Design And Performance Study Of Functional Gel Cathode For Lithium Sulfur Battery

Lithium-sulfur battery is regarded as one of the most promising energy storage battery systems due to its high theoretical specific energy（2600 Wh/kg）,low cost and environmental friendliness.However,due to the electronic insulation of sulfur and lithiumsulfide,the shuttle effect of polysulfide,the volume expansion of sulfur during charging and discharging,the actual discharge capacity and cycle performance of lithium-sulfur battery cannot meet the requirements of practical application.The purpose of this paper is to design the functional gel cathode of lithium-sulfur battery,attempting to solve the above problems and improve the overall performance of the battery.The research contents and main results are as follows:The modification of gel-coated sulfur cathode by ionic liquid Py₁₄TFSI as additional plasticizer was studied.The introduction of Py₁₄TFSI with moderate content can improve the ionic conductivity of the electrolyte and inhibit the dissolution of polysulfide.The modified gel coating was obtained by injecting modified electrolyte into P（AM-Co-AA）/PEO/PEDOT:PSS（PPP）polymer framework,which can effectively improve the electrochemical performance of the sulfur cathode.After 100 cycles at 0.2C current density,the discharge capacity can reach 786.1 mAh/g and the capacity retention is about 80%.The PPP polymer was compounded with carbon cloth to forma conductive skeleton,and the functional gel cathode constructed by absorbing polysulfide solution could hold a large number of polysulfide stably for a long time,thus inhibiting the shuttle effect.The composite framework provides a good electron/ion transport path and plays an effective in-situ catalytic role,thus promoting the kinetics of locally confined polysulfide conversion reaction.The gel cathode has the excellent long cycle stability,with an initial discharge capacity of 1435 mAh/g and the reversible capacity of nearly800 mAh/g after 500 cycles.Using cotton rounds as the main raw material,the porous carbon/r GO self-supporting conductive skeleton was prepared by freeze-drying and high-temperature carbonization technology,and the new polysulfide gel cathode was prepared by combining PVDF-HFP and Mo S₂.The self-supporting framework has stable structure,excellent electrical conductivity and outstanding sulfur carrying capacity.On this basis,PVDF-HFP physical barrier and Mo S₂ chemisorption were combined to confine polysulfide.The reversible capacity of the polysulfide gel cathode is still more than1000 mAh/g after 50 cycles when the sulfur loading is as high as 10.5 mg/cm².