All-solid-state lithium batteries (ASSLBs) employ high-capacity lithium (Li) metal as the anode and exhibit a higher energy density than that of conventional Li-ion batteries. However, the problems arose from the Li dendrites induce severely parasitic reaction between Li and electrolytes, leading to low coulombic efficiency (CE) and poor cyclic stability. Herein, a poly(vinylidene-co-hexafluoropropylene)/lithium nitrate (PVDF-HFP/LiNO₃, marked as PFH/LN) artificial layer is employed to modified Li and achieve high CE ASSLBs with polyethylene oxide-Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (PEO-LLZTO) electrolyte. LN serves as a functionalized additive to facilitate the formation of a robust solid electrolyte interface (SEI), efficiently suppressing the formation of Li dendrites. Additionally, LN as a "binder" effectively links PFH with Li, providing good contact. PFH possesses high mechanical strength and moderate flexibility, which can not only physically inhibit the growth of Li dendrites, but also maintain the structural integrity of artificial layer over long-term cycles. Finally, Li/Li cells with such artificial layer demonstrate ultralong cycle life of 1800 and 1000 h under 0.2 and 0.4 mA cm⁻¹, respectively. Furtherly, high CE can be achieved when applied in both LiFePO₄ full cells and Li-Cu half cells. This work offers a facile and efficient strategy to greatly promote CE in PEO-based ASSLBs.