Regulating Chemomechanical Interactions in a High-Compaction Na4Fe3(PO4)2P2O7 Cathode for Durable Sodium Storage

The polyanionic Na4Fe3(PO4)2P2O7 (NFPP) cathode is recognized for its cost-effectiveness and three-dimensional framework structure. However, its anisotropic lattice evolution induces internal stress accumulation. Furthermore, the pursuit of high energy density necessitates high-compaction processing, which exacerbates localized stress buildup. Herein, this study explores and regulates the chemomechanical interactions of NFPP under high-compaction conditions. The formation of microcracks and new reaction interfaces constitutes a chemomechanical failure pathway. To suppress this, the introduction of large-sized La promotes grain refinement and close packing, thereby enhancing mechanical strength. Meanwhile, lattice substitution triggers local FeO6 structural rearrangement, strengthening the Fe-O bonds and mitigating lattice strain. The optimized NFPP-La exhibits a remarkable reversible capacity of 90.4 mAh g-1 at 10 C and retains 92.2% capacity after 5000 cycles under high compaction conditions. Moreover, pouch cell evaluation validated its outstanding temperature adaptability (-40 to 60 °C) and robust cycling stability.