Rationally designed P2‐K_0.75[Ni_1/3Mn_2/3]O₂ is introduced as a novel cathode material for potassium‐ion batteries (KIBs). P2‐K_0.75[Ni_1/3Mn_2/3]O₂ cathode material designed through electrochemical ion‐exchange from P2‐Na_2/3[Ni_1/3Mn_2/3]O₂ exhibits satisfactory electrode performances; 110 mAh g⁻¹ (20 mA g⁻¹) retaining 86% of capacity for 300 cycles and unexpectedly high reversible capacity of about 91 mAh g⁻¹ (1400 mA g⁻¹) with excellent capacity retention of 83% over 500 cycles. According to theoretical and experimental investigations, the overall potassium storage mechanism of P2‐K_0.75[Ni_1/3Mn_2/3]O₂ is revealed to be a single‐phase reaction with small lattice change upon charge and discharge, presenting the Ni^4+/2+ redox couple reaction. Such high power capability is possible through the facile K⁺ migration in the K_0.75[Ni_1/3Mn_2/3]O₂ structure with a low activation barrier energy of ≈210 meV. These findings indicate that P2‐K_0.75[Ni_1/3Mn_2/3]O₂ is a promising candidate cathode material for high‐rate and long‐life KIBs.

中文翻译：

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用于高功率和长寿命钾离子电池的P2-K0.75 [Ni1 / 3Mn2 / 3] O2阴极材料

引入合理设计的P2-K _0.75 [Ni _1/3 Mn _2/3 ] O ₂作为钾离子电池（KIBs）的新型阴极材料。通过从P2-Na _2/3 [Ni _1/3 Mn _2/3 ] O ₂进行电化学离子交换而设计的P2-K _0.75 [Ni _1/3 Mn _2/3 ] O ₂正极材料具有令人满意的电极性能。110 mAh g ^-1（20 mA g ^-1）可在300个循环中保持86％的容量，出乎意料的高可逆容量约为91 mAh g ^-1（1400 mA g ^-1）在500个循环中具有83％的出色容量保持率。根据理论和实验研究，揭示了P2-K _0.75 [Ni _1/3 Mn _2/3 ] O ₂的整体钾存储机理是单相反应，充放电时晶格变化小，呈现Ni ^{4 + / 2 +}氧化还原反应。通过在K _0.75 [Ni _1/3 Mn _2/3 ] O ₂结构中以容易的K ⁺迁移以及约210 meV的低激活势垒能，实现如此高的功率能力。这些发现表明P2-K _0.75 [Ni _1/3 Mn_2/3 ] O ₂是用于高速率和长寿命KIB的有希望的候选阴极材料。