Superlithiophilic, Ultrastable, and Ionic‐Conductive Interface Enabled Long Lifespan All‐Solid‐State Lithium‐Metal Batteries under High Mass Loading

Garnet‐type Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) suffers from instability against moist air, poor interfacial contact with anode, and serious dendrite issue, which greatly impede its practical application in all‐solid‐state lithium batteries (ASSLBs). Herein, a superlithiophilic, moisture‐resistant, and robust interlayer is demonstrated to overcome these obstacles by in situ forming an AlF₃ interlayer on the LLZTO surface. Thanks to the unique property, the AlF₃‐modified LLZTO offers a significantly reduced interfacial resistance by more than two orders of magnitude (from 527.5 Ω cm² for the pristine Li/LLZTO to 1.3 Ω cm² for the surface‐engineered interface), achieves a critical current density of 1.2 mA cm⁻² and long‐term stability of over 4000–4700 h, and endows regulated Li plating/stripping behaviors. Specifically, ASSLBs coupled with LiFePO₄ and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathodes can stably charge/discharge over 400 and 100 cycles at 0.5 and 0.2 C at 25 °C, with retentions of >80.0% and Coulombic efficiencies of >99.9%, respectively. Particularly, the NCM811‐based full ASSLB with large mass loading of 8.3 mg cm⁻² also delivers a discharge‐specific capacity as high as 199.1 mAh g⁻¹ with good rate capability, even approaching to the liquid cells. This study demonstrates a practical solution to address the interfacial challenges and paves the way for practical progress of ASSLBs.