A Low-Voltage Layered Na2 TiGeO5 Anode for Lithium-Ion Battery

Abstract

Titanium-based anode materials have achieved much progress with the wide studies in lithium-ion batteries. However, these known materials usually possess high discharge voltage platforms and limited energy densities. Herein, a titanium-based oxide of Na₂ TiGeO₅ with layered structure, two-dimensional lamellar frame and exposed highly active (001) facet, exhibiting good electrochemical performance in terms of high capacity (410 mAh g^-1 with a current density of 50 mA g^-1 ), excellent rate capability and cycling stability with no obvious capacity attenuation after 4000 cycles, is reported. The appropriate discharge voltage plateau at around 0.2 V endows the Na₂ TiGeO₅ anode material high security compared with graphite and high energy density compared with spinel Li₄ Ti₅ O₁₂ . Combining the electrochemical tests and the density functional theory calculations, the Li⁺ storage mechanism of Na₂ TiGeO₅ is elucidated and the conversion reaction process is revealed. More importantly, this study provides a way to develop low-voltage and high-capacity titanium-based anode materials for efficient energy storage.

Keywords: Na 2TiGeO 5 sheets; amorphization; lithium-ion batteries; reaction mechanisms; titanium-based anode materials.