Electrode materials for potassium-ion batteries: structural innovation, interfacial engineering and future perspectives

Potassium-ion batteries (PIBs) are promising candidates for large-scale energy storage owing to the abundance and low cost of potassium resources. However, the large ionic size of K⁺ couples structural evolution, ion transport, mechanical deformation, and electrode-electrolyte interfacial reactions, while the finite potassium inventory in practical full cells imposes additional constraints on long-term reversibility. This Feature Article reviews recent advances in representative cathode and anode materials from the perspective of structure-reaction-interface relationships. Layered oxides, polyanionic compounds, and Prussian blue analogues are discussed with emphasis on redox chemistry, phase evolution, K⁺ transport, defect regulation, and interfacial stability, whereas carbon-based, alloy-type, and conversion-type anodes are examined in terms of K⁺ storage mechanisms, chemo-mechanical evolution, strain accommodation, and solid electrolyte interphase regulation. Across these chemistries, reversible structural evolution, bulk-interface co-design, and persistent K⁺/electron transport emerge as common requirements. The discussion further extends to dense, high-loading electrodes and realistic full cells, highlighting electrode compactness, potassium inventory, electrolyte quantity, N/P ratio, and manufacturability as key considerations for practical PIB development.