Investigation On Electrochemical Performance Of Water-free Prussian Blue Analogues Cathode Materials

In recent years,as the demand for lithium-ion batteries in electronic equipment,new energy vehicles and stationary energy storage applications has grown rapidly,tremendous pressure has been placed on the energy density and raw material requirements of batteries.As a common cathode material for alkali metal ion batteries,Prussian blue analogues have been extensively studied by scientific researchers due to their unique open framework structure,abundant redox sites,low cost,and high safety.However,traditional Prussian blue materials are synthesized in aqueous solution,so PBAs inevitably contain too much crystal water.The crystal water occupies the redox active sites,resulting in the actual discharge capacity of the Prussian blue material being much lower than the theoretical capacity,and the crystal water will escape from the structure of the Prussian blue during the cycle,causing side reactions to deteriorate the cycling stability of the electrode.In response to the above problems,the preparation of water-free Prussian blue analogues has been studied,and the specific research contents are as follows:Firstly,anhydrous ethanol and ethylene glycol were used as reaction solvents to avoid water entering the structure of Prussian blue during the reaction.The physical properties of the synthesized materials were investigated by XRD,SEM,TGA,FTIR,XPS and other characterization methods,prove that we succeeded in preparation of low crystallization water content of Fe Prussian blue material,and achieved high discharge capacity and stable cycle more than 500 cycles.Secondly,the Mn-based Prussian blue material was prepared by using the chelating agent Na₂EDTA,and the influence of drying conditions on the structure of Mn HCF was explored.Through XRD,TGA and other characterization methods,it was found that Na Mn HCF would change from monoclinic structure to rhombohedral structure with the reduction of water of crystallization content.The rhombohedral Na Mn HCF has a flat discharge platform and a high discharge capacity.Aiming at the higher discharge platform of Mn HCF,we applied it to lithium-ion batteries through the ion exchange method.By embedding a small amount of K⁺as a support,Mn-based Prussian Blue also has a higher discharge platform in lithium-ion batteries.