In:
Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 70, No. 19 ( 2021), p. 198101-
Abstract:
Silicon/carbon composite is one of the most potential high-capacity anode materials for lithium-ion batteries. The interface state between silicon and carbon of silicon/carbon composite is an important factor affecting its electrochemical performance. In this paper, Si〈sub〉〈i〉n〈/i〉〈/sub〉 (〈i〉n〈/i〉 ≤ 6) clusters with different numbers of Si atoms are constructed on graphene as a structural unit of carbon material. The geometric configuration, structure stability and electronic property of Si〈sub〉〈i〉n〈/i〉〈/sub〉 clusters adsorbed on graphene (Si〈sub〉〈i〉n〈/i〉〈/sub〉/Gr) are studied by the first-principles method based on density functional theory (DFT). The results show that when the number of Si atoms 〈i〉n〈/i〉 ≤ 4, the Si〈sub〉〈i〉n〈/i〉〈/sub〉 clusters are preferentially adsorbed on graphene in a two-dimensional configuration parallel to graphene. When 〈i〉n〈/i〉 ≥ 5, the Si〈sub〉〈i〉n〈/i〉〈/sub〉 clusters are preferentially adsorbed on graphene in a three-dimensional configuration. With the increase of the number of Si atoms 〈i〉n〈/i〉, the thermodynamic stability of Si〈sub〉〈i〉n〈/i〉〈/sub〉 clusters on graphene decreases significantly, the interface binding strength between Si〈sub〉〈i〉n〈/i〉〈/sub〉 clusters and graphene decreases, and the charge transfer between Si〈sub〉〈i〉n〈/i〉〈/sub〉 clusters and graphene becomes less. At the same time, the storage capacity of Li atoms in Si〈sub〉〈i〉n〈/i〉〈/sub〉/Gr complex is also studied. Li atoms are mainly stored on the graphene surface near Si〈sub〉〈i〉n〈/i〉〈/sub〉 clusters and around Si〈sub〉〈i〉n〈/i〉〈/sub〉 clusters. The complex synergistic effect of Si〈sub〉〈i〉n〈/i〉〈/sub〉 clusters and graphene enhances the thermodynamic stability of Li adsorption. When 〈i〉n〈/i〉 ≤ 4, storing two Li atoms is beneficial to improving the thermodynamic stability of 〈i〉x〈/i〉Li-Si〈sub〉〈i〉n〈/i〉〈/sub〉/Gr system, and the thermodynamic stability decreases with the increase of Li atom number. When 〈i〉n〈/i〉 ≥ 5, the thermodynamic stability of 〈i〉x〈/i〉Li-Si〈sub〉〈i〉n〈/i〉〈/sub〉/Gr system decreases with the increase of Li atom number. In the 〈i〉x〈/i〉Li-Si〈sub〉5〈/sub〉/Gr system, the C-C bond and Si-Si bond are mainly covalent bonds, while the Li-C bond and Li-Si bond are mainly ionic bonds with certain covalent properties.
Type of Medium:
Online Resource
ISSN:
1000-3290
,
1000-3290
DOI:
10.7498/aps.70.20210521
Language:
Unknown
Publisher:
Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
Publication Date:
2021
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