Liquid Gallium-Assisted Pyrolysis of MOF Affording CNT Non-Hollow Frameworks in High Yields for High-Performance Sodium-Ion Battery Anode.

Carbon materials have great potential for applications in energy, biology, and environment due to their excellent chemical and physical properties. Their preparation by carbonization methods encounters limitations and the carbon loss during pyrolysis in the form of gaseous molecules results in low yield of carbon materials. Herein a low-energy (600 °C) and high-yield (82 wt.%) carbonization strategy is developed using liquid gallium-assisted pyrolysis of metal-organic frameworks (MOFs) affording the N-doped carbon nanotube (CNT) non-hollow frameworks encapsulating Co nanoparticles. The liquid gallium layer offers protection against air, promotes heat transfer, and limits the escape of small carbonaceous gaseous molecules, which greatly improve the yields of the pyrolysis reaction. Experimental and theoretical results reveal that the synergistic interaction between CNTs and N/O-containing groups gives a non-hollow framework composed of N/O-enriched and open CNTs (NOCNTF-15, 15 denotes the 15 mm thickness of the liquid gallium layer during the pyrolysis) with high specific capacity (185 mAh g at 10 A g) and ultra-stable cyclability (stable operation at 10 A g and 50 °C for 20 000 cycles). This study provides a unique approach to carbonization that facilitates the practical application of low-cost CNTs and other MOFs-derived carbon materials in high-performance sodium-ion batteries (SIBs).