Ultrahigh rate capability and ultralong cycling stability of sodium-ion batteries enabled by wrinkled black titania nanosheets with abundant oxygen vacancies

Sodium-ion batteries (SIBs) have been considered as one of the promising alternatives for lithium-ion batteries, owning to the abundant reserve and low cost of sodium-related salts. However, SIBs usually suffer from the sluggish kinetics of Na and the serious volume expansion of anode materials, which inevitably restrict the performance of SIBs. Herein, electroconductive wrinkled anatase-phase black titanium oxide nanosheets with rich oxygen vacancies (OVs-TiO) was found to have an ultrafast Na insertion and extraction kinetics as anode material in SIBs. The wrinkled structure can significantly reduce the Na diffusion length, and the conductive networks formed by wrinkled OVs-TiO can boost the electron transfer during Na insertion and extraction processes. With the rapid Na insertion/extraction ability, wrinkled OVs-TiO delivers excellent sodium storage performance with high reversible capacity, ultra-high rate capability with the capacity reaches 91 mAh g even at 20,000 mA g, and ultra-long cycling stability. These properties demonstrated the great potential of wrinkled OVs-TiO to serve as a realistic choice of anode materials in SIBs.