Enhanced Electrochemical Properties of Sn-doped V2O5 as a Cathode Material for Lithium Ion Batteries

Abstract

Cation doping of lithium ion batteries (LIBs) cathode materials is beneficial to both ion-diffusion and charge transfer in the electrochemical intercalation processes and hence may improve battery rate capability. In the present study, a series of Sn-doped V2O5 microspheres were prepared for LIBs cathode via a microwave-assisted solvothermal synthesis. X-ray diffraction analysis suggests that Sn4+ ions with an ionic radius 22% larger than that of V5+ successfully entered into the crystal lattice and led to lattice expansion of V2O5. The doping of Sn4+ also induced the formation of oxygen vacancies that would allow more active sites for the intercalation/extraction reactions of Li+ ions. Compared with pristine V2O5, Sn-doped samples demonstrated both improved capacity and rate capability. Particularly, V2O5 doped with 4% Sn4+ (denoted as Sn0.04V1.96O5-δ) delivered a high reversible specific capacity of 292mAhg−1 in the voltage window of 2.0–4.0V (vs. Li/Li+) at a current density of 50mAg−1. Much enhanced rate performance was also attained for the doped samples (220.4mAhg−1 at 500mAg−1 and 162.5mAhg−1 at 2,000mAg−1 for Sn0.04V1.96O5-δ) compared to V2O5 (148.6mAhg−1 at 500mAg−1 and 72.3mAhg−1 at 2,000mAg−1). The improved electrochemical properties of Sn-doped V2O5 can be attributed primarily to the lattice expansion upon doping that led to higher lithium diffusion coefficient (4.45×10−11cm2s−1) than V2O5 (2.84×10−11cm2s−1) as well as the presence of rich oxygen vacancies.