Preparation Of MOF Derived Sulfide And The Properties In Cathode Of Lithium Sulfur Batteries

Lithium-sulfur batteries,which has several times higher of energy density than that of lithium-ion batteries,and a good application prospect.However,the realization of comprehensive industrial application still limited by the poor conductivity of sulfur,large volume expansion,shuttle effect of polysulfides and other problems.In order to alleviate the above problems,in this paper,from the perspective of cathode materials,the sulfur cathode composite was prepared by combining the MOF-derived sulfide with high catalytic activity and the r GO with high conductivity.The main research contents are as follows:Firstly,the etched CoAl-LDH was used as a template,and ZIF-67 was grown in situ,then vulcanized at high temperature to produce Co S₂/C,after that,the Co S₂/C with good catalytic activity were compounded with r GO by a convenient and easy controlled hydrothermal method to prepare Co S₂/C/r GO material,which was compounded with sulfur and used as the positive matierial of Li-S battery.Co S₂/C/r GO-S material has good conductivity,catalytic activity and rapid Li⁺diffusion ability,which can improve the redox kinetics of Li PSs,accelerate the deposition of Li PSs to Li₂S,inhibit the shuttle effect and effectively improve the electrochemical performance of the battery.The initial specific discharge capacity of Co S₂/C/r GO-S anode material is 820 m A h g^-1,and the coulombic efficiency is maintained at 99.81%after 500 cycles at 1 C.At a high current density of 3C,the Co S₂/C/r GO-S cathode material has an initial capacity of 693.6 m A h g^-1.After 500cycles,the specific discharge capacity still reaches 483 m A h g^-1,with a capacity retention rate of 70%.The synergistic effect of bimetals can improve the electrochemical performance of cathode materials,Ni Co-LDH was prepared using ZIF-67 as precursor by reflux,and the bimetallic sulfide Co S/Ni S₂/r GO composite was prepared by hydrothermal method after the synthesis of Ni Co-LDH and GO.Co S/Ni S₂/r GO composite materials have good catalytic capabilities,which can accelerate the catalytic conversion of polysulfides and the deposition of Li₂S.Co S/Ni S₂/r GO cathode has an initial discharge specific capacity of 793m A h g^-1 with a low capacity decay rate of 0.09%per cycle after 500 cycles at 1 C.It has excellent performance under high current density,with a discharge capacity of 639.2 m A h g^-1 at 3 C,after 500 cycles,the Co S/Ni S₂/r GO cathode material still has a discharge capacity of 545.8 mAh g^-1,with a capacity retention rate of 85.4%.