Application Of Eutectic Accelerator Modified Sulfurized Polyacrylonitrile Cathode In All-solid-state Lithium-sulfur Batteries

Among all solid cathode materials,elemental sulfur has the highest theoretical specific capacity(1675 mA h g^-1)which is about 10 times that of commercial cathode materials for lithium ion batteries,and it is a non-toxic,harmless,safe and inexpensive material with abundant reserves in nature.When combined with lithium metal anodes,a theoretical energy density of up to 2600 W h Kg^-1 is obtained for the lithium-sulfur battery which is about 5times larger than that of traditional lithium-ion batteries.However,in practical research,the following problems of lithium-sulfur batteries limit their application in industrial production:?1?the electronic insulation of sulfur element——sulfur is an electronic insulator,the electronic conductivity is as low as 5×10^-30 S cm^-1,resulting in low utilization of active material in sulfur cathode;?2?the dissolution of lithium polysulfide——the intermediate formed during electrochemical reaction is likely to dissolve in organic electrolyte and migrate to the negative electrode to react with lithium anode to reduce the efficiency of battery during charge and discharge process;?3?Volume change——the repeated expansion and shrink of the cathode during battery cycling leads to damage of the electrode structure,resulting in irreversible capacity.In addition,the organic electrolyte itself is flammable and volatile,which may lead to the danger of battery burning or even explosion in the case of short circuit,leakage,overcharge,thermal runaway and so on,causing serious safety accidents.In view of the above problems,a modified sulfurized polyacrylonitrile?S@pPAN?cathode material doped with the same main group element Se/Te was designed to assemble all-solid-state batteries.The results show that the doping of Se/Te can improve the electronic conductivity and lithium ion diffusion coefficient of the material.The doping elements can also contribute to the capacity as active material in the electrode;At a sulfur loading of 0.38mg cm^-2,the cathode capacity is 1200 mA h g^-1at current density of 0.1 C for Se_0.05S_0.95@pPAN.When the sulphur loading is 1 mg cm^-2,the capacity is more than 800 mA h g^-1 and a capacity retention of 81%was obtained after 150 cycles.In addition,the improvement of electrode-electrolyte interface by surface modification of cathode material is studied.After coating a solid-state lithium ion fast ionic conductor on the surface of electrode material,the rate performance and cycling stability are significantly improved,and the capacity of the battery is more than 600 mA h g^-1 at 1 C.