Research on potassium-ion batteries (PIBs) has recently been reemphasized because of the irreplaceable advantages of abundant resource, cheap price, and comparable standard redox potential to lithium, displaying great potential for large-scale energy conversion. Nevertheless, the development of PIBs is tremendously hindered due to the shortage of matching electrode materials that can reversibly uptake/release larger K + during discharging and charging. Herein, we report the fabrication of double-layer carbon-coated CoSe hollow nanocapsules (denoted as CoSe@C/HCPs) using a flexible template-assisted strategy. The as-prepared CoSe@C/HCPs exhibit enhanced electrochemical performance as an anode material for PIBs. In particular, they can deliver a high reversible capacity of 461 mAh g –1 at 100 mA g –1 , an extraordinary rate capability of 278 mAh g –1 at 3 A g –1 , and decent cycling stability with 182 mAh g –1 retained at 3 A g –1 after 300 cycles. More importantly, a full PIB cell (P2-type K 0.6 CoO 2 used as the cathode material) also demonstrates an improved electrochemical performance (168 mAh g –1 at 100 mA g –1 after 100 cycles). These current studies have made a vanguard attempt to synthesize selenium-based anodes with sophisticated hierarchical architectures for PIBs, which could provide extensive impetus for the evolution of advanced PIBs.