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

The two-dimensional layered framework, while conferring notable ion diffusion kinetics for potassium layered transition metal oxides (K_xTMO₂), 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_0.67Mn_0.47Li_0.06Co_0.125Ni_0.125Fe_0.125Cu_0.125O₂, 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 MnO₆ 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 CO₂ 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.