Research Of The Modified Polyolefin Membrane For Lithium Sulfur Batteries

Compared with the traditional lithium ion battery,lithium sulfur battery has a higher energy density and specific capacity,which close to the requirement of society.Theoretically,the energy density of lithium sulfur is much higher than traditional lithium ion battery.In addition,sulfur has the advantages of low cost,non-toxic,and no polluting,which makes sulfur a kind of environmentally friendly materials.So the lithium sulfur battery has become a promising energy storage material.But with the poor conductivity and shuttle effect,the battery cycle performance is poor,which limited the commercial application of lithium sulfur battery.In this paper,major works is designing and preparation of modified membrane materials based on a commercial separator to enhance the electrochemical properties of lithium-sulfur batteries.The contents and results of major research are as follows:Based on the membrane coated with Nafion,the zeolite is synthesized to dope the coating.A large amount of lithium-ion channels are formed,which reduces the impedance caused by the blocking of lithium ion on Nafion,so that the cycling performance is improved again.Despite other doping with several different ratios,the capacity of Nafion membrane doped with 1 wt% Zeolites remain 12.27% higher than the pure Nafion membrane.Using of oxidation treatment of the diaphragm,the carboxyl groups are generated on the surface to adsorb lithium polysulfide,and reduce the shuttle effect which would cause the loss of capacity.The capacity retaines 46.76% higher than the standard one after 100 cycles.However,after the oxidation membrane treatment,the amount of surface pore increases,which lead to the poor stability of the membrane.As the reaction progresses,the growth of the lithium dendrite in the anode zone finally leads to the short circuit of the puncture hole of the membrane.The self-assembled modified layer was introduced on the basis of the carboxyl-modified membrane,and the activation of the positive electrode region was induced by the electron conductivity.As a result,the capacity of the battery increased.After 100 cycles,one self-assembled modified membrane remains 15.68% higher capacity than the carboxylated membrane.With comparing two kinds of self-assembled separator with different polarity,the positive separator caused certain impediment to the lithium ion transmission,offsetting the activation effect,the outer negative charge is more favorable for this research.