Improving High-Rate and Long-Life Cycling of Li4Ti5O12 Anode by Dual Doping of Cd2+ and Ge4+

Abstract

A kinetically favored Cd2+ and Ge4+ dual-doped lithium titanate (Li4Ti5O12) anode material is designed for lithium-ion batteries (LIBs). Rietveld refinement reveals that introducing a 0.05 wt.% of Cd2+ at Li(8a) and Ge4+ at Ti(16d) sites brings no structural change in the spinel Li4Ti5O12. Scanning transmission electron microscopy (STEM) identifies Cd2+ and Ge4+ are homogenously doped in the Li4Ti5O12 lattice. High-resolution powder diffraction (HRPD) confirmed that Cd2+ and Ge4+ doping in Li4Ti5O12 brings expansion in the lattice, field emission scanning electron microscopy (FE-SEM) shows the reduction in the particle size due to of Cd and Ge in the LTO lattice, and X-ray photoluminescence spectroscopy (XPS) confirms the partial reduction of Ti4+ to Ti3+ ions on the surface of 0.05-Cd-Ge-LTO electrodes to the pristine LTO. Furthermore, the 0.05-Cd-Ge-Li4Ti5O12 electrode exhibits a superior rate performance and delivers a discharge capacity of approximate to 169.1 mAhg(-1) at 0.1 current rates. It is worth mentioning that, the 0.05-Cd-Ge-Li4Ti5O12 electrode brings outstanding cycling stability in Li+ half-cell, having a capacity retention of 98.79% after 300 cycles at 2C. This proves that dual-doping of Cd2+ at Li(8a) and Ge4+ at Ti(16d) sites in the Li4Ti5O12 lattice is an effective approach to obtain superior electrochemical performance as anode material in LIBs.