Embedded CoSe2 nanocrystals in hollow carbon nanobox walls with interfacial coupling for high-performance lithium storage

Transition metal chalcogenides, such as cobalt selenide (CoSe2), have high lithium storage capacity. However, their practical application is hindered by severe volume expansion and the dissolution of intermediate polyselenides during repeated cycling. Here, we develop a hollow-embedded architecture in which monodisperse CoSe2 nanocrystals “sprout” from the walls of porous carbon nanoboxes (H-CoSe2/C) via tannic acid etching, low-temperature carbonization, and vacuum selenization. This “wall-growth” strategy combines confinement with continuity: the porous carbon walls guide uniform nucleation and provide electrical conductivity, while the internal cavity buffers expansion and relieves stress. The embedded geometry shortens Li+ diffusion pathways, suppresses particle aggregation, and establishes robust Co–C coupling to enhance charge transport. As a result, the H-CoSe2/C electrode delivers a high reversible capacity of nearly 950 mAh g−1, along with outstanding cycling stability. Remarkably, when paired with a LiCoO2 cathode in a quasi-solid-state battery, the device achieves an impressive energy density of 355 Wh kg−1 and a power density of 3074 W kg−1. This study effectively overcomes the inherent defects of CoSe2 based on the hollow structure and interface engineering of metal-organic frameworks, providing an effective design for anode materials of lithium-ion batteries.