Catalytic Effect Of Metal Phthalocyanine On Conversion Of Lithium Polysulfide In Lithium Sulfur Batteries

Lithium-sulfur batteries are regarded as one of the most hopeful energy storage systems.However,the shuttle effect of soluble lithium polysulfide（LiPSs）causes rapid capacity decay and poor cycle stability of the battery,which hinders the commercial application of the battery.The slow kinetics of the conversion reaction of LiPSs makes it gradually accumulate in the electrolyte,which is an important reason for inducing the shuttle effect.Therefore,the introduction of catalytic materials to accelerate the conversion of soluble LiPSs is the fundamental method to overcome the shuttle effect.Metal phthalocyanine,a type of two-dimensional planar complex with 18πaromatic conjugated system,and its unique Metal-N₄ coordination structure has high catalytic activity for soluble LiPSs.In this artical,we use metal phthalocyanine complex molecules to explore the promotion of LiPSs conversion,the main works are as follows:1.Dissolve cobalt tetraaminophthalocyanine in DOL/DME electrolyte to form a homogeneous catalyst.Symmetrical batteries indicate that cobalt tetraaminophthalocyanine can promote the conversion of soluble LiPSs.When tetraamino phthalocyanine cobalt is applied to lithium-sulfur batteries,the shuttle effect of LiPSs is suppressed,so that the battery exhibits a high specific capacity of 1395m Ah g-1 and improved rate performance.2.Utilize theπ-πadsorption of graphene and cobalt phthalocyanine to overcome the self-aggregation of cobalt phthalocyanine molecules and build a composite of cobalt phthalocyanine molecularly dispersed on graphene.Symmetrical battery was used to evaluate the catalytic effect of cobalt phthalocyanine self-aggregation on the conversion of LiPSs.As the degree of molecular self-aggregation decreases,its catalytic effect becomes stronger.When cobalt phthalocyanine molecularly dispersed in graphene,it shows the best catalysis performance.3.Rotating disc electrodes and symmetric batteries were used to investigate the catalytic performance of different central metal phthalocyanines for LiPSs conversion.The results showed that with the change of the central metal of the phthalocyanine,the metal phthalocyanine showed a significant difference in its ability to promote the conversion of LiPSs.