Lithium Insertion in Nanostructured TiO₂(B) Architectures

Abstract

Electric vehicles and grid storage devices have potentialto become feasible alternatives to current technology, but only if scientists can develop energy storage materials that offer high capacity and high rate capabilities. Chemists have studied anatase, rutile, brookite and TiO2(B) (bronze) in both bulk and nanostructured forms as potential Li-ion battery anodes. In most cases, the specific capacity and rate of lithiation and delithiation increases as the materials are nanostructured. Scientists have explained these enhancements in terms of higher surface areas, shorter Li(+) diffusion paths and different surface energies for nanostructured materials allowing for more facile lithiation and delithiation. Of the most studied polymorphs, nanostructured TiO2(B) has the highest capacity with promising high rate capabilities. TiO2(B) is able to accommodate 1 Li(+) per Ti, giving a capacity of 335 mAh/g for nanotubular and nanoparticulate TiO2(B). The TiO2(B) polymorph, discovered in 1980 by Marchand and co-workers, has been the focus of many recent studies regarding high power and high capacity anode materials with potential applications for electric vehicles and grid storage. This is due to the material's stability over multiple cycles, safer lithiation potential relative to graphite, reasonable capacity, high rate capability, nontoxicity, and low cost (Bruce, P. G.; Scrosati, B.; Tarascon, J.-M. Nanomaterials for Rechargeable Lithium Batteries. Angew. Chem., Int. Ed.2008, 47, 2930-2946). One of the most interesting properties of TiO2(B) is that both bulk and nanostructured forms lithiate and delithiate through a surface redox or pseudocapacitive charging mechanism, giving rise to stable high rate charge/discharge capabilities in the case of nanostructured TiO2(B). When other polymorphs of TiO2 are nanostructured, they still mainly intercalate lithium through a bulk diffusion-controlled mechanism. TiO2(B) has a unique open crystal structure and low energy Li(+) pathways from surface to subsurface sites, which many chemists believe to contribute to the pseudocapacitive charging. Several disadvantages exist as well. TiO2(B), and titania in general, suffers from poor electronic and ionic conductivity. Nanostructured TiO2(B) also exhibits significant irreversible capacity loss (ICL) upon first discharge (lithiation). Nanostructuring TiO2(B) can help alleviate problems with poor ionic conductivity by shortening lithium diffusion pathways. Unfortunately, this also increases the likelihood of severe first discharge ICL due to reactive Ti-OH and Ti-O surface sites that can cause unwanted electrolyte degradation and irreversible trapping of Li(+). Nanostructuring also results in lowered volumetric energy density, which could be a considerable problem for mobile applications. We will also discuss these problems and proposed solutions. Scientists have synthesized TiO2(B) in a variety of nanostructures including nanowires, nanotubes, nanoparticles, mesoporous-ordered nanostructures, and nanosheets. Many of these structures exhi...

Observation of crystalline changes of titanium dioxide during lithium insertion by visible spectrum analysis

“…This reaction is a good example of our method because the electrochemical characteristics of TiO 2 highly depend on their structural parameters such as crystallinity and polymorphs. [11][12][13][14] This phenomenon is well interpreted by general ab initio principles and Maxwell's equations without any empirical limiting factors; therefore, we expect that our method can be applied to general types of materials and reactions.…”

Tuning TiO2nanoparticle morphology in graphene–TiO2hybrids by graphene surface modification

“…[7][8][9] In most of these applications, not only the phase and size of TiO 2 NPs, but also their shape and the extent to which different facets are developed determine the NP activity. [10][11][12] For example, while the {101} facets are the most thermodynamically stable in TiO 2 anatase, the {001} facets are often preferred due to their higher reactivity 13 and higher oxidating ability.…”

Tailoring Iron Oxide Nanostructures for High-Capacity Lithium Storage

“…Therefore, exploring alternative anode materials with high capacity and good safety has attracted growing attention. [4][5][6][7][8][9][10][11][12][13][14][15][16] Transition metal oxides (TMOs) represent a promising family of high-capacity anode materials for LIBs. [17] Based on a conversion reaction mechanism, they are able to provide a specific capacity of 700-1000 mAh·g -1 , which is two to three times to that of graphite.…”