Preparation Of Two-dimensional Nanoclay Modified Pp Separator And The Study Of Its Application In Lithium Sulfur Battery

Lithium-sulfur?Li-S?battery has high theoretical specific energy(1675 m Ah g^-1)and energy density(2600 Wh kg^-1),low cost and environmental friendliness,which has been considered as the most promising next generation commercial rechargeable battery.However,the"shuttle effect"of the lithium-sulfur batteries has leads to a serious decline of the capacity.Therefore,it is imperative for inhibit the“shuttle effect”and constructing a high performance of lithium-sulfur batteries.In order to inhibit the shuttle of the polysulfur,this work aims to modify the separator for improve the electrolyte wetting property and increase the mobility of lithium ions of the separator by add montmorillonite?MMT?naonosheet.The MMT nanosheet contains a large amount of metal oxides and negative charge was play the role of catalytic effect on the polysulfide and electrostatic repulsion with the Sn^2-,and effectively depressing the shuttle effect by combining the excellent conductivity of carbon nano tube?CNT?and graphene?GN?.The separator modification layer of composition and structure was optimized for inhibit the polysulfide shuttling,and construct an high-performance Li-S battery.This research contents as follows:1)Two-dimensional?2D?MMT nanosheet was prepared by ion exchange method.The 2D MMT nanosheet was characterized by physically and chemically means,such as,XRD,TEM,XPS,etc.The carbon nano tube-montmorillonite?CNT-MMT?composite was obtained by mixing the 2D MMT nanosheet and carbon nanotubes in ethanol.The modification layer of CNT-MMT separator was about 15?m and load capacity is 0.15 mg/cm²,and constructed by vacuum filtration CNT-MMT dispersion.The excellent adsorption and catalytic characteristics of MMT composites was characterized by static adsorption and Li₂S deposition experiments,XPS and CV ect.Thus,CNT-MMT composite modify the commercial separators and worked as an interlayer to trap polysulfides via physical adsorption and/or chemical interaction,and generally the increasing utilization of sulfur and inhibition of shuttle effect are observed.Furthermore,the electrochemical performance of lithium sulfur battery is significantly improved by use the separator of CNT-MMT=5as the interlayer.The improved lithium-sulfur batteries deliver an initial specific capacity of 1373m Ah/g at 0.1 C,and an ultralow capacity decay of 0.119%per cycle over 500 cycles at 1 C.2)Graphene oxide?GO?was prepared by modified Hummer's method.The GN and graphenen-montmorillonite?GN-MMT?composite was obtained by freeze-drying the GO and GO-MMT dispersion and heat treatment.The modified separtor was constructed by vacuum filtration GN and GN-MMT dispersion.The adsorption and catalytic characteristics of the GN and GN-MMT composites was characterized by polysulfur static adsorption and Li₂S deposition experiments,CV and EIS,ect.The results show that GN-MMT composite has adsorption and catalyze the conversion of polysulfur.Therefore,when the one-dimensional CNT was replace by two-dimensional GN,the separator modification layer constructed by GN-MMT composite could more effectively inhibit the polysulfur shuttle,and the electrochemical performance is significantly improved.The improved lithium-sulfur batteries deliver an initial specific capacity of 1026 m Ah/g at 0.1 C,and an ultralow capacity decay of 0.0864%per cycle over 600 cycles at 1 C.