Potassium-ion batteries (PIBs) have aroused considerable interest as large-scale energy storage candidates owing to a naturally abundant potassium resource and low cost. Since the birth of PIBs, the solid electrolyte interphase (SEI) has been a critical concern, which plays a vital role in the coulombic efficiency, cycling stability and even safety of batteries. However, the SEI of PIBs remains poorly understood. In this review, we begin with a discussion regarding the differences in the chemical composition and structure of the K-ion SEI versus the much better-known Li-ion and Na-ion SEI. Unanswered scientific questions on the nature of the K-ion SEI are clearly identified. We review findings used to understand the formation mechanism of the SEI on graphite, and the existence of the SEI in ether-based electrolytes is openly debated. The current understanding of the SEI on different types of anodes is comprehensively summarized and discussed, with an emphasis on how the enhanced stability of the SEI fundamentally affects the efficiency and reversibility of electrochemical reactions. Finally, we detail the major challenges of anodes and discuss the emerging research directions for further development of PIBs.

中文翻译：

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钾离子电池中的固态电解质相（SEI）

钾离子电池（PIB）由于天然丰富的钾资源和低成本而引起了人们的广泛兴趣，成为大规模的储能对象。自从PIB诞生以来，固体电解质中间相（SEI）就成为至关重要的问题，它对库仑效率，循环稳定性甚至电池的安全性都起着至关重要的作用。但是，对PIB的SEI知之甚少。在这篇综述中，我们将首先讨论K离子SEI与知名度更高的锂离子和钠离子SEI。明确确定了有关K-ion SEI性质的未解决科学问题。我们回顾了用于理解石墨上SEI形成机理的发现，并且公开讨论了醚基电解质中SEI的存在。全面总结和讨论了当前对SEI在不同类型阳极上的理解，重点是SEI增强的稳定性如何从根本上影响电化学反应的效率和可逆性。最后，我们详细介绍了阳极的主要挑战，并讨论了PIB进一步发展的新兴研究方向。