普鲁士蓝类钠离子正极材料的制备及改性研究进展

Progress in Preparation and Modification of Prussian Blue Analogues for Sodium-Ion Cathode Materials

摘要:

普鲁士蓝类似物（PBAs）具有较高理论比容量和开放式三维框架结构，被认为是最具应用前景的钠离子正极材料之一。然而，大部分通过水溶液反应合成的PBAs，普遍存在[Fe(CN)₆]^3-/[Fe(CN)₆]^4-空位，水分子不可避免进入PBAs框架中形成配位水，占据了原本Na⁺的容纳点位，影响了Na⁺的正常传输，降低了PBAs材料的比容量。PBAs晶体框架受空位影响，其离子导电性和循环稳定性在长时间循环下退化并变差，同时配位水与电解液发生副反应，进一步降低了电池的电化学性能。为解决上述问题，提高钠离子电池中PBAs基正极的比容量、循环稳定性、倍率性能和整体能量密度，重点介绍了PBAs正极材料的制备及改性方法，并总结了各制备及改性方法的特点及效果。PBAs的制备方法包括水热法、共沉淀法和单一铁源自分解法。改性方法包括制备工艺优化和材料复合改性，其中制备工艺优化包括螯合剂、脱水、提高前驱液Na⁺浓度和结构纳米化，材料复合改性包括元素掺杂、表面涂层、异质结构和复合材料。研究表明，在富含Na⁺的前驱液中，采用螯合剂辅助共沉淀法，通过合成过程的水浴加热及样品制备后的真空干燥，可获得空位少、水分少的高结晶度PBAs。将制备的PBAs样品与导电剂进行复合，可进一步改善其电子导电率及倍率性能，有望获得高容量、高循环特性及满足高倍率需求的正极材料 。综上所述，PBAs作为钠离子正极材料，可通过对其合成方法和改性研究的不断创新，进一步优化其电化学性能，使其在未来具有广阔的应用前景。

Abstract:

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.