Synergistic dual electrolyte additives for fluoride rich solid-electrolyte interface on Li metal anode surface: Mechanistic understanding of electrolyte decomposition

Shih-Huang Pan; Santhanamoorthi Nachimuthu; Bing Joe Hwang; Gunther Brunklaus; Jyh-Chiang Jiang

doi:10.1016/j.jcis.2023.06.147

Synergistic dual electrolyte additives for fluoride rich solid-electrolyte interface on Li metal anode surface: Mechanistic understanding of electrolyte decomposition

J Colloid Interface Sci. 2023 Nov:649:804-814. doi: 10.1016/j.jcis.2023.06.147. Epub 2023 Jun 24.

Authors

Shih-Huang Pan¹, Santhanamoorthi Nachimuthu¹, Bing Joe Hwang², Gunther Brunklaus³, Jyh-Chiang Jiang⁴

Affiliations

¹ Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 10617, Taiwan.
² Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 10617, Taiwan; National Synchrotron Radiation Research Center (NSRRC), Hsinchu 30076, Taiwan; Sustainable Energy Development Center, National Taiwan University of Science and Technology, Taipei 10617, Taiwan.
³ Helmholtz-Institute Münster, IEK-12, Forschungszentrum Jülich GmbH, Corrensstraße 46, 48149 Münster, Germany.
⁴ Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 10617, Taiwan. Electronic address: jcjiang@mail.ntust.edu.tw.

PMID: 37390528
DOI: 10.1016/j.jcis.2023.06.147

Abstract

Improving the quality of the solid-electrolyte interphase (SEI) layer is highly imperative to stabilize the Li-metal anodes for the practical application of high-energy-density batteries. However, controllably managing the formation of robust SEI layers on the anode is challenging in state-of-the-art electrolytes. Herein, we discuss the role of dual additives fluoroethylene carbonate (FEC) and lithium difluorophosphate (LiPO₂F₂, LiPF) within the commercial electrolyte mixture (LiPF₆/EC/DEC) considering their reactivity with Li metal anodes using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. Synergistic effects of dual additives on SEI formation mechanisms are explored systematically by invoking different electrolyte mixtures including pure electrolyte (LP47), mono-additive (LP47/FEC and LP47/LiPF), and dual additives (LP47/FEC/LiPF). The present work suggests that the addition of dual additives accelerates the reduction of salt and additives while increasing the formation of a LiF-rich SEI layer. In addition, calculated atomic charges are applied to predict the representative F_1s X-ray photoelectron (XPS) signal, and our results agree well with the experimentally identified SEI components. The nature of carbon and oxygen-containing groups resulting from the electrolyte decompositions at the anode surface is also analyzed. We find that the presence of dual additives inhibits undesirable solvent degradation in the respective mixtures, which effectively restricts the hazardous side products at the electrolyte-anode interface and improves SEI layer quality.

Keywords: Ab initio molecular dynamics (AIMD); Density functional theory (DFT); Dual additives; Interfacial reactivity; Lithium-ion batteries (LIBs); Solid-electrolyte interphase (SEI).