First principles investigation of Li x Si and Li x Sn alloys: Unraveling atomic-scale influences on material properties

Abstract

Commercial batteries have currently reached their peak specific capacity, which proves insufficient for the ongoing global energy transition. Consequently, there has been a surge of interest in developing new materials over the last decade, especially those based on silicon (Si) and tin (Sn), known for their high capacity. Despite numerous publications highlighting the advantages of these materials, crucial questions remain regarding volume expansion that must be addressed to propose effective solutions and facilitate their widespread commercial application. In this study, density functional theory was employed to investigate the formation of LixM (M = Si, Sn). Our analysis delves into crystal (c-LixM), amorphous (a-LixM), and amorphous slab (s-LixM) configurations during structural optimization calculations, with the aim of comparing and contrasting relevant findings. The exploration encompasses energetic aspects, volume expansion, and electronic properties. The obtained data enables the simulation of lithiation potential curves for each structural type, directly comparable with experimental results of these materials functioning as anodes in lithium-ion batteries. Notably, the volume expansion of a-LixM exhibits non-linear behavior, correlating with characteristic plateaus in the voltage profile curves.