Fluorine-regulated cathode electrolyte interphase enables high-energy quasi-solid-state lithium metal batteries

Lithium metal batteries (LMBs) enabled by quasi-solid electrolytes are under consideration for their prospect of reliable safety and high energy density. The limited oxidative stabilization inferior chemical compatibility toward high-voltage cathodes a long-standing challenge. Herein, we report that an additive level (0.05 M) LiPF6 is introduced to polymeric concentrated electrolyte (10 M LiFSI in poly-1,3-dioxolane [poly-DOL], ethylene carbonate [EC], ethyl methyl [EMC]) build situ fluorine-regulated cathode interphase (CEI) on highly catalytic LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode. CEI with conformal thickness ∼7 nm features fluorine-rich outer layer manipulative LiF/organofluorine species, which mitigates the detrimental side reactions between NCM maintains structure cycled NCM, as demonstrated characterizations SEM, TEM, XRD, Raman spectroscopy, AFM, EDS, XPS. As result, LiPF6-contained not only provides superior ionic conductivity 3.1 × 10−4 S cm−1 at 25 °C remarkable electrochemical stability window 5.5 V vs Li/Li+, but also achieves excellent capacity retention 74% after 100 cycles LiǁNCM811 quasi-solid-state LMB, bringing design strategy engineered chemistry LMBs.