A Polymer‐Assisted Spinodal Decomposition Strategy toward Interconnected Porous Sodium Super Ionic Conductor‐Structured Polyanion‐Type Materials and Their Application as a High‐Power Sodium‐Ion Battery Cathode

A general polymer‐assisted spinodal decomposition strategy is used to prepare hierarchically porous sodium super ionic conductor (NASICON)‐structured polyanion‐type materials (e.g., Na(3)V(2)(PO(4))(3), Li(3)V(2)(PO(4))(3), K(3)V(2)(PO(4))(3), Na(4)MnV(PO(4))(3), and Na(2)TiV(PO(4))(3)) in a tetrahydrofuran/ethanol/H(2)O synthesis system. Depending on the boiling point of solvents, the selective evaporation of the solvents induces both macrophase separation via spinodal decomposition and mesophase separation via self‐assembly of inorganic precursors and amphiphilic block copolymers, leading to the formation of hierarchically porous structures. The resulting hierarchically porous Na(3)V(2)(PO(4))(3) possessing large specific surface area (≈77 m(2) g(−1)) and pore volume (≈0.272 cm(3) g(−1)) shows a high specific capacity of 117.6 mAh g(−1) at 0.1 C achieving the theoretical value and a long cycling life with 77% capacity retention over 1000 cycles at 5 C. This method presented here can open a facile avenue to synthesize other hierarchically porous polyanion‐type materials.