The potassium–selenium (K–Se) battery is considered as an alternative solution for stationary energy storage because of abundant resource of K. However, the detailed mechanism of the energy storage process is yet to be unraveled. Herein, the findings in probing the working mechanism of the K‐ion storage in Se cathode are reported using both experimental and computational approaches. A flexible K–Se battery is prepared by employing the small‐molecule Se embedded in freestanding N ‐doped porous carbon nanofibers thin film (Se@NPCFs) as cathode. The reaction mechanisms are elucidated by identifying the existence of short‐chain molecular Se encapsulated inside the microporous host, which transforms to K₂Se by a two‐step conversion reaction via an “all‐solid‐state” electrochemical process in the carbonate electrolyte system. Through the whole reaction, the generation of polyselenides (K₂Se_n, 3 ≤ n ≤ 8) is effectively suppressed by electrochemical reaction dominated by Se₂ molecules, thus significantly enhancing the utilization of Se and effecting the voltage platform of the K–Se battery. This work offers a practical pathway to optimize the K–Se battery performance through structure engineering and manipulation of selenium chemistry for the formation of selective species and reveal its internal reaction mechanism in the carbonate electrolyte.

中文翻译：

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揭示小分子Se @ Peapod-like N掺杂碳纳米纤维中优良钾储存的性质

由于钾的丰富资源，钾-硒（K-Se）电池被认为是固定能量存储的替代解决方案。但是，能量存储过程的详细机制还有待进一步阐明。在此，通过实验和计算方法报道了探索硒阴极中K离子存储的工作机理的发现。通过将嵌在独立的N掺杂多孔碳纳米纤维薄膜（Se @ NPCFs）中的小分子Se用作阴极来制备柔性K-Se电池。通过鉴定微孔宿主内包裹的短链分子硒的存在来阐明反应机理，该分子转化为K ₂通过碳酸盐电解质系统中的“全固态”电化学过程通过两步转化反应实现硒。通过整个反应，polyselenides（K的产生₂硒_Ñ，3≤  Ñ  ≤8）被有效地通过硒为主电化学反应抑制_2个分子，从而显著提高Se构成的利用和实现所述K-Se构成的电压平台电池。这项工作为通过结构工程和硒化学的操纵来优化K-Se电池的性能提供了一条可行的途径，以形成选择性物质并揭示其在碳酸盐电解质中的内部反应机理。