Preparation And Electrochemical Performance Of Cathode Material And Electrolyte For Lithium Sulfur Batteries

With the rapid development of society,energy storage has become important.Lithium-sulfur batteries are widely concerned because of their high theoretical specific capacity,high energy density,abundant reserves and low price of sulfur.However,due to the low conductivity of sulfur and shuttle effect,the battery has many problems,such as high resistance,low utilization rate of sulfur,rapid attenuation of capacity,and poor cycling stability,which seriously limit its application.Therefore,in this work,the cathode material and electrolyte were used as the innovation points,and the lithium-sulfur battery with excellent performance were prepared.The research contents of this work are as follow:?1?BaTiO₃ is used as a multifunctional additive to bind polysulfide.Barium titanate precursor was prepared by sol-gel method,and barium titanate was prepared in Ar/H₂mixture,for the first time.The materials and their electrochemical properties were characterized and analyzed by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,atomic force microscopy?PFM?,and electrochemical impedance spectrum?EIS?.The results show that the B-BTO can bind polysulfide by ferroelectricity and chemisorption,and then inhibit shuttle effect.At the same time,the high conductivity of BaTiO₃ after Ar/H₂ mixture treatment promotes electronic transmission and improves the utilization rate of the active material.At the 0.1 C,the initial discharge capacity was as high as 1131 mAh/g;and at the 0.5 C,after 200 cycles,the capacity retention rate was about 80.1%.?2?Local electrolyte with high salt concentration inhibits the shuttle effect of lithium-sulfur battery.Polyethylene glycol dimethyl ether?PEGDME,M=500?,which has a limiting effect on shuttle effect,was studied as a new lithium-sulfur electrolyte system,and analyzed the electrochemical properties of the battery system.Since the short chain structure of PEGDME electrolyte can bind polysulfide,the capacity maintenance ability of lithium-sulfur battery is improved.Meanwhile,the high viscosity of PEGDME is not conducive to the transmission of lithium ions.The diluent teflon ethyl-teflon propyl ether?TTE?was added to the electrolyte,when the volume ratio of the two is 7:3,the optimal ionic conductivity and migration number is implemented,significantly reduce the viscosity of the electrolyte,so as to promote the transmission of lithium-ion and improve the reaction kinetics.More importantly,TTE can increase the local concentration of electrolyte,inhibit the shuttle effect of polysulfide,significantly improve the overall performance of the battery,and the initial discharge capacity can reach 1069 mAh/g at the rate of 0.1 C.