Layered Hydrogen Titanate Nanowires with Novel Lithium Intercalation Properties

Abstract

Layered hydrogen titanate nanowires were synthesized from TiO2 via an alkaline−hydrothermal process and subsequent acid treatment. The average diameter of as-prepared nanowires is about 100 nm with a uniform interlayer spacing of 0.81 nm. The framework of this hydrogen titanate nanowires holds the composition of H2Ti3O7 as determined by thermogravimetric analysis. The nanostructured electrode made from these nanowires shows large lithium intercalation capacity (reversible lithium intercalation with Li0.71H2/3TiO7/3), high discharge/charge rate capability, and excellent cycling stability, as revealed by galvanostatically charge/discharge cycling tests. The detailed cyclic voltammetric investigation, however, indicates that the hydrogen titanate nanowires show pseudocapacitive characteristic during the Li+ insertion process. The novel electrochemical properties of hydrogen titanate nanowires are attributed to the open layered structure with a much larger interlayer spacing than normal intercalation compounds for commercial lithium ion batteries. The layered hydrogen titanate nanowires with unique electrochemical performance may become a promising lithium intercalation material for high-energy rechargeable lithium ion batteries and electrochemical supercapacitors.

Protonated Titanates and TiO2 Nanostructured Materials: Synthesis, Properties, and Applications

“…[104] Nanofibrous titanate materials have been more extensively studied than nanotubular ones for lithium-battery applications. [38,101,105] These materials include protonated titanate nanofibers [106] produced by alkaline hydrothermal treatment followed by acid washing, spinel Li 4 Ti 5 O 12 nanofibers [107] produced from protonated titanate nanofibers by hydrothermal ion exchange, nanofibers of TiO 2 -B, [39,44,108] and titanate nanofibers calcined at 400°C. [109] The typical cyclic voltammogram of titanate nanofibers shows several pairs of peaks in the range of voltage 1.5 to 2.0 V relative to Li + /Li.…”

“…The amplitude of some of these peaks lineally depends on the potential sweep rate, whereas the amplitude of others has a square-root dependence on sweep rate, [38,105] indicating the pseudocapacitative and external diffusion-controlled nature of processes. The lithium insertion coefficient, x varies from 0.71 [106] to 0.91 [101] for nanofibrous structures.…”

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

“…Although LPTs have not been investigated as extensively as pure TiO 2 (anatase TiO 2 in particular) for different applications, they have already been demonstrated to possess great application potential in many areas such as ion adsorption, acid-based catalysis, and intercalation capability in addition to photocatalysis, lithium-ion batteries, and solar cells. [14][15][16][17][18][19] Moreover, from the perspective of materials synthesis, LPTs are very important because they could serve as unique precursors for the synthesis of different nanostructured TiO 2 -based functional materials. [20,21] Besides the sporadic reports on the direct synthesis of single-or multiple-layered protonated titanate nanosheets, [18,22] traditional alkaline hydrothermal methods usually result in alkali metal titanates with one-dimensional (1D) structures (for example, nanotubes, nanobelts, and nanorods), [23][24][25] which require an additional ion-exchange step to transform to their protonated forms.…”

Elongated Titanate Nanostructures and Their Applications

“…The use of nanostructured titanates and TiO 2 significantly improves the rate of the diffusion of intercalated lithium ions because of their small size and the featured crystal structure of the material, which provides sufficient space (interlayer spacing in the wall) for ionic transport. Higher capacity than that of P25 [107] 190 300 [108] 130 2500 [109] TiO 2 -(B) NT 240 50 Higher capacity than that of P25 [111] TiO 2 -(B) NF 200 200 Higher capacity than that of P25 [112,113] 100 2000 TiO 2 (anatase) NR 190 50 Plateau in current vs. potential curve [111,115] 240 36 NiO/TiO 2 -(B) NT 240 100 Durability, lower electrical resistance [118] 170 2000 C-TiO 2 (anatase) NR 204 70 Lower resistance, plateau in current vs. potential curve [116] Co-TiNF 350 50 Intercalated Li affects magnetic properties [117] Co-TiO 2 (anatase) NF 140 50 Ag/ TiNT 190 50 Higher cycling stability at higher discharge rate [119] 160 600 Sn/TiNT 312 30 SnLi alloying in pores of TiNT [120] TiO 2 -(B) NT 296 25 Effect of electrode thickness on the discharge kinetics [121] TiO 2 (anatase) NR 215 25…”

“…At the present time, the following elongated nanostructures have been studied for lithium storage: titanate nanotubes [104][105][106] (TiNT), titanate nanofibres [107][108][109][110] (TiNF), TiO 2 -(B) nanotubes [41,111] nanofibres [112][113][114] and TiO 2 (anatase) nanorods. [111,115] The last three nanostructures were obtained by calcination of the protonated forms of the corresponding titanates (see Figure 3).…”