Tailoring of Morphology and Crystalline Structure of Nanoporous TiO₂–TiO–TiN Composite Films for Enhanced Capacity as Anode Materials of Lithium-Ion Batteries

Abstract

We report a novel three-dimensional nanoporous TiO 2 -TiO-TiN (Np-TTT) ternary composite film with cylindrical pores of diameter φ30-50 nm and laminated tier thickness of 10-30 nm, which was fabricated straightforwardly on a Ti foil via a one-step anodization in an aqueous nitric electrolyte. The Np-TTT composite films consisted of amorphous TiO 2 matrix, quasi-crystalline TiO, and a small amount of TiN (∼2 at% as N), which are formed simultaneously during anodization through electrochemical and/or chemical reactions in the nitric electrolyte. As a binder-free and auxiliary-component-free anode material for lithium-ion batteries, the capacity and rate performance of the Np-TTT anodes were dependent on both the anodizing conditions and crystalline structure. Particularly, the Np-TTT composite film (∼800 nm-thick) that was annealed at 250 • C for 1 h exhibited the highest areal specific capacity of 440 μAh cm −2 at the 1 st cycle, a high retention of 95% from the 2 nd to the 50 th cycles, and a Coulombic efficiency of approximately 100%. The enhanced capacities of the Np-TTT composite films can be primarily attributed to the synergetic effect of the inclusion of conductive TiN component in bulk TiO 2 matrix films, the active TiO with quasi-crystalline cubic phase, and nanoporous structure with high surface area. Rechargeable lithium-ion batteries (LIBs) are considered one of the most important energy storage device and widely used in various potable electronic devices like mobile phones, cameras, and laptops, owing to their superior energy densities (120-180 W h kg -1 ), low memory effect, long life cycle, and low environmental impacts. 1-3Currently, their applications are quickly expanding to electric vehicles (EVs) and plug-in hybrid electric vehicles (HEVs), where much higher energy densities (above 500 W h kg -1 ) are necessary to supply sufficient power for long-distance driving, accelerating a vehicle quickly, and recovering energy during braking. [4][5][6] However, the safety issue of LIBs is becoming a severe problem because the conventional graphite anode (0.1 V vs. Li + /Li) is prone to experience the growth of lithium dendrites after repetitive charge/discharge, which hinders the development of large-capacity LIBs in EV and HEV applications. 4,6,7 Titanium dioxide materials have attracted increasing attention as promising LIB anode materials for replacing conventional graphite anodes owing to their superior features such as safety improvement, low cost, cycling stability, and satisfactory chemical and thermal stabilities.3,7-14 Particularly, TiO 2 exhibits very small volume expansion (<4%) and, more importantly, operates at a relatively high working voltage (1.7 V vs. Li/Li + ) during Li + insertion/extraction, which eliminates the influence of the solid electrolyte interface layer and avoids the risk of lithium electrodeposition from electrolytes in LIBs, thus further ensuring the cycling stability and safety of batteries. However, the poor Li ion diffusivity and low electronic conductivity of TiO 2 ma...

Fabrication and Electrochemical Performance of TiO2–TiN/Sn–SnO2 Composite Films on Ti for LIB Anodes with High Capacity and Excellent Conductivity

“…After anodization for 90 min in HNO 3 -LiNO 3 solution, the Np-TT specimen possessed a nanoporous structure with straight pores with diameters of 70-100 nm (Figure 1b). The pore size of the anodic titania film was larger than that previously reported (30-50 nm diameter) [34] because of the prolonged anodizing time. The increased pore size is beneficial for the subsequent electrodeposition of Sn ions.…”

“…The anodization process was successful for a longer time than that in previous research, and a thicker oxide film was formed on the entire surface of the Ti plate. [ 34 ] In addition, the voltages of Sn cathodic electrodeposition was ≈0.18 and 0.14 V for Sn 2+ and Sn 2+ + Sn 4+ solutions, respectively, which is about 1/140 of that in anodization. This indicates the improved conductivity of the Np‐TT film formed by smart anodization, [ 35 ] which is the decisive factor to enable the successive cathodic electrodeposition of metals, and this is first reported by the present study.…”

“…In our previous studies, we investigated the formation of nanoporous TiO 2 -TiO-TiN (Np-TTT) composite films on Ti plates via smart anodization in a nitric acid-based electrolyte. [33,34] The films exhibited better conductivity owing to the synergetic effect of conductive TiN in the bulk nanoporous TiO 2 matrix film, but the capacity is limited to that of the TiO 2 matrix and the conductivity also needs to be improved. Recently, we also developed a novel approach for fabricating SnO 2 -modified Np-TTT composite films on Ti sheets via a single hybrid anodization process.…”

Spontaneously Formed Mott‐Schottky Electrocatalyst for Lithium‐Sulfur Batteries

“…The two peaks located at 455.9 and 461.6 eV are due to the formation of the TiN bond. [ 17 ] While the peaks located at 457.3 and 463.0 eV correspond to TiNO bonds, the two stronger double peaks at 458.9 and 464.6 eV derive from the formation of TiO 2 . [ 18 ] Besides, a weak peak at ≈460.4 eV can be also observed, which can be attributed to Ti n O 2− n .…”

High-Performance and Binder-Free Anodized ZrTiAlV Alloy Anode Material for Lithium Ion Microbatteires

“…TiO 2 -based materials have recently attracted considerable interest as emerging anode candidates of lithium ion batteries (LIBs) due to their low cost and excellent cycling stability. − However, their performance in electron devices is not so laudable, which is limited by poor electron transport and low Li + diffusion. − To overcome these drawbacks and meet the requirement of high capacity, various nanogeometries of TiO 2 have been designed, such as nanowires, nanoparticles, nanorods, and nanotubes. ,− Nanotube designs are good for unidirectional electron transport and increase the available specific surface for better contact with the electrolyte. The nanotube structure can be synthesized via many methods: atomic layer deposition, template-assisted method, sol–gel synthesis, and so on. − Nevertheless, anodization as one of the most straightforward and fastest method has been widely used to prepare such nanostructured arrays. − Anodization can directly grow the nanotube structure on the metal instead of producing a slurry mixture with a polymer binder, conductive agent, and solvents. Furthermore, the optimized tube length and diameter can support a pathway and enough surface area for electron transport and electrolyte contact point. − …”