Sn(ii,iv) steric and electronic structure effects enable self-selective doping on Fe/Si-sites of Li2FeSiO4 nanocrystals for high performance lithium ion batteries

Abstract

We report Sn(II) and Sn(IV) self-selective dual-doping, respectively, on Fe and Si sites of Li₂FeSiO₄ nanocrystals due to the steric and electronic structure effects of Sn(II,IV). Combined with experimental studies and theoretical calculations, we investigate the structure–property relationship of tin doped Li₂FeSiO₄ as the cathode material for high performance Li-ion batteries, in which the dual-doping enhances the electronic conductivity and lithium-ion diffusion coefficient. The doped sample with 5% Sn(IV) source shows the best electrochemical performance due to the improved electronic conductivity and Li-ion diffusivity. Density functional theory (DFT) calculations also reveal that tin dual-doped Li₂FeSiO₄ has better electronic conductivity and lower voltage of delithiation than that of the undoped Li₂FeSiO₄, which is in accordance with our experimental results.