Solid-state potassium batteries are potentially supplementary to lithium batteries in large-scale energy storage due to their low cost, high safety, and energy density. However, potassium-ion solid electrolytes are quite limited and deliver lower ionic conductivities than lithium or sodium counterparts. Herein, K₂Mg₂TeO₆, an underexplored potassium-ion solid electrolyte with comparable high ionic conductivity, the capability to suppress metallic K dendrites, and mechanical-chemical and electrochemical stabilities against the metallic K anode, is reported. High potassium-ion conductivities of 1.65 × 10^–6 S cm^–1 at 20 °C and 5.15 × 10^–5 S cm^–1 at 120 °C are achieved. An ultrastable K stripping/plating behavior is implemented for 500 h under 0.02 mA cm^–2, and the critical current density reaches 0.14 mA cm^–2 at 60 °C. Cells coupling the KC composite anode and Prussian blue cathode deliver good rate performance (1 C, ∼64 mAh g^–1) and long-term cycling stability of 400 cycles with a capacity retention of 94%.

中文翻译：

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层状 K2Mg2TeO6 固体电解质可实现长寿命固态钾电池

固态钾电池因其成本低、安全性高、能量密度高等特点，在大规模储能领域有望成为锂电池的潜在补充。然而，钾离子固体电解质非常有限，并且其离子电导率低于锂或钠电解质。本文报道了K ₂ Mg ₂ TeO ₆，一种尚未开发的钾离子固体电解质，具有相当高的离子电导率、抑制金属K枝晶的能力以及对金属K阳极的机械化学和电化学稳定性。 20 °C 时钾离子电导率高达 1.65 × 10 ^–6 S cm ^–1，120 °C 时钾离子电导率高达5.15 × 10 ^–5 S cm ^–1。在 0.02 mA cm ^–2下实现了 500 小时的超稳定 K 剥离/电镀行为，并且在 60 °C 时临界电流密度达到 0.14 mA cm ^–2 。 KC复合阳极和普鲁士蓝阴极耦合的电池具有良好的倍率性能（1 C，∼64 mAh g ^–1）和400次循环的长期循环稳定性，容量保持率为94%。