Lithium ion storage in lithium titanium germanate

Abstract

lithium titanium-based oxides have been demonstrated as good anode materials for lithium-ion batteries. These materials perform at safe operating potential of the electrolyte, but suffer from low energy density. Here, we reported a new type titanium-based anode material, Li2TiGeO5, for lithium-ion batteries, which delivers a reversible specific capacity of 691 mA h g−1 and 68% initial coulombic efficiency under a current density of 0.02 A g−1, with operational potential of 0.5 V vs. Li/Li+. The experiments, including in-situ X-ray diffraction, in-situ Raman spectra, synchrotron-based X-ray absorption spectroscopy, coupled with first-principles calculations, demonstrated multi-electron reaction during discharge/charge process. The lithiation products including electronic conducting TiO and Li–Ge alloy simultaneously with Li-ion conducting Li2O provide good electrochemical performances of Li2TiGeO5 anode in lithium-ion batteries. Those results indicate a conversion reaction mechanism of lithium-ion storage with a high initial coulombic efficiency comparable to that of most other conversion-type anode materials. Our work provides a new class of anode material with large capacity and high safety in lithium-ion batteries.