Co-doping Nitrogen/Sulfur through a Solid-State Reaction to Enhance the Electrochemical Performance of Anatase TiO2 Nanoparticles as a Sodium-Ion Battery Anode

Nitrogen- and/or sulfur-doping has been used to enhance the electrochemical performance of TiO2 anodes in lithium-ion batteries. Multiple doping in one step presents a challenge to produce anodes with excellent performance. Herein, we reports a facile process to co-dope nitrogen and sulfur into black anatase TiO2 nanoparticles accomplished by using a solid-state reaction with dried TiO2 gel and thiourea. Co-doping introduced N and S atoms into the TiO2 matrix, increasing oxygen vacancies, thus enhancing the intrinsic electronic conductivity. Co-doping also decreased the size of TiO2 nanoparticles from 15.6 to 10.1nm, and increased the surface area from 77 to 129m(2)g(-1), facilitating insertion/extraction of Na ions during charge-discharge cycling. N/S co-doped TiO2 exhibited a signficantly higher performance as a sodium-ion battery anode than pristine black TiO2. The rate performance of the co-doped TiO2 is improved up to 80% in comparison with pristine black TiO2.