Preparation And Electrochemical Properties Of Prussian Blue Analogs And Derivatives

Prussian blue(PB)and its analogs(PBAs)materials have high specific capacity,stable electrochemical performance,long service life,environmental friendliness and cost as energy storage materials due to their open three-dimensional channel structure and face-centered cubic structure.At the same time,the corresponding metal oxides(TMOs)derivatives can be obtained by calcination of PBAs precursor,and the derivatives can inherit the structural properties of the precursors.In addition,if the PBAs precursor contains multiple metal elements,the obtained TMOs are multi-component metal TMOs material which can effectively improve the electrochemical performance of the TMOs.Therefore,Prussian blue analogs and derivatives have scientific prospects in energy storage materials,photocatalysis,and electrocatalysis.However,PB and PBAs synthesized by traditional co-precipitation method have many structural defects,high water content,low nucleation rate and poor crystallinity,which will affect the electrochemical properties of the subsequent TMOs products.In the thesis,different kinds of PB and PBAs were prepared by modified co-precipitation stategy by carfully selecting sodium citrate adjuvant,potassium ferricyanide(K₃[Fe(CN)₆])and different transition metal salts.Four kinds of metal source including cobalt nitrate,nickel nitrate,manganese nitrate and manganese acetate were added to obtain cobalt ferricyanide(PBC),nickel ferricyanide(PBN),?-manganese ferricyanide(PBM_?)and?-Manganese ferricyanide(PBM_?),repectively.Furhtermore,the corresponding Co₃O₄-Co Fe₂O₄?Ni O-Ni Fe₂O₄??Mn O₂-Mn Fe O₃and?Mn O₂-Mn Fe O₃TMOs by subsequent calcining the above precursors.The specific research ideas and experimental contents of the thesis are as follows:(1)The effects of different transition metal salts on the sodium storage properties of PBAs were investigated.The experimental results show that except for PBN,other PBAs precursor materials have three-dimensional cubic framework,and the Mn²⁺system can better accommodate K⁺.The CH3COO^-system is easier to form electrode materials with good crystallinity and regular particles.This may be due to the relatively slow release rate of Mn²⁺from CH3COO^-compared with NO₃^-,which is beneficial to reduce the nucleation rate of the metal framework and improve the crystallinity.Therefore,the PBM_?demonstrates best electrochemical performance owing to its low water content,high crystallinity,less defects,higher K⁺content and uniform shell thickness.Benefiting from these advantages,PBM_?exhibits the best electrochemical performance when PBAs are used as cathode materials for Na-ion batteries.PBM_?exhibits a reversible specific capacity of 95.1 m Ah/g at a current density of 0.1 A/g,and still exhibits a specific capacity of 75.4 m Ah/g after 300 charge-discharge cycles..(2)The effects of different PBAs precursors on the structural and lithium storage properties of the as-prepared TMOs were investigated.The experimental results show that all TMOs inherit the properties of the precursors.Due to the high K⁺content of PBM,it is difficult to remove impurities in subsequent experiments,which affects the performance,while PBN does not have a three-dimensional cubic skeleton,resulting in low performance.Benifitting from the low K⁺content and the hollow cubic structure of PBC.Benefiting from these advantages,Co₃O₄-Co Fe₂O₄exhibits the best electrochemical performance when TMOs are used as anode materials for Li-ion batteries.Co₃O₄-Co Fe₂O₄exhibits a reversible specific capacity of 616 m Ah/g at a current density of 0.5 A/g,and a specific capacity of 1250 m Ah/g after 1500 charge-discharge cycles.