Tuning the carbon content on TiO2 nanosheets for optimized sodium storage

Titanium dioxide (TiO2) has been considered as a promising anode candidate for sodium ion batteries (NIBs). In this work, we report the synthesis of anatase TiO2 nanosheets coated by nitrogen doped carbon derived from dopamine precursor (TiO2@C) as high performance anode materials for NIBs applications. The carbon contents can be controlled from 2.6 wt% to 10.4 wt% by varying the polymerization time of dopamine. X-ray diffraction patterns confirm there is no phase change after carbon coating. When employed as an anode for NIBs, the TiO2@C composites exhibit improved electrochemical performances in terms of higher specific capacity and better cycling stability compared to pure TiO2 nanosheets. Notably, with a carbon content of 4.8 wt%, the TiO2@C nanosheets delivers a reversible capacity of 180 mA h g−1 and shows stable cycling performance with no discharge capacity decay from 2nd cycle onward over 50 cycles. Even at high current density of 10C, the capacity still remains 82 mA h g−1. The excellent cycling stability and rate performances can be ascribed to the protective effects of carbon coating layer which reserves the structure stability and enhances electrical conductivity during cycling.