Li2TiSiO5: a low potential and large capacity Ti-based anode material for Li-ion batteries

Abstract

To date, anode materials for lithium-ion batteries (LIBs) have been dominated by carbonaceous materials, which have a low intercalation potential but easily allow lithium dendrites to form under high current density, leading to a safety risk. The other anode material, the “zero-strain” spinel-structured Li₄Ti₅O₁₂, with a ∼1.5 V vs. Li⁺/Li intercalation potential, exhibits excellent cycling stability and avoids the issues of dendrite growth and Li plating. The low capacity and high voltage of Li₄Ti₅O₁₂, however, result in low energy density. Herein, we report a new and environmentally friendly anode material, Li₂TiSiO₅, which delivers a capacity as high as 308 mA h g⁻¹, with a working potential of 0.28 V vs. Li⁺/Li, and excellent cycling stability. The lithium-storage mechanism of this material is also proposed based on the combination of in situ synchrotron X-ray diffraction, neutron powder diffraction with Fourier density mapping, ex situ X-ray absorption near edge structure analysis, ex situ transmission electron microscopy, and density-functional theory calculations with the projector-augmented-wave formalism. The lithium-storage mechanism of this material is shown to involve a two-electron (Ti⁴⁺/Ti²⁺ redox) conversion reaction between TiO and Li₄SiO₄.