(287f) Direct Growth of Unstacked Double-Layer Graphene and Graphene/Single-Walled Carbon Nanotube Hybirds for Li-S Batteries

In the past two decades, carbon nanotubes (CNTs) and graphene have attracted extensive attentions due to their unique mechanical, thermal, and electronic properties. However, the performance of both graphene and CNTs are seriously limited due to their tendency to aggregation. The direct growth of unstacked graphene and graphene/single-walled CNTs (SWCNTs) is considered a promising approach to solve this issue.

Here, the direct growth of unstacked double-layer graphene and graphene/SWCNT hybrids was successfully achieved by chemical vapor deposition (CVD) with layered double hydroxides (LDHs) as the catalyst precursor. Calcination of the LDHs led to the formation of their corresponding layered double oxides (LDOs) with metal oxides and spinals as the main components, on which hexagonal graphene layers were effectively deposited on both sides of the LDO flakes by CVD of methane. Then, reduction of the LDOs by H₂ introduced the formation of metal nanoparticles, which then served as the efficient catalyst for the growth of SWCNTs. After that, the LDOs were removed by subsequent acid and alkali treatments, and double-layer graphene and graphene/SWCNT hybrids with SWCNTs grown on the surface of the hexagonal graphene layers were obtained. The double-layer graphene was intrisincally unstacked due to the present of large amount of spacers between the two layers of graphene material. Besides, the combination of graphene and SWCNTs successfully prevented them from aggregating and the unique structure endowed the high-rate transportation of electrolyte ions and electrons throughout the electrode matrix, which gave rise to their high electrochemical performance. When the as-fabricated unstacked graphene and graphene/SWCNT hybrids were used as the electrode materials for supercapacitors and Li-S batteries, an excellent performance was demonstrated.