Li4Ti5O12 nanosheets as high-rate and long-life anode materials for sodium-ion batteries

Abstract

According to recent reports, a multiphase design can provide a new method to improve the performance of L₄T₅O₁₂–TiO₂ anodes for lithium-ion batteries (LIBs). But in the case of sodium-ion batteries (SIBs), little attention is paid to the investigation of whether TiO₂ phases have similar effects as they have in LIBs. In this paper, uniform pristine Li₄Ti₅O₁₂ (LTO) and Li₄Ti₅O₁₂–rutile TiO₂ (LTO–RT) nanosheets were successfully fabricated on a large scale via a simple hydrothermal reaction. Their electrochemical performance as anodes for SIBs was carefully compared for the first time. The results show that the existence of TiO₂ phases in LTO–TiO₂ composites has a positive effect on the capacity but a negative effect on the cyclability as anodes for SIBs, which is very different from the previously reported effects of TiO₂ phases in LTO–TiO₂ composites as anodes for LIBs. Moreover, LTO nanosheets fabricated by our synthesis method deliver a reversible capacity up to 145 mA h g⁻¹ at 1C and keep 91% capacity retention after 400 cycles. As far as we know, this is the longest cycle life to date for SIBs using LTO as anode materials. Based on a scan rate-dependent cyclic voltammetry test, a pseudocapacitive charge storage mechanism has been firstly proposed for Na-ion storage in a pristine LTO electrode, which contributes to the excellent rate capacity and such high cycling stability of LTO electrodes for SIBs.