Thermodynamically-Favorable Tailored Au–F Interface for Uniform Lithium Deposition in Anode-Free Solid-State Batteries

While the demand for high energy density and stable energy storage has driven the development of the anode-free solid-state lithium metal battery (AFSSLMB), challenges remain, particularly uncontrolled lithium (Li) nucleation and deposition on copper (Cu) current collectors (CCs), leading to dendrite growth and low Coulombic efficiency (CE). Initial Li nucleation and subsequent deposition modes influence the final Li growth morphology and interfacial stability. This study proposes synergistically tailored interface engineering using a fluorine (F)-doped gold (Au–F) layer on a Cu CC. The Au layer reduces the initial Li nucleation energy barrier, while the uniformly distributed F atoms provide mediating sites for diffusion control, modifying the surface potential energy and lowering the diffusion barrier for subsequent Li adatom deposition. The resulting Au–F@Cu CC, combining Au nucleation sites and F-mediated sites, promotes homogeneous initial Li nucleation, and even layer-by-layer deposition, suppressing dendrite growth, enhancing interfacial stability, and improving Li plating/stripping uniformity. When applied in an AFSSLMB with Ni_0.8Co_0.15Al_0.05O₂ cathode, the Au–F tailored interface layer achieves a capacity retention rate of 83.1% over 250 cycles. The Li||Au–F@Cu cell demonstrates an average CE of ≈99.5% over 500 cycles at 0.1 mAh cm⁻², and maintains a CE of 98.6% over 350 cycles at 0.5 mAh cm⁻². This study introduces an effective electrode design that enables stable cycling of AFSSLMBs with solid polymer electrolytes, offering a practical pathway to high-performance AFSSLMB.