Supercritical CO2-Fluid-Assisted Synthesis of TiO2 Quantum Dots/Reduced Graphene Oxide Composites for Outstanding Sodium Storage Capability

Building a rational nanoarchitecture of a quantum dots (QDs)/graphene composite is a promising method to satisfy the demands of high sodium-ion storage capacity, good rate capability, and superb cycling stability. Here, a powerful supercritical CO2-fluid strategy is provided to fabricate a TiO2 QDs/reduced graphene oxide (RGO) composite. The prepared nanocomposite shows a porous and stable structure with a tight union of TiO2 QDs (∼3.7 nm) and RGO supports, which offers numerous fast electron and ion transmission routes and high mechanical stability. When it cycles at 0.05 A g–1 as the anodic material for Na-ion batteries (SIBs), the TiO2 QDs/RGO electrode shows a reversible capacity of 241 mA h g–1 with a low capacity loss of 18.5% after 300 cycles. Even increasing the current density up to 5 A g–1, an excellent capacity as high as 108 mA h g–1 still can be achieved with a low capacity loss of 11.5% over 5000 cycles. This work demonstrates a new supercritical CO2-fluid-assisted strategy for future develo...