Building a Flexible and Highly Ionic Conductive Solid Electrolyte Interphase on the Surface of Si@C Anodes by Binary Electrolyte Additives

Linhu Song; Shiyou Li; Jie Wang; Junlong Zhu; Yinong Wang; Xingpeng Cai; Feifei Zong; Hui Wang; Xiaoling Cui; Dongni Zhao

doi:10.1021/acsami.3c08704

Building a Flexible and Highly Ionic Conductive Solid Electrolyte Interphase on the Surface of Si@C Anodes by Binary Electrolyte Additives

ACS Appl Mater Interfaces. 2023 Oct 25;15(42):49727-49738. doi: 10.1021/acsami.3c08704. Epub 2023 Oct 16.

Authors

Linhu Song^{1

2}, Shiyou Li^{1

2

3}, Jie Wang^{1

2}, Junlong Zhu^{1

2}, Yinong Wang^{1

2}, Xingpeng Cai^{1

2}, Feifei Zong^{1

2}, Hui Wang^{1

2}, Xiaoling Cui^{1

2

3}, Dongni Zhao^{1

2

3}

Affiliations

¹ School of Petrochemical Technology, Lanzhou University of Technology, Lanzhou 730050, P. R. China.
² Key Laboratory of Low Carbon Energy and Chemical Engineering of Gansu Province, Lanzhou 730050, P. R. China.
³ Gansu Lithium ion Battery Cathode Material Engineering Research Center, Baiyin 730900, P. R. China.

PMID: 37842985
DOI: 10.1021/acsami.3c08704

Abstract

Si@C as a high specific capacity anode material for lithium batteries (LIBs) has attracted a lot of attention. However, the severe volume change during lithium de-embedding causes repeated rupture/reconstruction of the solid electrolyte interphase (SEI), resulting in poor cycling stability of the Si-based battery system and thus hindering its application in commercial batteries. Using electrolyte additives to form an excellent SEI is considered to be a cost-effective method to meet this challenge. Here, the classical film-forming additive vinyl carbonate (VC), and the newly emerging lithium salt additive lithium difluorophosphate (LiDFP), are chosen as synergistic additives to improve the electrode-electrolyte interface properties. Final results show that the VC additive generates flexible polycarbonate components at the electrode/electrolyte interface, preventing the fragmentation of Si particles. However, the organic components show high impedance, inhibiting the fast transport of Li⁺. This defect can be supplemented from the decomposition substances of the LiDFP additive. The derived inorganic products, such as LiF and Li₃PO₄, can strengthen the reaction kinetics of the electrode, reduce the interfacial impedance, and promote the Li⁺ transport. Thus, the synergistic effect of VC and LiDFP additives builds an effective SEI with good flexibility and high ionic conductivity and then significantly improves the cycling and rate stability of Si@C anodes. The experimental results show that the utilization of LiDFP and VC additives to modify the Si@C anode interface enhances the capacity retention of the Si@C/Li half-cell after 100 cycles from 68.2% to 85.1%. Besides, the possible mechanism of action between VC and LiDFP is proposed by using the spectral characterization technique and density functional theory (DFT) calculations. This research opens up a new possibility for improvement of SEI, and provides a simple way to achieve high-performance Si-based LIBs.

Keywords: Si@C anode; electrolyte additive; lithium difluorophosphate; solid electrolyte interphase; synergistic effect; vinyl carbonate.