Metallic bismuth (Bi) has been widely explored as remarkable anode material in alkali-ion batteries due to its high gravimetric/volumetric capacity. However, the huge volume expansion up to ≈406% from Bi to full potassiation phase K3 Bi, inducing the slow kinetics and poor cycling stability, hinders its implementation in potassium-ion batteries (PIBs). Here, facile strategy is developed to synthesize hierarchical bismuth nanodots/graphene (BiND/G) composites with ultrahigh-rate and durable potassium ion storage derived from an in situ spontaneous reduction of sodium bismuthate/graphene composites. The in situ formed ultrafine BiND (≈3 nm) confined in graphene layers can not only effectively accommodate the volume change during the alloying/dealloying process but can also provide high-speed channels for ionic transport to the highly active BiND. The BiND/G electrode provides a superior rate capability of 200 mA h g-1 at 10 A g-1 and an impressive reversible capacity of 213 mA h g-1 at 5 A g-1 after 500 cycles with almost no capacity decay. An operando synchrotron radiation-based X-ray diffraction reveals distinctively sharp multiphase transitions, suggesting its underlying operation mechanisms and superiority in potassium ion storage application.

中文翻译：

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原位形成铋的纳米点/石墨烯纳米结构，用于超高速率和耐用的钾离子存储。

金属铋（Bi）由于其高的重量/体积容量而被广泛地用作碱金属离子电池的阳极材料。然而，从Bi到完全钾化阶段K3 Bi的巨大体积膨胀高达406％，导致动力学缓慢和循环稳定性差，阻碍了其在钾离子电池（PIB）中的应用。在这里，人们开发了一种简便的策略来合成分级铋铋纳米颗粒/石墨烯（BiND / G）复合材料，该复合材料具有自发自发地还原铋酸钠/石墨烯复合材料的超高速率和持久的钾离子存储能力。局限在石墨烯层中的原位形成的超细BiND（≈3nm）不仅可以有效地适应合金化/脱合金过程中的体积变化，而且还可以提供离子向高活性BiND传输的高速通道。BiND / G电极在10 A g-1时可提供200 mA h g-1的超高倍率容量，在500次循环后在5 A g-1时可提供213 mA h g-1的可逆容量，几乎没有容量衰减。基于操作同步辐射的X射线衍射显示出鲜明的多相跃迁，表明其潜在的运行机制和在钾离子存储应用中的优越性。