Heavily Cr3+-modified Li4Ti5O12: An advanced anode material for rechargeable lithium-ion batteries

Abstract

Heavily Cr[Formula: see text]-modified Li4Ti5O[Formula: see text] powders with a designed nominal composition of Li3Cr7Ti2O[Formula: see text] have been prepared by one-step solid-state reaction. X-ray diffraction (XRD) combined with Rietveld refinement indicates that these powders contain 96.5[Formula: see text]wt.% spinel Li[Formula: see text]Cr[Formula: see text]Ti[Formula: see text]O4 and 3.5[Formula: see text]wt.% Cr2O3. Due to the combination of Ti[Formula: see text]/Ti[Formula: see text] and Cr[Formula: see text]/Cr[Formula: see text] redox couples in Li[Formula: see text]Cr[Formula: see text]Ti[Formula: see text]O4 and the existence of Cr2O3, the composite exhibits a large first-cycle discharge capacity of 315[Formula: see text]mAh[Formula: see text] at a small current density of 62.5[Formula: see text]mA[Formula: see text]. Li[Formula: see text]Cr[Formula: see text]Ti[Formula: see text]O4 shows an improved Li[Formula: see text] ion diffusion coefficient and electronic conductivity, respectively arising from the small O[Formula: see text] ion fractional coefficient and unpaired 3d electrons in Cr[Formula: see text] ions. The majority of Cr2O3 is reduced to Cr after the first two lithiation processes, which benefits the electrical conduction between the Li[Formula: see text]Cr[Formula: see text]Ti[Formula: see text]O4 particles. Consequently, the composite exhibits a good rate performance and cyclability. Its capacity at 1000[Formula: see text]mA[Formula: see text] is as large as 141[Formula: see text]mAh[Formula: see text] with large retention of 90.1% after 100 cycles.