Prelithiation-coupled defluorination polymerization for constructing LiF-rich oligomers interface for highly stable SiO anode

Generally, the chemical prelithiation strategy can significantly improve the initial Coulombic efficiency (ICE) of the SiO-based anode, but it also faces huge challenges, such as the presence of residues and the inability to avoid serious interface side reactions. Herein, a multifunctional prelithiation system, Li-2-fluorobiphenyl-2-methyltetrahydrofuran (Li-FBP-MeTHF) solution, is developed to synchronously achieve controllable prelithiation and interfacial protection of the SiO-based electrodes. Specifically, the Li-FBP-MeTHF system would undergo defluorination and nucleophilic substitution reactions while performing prelithiation, and then the residual organic matters are polymerized by free radicals in the heat treatment process, allowing for the in-situ formation of a LiF-oligomer interface layer on the electrode surface. In this hybrid layer, the LiF and oligomer can preferentially adsorb LiPF6 to generate LiF-rich electrolyte interface film, while the highly elastic oligomers could perfectly accommodate the enormous volume strain of SiO, thereby avoiding serious interface side reactions. Furthermore, the LiF-oligomer layer also exhibits multifunctionality, such as fast ion migration, high hydrophobicity, and long-term air stability. As a result, the prelithiated SiO electrode with the improved ICE of 101.7% displays more stable cycling performance, even under extreme conditions such as high temperature and trace electrolyte.