Search

Carbon quantum dots (CQDs) as novel types of emerging materials have aroused tremendous attention in recent years. Herein, we report for the first time a new application of 3D CQD-based composite aerogels as excellent electrode materials for alkaline aqueous batteries. The scalable graphitic CQDs are prepared with high yields (>40%) and further utilized to fabricate the novel nitrogen-doped CQDs/reduced graphene oxide/porous Fe 2 O 3 (N-CQDs/rGO/Fe 2 O 3 ) composite aerogels with different contents of Fe 2 O 3 . Benefiting from the unique 3D network composite aerogel structure with a high surface area and hierarchical porous structure as well as the synergistic effect of high-capacity Fe 2 O 3 and highly conductive and stable N-CQDs/rGO, the composite aerogels achieve enhanced electrochemical properties with ultrahigh specific capacity, admirable rate property, and superior cycling performance. Furthermore, the N -CQDs/rGO/Fe 2 O 3 -1 electrode (Fe 2 O 3 , 34.9 wt %) exhibits the best rate capability (72.1, 58.9, and 46.2% capacity retention at 5, 50, and 100 A g -1 , respectively) and cycle performance (80.4% capacity retention at 3 A g -1 over 5000 cycles), while the N-CQDs/rGO/Fe 2 O 3 -3 electrode (Fe 2 O 3 , 62.3 wt %) displays the highest specific capacity (274.1 mA h g -1 at 1 A g -1 ). The current research provides a valuable guidance for developing high-performance 3D CQD-based composite aerogels for application in energy storage systems.

A high sulfur loading cathode is the most crucial component for lithium-sulfur batteries (LSBs) to obtain considerable energy density for commercialization applications. The major challenges associated with high sulfur loading electrodes are poor material utilization caused via the nonconductivity of the charged product (S) and the discharged product (Li 2 S), poor stability arisen from dissolution of lithium polysulfides (LiPSs) into most organic electrolytes and pulverization, and structural damage of the electrode caused by large volumetric expansion. A multifunctional synergistic composite enables ultrahigh sulfur content for advanced LSBs, which comprises the sulfur particle encapsulated with an ion-selective polymer with conductive carbon nanotubes and dispersed around Magnéli phase Ti 4 O 7 (MS-3) by the bottom-up method. The ion-selective polymer provides a physical shield and electrostatic repulsion against the shuttling of polysulfides with negative charge, whereas it can permit the transmission of lithium ion (Li + ) through the polymer membrane, and the carbon nanotubes twined around the sulfur promote electronic conductivity and sulfur utilization as well as strong chemical adsorption of LiPSs by means of Ti 4 O 7 . Because of this hierarchical construction, the cathode possesses a lofty final sulfur loading of 72% and large sulfur areal mass loading of 3.56 mg cm -2 , which displays the large areal specific capacity of 4.22 mA h cm -2 . In the same time, it can provide excellent cyclic performance with the corresponding capacity attenuation ratio of 0.08% per cycle at 0.5 C after 300 cycles. Especially, while sulfur areal mass loading is sharply enhanced to 5.11 mg cm -2 , the MS-3 composite exhibits a large initial areal capacity of 5.04 mA h cm -2 and still keeps a high reversible capacity of 696 mA h g -1 at 300th cycle even at a 1.0 C. The design of high sulfur content cathodes is a viable approach for boosting practical commercialized application of LSBs.