Enhanced electrochemical properties of lithium cobalt titanate via lithium-site substitution with sodium

Abstract

Na-doped Li2CoTi3O8 is prepared via Li-site substitution with Na for the purpose of improving its cycle performance as an anode. Upon Na-doping, Rietveld refinement result reveals that Na takes the tetrahedral sites (8c) shared with Li and Co in the structure. Due to the larger ionic radius of Na than Li, an increased disorder degree of ion locations in the structure is induced by Na doping. Furthermore, the lithium ion diffusion tunnel is also expanded after Na doping. Galvanostatic charge/discharge tests denote that Li1.90Na0.10CoTi3O8 displays better cycling property and higher reversible capacity than pristine Li2CoTi3O8 and other Li2−xNaxCoTi3O8 materials. It can be found that Li1.90Na0.10CoTi3O8 can maintain a reversible capacity of 268.9mAhg−1 at a current density of 100mAg−1 (0.14C) after 50 cycles, corresponding to 90.6% of the initial charge capacity. Even cycled at a high current density of 1426mAg−1 (2C), Li1.90Na0.10CoTi3O8 can also maintain a reversible capacity of 179.2mAhg−1 after 80 cycles. Besides, the reversible structural changes of Na-doped Li2CoTi3O8 are also proved by various in-situ and ex-situ observations. The significant improvements at cycling and rate performances demonstrate that Li1.90Na0.10CoTi3O8 is a promising anode material for rechargeable lithium-ion batteries.