Mesoporous nitrogen-doped carbon@graphene nanosheets as ultra-stable anode for lithium-ion batteries - Melamine as surface modifier than nitrogen source

Nitrogen-doped carbon materials are highly appealing next-generation anode for Li-ion battery owing to high energy density, conducting and porous structure, and a large number of ion-binding sites. However, the formation of micropores limits the ion/electrolyte diffusion at high discharge rate leading to underutilization of active material, capacity fading, and low cycle stability, hindering their practical application. Herein, we report mesoporous-rich carbon hybrid comprising of zeolitic imidazolate framework (ZIF)-derived nitrogen-doped carbon-anchored graphene using melamine as the surface modifier and pore expander. A high specific capacity of 775 (after 1100 cycles) and 675 mAh g(-1) (after 1000 cycles) were obtained at current densities of 1000 and 2000 mA g(-1) (4C) which is two-fold higher than the initial capacity. The melamine-modified anode exhibited excellent cycle retention of 163% at 1000 mA g(-1) after 800 cycles, compared to 91% for the unmodified anode, indicating the activation process through the mesoporous channels. Superior cycle retention and long cycle life were attributed to the melamine-induced features viz mesoporous structure and defective sites formed on carbon/graphene facilitating efficient electrolyte percolation/ion transport and Li-ion storage, respectively. This strategy provides a promising approach for the design of ZIFs-derived carbon materials for high-performance Li-ion batteries. (C) 2019 Elsevier Ltd. All rights reserved.