Amorphous Si_1-yC_y composite anode materials: ab initio molecular dynamics for behaviors of Li and Na in the framework

Although amorphous Si/C composite anode materials with various types of nanostructures Si/C materials have been experimentally proposed for rechargeable ion batteries for their structural durability, the atomistic mechanism primarily suggesting Li and Na monovalent ion intercalation into an amorphous Si/C composite matrix has not theoretically been understood to explore the thermodynamic and kinetic features of the a-Si/C composite phase regarding the effects on the carbon addition to an amorphous Si matrix. In this work, systematic ab initio molecular dynamics calculations (AIMDs) were conducted to identify electrochemical intercalation reactions involved in nanostructure evolutions, which correspond to favorable ion-intercalated formations, volume expansions, pair correlations, charge transfers, and diffusion behaviors of metals in a-M_xSi_1-yC_y (M_x: Li_x and Na_x) alloys with increasing x contents of atomic concentrations. AIMDs using the a-Si_1-yC_y composite phase might allow one to have an atomic-level understanding of the composite phase and further insightful comprehension of any implementations such as the controlled ratio of the Si_1-yC_y composite and multivalent ions inserted into the framework.