Design of Na2Ti3O7/Na2Ti6O13 nanorods for sodium-ion batteries from titanium oxysulfate solution

Sodium titanate is currently a widely studied anode electrode material for sodium-ion batteries, showing promising potential for large-scale production and applications. Current research focuses on Na2Ti3O7, Na2Ti6O13, and their mixed compositions Na2Ti3O7/Na2Ti6O13, utilizing high-purity titanium compounds as raw materials. In this study, precursors of biased titanate with three different sulfur contents (3.20 %, 2.04 %, 0.28 %) are prepared using a self-seeding hydrolysis method and a titanium oxysulfate (TiOSO4) solution as the starting material. During the synthesis of sodium titanate, sodium consumption occurs due to sulfur, resulting in a mixed phase comprising Na2Ti3O7/Na2Ti6O13. However, when the sulfur content is very low, a single phase of Na2Ti3O7 can be obtained. Notably, Na2Ti3O7/Na2Ti6O13 synthesized from biased titanate with high sulfur content exhibits a larger percent of Na2Ti6O13, which improves rate capability and cycling stability. The initial discharge specific capacity at 177 mA·g−1 is 57.4 mAh·g−1, and after 1000 cycles, the discharge capacity reaches 22.7 mAh·g−1. Designing mixed materials Na2Ti3O7/Na2Ti6O13 from TiOSO4 solution represents one of the pathways to achieve high-performance sodium titanate materials.