Preparation And Electrochemical Properties Of High-performance Prussian Blue Matrix Composites

In recent decades,lithium-ion batteries have been widely used in people’s daily life,bringing great convenience to people.However,due to the low content of lithium metal resources in the earth’s crust,the larger-scale application of lithium-ion batteries is limited.As the sodium element of the same main group,it has the advantages of abundant sodium resources and low cost,and has similar chemical and electrochemical properties to lithium,which has great potential in large-scale energy storage applications.The core of the development of sodium-ion batteries lies in electrode materials,among which cathode materials are currently the key to restricting the energy density of sodium-ion batteries.However,the large radius and molar mass of sodium ions make electrode materials require larger vacancies to accommodate sodium ions.Compared with other sodium-ion battery cathode materials(such as layered oxides and polyanionic compounds),Prussian blue-like compounds have shown great application potential due to their three-dimensional open frame structure,large theoretical capacity,and low cost.Among them,CoFe PBA and MnFe PBA have attracted much attention due to their double redox pairs.Therefore,this paper aims to study the morphology and structure,crystal water content and electrochemical properties of Prussian blue-like materials.The hollow structure is constructed by conditions such as chelating agents and morphology control additives;the structural stability is enhanced by doping and compounding of transition metals;finally,it is compounded with carbon materials to improve its electrical conductivity to enhance electrochemical performance.Based on this,the main research contents and results of this paper are as follows:Firstly,the co-precipitation method was used to explore the factors affecting the morphology of CoFe PBA and the controlling factors of crystal water in the structure.A series of Prussian blue compounds with different morphologies and crystal water were synthesized by regulating surfactants,chelating agents and reaction temperatures.The test results found that the interaction of surfactants and chelating agents can effectively regulate the morphology and structure of the product,increase the specific surface area,and reduce the ion transport distance,which helps to improve the electrochemical performance;in addition,controlling the temperature of the reaction can effectively control the crystal water content in the system,and the reduction of crystal water also greatly improves the stability of the material.Secondly,the structural tunability of PBA was used to explore the morphology,structure and electrochemical properties of MnFe PBA,and it was found that it has excellent specific capacity but poor cycle stability.Then,by co-doping Co and Mn,Prussian blue compounds with different proportions of cobalt and manganese were prepared at room temperature.With the gradual increase of manganese addition,the morphology and electrochemical properties of PBA gradually changed.When the molar ratio of manganese to cobalt was 1:1,the morphology and electrochemical properties of the nanoparticles showed the best level.Finally,this paper uses the good electrical conductivity of carbon materials to study the interface modification of CoFe PBA,MnFe PBA and 50% Mn-CoFe PBA.Activated carbon and reduced graphene oxide were introduced into the Prussian blue system to combine the excellent electrical conductivity of carbon materials and the excellent electrochemical properties of Prussian blue.The study found that the addition of carbon materials improved the stability and capacity of the Prussian blue material,and the addition of graphene significantly improved the conductivity of the material.The electrochemical test results fully showed that the composite material has certain advantages in the application of sodium-ion batteries.