Architecting 1D dual-confinement networks for mechanically resilient CoSe2 anodes in potassium-ion batteries

Cobalt selenide (CoSe 2 ) has emerged as a promising high-capacity anode for potassium-ion batteries. However, its practical application is hindered by severe volume expansion and subsequent structural degradation during potassiation. Conventional single‑carbon encapsulation is often insufficient for withstanding localized mechanical stress, leading to active material extrusion, particle agglomeration, and rapid capacity fading. To address these issues, we developed a 1D dual-confinement architecture that provides both internal and external structural reinforcement. In this design, CoSe 2 nanocrystals are encapsulated within a nitrogen-doped carbon (NC) matrix and integrated into a 1D carbon nanofiber (CNF) network. This architecture is denoted as CoSe 2 @NC/CNF. Unlike previously reported CoSe 2 @carbon-fiber composites relying on either a single carbon coating or simple physical loading onto fibers, this internal-external double‑carbon protection strategy provides simultaneous nanoscale confinement and macroscopic mechanical buffering, representing a structurally distinct dual-confinement design. While the internal NC matrix suppressed Ostwald ripening, the robust CNF network served as an elastic buffer, dissipating mechanical stress and preventing detachment of the active material. However, these structural advantages are not typically observed in traditional single-matrix configurations. Consequently, the CoSe 2 @NC/CNF electrode exhibits superior cycling stability, retaining 92% of its initial capacity over 200 cycles at 0.5 A g −1 , compared to that of CoSe 2 @NC control at 73%. Cross-sectional scanning electron microscopy (SEM) analysis confirmed this stability, showing a restricted apparent thickness expansion of 38.6%, which was significantly lower than that observed in the control sample (117.3%). Thus, the 1D dual-confinement strategy is an effective approach to designing high-performance, durable anode materials for PIBs.