A “Concentrated Ionogel-in-Ceramic” Silanization Composite Electrolyte with Superior Bulk Conductivity and Low Interfacial Resistance for Quasi-Solid-State Li Metal Batteries

The ideal composite electrolyte for the pursued safe and high-energy-density lithium metal batteries (LMBs) is expected to demonstrate peculiarity of superior bulk conductivity, low interfacial resistances, and good compatibility against both Li-metal anode and high-voltage cathode. There is no composite electrolyte to synchronously meet all these requirements yet, and the battery performance is inhibited by the absence of effective electrolyte design. Here we report a unique “concentrated ionogel-in-ceramic” silanization composite electrolyte (SCE) and validate an electrolyte design strategy based on the coupling of high-content silane-conditioning garnet and concentrated ionogel that builds well-percolated Li⁺ transport pathways and tackles the interface issues to respond all the aforementioned requirements. It is revealed that the silane conditioning enables the uniform dispersion of garnet nanoparticles at high content (70 wt%) and forms mixed-lithiophobic-conductive LiF-Li₃N solid electrolyte interphase. Notably, the yielding SCE delivers an ultrahigh ionic conductivity of 1.76 × 10⁻³ S cm⁻¹ at 25 °C, an extremely low Li-metal/electrolyte interfacial area-specific resistance of 13 Ω cm², and a distinctly excellent long-term 1200 cycling without any capacity decay in 4.3 V Li||LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) quasi-solid-state LMB. This composite electrolyte design strategy can be extended to other quasi−/solid-state LMBs.