| Lithium-sulfur（Li-S）batteries are considered one of the most promising electrochemical energy storage systems due to their high theoretical specific capacity(1675 m Ah·g-1)and energy density(2 600 Wh·kg-1).However,issues such as the insulation of the active material in Li-S batteries and the shuttle effect of lithium polysulfide（Li PS）remain a challenge for their industrialization.Adding a multifunctional interlayer to the battery is considered as an effective strategy to improve the battery performance.Carbon materials have good mechanical properties,high electrical conductivity,and metal-organic frameworks（MOF）have a large specific surface area and many metal sites.The interlayer material composed of the combination of the two can not only ensure the conduction rate of electrons,but also ease the dissolution and shuttling of Li PS.In this paper,ZIF-7@carbon fiber（ZIF-7@CNF）and Ui O-66@carbon cloth（Ui O-66@CC）composites were successfully prepared by simple chemical methods and used as interlayers to investigate their effects on the electrochemical performance of Li-S batteries.In this paper,MOF film is grown on a carbon material by a simple chemical method and used as a interlayer to study its effect on the electrochemical properties of Li-S batteries.（1）The needle-like ZnO nanorods were obtained by introducing a"zinc source"on the surface of carbon nanofibers through a water bath reaction,followed by hydrothermal reaction to transform the needle-like ZnO into a two-dimensional sheet-like ZIF-7 to obtain the ZIF-7@CNF material.The dense ZIF-7 MOF are neatly arranged on the surface of carbon fibers,the gaps between the MOF expose more adsorption sites,and the volume expansion of the cathode is also alleviated.Benefiting from these advantages,when ZIF-7@CNF interlayers are applied to Li-S batteries,the initial discharge specific capacity is 1 226.9 m Ah·g-1at a current density of 0.2 C,and capacity retention of 89%can still be achieved after 100 cycles.Under the long cycle of 1.0 C,the initial discharge specific capacity is 912.93 m Ah·g-1,and after 500 cycles a specific capacity of 718 m Ah·g-1remains,with a capacity decay rate of 0.04%/cycle.（2）In order to explore more suitable materials for interlayers in Li-S batteries,the substrates of the growth materials as well as the MOF materials are adapted in this paper.A rough surface and good hydrophilicity carbon cloth is chosen as the substrate to facilitate the growth of MOF and to ensure adequate electrolyte infiltration.Ui O-66 was grown on the surface of the carbon cloth by hydrothermal reaction to obtain the Ui O-66@CC interlayer.The ortho-octahedral Ui O-66 exposes more metal sites,and this structure facilitates the capture and catalytic conversion of lithium polysulfide by the interlayer,while being the upper collector can mitigate the volume change of the active material sulfur during charging and discharging.Thus,when the Ui O-66@CC interlayer is applied to Li-S battery,the specific capacity of the battery is 1 228.9 m Ah·g-1on the first cycle at a current density of 0.2 C,with a capacity retention rate of 95.9%after 100 cycles.When tested for600 charge/discharge cycles at a current density of 1.0 C,the first discharge specific capacity is 1 033.07 m Ah·g-1and after 600 cycles the discharge specific capacity is 579.16m Ah·g-1,with a capacity decay rate of 0.07% per cycle. |
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