Advanced electrochemical performance of Li4Ti5O12-based materials for lithium-ion battery: Synergistic effect of doping and compositing

Abstract

To improve the rate performance of Li4Ti5O12 (LTO), we employ a doping-compositing synergistic strategy that utilizes Cu2+ to alter intrinsic property and carbon nanotubes (CNTs) to engineer extrinsic conductivity. To realize cost-effective fabrication, solid state processing is adopted in the fabrication of the composite. X-ray diffraction measurement combined with Rietveld refinement shows that all doped samples have a spinel structure with Fd3¯m space group without any impurities, and that both lattice parameter and occupancy of non-Li+ ions in 8a sites increase with the amount of Cu2+ dopant. Through the Cu2+ doping, the electronic conductivity and Li+ diffusion coefficient of the particles are improved by at least two orders of magnitude and four times, respectively. Through further CNTs compositing, the electrical conduction between the particles is enhanced. Between 1.0 and 2.5 V vs. Li/Li+, the specific capacity of Li3.8Cu0.3Ti4.9O12/CNTs composite at 10 C is as high as 114 mAh g−1 with little loss after 100 cycles, whereas that of pristine one is only 11 mAh g−1. The excellent electrochemical performance can be ascribed to its higher electronic conductivity and enhanced lithium ion conductivity in the particles, as well as its improved electrical conduction between the particles.