Defect-engineered TiO2 nanocrystals for enhanced lithium-ion battery storage performance

• Published in: Applied surface science 2022-10, Vol.598, p.153869, Article 153869
• Main Authors: Wang, Guanzheng, Gao, Wei, Zhan, Zhaolin, Li, Zulai
• Format: Article
• Language: English
• Subjects: Hydrothermal method; Lithium-ion batteries; Oxygen defects; TiO2 nanocrystals
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2022.153869

EPR spectra of sintered samples. The reduced sample produces two strong EPR signals at g = 2.0010 and 1.9478, corresponding to the presence of oxygen defects and Ti3+, respectively. A more intense signal is generated with increasing reductive sintering time. The intensity ratio of the peak area after 3, 5 and 10h of reductive sintering was calculated to be ∼1:6.63:13.53. This shows that the concentration of oxygen defects gradually increases with increasing reductive sintering time. [Display omitted] •Sintering in a 5% H2 + 95% Ar atmosphere produced oxygen defects in TiO2 nanocrystals.•Oxygen defect concentration in the TiO2 nanocrystals can be controlled.•Reductive sintering converted Ti4+ to Ti3+ due to the generation of oxygen defects in TiO2.•The presence of oxygen defects and Ti3+ in TiO2 improved the its performance of electrode material. TiO2 nanocrystals containing oxygen defects were successfully prepared by a hydrothermal method with reductive sintering in a 5% H2 + 95% Ar mixed atmosphere. The high-resolution transmission electron microscopy and X-ray diffraction results showed that the prepared samples were all anatase TiO2. X-ray photoelectron spectroscopy analysis showed that the reductive sintering converted Ti4+ to Ti3+. The Ti3+/Ti4+ molar ratio of the TiO2 nanocrystals increased with increasing sintering time. The results of the electron paramagnetic resonance spectroscopy analysis showed that the reduced and sintered TiO2 nanocrystals produced strong signals at g = 2.0010 and 1.9478, corresponding to the presence of oxygen defects and Ti3+, respectively. Furthermore, stronger signals were generated with increasing sintering time, indicating a progressively higher concentration of oxygen defects. The TiO2 nanocrystalswere used as anode materials for lithium-ion batteries. One sample, H-TiO2-5, containing a moderate concentration of oxygen defects, presented a higher lithium ion diffusion coefficient (D = 5.1 × 10-13 cm2s−1) compared to the other TiO2 samples. This sample had a Ti3+/Ti4+ molar ratio of 0.179 and excellent cycling stability after 100 cycles. The discharge capacity was 124 mAh.g−1 after 500 cycles at a current density of 1C, which means that it has good cyclic stability.