Suppression of Jahn–Teller distortion in a layered Mn-based oxide cathode with Li substitution toward achieving stable K-storage

Abstract

Layered Mn-based oxide cathodes have attracted extensive attention for potassium-ion batteries because of their adjustable composition, easy synthesis, and abundant resources. However, their electrochemical performance is severely limited by the undesired phase transition and structural degradation caused by Jahn–Teller distortion. Here, Li was introduced into P3-K_0.67MnO₂ to restrain the abnormal elongation of Mn–O bonds and large lattice strain in [MnO₆] octahedra. Benefitting from the strengthened structure, the unfavorable phase transition of O3 → P′3 is completely suppressed in the as-optimized P3-K_0.67Li_0.07Mn_0.93O₂ sample. The corresponding capacity retention is up to 81.3% after 100 cycles, in contrast to 64.1% for K_0.67MnO₂. In addition, the introduction of Li decreases the diffusion energy barrier of K⁺, facilitating K⁺ diffusion. Even at 2C, K_0.67Li_0.07Mn_0.93O₂ retains a capacity of 63.1 mA h g⁻¹. This work provides an effective strategy for designing highly stable layered oxide cathodes for potassium-ion batteries and beyond.