Abstract: Polymer cathodes have attracted growing interest for potassium-ion batteries (PIBs) due to their tunable molecular structures, abundant redox-active sites, and sustainable elemental compositions. Compared with inorganic intercalation-type cathodes, polymer cathodes typically store charge through reversible redox reactions between K⁺ ions or electrolyte anions and organic functional groups, including carbonyl, imide, quinone, azo, imine, and nitrogen-containing heterocyclic units. Their electrochemical performance is governed not only by the intrinsic redox chemistry of the active sites, but also by the polymer backbone configuration, π-conjugation degree, aggregation behavior, pore structure, and the stability of the electrode/electrolyte interface. This review summarizes recent progress in polymer cathodes for PIBs, with a focus on potassium-storage mechanisms and structural optimization strategies. Representative mechanisms, such as carbonyl coordination, imide chelation, multielectron redox processes, bipolar charge compensation, and pseudocapacitive behavior, are discussed from the perspectives of molecular structure, ion-electrode interactions, and charge-transfer kinetics. In addition, the ion-specific differences among K⁺, Li⁺, and Na⁺ are analyzed in terms of solvation/desolvation behavior, local coordination environments, and redox-site utilization. Key optimization strategies, including polymerization-degree control, rigid π-conjugated backbone design, porous or three-dimensional network construction, conductive compositing, and electrolyte matching, are highlighted. Finally, the remaining challenges and future research directions are discussed to guide the rational design of high-performance polymer cathodes for PIBs.

Key words: Potassium-ion battery, Polymer cathode, Energy storage mechanism, Optimization strategy