Black anatase titania enabling ultra high cycling rates for rechargeable lithium batteries

Abstract

In this work we report the synthesis and the characterization of black anatase TiO₂. We show that this material displays a nanostructured architecture, with an electro-conducting trivalent Ti. The presence of trivalent Ti in this structure narrows the inherent high band gap energy to a semiconductor level, reaching a value as low as 1.8 eV, resulting in the very high electrical conductivity of 8 × 10⁻² S cm⁻¹. These extraordinary electro-conducting physical properties ensure an ultra fast Li⁺ insertion into and extraction from the host structure of anatase TiO₂ making it a unique, high rate electrode, delivering at a 100 C-rate (20 A g⁻¹) a discharge capacity of 127 mA h (g-TiO₂)⁻¹ with approximately 86% retention during 100 charge–discharge cycles at 25 °C and approximately 84% retention at −20 °C.