We introduce K₄Fe₃(PO₄)₂(P₂O₇) as a novel cathode material with superior electrochemical performance for K-ion batteries. First-principles calculation is used to predict the theoretical properties and detailed K⁺ storage mechanism of K₄Fe₃(PO₄)₂(P₂O₇), which are consistent with experimental results. K₄Fe₃(PO₄)₂(P₂O₇) exhibits a large specific discharge capacity of ∼118 mAh g^-1, approaching the theoretical capacity, at C/20 (1C = 120 mA g^-1) in the voltage range of 2.1-4.1V (vs. K⁺/K), allowing ∼3 mol of K⁺ de/intercalation per formula unit with a small volume change of ∼4% during charge/discharge. Even at 5C, up to ∼70% of its theoretical specific capacity is retained, and this outstanding power-capability is related to the low activation barrier energy for K⁺ diffusion, as verified through first-principles calculations. Furthermore, K₄Fe₃(PO₄)₂(P₂O₇) exhibits excellent cyclability with retention of ∼82% of the initial capacity after 500 cycles at 5C. The above theoretical and experimental results suggest the feasibility of using K₄Fe₃(PO₄)₂(P₂O₇) as a cathode material for rechargeable potassium batteries.

我们介绍了K ₄ Fe ₃（PO ₄）₂（P ₂ O ₇）作为一种新型的阴极材料，具有优异的电化学性能，适用于K离子电池。第一性原理计算用于预测K ₄ Fe ₃（PO ₄）₂（P ₂ O ₇）的理论性质和详细的K ⁺储存机理，与实验结果一致。K ₄ Fe ₃（PO ₄）₂（P ₂ O ₇）呈现~118毫安g的大的比放电容量^-1，接近理论容量，在C / 20（1C =120毫安克^-1在2.1-4.1V的电压范围内）（对比ķ ⁺ / K） ，每个分子式单位允许〜3 mol K ⁺脱除/嵌入，在充电/放电期间体积变化约为〜4％。甚至在5°C时，仍保留了约70％的理论比容量，而且这种出色的功率容量与K ⁺扩散的低活化势垒能有关，这已通过第一性原理计算得到了验证。此外，K ₄ Fe ₃（PO ₄）₂（P ₂ O ₇）具有极好的可循环性，在5C下经过500次循环后，保留了约82％的初始容量。上述理论和实验结果表明使用K ₄ Fe ₃（PO ₄）₂（P ₂ O ₇）作为可充电钾电池正极材料的可行性。