Pseudocapacitive Na+ Insertion in Ti–O–C Channels of TiO2–C Nanofibers with High Rate and Ultrastable Performance

Ti–O–C channels for ultrafast sodium storage were constructed in N/S-co-doped TiO2–C nanofibers, which deliver a high rate performance of 181.9 mAh g–1 at 5 A g–1 after 3000 cycles. The existence of Ti–O–C bonds at the interface of TiO2–C phases was revealed by synchrotron radiation X-ray absorption spectra. Based on this, first-principles calculations further verified the low energy barrier for Na+ insertion/extraction in the Ti–O–C channels formed by the intimately integrated graphite layer with TiO2 near the surface. In addition, surface defects induced by heteroatoms accelerate the Na+ mass transfer through the pathway from the carbon surface to the Ti–O–C channel.