High-yield production of non-layered 2D carbon complexes: Thickness manipulation and carbon nanotube branches for enhanced lithium storage properties

Non-layered two-dimensional (2D) carbon complexes manifest great potential in energy-related applications owing to their exotic electronic structures, large electrochemically active surface, and intriguing synergistic effects. However, reliable method for mass production and thickness manipulation of 2D carbon complexes remains great challenges. Here, inspired by blowing chewing gum into bubbles, a “tailored gel expanding” strategy is proposed for high-yield synthesis of non-layered 2D carbon complexes with tailored thickness from ~12 nm to ~1 μm, by controllable pyrolysis of metal-polymeric gel with adequate crosslinking degree. The key feature for thickness manipulation is introducing NH4NO3 in sol–gel process, which tailors the expansion behavior of gel precursor during subsequent pyrolysis. Various of 2D sheets with intimately coupled N,O-doped carbon (NOC) and NiCo-based (NiCo, (NiCo)S2, (NiCo)Se2, NiCo2O4, (NiCo)(PO3)2) nanocrystals are obtained on a large scale and without any impurities. Moreover, these 2D products are branched with in-situ grown CNTs on the surface, accelerating electrons transfer and preventing the nanosheets from stacking. As a demonstration, the 2D (NiCo)S2/NOC with optimized thickness manifests excellent lithium storage properties in both half and full cells. This method paves a new path for massive and controlled production of non-layered 2D materials with tailored thickness and robust structure stability for energy-related applications.