Low Temperature Rapid Interfacial Kinetics Achieved by Sodium Titanate Anode Co-Intercalation Storage Mechanism and Stable Solid Electrolyte Interface

Abstract

Quasi-layered sodium titanates have been extensively studied as anode materials for sodium-ion batteries (SIBs) owing to their quasi-zero-strain intercalative storage chemistry and high theoretical capacity. However, their sluggish sodiation kinetics and unstable electrode/electrolyte interface lead to rapid capacity decay at low temperatures. Herein, the local electronic structure and interlayer spacing of Na₂Ti₂O₅ are finely regulated by heteroelement Sn-doping, oxygen rich vacancies, and carbon-confined structure (Sn-HNTO@C) to improve low-temperature performance. Theoretical calculations and Sn doping concentration control confirm that appropriate concentrations of heteroelement Sn-doping and vacancy defects can redistribute charge density, enhance Na⁺ adsorption, reduce Na⁺ diffusion energy barriers, and endow Sn-HNTO@C anode with stable capacity. In addition, optimizing electrolyte systems at low temperatures allows Sn-HNTO@C to exhibit a Na⁺-solvent co-intercalation storage mechanism in ether-based electrolytes, avoiding high desolvent energy barriers and reducing charge transfer activation energy. Furthermore, the thin, stable solid electrolyte interface rich in organic components promotes the low-temperature interfacial Na⁺ kinetics. Consequently, Sn-HNTO@C anode delivers high capacity over 500 cycles (177 mAh g⁻¹) and Sn-HNTO@C//Na₃(VPO₄)₂F₃ full cell presents 91 mAh g⁻¹ over 200 cycles (−15 °C). This study provides unique guidance for optimizing sodium titanate anodes and emphasizes the importance of the low-temperature electrode/electrolyte interface for SIBs.