Potassium-ion batteries (KIBs) are a potential candidate to lithium-ion batteries (LIBs) but possess unsatisfactory capacity and rate properties. Herein, the metallic cobalt selenide quantum dots (Co_0.85Se-QDs) encapsulated in mesoporous carbon matrix were designed via a direct hydrothermal method. Specifically, the cobalt selenide/carbon composite (Co_0.85Se-QDs/C) possesses tertiary hierarchical structure, which is the primary quantum dots, the secondary petals flake, and the tertiary hollow micropolyhedron framework. Co_0.85Se-QDs are homogenously embedded into the carbon petals flake, which constitute the hollow polyhedral framework. This unique structure can take the advantages of both nanoscale and microscale features: Co_0.85Se-QDs can expand in a multidimensional and ductile carbon matrix and reduce the K-intercalation stress in particle dimensions; the micropetals can restrain the agglomeration of active materials and promote the transportation of potassium ion and electron. In addition, the hollow carbon framework buffers volume expansion, maintains the structural integrity, and increases the electronic conductivity. Benefiting from this tertiary hierarchical structure, outstanding K-storage performance (402 mAh g⁻¹ after 100 cycles at 50 mA g⁻¹) is obtained when Co_0.85Se-QDs/C is used as KIBs anode. More importantly, the selenization process in this work is newly reported and can be generally extended to prepare other quantum dots encapsulated in edge-limited frameworks for excellent energy storage.

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钾离子电池（KIB）是锂离子电池（LIB）的潜在候选者，但容量和倍率性能不理想。本文中，通过直接水热法设计了包埋在介孔碳基体中的金属硒化钴量子点（Co _0.85 Se-QDs）。具体而言，硒化钴/碳复合材料（Co _0.85 Se-QDs / C）具有三级结构，即一级量子点，二级花瓣片状和三级空心微多面体骨架。Co _0.85 Se-QDs均匀地嵌入碳瓣片中，该片构成空心的多面体框架。这种独特的结构可以利用纳米级和微米级特征的优势：Co _0.85Se-QDs可以在多维可延展的碳基体中膨胀，并减小颗粒尺寸中的K插层应力。花瓣可以抑制活性物质的团聚并促进钾离子和电子的运输。此外，中空碳骨架可缓冲体积膨胀，保持结构完整性并增加电子导电性。从这个第三分层结构中受益，优秀ķ吸留性能（402毫安克^-1在50mA克100次循环后^-1）得到如果Co _0.85Se-QDs / C用作KIBs阳极。更重要的是，这项工作中的硒化过程是新近报道的，可以广泛扩展以制备封装在边缘受限框架中的其他量子点，以实现出色的能量存储。

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