 2011)

We have designed a unique hybrid structure by directly growing ultrathin anatase TiO(2) nanosheets onto graphene support for fast lithium storage. With exposed (001) high-energy facets, these TiO(2) nanosheets serve as ideal hosts for fast and efficient lithium storage. On the other hand, the graphene support serves as a highly conductive substrate that is beneficial to the high-rate performance., (© The Royal Society of Chemistry 2011)

In this work, we report a rational design of graphene sheets-wrapped anatase TiO(2) hollow particles. This unique hybrid structure demonstrates significantly enhanced lithium storage capabilities compared to the pure TiO(2) counterpart, which clearly uncovers the merit of structural design and rational integration with graphene sheets., (© The Royal Society of Chemistry 2011)

A simple approach was proposed to synthesize three types of ellipsoidal hollow nanostructures whose shells are assembled from anatase TiO(2) nanosheets (NSs) with exposed (001) facets. Among them, ellipsoid Fe(3)O(4)@TiO(2)-NS nanorattles can be readily generated as a magnetically separable photocatalyst with enhanced activity through in situ reduction of the α-Fe(2)O(3) core.

Facile hydrothermal methods have been developed to synthesize large Co3O4 nanocubes, β-Co(OH)2 hexagonal nanodiscs and nanoflowers. Samples are thoroughly characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller method, and thermogravimetric analysis. The Co3O4 nanocubes have an average size of about 350 nm with a perfect cubic shape, and the β-Co(OH)2 nanodiscs are uniform hexagonal platelets, whereas the β-Co(OH)2 nanoflowers are assembled from large sheetlike subunits. After thermal annealing in air at a moderate temperature, the as-prepared β-Co(OH)2 samples can be converted into spinel Co3O4 without significant alterations in morphology. We have also investigated the comparative lithium storage properties of these three Co3O4 samples with distinct morphologies. The nanoflower sample shows highly reversible lithium storage capability after 100 charge-discharge cycles.

In this work, we developed a facile hydrothermal system to synthesize self-supported copper oxides with different nanostructures. In this system, we used copper foam as both the substrate and the copper source, and selected a wide range of sodium salts to serve as directing agents, promoting the formation of copper oxide with different nanostructures. We first show that, at 30 mM of sodium fluoride, we can successfully grow nanocubes on the copper foam substrate that comprise both CuO and Cu2O. Such a mixed composition is unique among the investigated salts. However, if a lower concentration of NaF or a different salt is used, Cu2O nanocrystals of different structures, such as nanoplatelets or irregular particles, can be obtained. When these samples were tested in supercapacitors, they demonstrated contrasting pseudocapacitive properties where the initial mixed Cu2O/CuO nanocube sample demonstrated a very stable reversible capacitance of about 400 mF cm−2 for 1600 cycles. This is significantly higher than that for the other samples, as well as advantageous compared to other copper-oxide-based electrode materials. The impedance analysis suggested that such a performance could be attributed to the low diffusion resistance of this sample. [ABSTRACT FROM AUTHOR]

This work describes a versatile hydrothermal approach to synthesize different types of hierarchical structures composed of single crystalline β-Ni(OH) 2 nanosheets. We use the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride (BmimCl) as a structure directing agent, which allows the formation of films consisting of β-Ni(OH) 2 nanosheets on the nickel foam substrate. It is found that the IL not only controls the formation of the sheet-like structure, but also promotes the growth of the nanosheets on the substrate, building an intimate contact between the active hydroxide film and the conducting metal foam. This IL agent is so effective that such a hierarchical film can also be obtained with different thickness and organization if different nickel salt precursor is used. When these film samples were applied as the electrode materials for pseudocapacitor, they exhibited promising capacitive properties with a high capacitance of about 700 F g −1 even at a high charge-discharge current rate of 5 A g −1 for prolonged cycling. [ABSTRACT FROM AUTHOR]

Abstract: Anatase TiO2 nanosheets with largely exposed (001) facets have been synthesized by a modified method. Exploitation of these nanosheets as a host structure for reversible lithium insertion/extraction has been investigated. It is found that these TiO2 nanosheets manifest much lower initial irreversible losses compared to other anatase TiO2 nanostructures, and excellent cycling performance at a charge–discharge rate as high as 20C. The superior reversible lithium storage capability can be attributed to the ultrathin nanosheet structure: a large exposed effective area and a very short diffusion path. It thus attests the promising use of these anatase TiO2 nanosheets in high-power lithium–ion batteries. [Copyright &y& Elsevier]