Preparation Of Prussian Blue Analogue Derivatives-metal Oxides And Their Application In Lithium-sulfur Batterie

Prussian Blue（PB）and its analogues（PBAs）have attracted extensive attention due to their unique metal framework structure,controllable microstructure,environmental friendliness,low cost and stable electrochemical performance.In addition,multi-metal oxides（TMOs）obtained by high-temperature calcination can inherit the morphology and structure of the precursor completely and exhibit good synergistic effects between the multi-component metal oxides when used for electrochemical energy storage.Therefore,multi-component metal oxides have opened up new avenues for research in electrochemical energy storage.Lithium-sulfur batteries,which have high theoretical capacity(1675 m Ah g^-1)and theoretical energy density(2600 Wh kg^-1),have been widely studied in recent years and are considered to be the most promising energy storage device to replace lithium-ion batteries in the future.However,lithium-sulfur batteries suffer from poor conductivity of sulfur cathode,large volume expansion of sulfur during charge-discharge processes,shuttle effect caused by soluble intermediate polysulfides crossing the membrane,and reaction with negative lithium electrode leading to continuous loss of metallic lithium,leading to greatly reduced cycling performance of lithium-sulfur batteries,which seriously hinders their commercial application.To further promote the commercialization of lithium-sulfur batteries,researchers have used porous carbon or metal oxides as sulfur cathode hosts.Porous carbon can improve the conductivity of cathode materials and alleviate the shuttle effect through physical adsorption,but the shuttle effect has not been fundamentally solved.Metal oxides have good catalytic performance through strong polar adsorption ability and reaction with lithium sulfide.Based on this,the idea of this study is to combine metal oxides with porous carbon as a composite sulfur cathode host for lithium-sulfur batteries,which can not only improve the transmission dynamics of electrons and ions but also adsorb polysulfides and accelerate their conversion,thus effectively improving the comprehensive performance of lithium-sulfur batteries.The contents of this paper are as follows:The first and second parts of this thesis mainly focus on preparing PBAs based on different metal salts,including manganese-based（Mn-PBA）and cobalt-based（Co-PBA）by co-precipitation method.TMOs were obtained through heat treatment,and then TMOs@C materials were prepared by using a hydrothermal synthesis method.The electrochemical performance of different TMOs@C materials in lithium-sulfur batteries was investigated.The results showed that TMOs@C@S electrode materials had excellent electrochemical performance(the Mn O₂-Mn Fe O₃@C@S electrode reached as high as 1187.6 m Ah g-1 at a current density of 0.1 C,with a capacity retention rate of 47.9%after 300 cycles and a capacity decay rate of 0.17%per cycle;the Co₃O₄-Co Fe₂O₄@C@S electrode reached 1101.1m Ah g^-1at a current density of 0.1 C,with a capacity retention rate of 46.7%after 300 cycles and a capacity decay rate of 0.18%per cycle).The excellent electrochemical performance above is due to the synergistic effect of the conductivity of carbon materials and the chemical adsorption-catalytic effect of TOMs,which effectively promotes the conversion reaction of polysulfides,promotes the transfer efficiency of charges,and improves the electrochemical performance of the material.The goal of the third part is to design TMOs/porous carbon fiber composite（TMOs@PCNF）by electronic spinning strategy,followed by utilizing sulfur sublimation to produce TMOs@PCNF@S.Benefitting from the synergistic effect of physical barriers provided by carbon nanofibers and chemical adsorption-catalysis of TMOs,TMOs@PCNF@S demonstrated excellent electrochemical performance.The initial discharge specific capacity of Mn O₂-Mn Fe O₃@PCNF@S was 869.5 m Ah g^-1at 0.1 C,while that of Co₃O₄-Co Fe₂O₄@PCNF@S was 518.9 m Ah g^-1at 0.1 C...