The synergistic effect of P-doping and carbon coating for boosting electrochemical performance of TiO2 nanospheres for sodium-ion batteries

P-doping is an effective way to modulate the electronic structure and improve the Na+ diffusion kinetics of TiO2, enabling enhanced electrochemical performance. However, it is a challenge to prepare TiO2 with a high P-doping concentration starting from TiO2 in a crystalline state. In this work, we design a novel two-step route for constructing a carbon-coated anatase P-doping TiO2 nanospheres (denote as (P-AnTSS)@NC) with high P-doping concentration, by utilizing amorphous TiO2 nanospheres with the ultra-high specific area as P-doping precursor firstly, and followed by carbon coating treatment. Experimental results demonstrate that P is successfully doped into the crystal lattice and carbon layer is well coated on the surface of TiO2, with P-doping and carbon-coating contents of ~13.5 wt% and 10.4 wt%, respectively, which results in the enhanced pseudocapacitive behavior as well as favorable Na+ and electron transferring kinetics. The (P-AnTSS)@NC sample shows excellent rate and cycle performance, exhibiting specific capacities of 177 and 115 mAh/g at 0.1 and 1.0 A/g after 150 and 2000 cycles, respectively.