N,S-codoped TiO2 microspheres with obviously enhanced electrochemical performance for sodium-ion batteries

Heteroatom doping enhances the electrochemical properties of battery electrodes, but conventional multi-step syntheses limit practical applications. Herein, we report a single-step pyrolysis strategy for simultaneous nitrogen–sulfur codoping of anatase TiO 2 microspheres (NS-TiO 2 ) using thiourea as a dual-functional precursor. X-ray photoelectron spectroscopy reveals a synergistic dual-site doping mechanism: sulfur substitutes at Ti sites (2.33 surface at.%) while nitrogen occupies interstitial positions (1.48 surface at.%). This architecture, alongside codoping-induced Ti 3+ defect states (∼3.77%) and oxygen vacancies, inherently enhances electronic conductivity and facilitates Na + transport. Consequently, the charge-transfer resistance decreases dramatically from 156.5 Ω in undoped TiO 2 to 49.48 Ω in the codoped material, which promotes predominant pseudocapacitive charge storage (84% at 2 mV·s −1 ). This optimized configuration delivers exceptional rate capability (55.1 mAh·g −1 at 5 A·g −1 ) and outstanding long-term cyclability (95.9% capacity retention over 2000 cycles at 1 A·g −1 ), significantly outperforming single-element doped analogues. Ultimately, this work establishes clear design principles for multi-element doped metal oxides, uniting synthetic simplicity with superior electrochemical functionality.