A universal strategy for bridging Prussian blue analogues and sodium layered oxide cathodes: direct fast conversion, dynamic structural evolution, and sodium storage mechanisms

Prussian blue analogues (PBAs) are widely recognized as one of the most promising cathode materials for sodium-ion batteries (SIBs). However, many unqualified PBAs with unsatisfactory electrochemical performance are difficult to dispose of and pose a risk of environmental contamination. Additionally, the production process of layered oxides, another popular cathode material for SIBs, requires prolonged high-temperature sintering, resulting in significant energy consumption. To address the aforementioned issues, a "two birds with one stone" strategy is proposed. This approach not only demonstrates the feasibility of directly preparing layered oxides with PBAs as precursors through a fast sintering process but also simultaneously addresses the challenge of treating unqualified PBAs while minimizing excessive energy consumption during the preparation of layered oxides. Furthermore, a series of binary, ternary, and quaternary layered oxides were synthesized directly by utilizing PBAs with varying compositions, showcasing the universality of this strategy. This innovative approach breaks the boundaries between different types of sodium cathode materials and builds a distinctive bridge for the direct conversion of PBAs into layered oxides, thereby widening the feasibility of the cathode for SIBs.