An atomistic perspective on lithiation kinetics and morphological evolution in void-involved silicon/carbon nanohybrid

Abstract

Void-involved silicon (Si)/carbon (C) nanohybrid has been considered as a promising anode material for the lithium ion batteries (LIBs). However, further optimizing the design and improving the performance of the void-involved Si/C electrodes still remain challenging. Here, the lithiation kinetics and morphological evolution in lithiated Si@CNT nanohybrids are investigated using large-scale atomistic simulations based on reactive force field (ReaxFF), and the effects of both size of C shell and contact mode between Si and C phase on the lithiation behavior are explored systematically. The simulation results quantitatively reveal that the constraint effect of C shell causes the Li capacity loss, and the barrier function of the void space retards the lithiation rate. Regulating the size of coating layer can mediate the constraint effect and barrier function. Furthermore, regulating the contact mode between Si and C phase to form an eccentric structure can effectively enhance the lithiation capacity (up to 10%) and lithiation rate at initial stage. Besides, the malleability and deformability of the lithiated a-LixSi phase are investigated at atomic-level. The findings not only provide theoretical rational for the lithiation mechanism of core-hollow shell nanohybrid, but also open avenues for optimizing the void-containing electrode design for high-performance LIBs.