2D Se‐Rich ZnSe/CoSe2@C Heterostructured Composite as Ultrastable Anodes for Alkaline‐Ion Batteries

2D transitional metal selenide heterostructures are promising electrode materials for potassium‐ion batteries (PIBs) owing to the large surface area, high mechanical strength, and short diffusion pathways. However, the cycling performance remains a significant challenge, particularly concerning the electrochemical conversion reaction. Herein, 2D Se‐rich ZnSe/CoSe2@C heterostructured composite is fabricated via a convenient hydrothermal approach followed by selenization process, and then applied as high‐performance anodes for PIBs. For example, the capacity delivered by the heterostructured composite is mainly contributed to the synergistic effect of conversion and alloy/de‐alloy processes aroused by K+, where K+ may highly insert or de‐insert into Se‐rich ZnSe/CoSe2@C. The obtained electrode delivers an outstanding reversible charge capacity of 214 mA h g‐1 at 1 A g‐1 after 4000 cycles for PIBs, and achieves 262 mAh g‐1 when coupled with a PTCDA cathode in the full cell. The electrochemical conversion mechanism of the optimized electrode during cycling is investigated through in situ XRD, Raman, and ex situ HRTEM. In addition, the heterostructured composite as anodes also displays excellent electrochemical performances for sodium‐ion batteries (SIBs) and lithium‐ion batteries (LIBs). This work opens up a new window for investigating novel electrode materials with excellent capacity and long durability. 2D Se‐rich ZnSe/CoSe2@C heterostructures are promising electrodes materials, which deliberately accelerate the electrochemical conversion reaction during insertion and desertion processes. The electrode holds ultrastable cycling performance of 214 mA h g‐1 at 1 A g‐1 after 4000 cycles for PIBs, and also presents extraordinary cycling performances for LIBs and SIBs, which opens a new window for anode materials and exploring the relationship between cycling performances and redox conversion reactions.