Extended lattice space of TiO2 hollow nanocubes for improved sodium storage

Sodium-ion batteries (SIBs) are considered as promising new-fashioned energy storage devices. Among these anode materials of SIBs, the low specific capacity and poor rate capability of TiO2 are two significant factors of hindering the widely application. Here, a unique hollow TiO2/carbon nanocubes (hollow-TiO2@C-800) with enlarged lattice spacing of TiO2 have been synthesized. Experimental results demonstrate that the enlarged lattice spacing of TiO2 could facilitate Na ions desertion/insertion and inhibit the irreversible side reactions, resulting in fast Na ion transfer kinetics. Moreover, N-doped hollow porous carbon framework could boost the conductivity, inhibit the agglomeration of the smaller TiO2 and shorten the distance for Na+ transfer, which lead to lower mechanical stresses and smaller capacity loss during cycles. As expected, hollow-TiO2@C-800 shows a superior cycling stability (154.6 mAh g(-1) after 6000 cycles at 5000 mA g(-1)) and an excellent rate capability (150 mAh g(-1) at 8000 mA g(-1)). This simple synthetic method would open a new avenue to prepare the superior SIBs anode.