Synergistic Approach toward Developing Highly Compatible Garnet‐Liquid Electrolyte Interphase in Hybrid Solid‐State Lithium‐Metal Batteries

The hybrid solid‐liquid electrolyte concept is one of the best approaches for counteracting the interface problems between solid electrolytes and Li anodes/cathodes. However, a solid‐liquid electrolyte layer forming at the interfaces degrades battery capacity and power during a longer cycle due to highly reactive chemical and electrochemical reactions. To solve this problem in the present study, a synthetic approach is demonstrated by combining AlCl 3 Lewis acid and fluoroethylene carbonate as additives in a conventional LiPF 6 ‐containing carbonate‐based electrolyte. This electrolyte design triggers the fluoroethylene carbonate polymerization by AlCl 3 addition and can also form a mechanically robust and ionically conductive Al‐rich interphase on the surface of Li 7 La 2.75 Ba 0.25 Zr 1.75 Ta 0.25 O 12 garnet‐type structured solid electrolytes, Li anodes and LiNi 0.6 Mn 0.2 Co 0.2 O 2 cathodes. Benefitting from this approach, the assembled Li symmetric cell exhibits a remarkably high critical current density of 4.2 mA cm −2 , and stable long‐term cycling over 3000 h at 0.5 mA cm −2 at 25 °C. The assembled hybrid full cell shows an impressive specific capacity retention of 92.2% at 1 C till 200 cycles. This work opens a new direction in developing safe, long‐lasting, and high‐energy hybrid solid‐state lithium‐metal batteries.