A Ti-site deficient spinel Li2CoTi3O8 anode with superior cycling performance for lithium-ion batteries

A series of Ti-site deficient Li2CoTi3O8-based materials are synthesized by a simple citric-nitrate method. The elemental ratio is determined by X-ray diffraction (XRD) Rietveld refinement and X-ray photoelectron spectroscopy (XPS) measurement. Ti-deficiency is compensated by the increase of Co element valence, resulting in the excess Co3+/Co2+ and Co4+/Co2+ redox processes during cycling that allows more lithium-ions insertion in the structure, thus endowing the material with a higher theoretical specific capacity. Besides, the Ti-deficiency introduction significantly enhances both the electronic and ionic conductivities and thus the electrode reaction kinetics. The synthesized Li2CoTi2.703O8 anode displays a higher specific capacity (similar to 320 mAh g(-1) at 100 mA g(-1)) and a better rate-capability (185 mAh g(-1) at 8000 mA g(-1); no capacity decay over 500 cycles). The Ti-deficiency design concept in this work can be extended for the development of other energy storage materials with high energy/power density.