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

Abstract Garnet‐type Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (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 AlF 3 interlayer on the LLZTO surface. Thanks to the unique property, the AlF 3 ‐modified LLZTO offers a significantly reduced interfacial resistance by more than two orders of magnitude (from 527.5 Ω cm 2 for the pristine Li/LLZTO to 1.3 Ω cm 2 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 LiFePO 4 and LiNi 0.8 Co 0.1 Mn 0.1 O 2 (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.