Enhanced electrochemical performance of oxygen-deficient Li4Ti5O12−x anode material induced by graphene oxide

Li4Ti5O12−x anode powder containing oxygen vacancies was synthesized via ball-milling assisted solid-state reaction between LiOH⋅H2O, TiO2 and graphene oxide as reactants. Different from previous reports, graphene oxide played the role of reducing agent in promoting the conversion of Ti(IV) into Ti(III) during the calcination process, the process is accompanied by the formation of oxygen vacancies. This assumption was confirmed by XPS and EPR results. SEM, TEM and Raman shows there is a small amount of residual graphene in the material, but the content of carbon is only 0.026%. The lithium-ion diffusion coefficient of oxygen-deficient Li4Ti5O12−x is calculated to be 1.02 ⋅ 10−12 cm2 s−1, ten times higher than 1.61 ⋅ 10−13 cm2 s−1 for pure Li4Ti5O12. As a result, the as-prepared Li4Ti5O12−x exhibits excellent electrochemical performance, presenting an initial discharge capacity of 172.4 mA h g−1 at 0.5 C with a capacity retention of 96.7% over 100 cycles.