An Adaptive High‐Entropy Superstructure Cathode: Concurrently Tackling Phase Transition, Oxygen Redox, and Ambient Stability for Potassium‐Ion Batteries

ABSTRACT The two‐dimensional layered framework, while conferring notable ion diffusion kinetics for potassium layered transition metal oxides (K x TMO 2 ), concurrently suffers from inherent structural degradation, limited charge compensation sites and poor air stability. Herein, an entropy‐tailored dual‐site Li‐doped high‐entropy superstructure oxide, K 0.67 Mn 0.47 Li 0.06 Co 0.125 Ni 0.125 Fe 0.125 Cu 0.125 O 2 , is proposed as a cathode for potassium‐ion batteries. The unexpected phase transitions of P‐O and P‐P' induced by Jahn–Teller (J–T) lattice distortion and MnO 6 layer gliding can be completely suppressed by high‐entropy, superlattice stabilization, and geometric and electronic interlayer pinning effect, thus enabling a single‐phase solid‐solution K‐ion storage mechanism. Meanwhile, [K‐O‐Li] configuration, along with high‐entropy composition, elevates O 2p non‐bonding orbital energy, enabling differentiated hybridization with multi‐TM d‐orbitals to establish a continuous and broad distribution of coupled hybrid network, which facilitates highly reversible cationic‐anionic charge compensation. In situ formed spinel‐like layer acts as an electronically passivated barrier with markedly reduced CO 2 chemisorption on (010) facet to curtail the possibility of acid‐driven degradation reactions occurring on layered oxide bulk, a primary pathway for air‐induced deterioration, thus fundamentally enhancing ambient resistance. Therefore, high‐entropy electrode contributes high energy density, superior rate capability and cyclic stability in half‐cell and solid‐state full‐batteries. This work provides insights into the design of high‐stability layered oxide cathodes for practical application.