Stable Lithium Plating and Stripping Enabled by a LiPON Nanolayer on PP Separator

The practical application of the Li metal anode (LMA) is hindered by its low coulombic efficiency and dendrite formation. Although solid-state electrolytes hold promise as ideal partners for LMA, their effectiveness is limited by the poor workability and ionic conductivity. Herein, a modified separator combining the rapid Li⁺ transport of a liquid electrolyte and the interfacial stability of a solid-state electrolyte is explored to realize stable cycling of the LMA. A conformal nanolayer of LiPON is coated on a polypropylene separator by a scalable magnetron sputtering method, which is compatible with current Li-ion battery production lines and promising for the practical applications. The resulting LMA–electrolyte/separator interface is Li⁺-conductive, electron-insulating, mechanically and chemically stable. Consequently, Li|Li cells maintain stable dendrite-free cycling with overpotentials of 10 and 40 mV over 2000 h at 1 and 5 mA cm^-2, respectively. Additionally, the Li|LiFePO₄ full cells achieve a capacity retention of 92% after 550 cycles, confirming its application potential.