Nanointerface-driven pseudocapacitance tuning of TiO2 nanosheet anodes for high-rate, ultralong-life and enhanced capacity sodium-ion batteries

摘要

Titanium dioxide recently gained attention as sodium-ion battery anode material. However, its practical application is hindered by low specific capacity (similar to 150 mAh/g), and mediocre cycling stability. Here we report for the first time, nanointerface-driven Na-ion intercalation pseudocapacitance tuning as a strategy to substantially improve the performance of TiO2 anodes. This is achieved by tuning the crystal mismatch between anatase and bronze crystallites of hierarchical TiO2 nanosheets. Hybrid TiO2 nanosheets composed of similar to 10 nm sized anatase (similar to 85%) and bronze (similar to 15%) crystallites exhibited significantly higher pseudocapacitive Na-ion storage compared to phase-pure bronze and anatase TiO2 nanosheets. High specific capacity of 290 mAh/g (similar to 0.87 mol Na-ions) at a current density of 25 mA/g is obtained for this composition. Hybrid TiO2 maintained a specific capacity of 120 mAh/g even at a high current density of 1 A/g. Coulombic efficiency (similar to 100%) and cycling stability are outstanding, retaining 90% of the initial capacity after 2500 galvanostatic cycles. These electrochemical performances are noticeably superior to amorphous and crystalline TiO2 reported earlier. Mechanistic studies proved Na-ion intercalation pseudocapacitance without considerable structural changes. Excellent electrochemical performance of dual-phase hierarchical TiO2 nanosheets is credited to the superior Na-ion intercalation pseudocapacitance resulting from anatase-bronze nanointerfaces. The demonstrated strategy of nanointerface-driven pseudocapacitance tuning provides new opportunities for the designing of advanced Na-ion battery anodes.