Research On Preparation And Electrochemical Performance Of Functional Separator In Lithium-sulfur Battery

In order to meet the modern society’s demand of energy,researchers have developed a series of energy conversion devices.As far as in the field of energy storage are concerned,the battery market is still dominated by lithium-ion batteries currently.Among them,lithium-sulfur batteries that have been developed due to some advantages of their own high energy density and low cost,but those are covered by the non-conductivity of active materials and shuttle effect that it is not entry into the battery market so far.In order to improve its electrochemical performance,this article is mainly about the lithium-sulfur battery separator,and it is from two kind of different separator modified materials’ preparation to research their electrochemical performance when applied to lithium-sulfur battery.The main contents and innovations of these work are as follows:1.A nitrogen-doped cobalt sulfide polyhedral membrane modification material（Co9S8@N-C）derived from a metal organic framework was designed for lithium-sulfur batteries.The N has a strong polar adsorption effect on polysulfides（Li PSs）,and the catalysis brought by Co9S8 can accelerate the rapid conversion of polysulfides and reduce their accumulation on adsorption sites;the synthetic material maintains the polyhedral structure,promotes the transmission of electrons,and accelerates the rate of redox reaction,not only blocks the shuttle of polysulfide ions,but also retains the migration channel of Li+ at the same time.The synergy of these advantages makes the lithium-sulfur battery with Co9S8@N-C/rGO separator’s discharge capacity can reach as high as 827.82 m Ah·g-1 after cycle 100 times at a rate of 0.1 C,and the capacity retention rate is 70.27%.2.A composite（TiO₂/TiN/rGO）of titanium dioxide/titanium nitride（TiO₂/Ti N）heterostucture nanowires and reduced graphene（rGO）was designed by electrospinning to modify polypropylene separator.The linear structure not only promotes electron transport along the longitudinal direction,but also provides large area for electrode with electrolyte to contact.Among them,the TiO₂/Ti N heterostructure has a strong chemical interaction on Li PSs,it is through the adsorption of TiO₂ and the catalytic conversion properties of Ti N to inhibit the shuttle of dissolved Li PSs.The initial specific capacity of the Li-S battery with the TiO₂/Ti N/rGO modified separator is 856.6 m Ah·g-1 when the current density at 1 C,and its specific capacity remains at 491 m Ah·g-1 after 300 cycles,the capacity decay rate is only 0.14% per cycle.