Synergistic fluorine–nitrogen interfaces enabling stable high-voltage sulfide-based all-solid-state lithium metal batteries

Sulfide-based all-solid-state lithium metal batteries (ASSLMBs) are promising for high-energy-density and safe energy storage. But the poor compatibility of sulfide electrolytes with both high-voltage cathodes and lithium metal anodes hinders their practical application. Here, we disclose a fluorine–nitrogen synergistic interfacial engineering strategy by modifying Li_5.5PS_4.5Cl_1.5 (LPSC) with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The modified LPSC electrolyte shows a high ionic conductivity of 2.88 mS·cm⁻¹. Moreover, LiTFSI induced dual-functional interphases, a fluorine-rich cathode–electrolyte interphase (CEI) (LiF/Li_xPO_yF_z) and a fluorine–nitrogen composite solid electrolyte interphase (SEI, Li₃N/LiF/Li_xPO_yF_z), contributing to high oxidation stability (LiNi_0.8Co_0.1Mn_0.1O₂//LiIn battery retains 107% capacity retention after 13,000 cycles at 15 C) and excellent lithium dendrite inhibition ability (Li//Li: critical current density (CCD) 3.4 mA·cm⁻², stably cycling 2600 h at 0.5 mA·cm⁻²). As a result, the LiNi_0.8Co_0.1Mn_0.1O₂//Li cell with modified electrolyte demonstrates 1000 stable cycles at a high cut-off voltage of 4.5 V and wide-temperature adaptability (−20–50 °C). This work shows a facile and effective method for constructing long-life and high-energy-density sulfide based ASSLMBs.