Dual-functional Co_5.47N/Fe₃N heterostructure interconnected 3D N-doped carbon nanotube-graphene hybrids for accelerating polysulfide conversion in Li-S batteries

The lithium-sulfur battery is emerging as a promising alternative for the state-of-the-art lithium-ion battery because of its high theoretical specific capacity. However, the shuttle effect results from a sluggish conversion reaction of lithium polysulfides (LiPSs), reduces the sulfur utilization, promptly capacity degradation, and thus prevents its industrial application. Recently, the development of catalysts that can accelerate the conversion reaction of LiPSs has received tremendous attention. Herein, we use a novel in-situ one-step approach to prepare the Co_5.47N/Fe₃N heterostructure wrapped with the 3D nitrogen-doped carbon nanotube and graphene framework (3D Co_5.47N/Fe₃N@N-CNT-G). Density functional theory (DFT) calculation suggests that the formation of Co_5.47N/Fe₃N heterostructures could improve the density of states at the Fermi level, which enhances the redox kinetics, LiPS conversion and adsorption capability. The combination of highly catalytic activity Fe₃N and adsorptive Co_5.47N in the abundant-heterojunctions Co_5.47N/Fe₃N nanostructure provide an effective trapping host and conversion catalyst for LiPS. Moreover, 3D N-CNT-G framework with high surface area serves as a highly conductive channel for electron transport and promote the Li₂S nucleation. The sulfur-loaded 3D Co_5.47N/Fe₃N@N-CNT-G cathode exhibits an exceptional capacity of ~1293 mAh g⁻¹ at 0.1C and long cycle-life for 500 cycles (capacity fading of 0.029% per cycle at 1C).