Due to the abundant and low‐cost K resources, the exploration of suitable materials for potassium‐ion batteries (KIBs) is advancing as a promising alternative to lithium‐ion batteries. However, the large‐sized and sluggish‐kinetic K ions cause poor battery behavior. This work reports a metallic octahedral CoSe₂ threaded by N‐doped carbon nanotubes as a flexible framework for a high‐performance KIBs anode. The metallic property of CoSe₂ together with the highly conductive N‐doped carbon nanotubes greatly accelerates the electron transfer and improves the rate performance. The carbon nanotube framework serves as a backbone to inhibit the agglomeration, anchor the active materials, and stabilize the integral structure. Every octahedral CoSe₂ particle arranges along the carbon nanotubes in sequence, and the zigzag void space can accommodate the volume expansion during cycling, therefore boosting the cycling stability. Density functional theory is also employed to study the K‐ion intercalation/deintercalation process. This unique structure delivers a high capacity (253 mAh g⁻¹ at 0.2 A g⁻¹ over 100 cycles) and enhanced rate performance (173 mAh g⁻¹ at 2.0 A g⁻¹ over 600 cycles) as an advanced anode material for KIBs.

Potassium‐ion batteries (PIBs) exhibit a considerable application prospect for energy storage systems due to their low cost, high operating voltage, and superior ionic conductivity. As a vital configuration in PIBs, the two‐phase interface, which refers to K‐ion diffusion from the electrolyte to the electrode surface (solid–liquid interface) and K‐ion migration between different particles (solid–solid interface), deeply determines the diffusion/reaction kinetics and structural stability, thus significantly affecting the rate performance and cyclability. However, researches on two‐phase interface are still in its infancy and need further attentions. This review first starts from the fundamental understanding of solid–liquid and solid–solid interfaces to in‐depth analyzing the effect mechanism of different improvement strategies on them, such as optimization of electrolyte and binders, heterostructure design, modulation of interlayer spacing, etc. Afterward, the research progress of these improvement strategies is summarized comprehensively. Finally, the major challenges are proposed, and the corresponding solving strategies are presented. This review is expected to give an insight into the importance of two‐phase interface on diffusion/reaction kinetics, and provides a guidance for developing other advanced anodes in PIBs.