Preparation Of Metal-Organic Frameworks Derivatives And Their Apprications For Lithium-Sulfur Batteries

The rechargeable Li-S batteries are considered as one of the most promising"post-Li-ion" energy storage devices because of their high theoretical capacity(1675 mAh/g),energy density(2600Wh/kg),low cost and environmental benignity.Li-S batteries are highly challenging due to a series of fundamental issues,especially the most notorious shuttle effect of soluble polysulfide.For years,the research on the sulfur cathode is nostly focused on designing proper host materials for the immobilization and entrapment of polysulfides,but the shuttle effect has yet to be satisfactorily solved.Herein,we demonstrate that the cathode catalyst could accelerate the reduction of low-order polysulfides by chemical adsorption and electrocatalytic reaction.We select carbon fiber cloth as the current collector and try to grow MOF arrays on it,aiming to solve the incompatibility issue between electroactive materials and the current collector.Meanwhile,we choose metal-organic franeworks derivatives as the cathode catalyst for Li-S batteries.The main contents including:1.Wc explored the growth conditions of MOFs(Metal-Organic Frameworks)arrays supported on the carbon fiber and discussed the formation mechanism.Ni2P was obtained by phosphorized under Ar flow.The as-prepared Ni2P arrays were applied for Li-S batteries.The performance enhanced mechanism has been discussed.Ni2P can exhibit a reversible specific capacity of>600 mAh/g(1.6 mA/cm2),and the rate performance is also satisfactory.2.We synthesized carbon-coated molybdenum carbide by pyrolysis of NENU-5(Northeast Nonnal University No.5).The performance enhanced mechanism has been deeply analyzed by characterization,chemical adsoration and electrocatalytic measurements.The final product can show a specific capacity of>900 mAh/g(1.0 mA/cm2)and good cycling stability of more than 500 cycles.3.We prepared ultradispersed tungsten carbide nanoparticles by pyrolysis of NENU-3 under vacuum.The performance enhanced mechanism has been profoundly studied by characterization,chemical adsorption,electrocatalytic tests and theoretical calculations.At a current density of 6.4 mA/cm2,WxC/md-C as the cathode catalyst exhibited long cycling stability(620 mAh/g remained after 1000 cycles).Besides,we found that tungsten carbide significantly enhanced activation of lithium sulfide in Li-S cell.