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

Abstract

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 CO 2 -fluid strategy is provided to fabricate a TiO 2 QDs/reduced graphene oxide (RGO) composite. The prepared nanocomposite shows a porous and stable structure with a tight union of TiO 2 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 TiO 2 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 CO 2 -fluid-assisted strategy for future development of brilliant QDs/RGO composite materials for high-performance SIBs.

Synthesis of MnSe @C yolk‐shell nanospheres via a water vapor‐assisted strategy for use as anode in sodium‐ion batteries

“…Since lithium reserves are limited, SIBs have attracted considerable research highlight as a potential candidate that can replace the currently dominant lithium‐ion batteries (LIBs) 1‐5 . The electrochemical reaction mechanism of SIBs is similar to that of LIBs, but since sodium ions have larger ionic radii than lithium ions, SIBs usually exhibit poor cycle stability compared to LIBs 6,7 . Therefore, the rational design of anode materials for SIBs that can effectively accommodate the volume change that occurs during the electrochemical reaction is in urgent need.…”

Supercritical carbon dioxide technology in synthesis, modification, and recycling of battery materials

“…[ 88 ] In this regard, SC‐CO 2 method is put forward to synthesize TiO 2 quantum dots (QDs)/RGO composites with rational nano‐architecture by Zhang's group. [ 89 ] As shown in Figure 5a, with the assistance of SC‐CO 2 fluid, tetrabutyl titanate (TBOT) precursor is fully carried into the interlayer of graphene with uniform distribution, and the layer structure of graphene can expand through the rapid pressure release of SC‐CO 2 . As a result, TiO 2 QDs/RGO synthesized by SC‐CO 2 exhibits uniform distribution of nano‐scaled TiO 2 QDs, and no discrete particles are observed in the composite (Figure 5b).…”

“…Reproduced with permission: Copyright 2018, ACS Publications. [ 89 ] (d) Schematic of the preparation of TiO 2 nanowires/RGO (NWs/RGO) architecture through SC‐CO 2 ; (e) SEM and (f) TEM images of TiO 2 NWs/RGO. Reproduced with permission: Copyright 2018, Royal Society of Chemistry.…”

Recent progress in quantum dots based nanocomposite electrodes for rechargeable monovalent metal-ion and lithium metal batteries

“…The conducting, flexible porous architecture of 0D SnS 2 –3D rGO with strong inter-component architecture enabled a high initial capacity of 397 mA h g −1 at 0.1 A g −1 current, good rate capability with 97 mA h g −1 capacity retention at 5 A g −1 , and good electrochemical stability with 233 mA h g −1 capacity retention at 0.5 A g −1 current after 200 cycles. Yu et al 195 demonstrated that supercritical CO 2 , with unique characteristics of good permeability and high diffusivity, can be employed to fabricate a homogeneously distributed metal oxide QDs/rGO nanohybrid with a controllable QD size. Supercritical CO 2 can penetrate inside the graphitic layers (80 bar CO 2 pressure) and can carry the desired metal precursors (here tetrabutyl titanate) with it and homogeneously distribute them inside graphitic layers.…”