High Entropy‐Tuning Enables Suppressed Phase Transition of Layered Manganese‐Based Oxides for High‐Mass‐Loading Potassium‐Ion Batteries

Abstract Layered manganese‐based oxides are regarded as promising cathode materials for potassium‐ion batteries (PIBs). However, their practical application is hindered by sluggish reaction kinetics and poor cycling stability, primarily due to multiple phase transitions and pronounced Jahn–Teller distortion. Herein, a high‐entropy layered oxide, K 0.45 Mn 0.75 Mg 0.05 Al 0.05 Cr 0.05 Co 0.05 Ti 0.05 O 2 is reported, in which the synergistic effect of multicomponent incorporation effectively addresses these challenges. The Cr 3+ /Cr 6+ redox couple provides additional charge compensation and reduces the dependence on the Mn 3+ /Mn 4+ redox pair, thereby mitigating Jahn–Teller distortion. Moreover, the increased configurational entropy suppresses the formation of the unfavorable P3″ phase and delays the P3′ phase transition during cycling, which enhances K + diffusion kinetics and inhibits microcrack propagation. As a result, the synthesized cathode delivers a high discharge capacity of 124.2 mAh g −1 at 20 mA g −1 and retains 81% of its capacity after 120 cycles in a full‐cell. Notably, a thick electrode with an ultrahigh mass loading of 48.5 mg cm −2 achieves an areal capacity of 4.0 mAh cm −2 , representing a record‐high value among PIB cathodes. This work offers a new pathway for the rational design of high‐performance cathode materials, underscoring their promise for high‐energy‐density PIBs.