Graphene decorated with bimodal size of carbon polyhedrons for enhanced lithium storage

A sandwich-like hierarchical structure made of graphene and bimodal size of zeolitic imidazolate framework (ZIF-8) crystals is successfully synthesized, in which ZnO nanoparticles and Zn²⁺ ions within graphene framework induce the growth of micrometer-sized and nanometer-sized ZIF-8, respectively. The final carbonization product, N-doped carbon polyhedron/three-dimensional graphene (NCP/3DG-800) hybrid, inherits large surface area (565.4 m² g^-1), high-level nitrogen content (14.1 at%) and excellent electrical conductivity. On one aspect, 3DG not only act as flexible and conductive substrates to anchor NCPs to prevent their aggregation, but also maintain the structural integrity and electrical conductivity of the as-prepared hybrid. On the other aspect, NCPs provide both abundant hierarchical micro-/mesopores to facilitate ion transport, and high-level N doping to achieve extrinsic active sites for lithium storage. Benefiting from the advanced synergistic effect, NCP/3DG-800 delivers highly reversible capacity of 1460 mAh g^-1 at a current density of 100 mA g^-1 and excellent rate capability. Overall, the strategy and synergistic effect presented here provide a new material platform for the development of high-performance anode materials.