Oxygen 2p Band Pinning Stabilizes High‐Voltage Potassium‐Ion Batteries

ABSTRACT Potassium‐ion batteries have emerged as a promising candidate for large‐scale energy storage applications, owing to the natural abundance of potassium resources. However, their development has been hampered by the structural instability and surface degradation of cathode materials. Herein, we demonstrate a O 2p Band pinning strategy that employs an epitaxial layer of a strongly correlated Mott insulator to stabilize the cathode‐electrolyte interface. This epitaxial interfacial electronic structure regulation (i) enables stable operation at a high cut‐off voltage of 4.6 V (vs K + /K) and (ii) captures and disperses high‐energy holes at the surface, stabilizing the valence state of lattice oxygen, thereby suppressing the formation of reactive oxygen species at the source. The O 2p band pinning CuO‐modified K 0.5 Mn 0.95 Ti 0.05 O 2 (KMTO‐SP) cathode delivers a high energy density of over 430 Wh kg −1 . Moreover, a full cell assembled with a graphite anode demonstrates exceptional cycling stability, maintaining performance over 3300 cycles at a current density of 500 mA g −1 , highlighting its promising practical applicability. This work establishes a new paradigm for designing high‐voltage cathodes through electronic interface regulation, demonstrating significant potential for energy storage systems.