Elucidating the role of embedding dispersed cobalt sites in nitrogen-doped carbon frameworks in Si-based anodes for stable and superior storage

Abstract

Unsatisfactory conductivity and volume effects have hindered the commercial application of silicon-based materials as advanced anode materials for high-performance lithium-ion batteries. Herein, nitrogen doped carbon silicon matrix composite with atomically dispersed Co sites (Si/Co-N-C) is obtained via the design of the frame structure loaded with nano-components and the multi-element hybrid strategy. Co atoms are uniformly fixed to the N-C frame and tightly packed with nanoscale silicon particles as an activation and protection building block. The mechanism of the N-C framework of loaded metal Co in the Si alloying process is revealed by electrochemical kinetic analysis and ex situ characterization tests. Impressively, the nitrogen-doped Co site activates the intercalation of the outer carbon matrix to supplement the additional capacity. The Co nanoparticles with high conductivity and support enhance the conductivity and structural stability of the composite, accelerating the Li+/Na+ diffusion kinetics. Density functional theory (DFT) calculation confirms that the hetero-structure Si/Co-N-C adjusts the electronic structure to obtain good lithium-ion adsorption energy, reduces the Li+/Na+ migration energy barrier. This work provides meaningful guidance for the development of high-performance metal/non-metal modified anode materials.