Unusual Formation of CoSe@carbon Nanoboxes, which have an Inhomogeneous Shell, for Efficient Lithium Storage

Hybrid hollow nanostructures with tailored shell architectures are attractive for electrochemical energy storage applications. Starting with metal-organic frameworks (MOFs), we demonstrate a facile formation of hybrid nanoboxes with complex shell architecture where a CoSe-enriched inner shell is intimately confined within a carbon-enriched outer shell (denoted as CoSe@carbon nanoboxes). The synthesis is realized through manipulation of the template-engaged reaction between Co-based zeolitic imidazolate framework (ZIF-67) nanocubes and Se powder at elevated temperatures. By virtue of the structural and compositional features, these unique CoSe@carbon nanoboxes manifest excellent lithium-storage performance in terms of high specific capacity, exceptional rate capability, excellent cycling stability, and high initial Coulombic efficiency.