Investigation On Cathode Material Of Secondary Battery Based On Polyanion Compound

With the increasing demand for energy storage,the density and cycle stability of traditional cathode materials for secondary battery are challenged.As one of the cathode material systems for alkaline metal secondary batteries,polyanionic compounds have received extensive attention owing to their stable structure,high energy densities,cost-effective and high safety.However,the low intrinsic conductivity and the large ion transport resistance in the bulk phase of polyanionic compounds,which limits the actual specific capacity,rate performance and stability of the materials.In this paper,by designing experiments,aiming at the above problems,the vanadium-based phosphate compounds and Prussian blue compounds are studied.The main research contents are as follows:Firstly,we improved the conductivity of VOPO₄·2H₂O electrode material.By changing the voltage range,we realized the intercalation of double sodium ions in the material for the first time,which greatly enhanced the capacity of the material.The mechanism of sodium ion intercalation and the reversibility of the electrode reaction were systematically investigated with various characterization methods including ex-situ XRD,FTIR,XPS,GITT and EDS.the migration path of sodium ions was simulated by bond valence sum(BVS)mismatch maps.The multi-electron reaction is further confirmed in the layered VOPO₄·2H₂O material with high electrochemical stability.Secondly,we prepared different types of lithium Prussian blue analogues through different control methods,which can be used in lithium-ion batteries with low cost,high rate,high cycle stability,and wide temperature range,the cathodes exhibit excellent electrochemical performance,and the material structure was revealed through SEM,XRD,EPR,TGA,BET,FTIR,Raman,XPS and other characterization methods and the relationship between particle size and electrochemical performance was discussed.