Potassium deficiency and irreversible loss of potassium at the initial cycle of potassium-ion batteries inevitably reduce their energy density and cycle life. Cathode pre-potassiation before battery assembling is an efficient method to address these issues but faces problems such as safety risks and high cost. Herein, we report an economic and facile potassium compensation strategy employing a self-sacrificial agent (i.e., K₂C₄O₄) at cathodes to improve the performances of potassium-ion batteries. We found that with the addition of K₂C₄O₄ in a P3-type K_0.5MnO₂ cathode, the initial Coulombic efficiency of the electrode can be significantly improved from 53.6% to the reported highest one of 93.5%. Moreover, we demonstrate that the decomposition of K₂C₄O₄ during the charge process contributes to the formation of a thin and F-rich cathode electrolyte interphase layer on the surface of the electrode, benefiting for the improved kinetics and interfacial stability of K_0.5MnO₂ cathodes. As a result, a K₂C₄O₄-assisted potassium-ion full cell shows about three times higher energy density (220 W h kg⁻¹) and much enhanced capacity retention than the K₂C₄O₄-free cell without any pre-potassiation treatment. The potassium compensation strategy provides an effective approach to overcome the existing technical hurdles for the development of potassium-based energy storage systems.

中文翻译：

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方酸二钾用于钾离子电池的高效阴极钾补偿和界面稳定性改善

钾离子电池在初始循环时缺钾和钾的不可逆损失不可避免地会降低其能量密度和循环寿命。电池组装前的阴极预钾化是解决这些问题的有效方法，但面临安全风险和成本高等问题。在此，我们报告了一种经济且简便的钾补偿策略，该策略在正极采用自牺牲剂（即K ₂ C ₄ O ₄）来提高钾离子电池的性能。我们发现，在 P3 型 K _0.5 MnO _{2中加入 K 2} C ₄ O ₄阴极时，电极的初始库仑效率可以从 53.6% 显着提高到报道的最高 93.5%。此外，我们证明了在充电过程中K ₂ C ₄ O ₄的分解有助于在电极表面形成薄且富含F的正极电解质界面层，有利于改善K的动力学和界面稳定性。_0.5 MnO ₂阴极。结果，K ₂ C ₄ O _{4辅助钾离子全电池显示出比 K 2}高约三倍的能量密度（220 W h kg ^-1）和大大增强的容量保持率未经任何预钾化处理的无C ₄ O _4细胞。钾补偿策略为克服钾基储能系统开发的现有技术障碍提供了一种有效的方法。