Progress in Preparation and Modification of Prussian Blue Analogues for Sodium-lon Cathode Materials
Prussian blue analogues(PBAs)are considered to be one of the most promising sodium ion cathode materials due to their high theoretical specific capacity and open three-dimensional framework structure.However,most PBAs synthesized through aqueous solution reactions commonly have[Fe(CN)6]3-/[Fe(CN)6]4-vacancies,so water molecules inevitably enter the PBAs framework to form coordinated water.The coordinated water occupies the original accommodation point of Na,affecting the normal transmission of Na+,thereby reducing the specific capacity of the PBAs material.The crystal framework of PBAs is affected by vacancies,and its ionic conductivity and cycling stability degrade and become worse under long-term cycling.Meanwhile,side reactions between the coordination water and the electrolyte further reduce the electrochemical performance.In order to solve the above problems,researchers focus on the preparation and modification of PBAs cathode materials,aiming to improve the specific capacity,cycle stability,rate performance,and overall energy density of PBAs-based cathodes in sodium-ion batteries.This paper introduces the structural characteristics of PBAs,summarizes the different preparation and modification methods of PBAs,and points out the characteristics and effects of each method.PBAs preparation methods include hydrothermal method,co-precipitation method and single iron source decomposition method.Modification methods include optimization of preparation process and composite modification of materials.Optimization of preparation process includes chelating agent,dehydration,which increases Na+concentration of precursor solution and structural nanometers.Chemical and composite modification of materials include element doping,surface coatings,heterostructures and composite materials.Comprehensive analysis shows that high-quality PBAs can be prepared through a chelating agent-assisted co-precipitation method in a Na+-rich precursor solution.Water bath heating during the synthesis process and vacuum drying after sample preparation are used to achieve dehydration,resulting in high quality high crystallinity PBAs with less vacancies and less moisture;the combination of the prepared PBAs samples with conductive agents can further improve electronic conductivity and rate performance,and is expected to achieve high capacity and high cycle characteristics while also meeting high rate requirements.As sodium ion cathode materials,PBAs can achieve optimized electrochemical performances through continuous innovation in their preparation methods and modification research,thereby exhibiting broad application prospects in the future.
sodium ion batteryprussian blue analogues(PBAs)cathode materialpreparation processmaterial modificationelectrochemical performancechelating agentresearch progress
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