Zero‐Waste Polyanion and Prussian Blue Composites toward Practical Sodium‐Ion Batteries

Abstract Closed‐loop transformation of raw materials into high‐value‐added products is highly desired for the sustainable development of the society but is seldom achieved. Here, a low‐cost, solvent‐free and “zero‐waste” mechanochemical protocol is reported for the large‐scale preparation of cathode materials for sodium‐ion batteries (SIBs). This process ensures full utilization of raw materials, effectively reduces water consumption, and simplifies the operating process. Benefiting from the synergistic effect between the cubic Prussian blue analogs (c‐NFFHCF) and dehydrated polyanionic sulfates (m‐NFS), the generated composite exhibits promising wide‐temperature electrochemical performance and excellent practical application potential. The synergistic effect between m‐NFS and c‐NFFHCF in the composite is revealed through multiple in situ characterizations and density functional theory calculations. The proposed mechanochemical strategy can be scaled to a kilogram‐grade level, providing a sustainable method for the value‐added utilization of the by‐products during Prussian blue analogs synthesis, advancing the design of “zero‐waste” cathode materials for low‐cost practical SIBs.