Solvent-free synthesis of N-doped carbon coated ZnO nanorods composite anode via a ZnO support-induced ZIF-8 in-situ growth strategy

The N-doped carbon coated ZnO nanorods (ZnO/NC-Z NRDs) are synthesized through a simple solvent-free method, in which the N-doped carbon is derived from thermal treatment of the in-situ grown zeolitic imidazolate framework-8 (ZIF-8) on the surface of ZnO NRDs. The in-situ coated N-doped carbon layer can not only enhance the electrical conductivity of ZnO NRDs and thus increasing the diffusion rate of Li ions, but also serve as a buffer layer to impede the volume expansion during the charge-discharge processes. When utilized as anodes for lithium-ion batteries (LIBs), the as-synthesized ZnO/NC-Z NRDs deliver a high capacity of 1011 mA h g(-1) at 200 mA g(-1) after 200 cycles and remain 544 mA h g(-1) at 1000 mA g(-1) after 850 cycles, holding a capacity retention of as high as 87.7%. In addition, the as-synthesized ZnO/NC-Z NRDs can also act as a precursor for the preparation of high performance N-doped carbon tube (1001.1 mA h g(-1) at 200 mA g(-1) with the retention of 99.1% after 100 cycles) with an ultrathin wall thickness. Such solvent-free synthetic method can not only simplify the synthesis process, but also pave a new strategy to synthesize Zn-based materials for the application of energy storage devices. (C) 2017 Published by Elsevier Ltd.