Oxygen vacancy-modulated zeolitic Li4Ti5O12 microsphere anode for superior lithium-ion battery

Abstract

Spinel Li4Ti5O12 (LTO) is a promising anode material for state-of-the-art high-power lithium-ion batteries (LIBs) owing to its “zero strain” characteristics during fast charging/discharging, long cycle life, and high rate capability. However, the poor ionic/electronic conductivity and sluggish ionic diffusion coefficient of LTO restrict its practical utility. Porous zeolitic LTO (Z-LTO) microspheres were synthesized herein as anode materials for LIBs using TiO2 and LiOH∙H2O via a hydrothermal method combined with Ar/H2 thermal treatment. The increased concentration of Ti3+ self-doping-derived oxygen vacancies in as-synthesized Z-LTO and porous microspherical Z-LTO aggregates greatly improved the electronic conductivity and structural stability. These features contributed to achieving much higher discharge capacities of ∼210 and ∼180 mAh g−1 at 0.5 C and 1 C rates, respectively, as well as excellent ultra-high rate capability of 45 mAh g–1 at 50 C rate, while still maintaining the outstanding long-life cyclic stability (∼181 mAh g−1 at 5 C rate after 2000 cycles), with 90% capacity retention, compared to commercial LTO (C-LTO). Charge contribution kinetics analysis indicated that the lithium storage mechanisms in Z-LTO, particularly at a high rate, were dominantly diffusion-controlled due to the larger ion-diffusion ability (DLi ≈ 4.18 × 10−8 cm2 s−1). This finding confirms that the generation of surface defects by creating Ti3+/Ti4+ pairs and oxygen vacancy engineering in LTO is an effective approach for enhancing the ion/electron mobility, which can be extended to boost the battery performance of other materials with low ionic conductivities for advanced energy storage systems.