Laser constructed bulk oxygen vacancy caused high P doping for boosting the sodium-storage capability

Abstract

Defect-assisted heteroatom doping can effectively enhance the intrinsic transfer characteristics of carriers in the crystal structure, which advantages over fast and efficient charge storage. In this work, a three-dimensional self-supporting titanium dioxide nanoparticle rich in bulk vacancies (L-TiO_x) on titanium substrate is synthesized by pulsed laser. Different from the surface vacancies, the bulk oxygen defects of L-TiO_x cause a uniform and bulk phosphorus (P) doping with a high concentration of ~5.71 at %, which endows the elevated electronic conductivity, and accelerates the transport of Na⁺. The obtained P-doped L-TiO_x (LP-TiO_x) as an anode material in sodium-ion batteries (SIBs) provides a reversible capacity of 400 mAh g⁻¹ at 200 mA g⁻¹, outstanding rate capability of 196 mAh g⁻¹ at 10,000 mA g⁻¹, and maintains stable performance over 1000 cycles. In situ X-ray diffraction and ex situ high-resolution transmission electron microscopy show that LP-TiO_x exhibits robust mechanical behavior with almost no lattice change under (de)sodiation. This work supplies a novel idea for high-concentration bulk heteroatoms doping to enhance the electrochemical performance of SIBs.