Robust and Intimate Interface Enabled by Silicon Carbide as an Additive to Anodes for Lithium Metal Solid-State Batteries

Garnet-type solid-state electrolytes are among the most reassuring candidates for the development of solid-state lithium metal batteries (SSLMB) because of their wide electrochemical stability window and chemical feasibility with lithium. However, issues such as poor physical contact with Li metal tend to limit their practical applications. These problems were addressed using β-SiC as an additive to the Li anode, resulting in improved wettability over Li_6.75La₃Zr_1.75Ta_0.25O₁₂ (LLZTO) and establishing an improved interfacial contact. At the Li–SiC|LLZTO interface, intimacy was induced by a lithiophilic Li₄SiO₄ phase, whereas robustness was attained through the hard SiC phase. The optimized Li–SiC|LLZTO|Li–SiC symmetric cell displayed a low interfacial impedance of 10 Ω cm² and superior cycling stability at varying current densities up to 5800 h. Moreover, the modified interface could achieve a high critical current density of 4.6 mA cm⁻² at room temperature and cycling stability of 1000 h at 3.5 mA cm⁻². The use of mechanically superior materials such as SiC as additives for the preparation of a composite anode may serve as a new strategy for robust garnet-based SSLMB.