Electrodeposition of Ag nanoparticles onto bamboo-type TiO₂ nanotube arrays to improve their lithium-ion intercalation performance

Abstract

Bamboo-type TiO₂ nanotube arrays prepared via anodic oxidation are modified with Ag nanoparticles by pulsed electrochemical deposition, for improved lithium-ion intercalation property as the anode material in lithium-ion batteries. Heat treatment converts as-formed nanotubes into anatase for Ag deposition. Bare and Ag-modified nanotubes are cycled at a current density of 800 μA cm⁻² between 1.0 and 2.6 V (vs. Li/Li⁺). All Ag-modified nanotubes exhibit significantly improved or even doubled areal discharge capacities and better cycleability compared to bare nanotubes. Particularly, the nanotubes modified using 100 Ag deposition cycles deliver the highest initial discharge capacity of 199.6 μA h cm⁻² and the largest final discharge capacity of 131.7 μA h cm⁻² after 50 electrochemical cycles, while bare nanotubes exhibit an initial capacity of 93.5 μA h cm⁻² and a final discharge capacity of 54.8 μA h cm⁻². The former also exhibits 10 % higher capacity retention efficiency than the latter. In addition, an increase in the capacity of modified nanotubes is observed with more Ag deposition, but superfluous Ag content yields reduced capacities due to slower Li-ion transfer inside. Finally, kinetic characteristics of TiO₂ nanotubes are explored using cyclic voltammetry to understand the origin of improvements in electrochemical properties of Ag-modified nanotubes.