The Application Of Small Molecule Mediator In The Cathode Material Of Lithium Sulfur Batteries

Lithium-sulfur batteries have great prospects for development due to their low cost and high specific energy.However,sever shuttle effect and the complex interface reactions between the cathode and electrolyte in Li-S batteries are big obstacles for their application.In this paper,small molecule mediator materials were introduced into convention cathode to accelerate the kinetics of polysulfide conversion in liquid phase and the efficiency of solid-liquid phase transformation.The main contents are as follows:?1?The small molecule tris?4-fluorophenyl?phosphine was added to the carbon nanotubes?CNTs?-sulfur composite and the resulting cathode are called CNTs-S-TFPP.The optimized cathodes showed a higher initial capacity of 1492 mAh g^-1 at 0.2 C,and when the current rate was increased to 5 C over 1000 cycles,the attenuation rate of each cycler was0.042%.In addition,a CNTs-S-TFPP cathode with a sulfur loading of4.2 mg cm^-2 maintained the capacity of 545 mAh g^-1 after 140 cycles at0.1 C,in conjunction with a capacity retention rate of 84.6%.?2?As₂S₃ was selected as a mediator for cathode-electrolyte interface of Li-S batteries during charge-discharge process.At 0.2 C,the initial capacity of cathode consisting from CNTs-sulfur composite andAs₂S₃?that is,CNTs-S-As₂S₃?was better than that of conventional CNTs-S cathode.Meanwhile,the reversible capacity of the CNTs-S-As₂S₃ batteries was higher after 400 cycles at a rate of 1 C,compared with that of the batteries without mediator.