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

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.