Preparation And Eelectrochemical Performance Of Cathode Materials For Sulfur/Carbon Composite

Lithium-sulfur(Li-S)batteries have been deemed as the best alternative for the new generation of energy storage devices.Li-S cathode materials have a high theoretical capacity of 1675 mAh/g.Li-S batteries are considered to be the most promising lithium secondary batteries due to the sulfur element with low cost,abundant reserves and environmental friendliness.However,Li-S batteries practical commercial applications are still hindered by cycle stability degrade rapidly stemming from electrode sulfur insulated and the shuttle effect of soluble polysulfides.In this paper,the above mentioned issues of Li-S batteries to be solved by constructing of new carbon-sulfur composite cathode materials and preparing novel modified separator.The main investigation are summarized as follows:The Mesoporous carbon hollow spheres(MCHS)with a specific surface area of 965.95 m2/g was achieved by using SiO2 as templates.MCHS carbon serving as the carriers could limit the dissolution of polysulfides through capillary action of mesoporous.Therefore,the resultant MCHS could reduce the shuttle effect in Li-S batteries.The Sulfur/Carbon composite materials were systhesized via the chemical impregnation method and the melt calcination method.The discharge specific capacity of MCHS/Sulfur composites after the 100 cycles at 0.5 C still retains 301.2 mAh/g.BaTiO7 was introduced to overcome the limitation of the adsorption of polar polysulfides by non-polar carbon materials to enhance the eletrochemical performance.BTO has been introduced into the cathode,as the novel polysulfides' trap to stabilize the Li-S batteries.The MCHS/S-BTO composite materials were prepared by physical low temperature calcination to intromit into the MCHS.The effects of eletrochemical performance from different sulfur loading contents were investigated in detail.The composite material with sulfur content of 70%and 15 wt%BTO has the best cycle performance,which delivers a discharge capacity of 539.1 mAh/g after 100 cycles.In order to further improve the rate performance of Li-S batteries.Herein we introduced the CoS2/MCHS nano composite materials into Li-S batteries through the separator modification for its simple operation method.CoS2/MCHS composite materials were served as the polysulfides trap owing to the strong chemical affinity accelerating the conversion of polysulfides.It delivered 1085.6 mAh/g in the initial discharge progress and 649.5mAh/g after 500 cycles at a current density of 1.0 C.Therefore,Li-S batteries with the CoS2/MCHS modified separators have huge potential application because of its outstanding excellent rate performance and remarkable stable cycling life.