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/CoSe 2 –C@Cu) as an advanced anode for potassium-ion battery (PIBs). The conductive CoSe/CoSe 2 heterojunction with rich Se vacancy defects, conductive sp 2 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/CoSe 2 –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/CoSe 2 –C@Cu heterostructure, which buffers the deformation of structure and volume and greatly promotes the cycle life during the potassium/depotassium process. Graphical abstract