Herein, we propose P’2-K_x[Ni_0.05Mn_0.95]O₂ as a promising cathode material for high-energy-density potassium-ion batteries (KIBs). The P’2-K_0.83[Ni_0.05Mn_0.95]O₂ delivers a high discharge capacity of 155 mAh g⁻¹ (52 mA g⁻¹) as well as a high energy density of 420 Wh kg⁻¹ in the voltage range of 1.5–4.3 V. Surprisingly, the fast K-ion migration in the P’2-K_0.83[Ni_0.05Mn_0.95]O₂ structure with a low activation barrier energy of ∼271 meV enables achievement of high capacity at high currents, 78 mAh g⁻¹ at 2600 mA g⁻¹, as well as long-term cycling stability with capacity retention of ∼77% after 500 cycles at 520 mA g⁻¹. Operando synchrotron X-ray diffraction analysis reveals that P’2-K_0.83[Ni_0.05Mn_0.95]O₂ retains the P’2-phase without P’2-OP4 phase transition during charge/discharge in the voltage range of 1.5–4.3 V, which is abnormal compared to the other P’2-based layered cathode materials for sodium-ion batteries, being responsible for the long-term cycle stability of P’2-K_0.83[Ni_0.05Mn_0.95]O₂. First-principles calculation results indicate that the excellent electrochemical performance results from the structural stability associated with a single -phase reaction upon K⁺ extraction/insertion out of/into the host structure. The remarkable potassium storage capability of P’2-K_0.83[Ni_0.05Mn_0.95]O₂ makes it a promising cathode candidate for KIBs.

本文中，我们提出P'2-K _x [Ni _0.05 Mn _0.95 ] O ₂作为高能量密度钾离子电池（KIBs）的有希望的阴极材料。P'2-K _0.83 [Ni _0.05 Mn _0.95 ] O ₂在电压范围内可提供155 mAh g ^-1（52 mA g ^-1）的高放电容量以及420 Wh kg ^-1的高能量密度1.5-4.3V。令人惊讶的是，P'2-K _0.83 [Ni _0.05 Mn _0.95 ] O _2中的快速K离子迁移结构的~271低激活势垒能兆电子伏使得能够高容量实现在高电流，78毫安克^-1在2600毫安克^-1，以及长期与500次循环后的~77％容量维持循环稳定性在520 mA g ^-1下。Operando同步加速器X射线衍射分析表明，在1.5–4.3的电压范围内，P'2-K _0.83 [Ni _0.05 Mn _0.95 ] O ₂保留P'2-相，而P'2-OP4没有相变。 V，与钠离子电池的其他基于P'2的分层阴极材料相比是不正常的，它负责P'2-K的长期循环稳定性_0.83[Ni _0.05 Mn _0.95 ] O ₂。第一性原理计算结果表明，优异的电化学性能归因于与在K ⁺提取/插入主体结构中/插入主体结构中时的单相反应相关的结构稳定性。P'2-K _0.83 [Ni _0.05 Mn _0.95 ] O ₂的出色的钾存储能力使其成为KIBs的有希望的阴极候选物。