Three-dimension ivy-structured MoS2 nanoflakes-embedded nitrogen doped carbon nanofibers composite membrane as free-standing electrodes for Li/polysulfides batteries

Highlights: • 3D ivy-structured MoS₂@N-CNFs has been synthesized for Li/polysulfides batteries. • The chemical interaction between LiPs and MoS₂ was revealed by DFT calculations. • The cathode with high sulfur loading exhibited stable electrochemical properties. -- Abstract: Three-dimension ivy-structured MoS₂ nanoflakes @ nitrogen doped carbon nanofibers (MoS₂@N-CNFs) composite membrane was designed by a combined electrospinning and hydrothermal technique. The MoS₂@N-CNFs membrane is employed as a free-standing cathode for Li/polysulfides batteries. N-CNFs membrane with high electrical conductivity is used as a current collector to effectively reduce the internal resistance in the electrode and immobilize the dissolved lithium polysulfides with mesoporous N-CNFs with pyridine nitrogen. The MoS₂ nanoflakes introduced into N-CNFs membrane offer a hierarchical composite structure, in which the MoS₂ nanoflakes not only have chemical binding with the lithium polysulfides, but also promote fast redox reaction kinetics with high capacity and low voltage polarization. Meanwhile, the MoS₂ nanoflakes have been demonstrated to show strong binding energy and be capable of anchoring polysulfides based on density functional theory calculations. As a result, with a high sulfur loading of 7.11 mg, the assembled cell with MoS₂@N-CNFs + Li₂S₆ cathode demonstrates excellent electrochemical performances with a capacity decay rate of 0.08% per cycle over 250 cycles at 0.2C. Moreover, when the sulfur loading is further increased to 11.84 mg, a capacity decay rate of 0.25% per cycle over 100 cycles is achieved. Consequently, the method used in here provides a new insight to produce N-doped carbon nanofibers with metal sulfides/metal oxides nanoflakes composites as free-standing materials with the high sulfur loading for lithium-sulfur batteries.