The application of plasma treatment for Ti3+ modified TiO2 nanowires film electrode with enhanced lithium-storage properties

Abstract

Hydrogen plasma processing offers improved thermodynamics, kinetics and optimal reductive environment over conventional, thermal processing. In the current work, we report the first demonstration of hydrogen plasma treatment as a simple and effective strategy to fundamentally improve the performance of TiO2 nanowires for lithium storage. In comparison to pristine TiO2 nanowires, the hydrogen plasma treated TiO2 (H-TiO2) samples show substantially enhanced electron conductivity due to Ti3+ introduction, which are successfully confirmed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and four-probe testing instrument. More importantly, the H-TiO2 electrode exhibits a higher rate capability and better reversibility. At charge/discharge current of 200, 800, 1600 and 3350mA/g (10C), the discharge capacity of the H-TiO2 electrode is 200, 162, 144 and 130mAhg−1. After 200 cycles at current of 200mA/g, its capacity retention was 99.8% with almost no capacity fading. The electrochemical impedance spectra analyses and theoretical energy calculations using density functional theory (DFT) finally suggest that the hydrogenation process not only improves electronic conductivity due to the formation of Ti3+ in the hydrogenation process but also dramatically augments lithium-ion mass transport within the crystalline lattice due to the introduction of Ti3+.