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

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 thorn 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 freestanding materials with the high sulfur loading for lithium-sulfur batteries. (C) 2019 Elsevier Ltd. All rights reserved.