Scalable Template-Free Synthesis of Na2Ti3O7/Na2Ti6O13 Nanorods with Composition Tunable for Synergistic Performance in Sodium-Ion Batteries

Abstract

Sodium-ion batteries are regarded as one of the potential candidates to substitute lithium ion batteries in large-scale electric energy storage applications in the near future. Several forms of sodium titanates including Na2Ti3O7, Na2Ti6O13 and Na4Ti5O12 have recently been applied as anode in sodium ion batteries. Here, we present an energy-efficient solid-state synthesis, via the addition of carbon, to mass-produce a series of uniform and single-crystalline Na2Ti3O7/Na2Ti6O13 nanorods with tunable composition as anode materials for sodium-ion batteries.1 Due to the extra local heat generation and CO2/CO release from carbon oxidation, the carbon added in the synthesis provides an alternative low-temperature route for the Na2Ti3O7 formation at 450 °C, a reaction temperature much lower than that of conventional solid-state methods (750–1000 °C), and Na2CO3 is regenerated to be recycled in the synthesis. The high theoretical capacity of Na2Ti3O7 and low volume expansion of Na2Ti6O13 upon charge–discharge are synergistically exploited to achieve high electrochemical performance and stability.