Potassium‐ion (K‐ion) rechargeable batteries, considered to be lucrative low‐cost battery options for large‐scale and capacious energy storage systems, have been garnering tremendous attention in recent years. However, due to the scarcity of cathode materials that can allow the reversible reinsertion of large K‐ions at feasible capacities, the viability of K‐ion batteries has been greatly undercut. Herein, a potential cathode material is explored in the K₂O–Fe₂O₃–MnO₂ ternary phase system, which not only demonstrates reversible K‐ion reinsertion but also manifests relatively fast rate capabilities. The titled cathode compound, K_0.4Fe_0.5Mn_0.5O₂, demonstrates a reversible capacity of ≈120 mAh g⁻¹ at 10 h of (dis)charge (viz., C/10 rate) with ≈85% of the capacity retained at a 1 h of (dis)charge (1 C rate), which is considered to be good capacity retention. In addition, both hard and soft X‐rays are used to unravel the mechanism by which K‐ions are reversibly inserted into K_0.4Fe_0.5Mn_0.5O₂. The results reveal a cumulative participation of both manganese cations and oxygen anions in K_0.4Fe_0.5Mn_0.5O₂, illustrating its potential as a high‐capacity K‐ion battery cathode material that relies on both anion and cation redox. Further development of related high‐capacity cathode compositions can be anticipated.

中文翻译：

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一种可充电钾离子电池诱导锰阳离子和氧阴离子氧化还原的潜在阴极材料：缺钾K0.4Fe0.5Mn0.5O2

钾离子（K-ion）充电电池被认为是用于大型且功能强大的储能系统的低成本低成本电池选择，近年来受到了极大的关注。但是，由于阴极材料的稀缺性使得可以在可行的容量下可逆地重新插入大型K离子，因此大大削弱了K离子电池的生存能力。在此，在K ₂ O–Fe ₂ O ₃ –MnO ₂三元系统中探索了一种潜在的阴极材料，它不仅证明了可逆的K离子重新插入，而且还显示了相对较快的倍率能力。标题为阴极的化合物K _0.4 Fe _0.5 Mn _0.5 O ₂展示了在（放电）放电（h / C / 10速率）10 h时可逆容量≈120mAh g ^-1，在（放电）放电（1 c速率）1 h时保留了约85％的容量），这被认为是良好的容量保持率。此外，硬X射线和软X射线均用于阐明将K离子可逆地插入K _0.4 Fe _0.5 Mn _0.5 O ₂的机理。结果表明，锰阳离子和氧阴离子在K _0.4 Fe _0.5 Mn _0.5 O _2中的累积参与，说明了其作为依赖于阴离子和阳离子氧化还原的高容量K离子电池正极材料的潜力。可以预期相关高容量阴极组合物的进一步发展。