Potassium-ion batteries (KIBs) are considered an important alternative for lithium-ion batteries owing to the abundant potassium (K) resources and low-cost. To date, most reported anode materials for KIBs have been limited to carbonaceous materials which can well accommodate the large potassium ions (K⁺) but show humble capacity performance. As compared, metal oxide-based anodes can potentially provide higher capacity yet cyclability is poor, which has been rarely researched. Herein, we report a sequential phase evolution mechanism for bimetallic oxide anode. Upon potassiation, the microflower-like Bi₂WO₆ undergoes a multistep evolution process, which first combines with K⁺ then converts into a highly reversible phase of Bi, then via a solid-solution reaction eventually it forms the K₃Bi alloy. After repeated cycling process, such unique hierarchical and mesoporous morphology of Bi₂WO₆ can be well maintained, leading to superior cyclability with a high specific potassium storage capacity (652 mAh g⁻¹ at 100 mA g⁻¹). Even at a large current density of 1 A g⁻¹, a reversible specific capacity of 216 mAh g⁻¹ can still be delivered over 300 cycles. Such a novel working mechanism of bimetallic oxide anodes will promote the practical use of KIBs in diverse energy storage applications.

由于钾（K）资源丰富且成本低廉，钾离子电池（KIB）被认为是锂离子电池的重要替代品。迄今为止，大多数报道的用于KIB的阳极材料仅限于碳质材料，该材料可以很好地容纳大钾离子（K ⁺），但显示出较低的容量性能。相比之下，基于金属氧化物的阳极可以潜在地提供更高的容量，但循环性较差，对此鲜有研究。在本文中，我们报告了双金属氧化物阳极的相序演化机理。在钾化作用下，类似微花的Bi ₂ WO ₆经历了多步进化过程，该过程首先与K ⁺然后转变成高度可逆的Bi相，然后通过固溶反应最终形成K ₃ Bi合金。重复循环过程中，这样的唯一层级和Bi中孔形态后₂ WO ₆可以很好地维持，从而导致优异的可循环性有高的比钾的存储容量（652毫安克^-1在100mA克^-1）。即使在1 A g ^-1的大电流密度下，在300个循环中仍可提供216 mAh g ^-1的可逆比容量。这种双金属氧化物阳极的新颖工作机制将促进KIB在各种储能应用中的实际使用。