Sandwich‐Like, Stacked Ultrathin Titanate Nanosheets for Ultrafast Lithium Storage

Abstract

Nanomaterials in architecture for green energy conversion and/ or storage provide one of the most desirable approaches to alleviate environmental and energy issues. [1][2][3][4] As a result, there is increasing interest in developing high-power anode materials, which can match with the state-of-the-art high-power cathode materials, for next generation high-performance rechargeable Li-ion batteries. [5][6][7] Titanium dioxide is regarded as one of the ideal candidates for high-rate anode materials, owing not only to its structural characteristics and special surface activity, [8][9][10][11] but also to its low cost, safety, and environmental benignity. The lack of open channels in bulk TiO 2 is the main drawback that restricts its capacity and rate capability for reversible lithium insertion and extraction. A reduction in the effective size and construction of open channels in the material are the main strategies currently employed to increase the rate performance. [ 1 , 4 ] The capacity could also be improved by reducing the path length of lithium ion migration and improving electron transport at the surface or in the bulk of the material. [ 10 , 12,13 ] With these strategies, the capacity of ultrafi ne TiO 2 nanocrystals and nanotubes, for example, is signifi cantly enhanced at lower rates. However, their capacity and cycle life deteriorate dramatically at higher rates. [ 9 , 14-17 ] In this respect, signifi cant efforts have recently been made on the fabrication of anatase TiO 2 nanosheets with exposed highly reactive (001) facets. [ 18 -21 ] These TiO 2 nanosheets are shown to be an excellent host structure for lithium insertion and extraction due to the presence of exposed (001) facets and short path along the [001] direction for lithium ion diffusion.Although the anatase framework undergoes insignifi cant structural distortion during lithium insertion and extraction, [ 22 ] the rate of lithium diffusion is still limited by the narrow space of the host Ti-O lattice. Also, strongly caustic NaOH and corrosive HCl or HF are commonly used for the synthesis of TiO 2 nanomaterials. [ 17,18 ] Beyond these, there is still potential danger in the high-temperature and high-pressure process in low boiling point infl ammable solvents. [ 21 ] Therefore, it is highly desirable but challenging to synthesize novel TiO 2 nanostructures as high-rate anode materials through a facile and green route. As an important group of solvents, ionic liquids (ILs), which exhibit unique properties including low volatility, a wide liquid temperature range, good dissolving ability, and designability, have been intensively used in organic synthesis, catalysis, and inorganic nanomaterials synthesis. [23][24][25][26] This inspires us to design a facile ILs-based synthetic system to prepare an attractive framework for high-effi ciency lithium storage.One such framework of TiO 2 active materials is ultrathin 2D nanosheets, which allow ultrafast surface lithium storage due to maximized Li + ion diffusion and electron transport and the elimin...

Ultrathin Anatase TiO2 Nanosheets Embedded with TiO2‐B Nanodomains for Lithium‐Ion Storage: Capacity Enhancement by Phase Boundaries

“…This capacity loss is relatively low compared to those in previous reports, in which nanostructured electrode materials or low temperaturetreated TiO 2 materials show a fi rst irreversible capacity loss of 20%−40%. [ 2,48 ] One possible reason to the fi rst-cycle capacity loss is presented as follows. The annealing of hydrogen titanate at 550 °C did not completely eliminate the surface impurities.…”

Sandwich‐Like, Graphene‐Based Titania Nanosheets with High Surface Area for Fast Lithium Storage

“…This phenomenon is similar to that reported for nanostructured titania with high capacity, in which an additional surface lithium storage mechanism exists. [ 11 ] Thereby, such surface lithium storage combined with the classic interlayer storage gives rise to a high capacity of 202 mAh g − 1 for G-TiO 2 nanosheets during the initial charging process. Although this value is almost the same as that of TiO 2 nanosheets without graphene at the fi rst cycle (Figure S4), the capacity loss between G-TiO 2 and TiO 2 becomes large as the cycle number is increased (Figure 4 c), demonstrating that the graphene layers in titania nanosheets play an essential role for the improvement of the cycle performance.…”

Synthesis of Uniform Layered Protonated Titanate Hierarchical Spheres and Their Transformation to Anatase TiO2 for Lithium‐Ion Batteries

“…[35] Moreover, it is highly possible for organic species to intercalate into the interlayer spacing of the layered structure. [39] We further investigated the effects of synthesis parameters on the structure of the LTHSs. It was found that the size and morphology of LTHSs are tunable by controlling Scheme 1.…”