Enhanced energy storage of alkali (Li, Na) titanates by sucrose carbonization

Abstract

In this work, a simple and effective synthesis procedure was performed in order to prepare hybrid alkali titanate materials, as negative electrodes for lithium-ion battery applications. Lithium titanate Li4Ti5O12 (LTO) and sodium titanates Na2Ti3O7 (NTO237) and Na2Ti6O13 (NTO2613) compounds were synthesized through a solid-state method; then a carbon coating was performed using sucrose impregnation followed by a dehydration step with strong acid medium, and finally calcined at high temperature. XRD and Raman spectroscopy analysis of the composites indicated that the strong acid medium in the carbonization step affects the titanate structure. A calcination temperature at 700 °C proved to be adequate to obtain the LTO/C material without significant changes and with a homogeneous carbon coating, so it was used to obtain further the hybrids NTO237/C and NTO2613/C materials. The carbon coating improved the good behavior obtained before in bare LTO compound about specific capacity for electric charge storage, but mainly produced huge improvements in the poor specific capacities observed for both bare NTO compounds. All the hybrid alkali titanates exhibited a great stability of charge/discharge cycling and a very good rate capability response, showing a robust behavior recovering the initial specific capacity at low rate after several discharge cycles at high rates (10 C). Such increase in the specific storage capacity in all hybrid alkali titanate materials is associated with the enhancement in the inter-particle connectivity generated by the carbonaceous coating.