Synergistic storage of lithium ions in defective anatase/rutile TiO2 for high-rate batteries

Abstract

Fabrication of heterostructured materials is a strategy to boost the charge-transfer kinetics and the performance of high-rate lithium storage. Here, a facile, lowtemperature method for the synthesis of high-area TiO2 nanospheres containing both anatase and rutile phases is described. The as-prepared materials contain a high concentration of oxygen vacancies facilitating electron conduction in the anatase phase and theoretical calculations provide evidence of a low energy barrier for Li + transport in the rutile phase. The synergy between the two phases renders the shared conduction of electrons through anatase and Li + ions via rutile at high-current rates, leading to the anodes that outperform the alternate TiO2 systems when the combination of capacity at high current densities and cycle stability are considered, displaying a capacity of 95.4 mAh g-1 at 10 A g-1 and a 97.2 % retention of capacity over 500 cycles at 1 A g-1 .

Recent Developments of Nanomaterials and Nanostructures for High‐Rate Lithium Ion Batteries

“…[182] As an example, TiO 2 nanotubes with high surface area (235 m 2 g À 1 , estimated by BET) based on the heterostructure of anatase and rutile phases were synthesised by a combination of low-temperature hydrothermal reaction at 150°C and an annealing process at 300°C. [183] The interfacial boundaries were observed with the presence of distortion and defects in the lattice cross-section of both phases. Density functional theory calculations were conducted to investigate the properties of ion migration in anatase and rutile phases, as shown in schemes of ion intercalation and migration in Figure 19 a.…”

“…As an example, TiO 2 nanotubes with high surface area (235 m 2 g −1 , estimated by BET) based on the heterostructure of anatase and rutile phases were synthesised by a combination of low‐temperature hydrothermal reaction at 150 °C and an annealing process at 300 °C . The interfacial boundaries were observed with the presence of distortion and defects in the lattice cross‐section of both phases.…”

“…In that report, the authors argued that the synergistic effects offered by the unique heterostructure facilitated the electronic transport in anatase phase as well as ion migration in rutile phase, and excellent rate performance was achieved under ultrahigh current rates (95 mAh g À 1 at 60 C, 1 C = 168 mA g À 1 ). [183] In addition to creating heterostructures, TiO 2 based nanocomposites were formed by the incorporation of multiwalled carbon nanotubes (MWCNTs), which was reported to enhance the rate performance as well as mass loading (up to above 6 mg cm À 2 ) of anode at the same time. [184] The synthesised hierarchical anatase TiO 2 micro-clews are in tetragonal shape (6 μm in diameter) and they are embedded in the network of MWCNTs by strong interface coupling, as shown in Figure 19b.…”

“…(a) Schematic diagram of lithium ion migration in anatase and rutile TiO 2 and the corresponding correlation between energy and migration periodic distance in each phase. [183] Reproduced with permission from Ref. [183].…”

Effect of Vinylene Carbonate Electrolyte Additive on the Surface Chemistry and Pseudocapacitive Sodium-Ion Storage of TiO2 Nanosheet Anodes

“…Hierarchical TiO 2 nanosheets composed of anatase and bronze nanocrystallites were synthesized through a solvothermal method, followed by controlled heat treatment. Ethylene glycol was used as solvent to facilitate nanosheet formation through the interaction of OH groups of glycol with Ti-OH groups [48,49]. This resulted in the free energy change of the TiO 2 crystallographic planes and an associated anisotropic crystal growth [29,49].…”