The balance of structural compatibility and distortion in titanium sources for the preparation of a high performance Na2Ti6O13 anode

Abstract

The performance of the sodium-ion battery anode material Na₂Ti₆O₁₃ (NTO) is closely related to the choice of the titanium source. This study uses a synergistic strategy with anatase and rutile TiO₂, overcoming limitations of traditional single titanium sources and addressing the gap in understanding rutile's effects on NTO. The open structure of anatase, with its point/edge-sharing Ti–O octahedra, is highly compatible with NTO and serves as the main titanium source to construct the layered framework. Rutile, with its larger Ti–O bond lengths and higher density of octahedral connections, synergistically induces lattice distortion with anatase at high temperatures, expanding the [010] interplanar spacing of NTO. The widened channels significantly alleviate structural strain during Na⁺ insertion/extraction and reduce the formation of irreversible Ti⁰ metal. The sample prepared with an anatase and rutile mass ratio of 85 : 15 as the titanium source showed excellent long cycle stability under high-current conditions. It maintains a reversible capacity of 130.36 mA h g⁻¹ after 1500 cycles at 1000 mA g⁻¹ and achieves a capacity retention rate of 119.8% after 5000 cycles at 2000 mA g⁻¹. The dual-titania precursor “1 + 1 > 2” model provides a universal and efficient strategy for balancing the kinetic performance and structural stability of NTO.