Inorganic-Organic Bi-Layered on Li Metal with Reduceable Li Salt@ptfe Layer for High Energy Density Li Metal Batteries

Lithium (Li) metal is considered a promising anode material for high-energy-density batteries. However, the formation of lithium dendrites during Li plating/stripping results in low Coulombic efficiency and safety concerns. These issues can be mitigated by engineering the interface between Li metal and electrolytes to improve Li-ion kinetics and interfacial stability. In this study, we developed an inorganic/organic bi-layer protection system, consisting of a 200 nm-thick inorganic inner layer (LiF, Li3N, Li2S) adjacent to the Li metal, and an outer porous PTFE polymer layer facing the electrolyte. The robust inorganic layer effectively suppresses dendritic Li growth, while the flexible and porous polymer layer maintains structural integrity and allows high Li-ion flux. In symmetric cell tests, Li metal with the bi-layer protection exhibited stable cycling for over 600 hours at a current density of 1 mA cm-2 with a capacity of 5 mAh cm-2. In full cell tests, a 20 μm Li metal anode with the bi-layer protection, paired with a high-nickel NCM811 cathode (5 mAh cm-2), demonstrated stable cycling for over 200 cycles, with an anode efficiency of 99.6%, as calculated by the average Coulombic efficiency.