Bistrifluoroacetamide‐Activated Double‐Layer Composite Solid Electrolyte for Dendrite‐Free Lithium Metal Battery

Abstract The achievement of high ionic conductivity for solid‐state electrolyte and low interface resistance between electrodes and electrolyte are keys to successful solid‐state lithium ion batteries. In this paper, an efficient solid‐state electrolyte with dual‐layer structure for dendrite‐free lithium metal battery is designed. A Li metal‐friendly poly(ethylene oxide) (PEO) can serve as low‐voltage stable polymer electrolyte and ceramic‐dominating poly(vinylidene fluoride)–lithium aluminum titanium phosphate (PVDF–LATP) composite solid electrolyte is able to resist higher voltage facing cathode. More importantly, bistrifluoroacetamide (BTFA), as a polar molecular plasticizer, can simultaneously inhibit polymer crystallization, coordinate the delocalization of negative charges, and facilitate the solvation of lithium salts, providing absorption sites for lithium ion migration. The obtained BTFA‐activated PEO/PVDF–LATP double‐layer solid electrolyte exhibits satisfied ionic conductivity (4.4 × 10 −4 S cm −1 at 25 °C), high Li + ‐transfer number (0.68), and wide electrochemical stable windows (0–5.092 V vs Li/Li + ). Moreover, both the assembled full cells with LiFePO 4 and high‐voltage LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathodes show high initial discharge capacities (163.3 and 219.5 mAh g −1 at 0.1 C, respectively), excellent cycling, and rate performance.