An interlayer defect promoting the doping of the phosphate group into TiO2(B) nanowires with unusual structure properties towards ultra-fast and ultra-stable sodium storage

Abstract

Heteroatom doping is an effective way to modulate the local structure of TiO₂-based materials, enabling enhanced electrochemical performance. However, current studies generally adopt a single atom doping strategy, and ionic group doping has rarely been achieved and is a distinctly bigger challenge. Herein, doping of the phosphate group at high concentrations into blue TiO₂(B) nanowires is proposed and realized for the first time by skillfully utilizing the defects induced during the dehydration and topology transformation process of the H-titanate precursor; based on experimental characterization and first-principles calculations, it has been demonstrated that this material possesses exceptional electrical properties, a remarkably reduced band gap, magnetic characteristic from the extra electrons outside the Ti atomic nucleus and remarkable phase stability. Benefiting from the unusual structure properties, phosphate-doped TiO₂(B) exhibits the ultra-fast sodium storage capability of 124 mA h g⁻¹ at the extremely high rate of 50 A g⁻¹ and excellent long cycling stability even at 10 A g⁻¹ after 5000 cycles. Moreover, this electrode material was tested at low temperatures and exhibited comparable reversible capacity and outstanding cycling stability to those at normal temperatures. We also assembled a B–TiO₂(B)–P//(NVPF) full cell, which delivered the maximum energy density of 170 Wh kg⁻¹ and the maximum power density of 5000 W kg⁻¹.