Lithium titanate as anode material for lithium ion batteries: Synthesis, post-treatment and its electrochemical response

Abstract

The relationship between the structure and crystallinity of lithium titanate Li4Ti5O12, at different synthesis post-treatment conditions on the electric energy storage capacity is discussed. Li4Ti5O12 was synthesized by solid-state reaction at a high temperature and time (950 °C, 24 h) and the resulting material was post-treated with a ball milling process at different times. Additional samples were prepared with a post-calcination after and adding graphite carbon previously to the longer applied ball-milling time. All the obtained materials were structurally and morphologically characterized by XRD and SEM techniques. To study the effect of ball milling time on the lithium-ion storage capacity, electrochemical experiments of galvanostatic charge-discharge cycling, cyclic voltammetry, and rate capability experiments were performed. The application of high-energy milling showed that the obtained specific capacity increased with particle size reduction as long as the crystallinity degree of the LTO material remained high. The Li-ion diffusion coefficient for each material was obtained, as well as its specific resistivity and the intrinsic rate constant for the electrochemical process. It was possible to observe that the ball-milling treatment producing improvements in the charge storage capacity leads also to improvements in mass transport and electrical conduction, although not necessarily produce better electrochemical kinetic behavior. The inter-particle connectivity was analyzed in terms of state-of-the-art percolation modeling.