In the development of electrolytes for high-performance alkali metal batteries, significantly different electrochemical performances were often reported among lithium (Li), sodium (Na), and potassium (K) metals tested in the electrolytes with similar compositions but the underlying mechanism behind these observed discrepancies remains unclear. Here, by adopting a suite of complementary analytical techniques aided with theoretical calculations, we show a close correlation between the Lewis acidity of alkali metal ions and the electrochemical performance of corresponding alkali metals. The lower Lewis acidity of K compared with that of Li and Na endows K with distinctive advantages to easily strip off the reduction-vulnerable solvent and greatly reduces the dissociation degree of K salts to form an anion-rich solvation sheath, resulting in a robust solid electrolyte interphase. These features lead K metal to outperform Li and Na metals in terms of both electrochemical cycling reversibility and calendar aging stability in the present study.

中文翻译：

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较温和的路易斯酸度使碱金属阳极具有优异的电化学性能

在高性能碱金属电池电解质的开发中，在具有相似成分的电解质中测试的锂（Li）、钠（Na）和钾（K）金属之间经常报告显着不同的电化学性能，但这些背后的潜在机制观察到的差异仍不清楚。在这里，通过采用一套辅助分析技术和理论计算，我们证明了碱金属离子的路易斯酸度与相应碱金属的电化学性能之间的密切相关性。与Li和Na相比，K的路易斯酸度较低，这使得K具有独特的优势，可以轻松剥离易还原的溶剂，并大大降低K盐的解离度，形成富含阴离子的溶剂化鞘，从而形成坚固的固体电解质界面。在本研究中，这些特性导致钾金属在电化学循环可逆性和日历老化稳定性方面均优于锂和钠金属。