Co0.85Se@N-doped reduced graphene oxide hybrid polyhedron-in-polyhedron structure assembled from metal-organic framework with enhanced performance for Li-ion storage

Abstract

Structure control is widely admitted as a feasible strategy to restrain volume change and enhance electrical conductivity for chalcogenide anode materials. Herein, three-dimensionally hierarchical structure Co_0.85Se@N-doped graphene hybrid is well-designed and synthesized by a facile hydrothermal strategy and post-calcination. It is noted that, owing to the nanoscale Kirkendall effect, the Co_0.85Se nanograins derived from uniform zeolitic imidazolate framework (ZIF-67) precursor are incorporated into a polyhedron-in-polyhedron structure, which is consisted of in-situ formed amorphous carbon and interconnected pliable graphene nanosheets with enormous N-doping atoms. This unique dual-carbon protecting layers are beneficial to mitigate the volume expansion with high integrity, and facilitate the fast Li/electron transport with improved conductivity simultaneously, thus resulting in the superior Li-storage performance. As expected, the framework-controlled Co_0.85Se@N-doped rGO composite demonstrates an outstanding cycling stability (787.7 mA h g^-1 after 1000 cycles at 2 A g^-1) and remarkable rate capability (400.8 mA h g^-1 at ultrahigh rate of 10 A g^-1). This work presents an enlightened strategy to design chalcogenide anode with desired nano-/microstructure by structure control and kinetic increase.

Keywords: Chalcogenide anode materials; Dual carbon; Kirkendall effect; Li-ion battery; Polyhedron-in-polyhedron.