The application of a layered K_0.5MnO₂ cathode in potassium-ion batteries is limited by its poor cycling performance when charged above 4.0 V (vs K⁺/K), and the underlying mechanism for this electrochemical instability is still unclear. Here, it is discovered that ethylene carbonate (EC) will intercalate into the depotassiated K_0.5MnO₂, causing the exfoliation of the layered compound and the capacity decay under high charge cutoff voltage. When the carbonates are replaced with a nonflammable phosphate, the electrochemical performance of K_0.5MnO₂ above 4.0 V (vs K⁺/K) is significantly enhanced with a large reversible capacity (120 mAh g^–1) and high capacity retention of 84% after 400 cycles. This phosphate-based electrolyte also demonstrates good compatibility with the commercial graphite anode, enabling the encouraging electrochemical performance of the K_0.5MnO₂|graphite full-cell. The present study provides new insights on further exploration of other electrolytes to advance the emerging low-cost and high-performance potassium-ion batteries.

中文翻译：

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低成本钾离子电池的不可燃电解质高性能K _0.5 MnO ₂阴极

当在高于4.0 V（vs K ⁺ / K）充电时，层状K _0.5 MnO ₂阴极在钾离子电池中的应用受限于其较差的循环性能，并且这种电化学不稳定性的潜在机制仍不清楚。在此，发现碳酸亚乙酯（EC）会嵌入到去钾化的K _0.5 MnO _2中，引起层状化合物的剥离并在高电荷截止电压下容量下降。当碳酸盐替换为不可燃的磷酸盐时，K _0.5 MnO ₂的电化学性能高于4.0 V（vs K ⁺/ K）通过大的可逆容量（120 mAh g ^–1）和400次循环后84％的高容量保持率而得到显着增强。该磷酸盐基电解质还显示出与市售石墨阳极的良好相容性，从而使K _0.5 MnO ₂石墨全电池具有令人鼓舞的电化学性能。本研究为进一步探索其他电解质以推动新兴的低成本和高性能钾离子电池提供了新的见识。