The electrochemical effect of Al-doping on Li4Ti5O12 as anode material for lithium-ion batteries

Abstract

This work investigates the electrochemical performance of Al-doped Li4Ti5O12 (LTO) on the Li site (Li4-xAlxTi5O12) and Ti site (Li4Ti5-xAlxO12) (x = 0.15), evaluated by galvanostatic charge-discharge tests and the electrochemical impedance spectroscopy. The physical properties of the synthesized materials were determined by XRD, SEM, Raman and XPS analyses. The Al dopant observed on different sites of Li4Ti5O12 showed resultant effects on the morphology, particle size, structural arrangement and crystallinity of the materials. XRD and XPS results showed peak shifts to higher angles and lower binding energies, respectively. Moreover, XPS revealed the majority of Al doped into the Ti site for Li4Ti4.85Al0.15O12 and into the Li site for Li3.85Al0.15Ti5O12. Li4Ti4.85Al0.15O12 has shown much improvement of the reversible capacity and rate capability of LTO without Li deficiency compared with Li3.85Al0.15Ti5O12. Li4Ti4.85Al0.15O12 also demonstrated superior reversible capacity at 0.2 C (172.7 mAh/g), 0.5 C (143.7 mAh/g) and 1 C (132.1 mAh/g). These were comparatively higher than Li4Ti5O12 (154.8, 124.1 and 100.7 mAh/g, respectively) and Li3.85Al0.15Ti5O12 (154.4, 133.6 and 120.3 mAh/g, respectively).