Hierarchical porous titanium dioxide nanosheets with surface-engineering for exceptional sodium storage performance

Structural reconstruction derived from surface engineering has substantially improved fast and high-efficient charge storage for sodium-ion batteries. Here, a surface engineering strategy including phosphorus doping and nitrogen-doped carbon coating simultaneously realizes surface structural reconstruction and establishes a conductive network, which significantly enhances Na⁺ storage kinetics of TiO₂. Expectedly, functionalized TiO₂ nanocrystals with phosphorus doping and nitrogen-doped carbon coating present expedited electron and Na⁺ transfer and enhanced structural stability during Na⁺ insertion/extraction, fueled by the enhanced surface electrochemical reactivity and unique hybrid structure. Therefore, surface-engineered two-dimensional (2D) TiO₂ nanosheets achieve exceptional Na⁺ storage performance including the ultralong cycling stability with reversible capacities of 223 mAh/g at 5C for 10,000 cycles at 5C, 212 mAh/g at 10C for 20,000 cycles, and 203 mAh/g at 20C for 5000 cycles, as well as an ultrahigh rate capability of 181 mAh/g up to 50C. This functionalizing strategy fueled by surface engineering paves a new way for achieving high-performed anode materials for sodium-ion batteries.