Insights into the Li Diffusion Dynamics and Nanostructuring of H₂Ti₁₂O₂₅ To Enhance Its Li Storage Performance

Abstract

Dodecatitanate H 2 Ti 12 O 25 crystal has a condensed layered structure and exhibits noteworthy Li storage performance that makes it an anode material with great potential for use in Li-ion batteries. However, an unknown Li diffusion mechanism and a sluggish level of Li dynamics through elongated diffusion paths inside this crystal has impeded any forward development in resolving its limited rate capability and cyclic stability. In this study, we investigated the Li diffusion dynamics inside the H 2 Ti 12 O 25 crystal that play an essential role in Li storage performance. A study of density functional theory combined with experimental evaluation confirmed a strong dependence of Li storage performance on its diffusion. In addition, a nanostructured H 2 Ti 12 O 25 containing a bundle of nanorods is developed via the introduction of a kinetic gap during the structural transformation, which conferred a significantly shortened diffusion time/length for Li in H 2 Ti 12 O 25 . The nanostructured H 2 Ti 12 O 25 has high specific capacity (∼230 mAh g −1 ) and exhibits enhanced cyclic stability and rate capability compared with conventional bulky H 2 Ti 12 O 25 . The H 2 Ti 12 O 25 proposed in this study has high potential for use as an anode material with excellent safety and stability.

High Lithium Insertion Voltage Single‐Crystal H2Ti12O25 Nanorods as a High‐Capacity and High‐Rate Lithium‐Ion Battery Anode Material

“…As observed in Figure a–c, the various crystal facets of H 2 Ti 12 O 25 in the [1 0 0], [0 1 0], and [0 0 1] directions correspond to different atom‐bonding models. It was reported that moving along the [0 1 0] direction ( c axis) may correspond to a low‐energy barrier pathway for Li + ‐ion diffusion . Hence, diffusion along the [0 1 0] direction of the (0 1 0) facet may present the lowest energy barrier pathway for Li + ‐ion diffusion.…”

“…Such a result demonstrates the excellent cyclic stability of m‐H 2 Ti 12 O 25 , especially at an ultrahigh charging and discharging current density of 20C. Such outstanding high‐rate characteristics of the m‐H 2 Ti 12 O 25 nanorods is, to the best of our knowledge, much greater than those of currently reported H 2 Ti 12 O 25 listed in Table S2.…”

“…Furthermore, relative to that shown by Li 4 Ti 5 O 12 , H 2 Ti 12 O 25 shows an outstanding theoretical capacity of 274.6 mAh g −1 , higher protonic conductivity of 8.71×10 −9 S cm −1 , and better cycle performance . In addition, the low exothermic behavior of H 2 Ti 12 O 25 also guarantees safety and thermal stability . These outstanding features are conducive in promoting the application of H 2 Ti 12 O 25 as a lithium‐ion battery anode to power hybrid electric vehicles.…”

“…prepared H 2 Ti 12 O 25 particles (≈1 μm) with Na 2 Ti 6 O 13 as the precursor by the soft‐chemical method, and these particles delivered a reversible capacity of 190 mAh g −1 at 1C. Park et al . synthesized H 2 Ti 12 O 25 nanobundles with an initial discharge capacity of >240 mAh g −1 at 0.05C by recrystallizing TiO 2 to Na 2 Ti 3 O 7 .…”

“…successfully prepared H 2 Ti 12 O 25 nanorods with a diameter of 50–250 nm by a hydrothermal process in an alkaline environment, and this material delivered an initial discharge capacity of 204 mAh g −1 at 1C. Despite the various H 2 Ti 12 O 25 systems reported in recent years, inherently sluggish Li + insertion/extraction into the structures and the significant capacity decay after long‐term cycling have inevitably limited their commercial application as a result of their poor rate performance and low cyclic life …”