Cationic Interfacial Layer toward a LiF-Enriched Interphase for Stable Li Metal Batteries

Lithium (Li) metal is one of the most promising anode materials for next-generation high-energy rechargeable batteries but suffers from an unstable solid electrolyte interphase (SEI) and dendrite growth. Here, we design an interfacial layer through electrostatic integration of the cationic polymer poly(diallyldimethylammonium chloride) with commercial bamboo fibers (PBF) to precisely regulate the SEI at the molecular level. Numerous cationic sites exist on the surface of this PBF layer that adsorb electrolyte anions, which remarkably accelerates the decomposition kinetics of fluorinated salts in the electrolyte. Consequently, a LiF-enriched SEI film is developed, thus ensuring improved interfacial stability and cycling performance of the Li metal anode. The PBF-based symmetrical cell delivers a long-term cycling lifespan of more than 4800 h (∼12000 cycles) at 5 mA cm–2. More importantly, the practical full cell with a low negative/positive capacity ratio (∼3.7) and a high-mass-loading cathode (2.7 mAh cm–2) exhibits enhanced cyclability of over 350 cycles.