Oxygen Vacancy Engineering in Titanium Dioxide for Sodium Storage

Abstract

Titanium dioxide (TiO2) is a promising anode material for sodium‐ion batteries (SIBs) due to its low cost, natural abundance, nontoxicity, and excellent electrochemical stability. Oxygen vacancies, the most common point defects in TiO2, can dramatically influence the physical and chemical properties of TiO2, including band structure, crystal structure and adsorption properties. Recent studies have demonstrated that oxygen‐deficient TiO2 can significantly enhance sodium storage performance. Considering the importance of oxygen vacancies in modifying the properties of TiO2, the structural properties, common synthesis strategies, characterization techniques, as well as the contribution of oxygen‐deficient TiO2 on initial Coulombic efficiency, cyclic stability, rate performance for sodium storage are comprehensively described in this review. Finally, some perspectives on the challenge and future opportunities for the development of oxygen‐deficient TiO2 are proposed.

Hydrogenated Anatase and Rutile TiO2 for Sodium-Ion Battery Anodes

“…The improved cycling stability of TiO 2 after hydrogenation is attributed to the increased conductivity and promoted charge transfer and Na + transport within the electrode, which facilitate Na + insertion/extraction and thus reaction reversibility. Moreover, the OVs provide a more open architecture for better accommodation of Na + ions during charging/discharging without structural collapse. ,, Such high electrode durability is vital for practical large-scale energy storage applications.…”

“…The incorporation of defects, such as oxygen vacancies (OVs) and trivalent titanium (Ti 3+ ), can modify the electronic structures and provide more open channels for Na + transport. , The OVs can act as shallow donors, decreasing the bandgap and raising the density of states below the Fermi level for TiO 2 . , The electronic conductivity can thus be increased. Their presence can also enhance the pseudocapacitive charge-storage performance. , Several methods have been proposed to introduce OVs in the TiO 2 matrix, such as vacuum treatment, pyrolysis/Mg reduction, H 2 plasma treatment, hydrothermal treatment, chemical reduction, and electrochemical treatment . Some procedures involve extra chemicals and reaction solvents.…”

“…Their presence can also enhance the pseudocapacitive charge-storage performance. 40,42 Several methods have been proposed to introduce OVs in the TiO 2 matrix, such as vacuum treatment, 43 pyrolysis/Mg reduction, 44 H 2 plasma treatment, 40 hydrothermal treatment, 45 chemical reduction, 38 and electrochemical treatment. 46 Some procedures involve extra chemicals and reaction solvents.…”

Surface engineering of anode materials for improving sodium-ion storage performance

“…Metal oxides, such as titanium dioxide (TiO 2 ), [59][60][61][62][63] tin dioxide (SnO 2 ), 64,65 vanadium oxide (V 2 O 5 ), 66 and sodium titanate (Na 2 Ti 3 O 7 ) 67,68 are promising anode candidates for NIBs. For example, TiO 2 has merits of excellent cycling stability and low cost.…”

“…Introduction of OVs on the surface of metal oxides can signicantly enhance electronic conductivity and lower the sodiation energy barrier to facilitate Na ion intercalation and migration kinetics, achieving enhanced charge transport kinetics. 59,74 The typical OV fabrication methods include treatment using a reductant (e.g., NaHB 4 or urea) 61,63,67 or in a reductive atmosphere (e.g., H 2 ), 68 and carbothermal reduction. 65 Ji and co-workers employed NaBH 4 as a reductant to treat anatase to introduce surface OVs into TiO 2 .…”