A tightly integrated sodium titanate-carbon composite as an anode material for rechargeable sodium ion batteries

A novel sodium titanate-carbon (Na sub(2)Ti sub(3)O sub(7)/C) composite has been successfully synthesized via a rheological phase method. The homogeneous-dispersed carbon not only sheathes the single Na sub(2)Ti sub(3)O sub(7) particle but also combines all individual Na sub(2)Ti sub(3)O sub(7) particles to a stable union, as characterized by X-ray diffraction, scanning electron microscopy (SEM), and high-resolution transmission microscopy (HRTEM). The uniformly distributed carbon forms a good network of electrically conductive paths among the Na sub(2)Ti sub(3)O sub(7) particles, which is closely interlinked with each other. So Na sub(2)Ti sub(3)O sub(7) active material can get electrons from all directions and be fully utilized for sodium ion insertion and extraction reactions, which can improve sodium storage properties with enhanced rate capability and super cycling performance. The Na sub(2)Ti sub(3)O sub(7) /C composite exhibits much better electrochemical performance than bare Na sub(2)Ti sub(3)O sub(7), which displays a stable discharge capacity of 111.8 mAh g super(-1) at 1C after 100 cycles, while only 48.6 mAh g super(-1) for bare Na sub(2)Ti sub(3)O sub(7) at the same conditions. Furthermore, the composite shows relatively stable storage capacities during long term cycling even at 5C. The remarkably improved cycling performance and rate capability of Na sub(2)Ti sub(3)O sub(7) are attributed to the tight integration between carbon and Na sub(2)Ti sub(3)O sub(7) which may enhance the electronic conductivity, decrease the charge transfer resistance and improve the electrochemical stability during cycling, thus making a compelling case for its development as an advanced anode material for sodium ion batteries.