Mn-based layered oxide is extensively investigated as a promising cathodematerial for potassium-ion batteries due to its high theoretical capacity andnatural abundance of manganese. However, the Jahn–Teller distortion causedby high-spin Mn3+(t2g3eg1) destabilizes the host structure and reduces thecycling stability. Here, K0.02Na0.55Mn0.70Ni0.25Zn0.05O2(denoted asKNMNO-Z) is reported to inhibit the Jahn–Teller effect and reduce theirreversible phase transition. Through the implementation of a Zn-dopingstrategy, higher Mn valence is achieved in the KNMNO-Z electrode, resultingin a reduction of Mn3+amount and subsequently leading to an improvementin cyclic stability. Specifically, after 1000 cycles, a high retention rate of 97%is observed. Density functional theory calculations reveals that low-valenceZn2+ions substituting the transition metal position of Mn regulated theelectronic structure around the Mn–O bonding, thereby alleviating theanisotropic coupling between oxidized O2−and Mn4+and improving thestructural stability. K0.02Na0.55Mn0.70Ni0.25Zn0.05O2provided an initialdischarge capacity of 57 mAh g−1at 100 mA g−1and a decay rate of only0.003% per cycle, indicating that the Zn-doped strategy is effective fordeveloping high-performance Mn-based layered oxide cathode materials inPIBs