A first-principles study on the effect of oxygen content on the structural and electronic properties of silicon suboxide as anode material for lithium ion batteries

Abstract

Silicon suboxide is currently considered as a unique candidate for lithium ion batteries anode materials due to its considerable capacity. However, no adequate information exist about the role of oxygen content on its performance. To this aim, we used density functional theory to create silicon suboxide matrices of various Si:O ratios and investigated the role of oxygen content on the structural, dynamic, electronic properties and lithiation behavior of the matrices. Our study demonstrates that the O atoms interact strongly with the inserted Li atoms resulting in a disintegration of the host matrix. We found that higher concentration of oxygen atoms in the mixture reduces its relative expansion upon lithiation, which is a desirable quality for anode materials. It helps in preventing crack formation and pulverization due to large fluctuations in volume. Our study also demonstrate that a higher oxygen content increases the lithium storage capacity of the anode. However, it can also cause the formation of stable complexes like lithium silicates that might result into reversible capacity loss as indicated by the voltage-composition curves. The study provides valuable insights into the role of oxygen in moderating the interaction of lithium in silicon suboxide mixture in microscopic details.

Tailoring the oxygen content in lithiated silicon oxide for lithium‐ion batteries

“…We found that the formation energy of SiO x with relatively low O content (x < 0.5) dramatically increased as oxygen content increased until x = 0.5, at which point it began to decrease. 42,45,47 Si has four valence electrons, requiring four more to fill the octet. At low O content, it is difficult for Si to gain a partial charge from O.…”

“…25,42,43 Despite these encouraging developments of Si suboxide anodes, the fundamental understanding of lithiation mechanism of SiO x is still limited, and there have been no experimental or theoretical reports focused on tailoring the oxidation of SiO x for use as an anode. [44][45][46][47][48][49][50] In this study, we investigate the structural stability of SiO x (0 ≤ x ≤ 2) and reaction mechanisms of Li in quartz (SiO 2 ); furthermore, we discuss the structural evolution and voltage profile of Li y SiO x (0 ≤ y ≤ 4) during lithiation using density functional theory (DFT) calculations. The reaction products during lithiation are clarified based on the charge analysis of SiO x .…”

“…It has been reported that highly oxidized SiO x ( x ≤ 1.5) can cause an increase in the initial capacity and cyclability compared to those of Si, 39‐41 and this increase is not limited to cases entailing low oxygen content in SiO x ( x ≤ 0.5) 25,42,43 . Despite these encouraging developments of Si suboxide anodes, the fundamental understanding of lithiation mechanism of SiO x is still limited, and there have been no experimental or theoretical reports focused on tailoring the oxidation of SiO x for use as an anode 44‐50 …”

First‐principle calculation of distorted T‐carbon as a promising anode for Li‐ion batteries with enhanced capacity, reversibility, and ion migration properties

“…13,14 However, the inevitable large volume expansion during the cycling process leads to the pulverization of the active materials from the current collector, inhibiting their lifetime. 15,16 To this end, it is necessary to explore and design novel anode materials, which have not only a higher capacity but also a lower volume expansion compared with the conventional graphite anode.…”

“…In this regard, Si, Ge, and Sn‐based alloys with the enhanced gravimetric capacity (theoretical value of Si: 4198 mAh/g, Ge: 1625 mAh/g, and Sn: 994 mAh/g) have been extensively investigated as potential alternatives for LIB anode 13,14 . However, the inevitable large volume expansion during the cycling process leads to the pulverization of the active materials from the current collector, inhibiting their lifetime 15,16 . To this end, it is necessary to explore and design novel anode materials, which have not only a higher capacity but also a lower volume expansion compared with the conventional graphite anode.…”