Altering the Alkaline Metal Ions in Lepidocrocite-Type Layered Titanate for Sodium-Ion Batteries

Abstract

The relatively large ionic radius of the Na ion is one of the primary reasons for the slow diffusion of Na ions compared to that of Li ions in de/intercalation processes in sodium-ion batteries (SIBs). Interlayer expansion of intercalation hosts is one of the effective techniques for facilitating Na-ion diffusion. For most ionic layered compounds, interlayer expansion relies on intercalation of guest ions. It is important to investigate the role of these ions for material development of SIBs. In this study, alkalimetal ions (Li + , Na + , K + , and Cs + ) with different sizes were intercalated into lepidocrocite-type layered titanate by a simple ion-exchange technique to achieve interlayer modulation and those were then evaluated as anode materials for SIBs. By controlling the intercalated alkaline ion species, basal spacings of layered titanates (LTs) in the range of 0.68 to 0.85 nm were obtained. Interestingly, the largest interlayer spacing induced by the large size of Cs did not yield the best performance, while the Na intercalated layered titanate (Na-ILT) demonstrated a superior performance with a specific capacity of 153 mAh g −1 at a current density of 0.1 A g −1 . We found that the phenomena can be explained by the high alkaline metal ion concentration and the efficient utilization of the active sites in Na-ILT. The detailed analysis indicates that large intercalating ions like Cs can hamper sodium-ion diffusion although the interlayer spacing is large. Our work suggests that adopting an appropriate interlayer ion species is key to developing highly efficient layered electrode materials for SIBs.

Solvent-Driven Self-Assembly of One-Dimensional Lepidocrocite Titanium-Oxide-Based Nanofilaments

“…Since these materials are 1D, they are essentially all surface, presenting two primary types of O environmentsboth bridging (O 2 ) and terminal (O 1 )denoted in Figure B. In accordance with the literature, , TMA + cations are presumably localized between O 2 sites on adjacent 1DLs. However, the potential for protons to localize on these terminations cannot be dismissed.…”

“…In many other studies, it is much wider, which, in some cases, results in tubular morphologies. 10−13 Notably, 1DLs require the presence of tetramethylammonium hydroxide (TMAOH) during formation, and when alkali hydroxides are used instead of TMAOH, phases similar to the alkali LTs reported in the literature 4,8 are obtained. 22 As such, it is believed that the TMA + cation acts as a templating agent, 23 upon which the formation of 1DLs depends.…”

“…Lepidocrocite titanates (LTs) are layered structures that are comprised of edge-sharing TiO 6 octahedra that require cations to exist between the layers for charge balance. , LTs can undergo cation exchange, which expands their versatility over titania, their neutral counterpart, to include important applications like dye sensitized solar cells and batteries . By exchanging metal ions for the native cation from the synthesis, LTs can act as catalyst supports for the incoming ion .…”

“… 1 , 2 LTs can undergo cation exchange, which expands their versatility over titania, their neutral counterpart, to include important applications like dye sensitized solar cells 3 and batteries. 4 By exchanging metal ions for the native cation from the synthesis, LTs can act as catalyst supports for the incoming ion. 5 Like titania, they can also be used as photocatalysts.…”

Structure, Properties, Preparation, and Application of Layered Titanates

“…The addition of organic macromolecules can expand the interlayer distance, which can promote the occurrence of exchange, intercalation, and exfoliation . The typical protonated layered titanate with lepidocrocite structure is very easy to undergo the above reaction because of its low interlayer charge density, so it is used as a precursor in many fields. − However, the high charge density between layers of layered niobate makes it difficult for bulky ions or molecules to intercalate into the interlayer, and an intercalation reaction is not easy to occur …”