Molecular Understanding of Electrochemical–Mechanical Responses in Carbon-Coated Silicon Nanotubes during Lithiation

Abstract

Carbon-coated silicon nanotube (SiNT@CNT) anodes show tremendous potential in high-performance lithium ion batteries (LIBs). Unfortunately, to realize the commercial application, it is still required to further optimize the structural design for better durability and safety. Here, the electrochemical and mechanical evolution in lithiated SiNT@CNT nanohybrids are investigated using large-scale atomistic simulations. More importantly, the lithiation responses of SiNW@CNT nanohybrids are also investigated in the same simulation conditions as references. The simulations quantitatively reveal that the inner hole of the SiNT alleviates the compressive stress concentration between a-LixSi and C phases, resulting in the SiNT@CNT having a higher Li capacity and faster lithiation rate than SiNW@CNT. The contact mode significantly regulates the stress distribution at the inner hole surface, further affecting the morphological evolution and structural stability. The inner hole of bare SiNT shows good structural stability due to no stress concentration, while that of concentric SiNT@CNT undergoes dramatic shrinkage due to compressive stress concentration, and that of eccentric SiNT@CNT is deformed due to the mismatch of stress distribution. These findings not only enrich the atomic understanding of the electrochemical–mechanical coupled mechanism in lithiated SiNT@CNT nanohybrids but also provide feasible solutions to optimize the charging strategy and tune the nanostructure of SiNT-based electrode materials.

Special Issue “Theoretical Calculation and Molecular Modeling of Nanomaterials”

“…The simulations demonstrated that the SiNT@CNT anode exhibited higher lithium capacity and faster lithiation rate compared to its silicon nanowire (SiNW) counterparts due to the alleviation of compressive stress concentration within the SiNT structure. This study also highlighted the influence of contact mode on stress distribution and structural stability, providing insights for optimizing the charging strategies and nanostructural design of SiNT-based electrode materials [6].…”

Mechanical Behaviors of Si/CNT Core/Shell Nanocomposites under Tension: A Molecular Dynamics Analysis

“…Another way to enhance the mechanical reliability of LIBs is to design a core/shell nanocomposite using carbon-based materials, for example, graphene, fullerene, and carbon nanotubes (CNTs). Excellent mechanical properties and electronic conductivity of carbon-based materials were found to improve the performance of electrode materials [ 6 , 7 , 8 ]. Via chemical vapor deposition, Son et al [ 9 ] fabricated a nanocomposite anode consisting of a graphene–silica assembly and realized a charge capacity retention of 78.6% after 500 cycles.…”

Atomistic Insight into the Role of Porous Structure in Accommodating the Volume Expansion of Silicon Anodes for Lithium-Ion Batteries

“…A reactive molecular dynamics approach is another powerful tool used for elucidating the atomistic behaviors of materials, and the method has quite widely been employed to investigate the dynamic processes during the lithiation of nanostructured silicon. [37][38][39][40] However, there is a lack of study on the effect of the porous structure, 41,42 and several atomistic aspects of the (de) lithiated porous silicon remain to be explored. Particularly, the correlation between the chemical evolution at an atomistic level and the meso-/microscopic level change of the porous structure remains undisclosed.…”