A N–CoSe/CoSe2–C@Cu hierarchical architecture as a current collector-integrated anode for potassium-ion batteries

The highly reversible insertion/extraction of large-radius K⁺ into electrode materials remains a tough goal, especially for conversion-type materials. Herein, we design a current collector-integrated electrode (N–CoSe/CoSe₂–C@Cu) as an advanced anode for potassium-ion battery (PIBs). The conductive CoSe/CoSe₂ heterojunction with rich Se vacancy defects, conductive sp² N-doped carbon layer, and the elastic copper foil matrix can greatly accelerate the electron transfer and enhance the structural stability. Consequently, the well-designed N–CoSe/CoSe₂–C@Cu current collector-integrated electrode displays enhanced potassium storage performance with regard to a high capacity (325.1 mAh·g⁻¹ at 0.1 A·g⁻¹ after 200 cycles), an exceptional rate capability (223.5 mAh·g⁻¹ at 2000 mA·g⁻¹), and an extraordinary long-term cycle stability (a capacity fading of only 0.019% per cycle over 1200 cycles at 2000 mA·g⁻¹). Impressively, ex situ scanning electron microscopy (SEM) characterizations prove that the elastic structure of copper foil is merged into the cleverly designed N–CoSe/CoSe₂–C@Cu heterostructure, which buffers the deformation of structure and volume and greatly promotes the cycle life during the potassium/depotassium process.

Graphical abstract