Long-Term Cycling Stability and Dendrite Suppression in Garnet-Type Solid-State Lithium Batteries via Plasma-Induced Artificial SEI Layer Formation

Abstract

The garnet-based solid-state-electrolyte Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZTO) faces challenges due to its poor contact with Li-metal, resulting in high interfacial-resistance and dendrite growth. To address this, an SnO₂-Al (SA) ultra-thin film on LLZTO is fabricated using direct-current/radio-frequency plasma magnetron co-sputtering. This modification layer reacts with molten Li in situ to form a dense and continuous artificial solid-electrolyte-interphase (SEI) layer, composed of Li₂O, Li-Al-O, Li_xSn, and Li₉Al₄ alloy. Density-functional-theory calculations and in situ optical-microscopy characterization confirm the effectiveness of this interlayer in improving interfacial-modification. Consequently, an ultrahigh critical-current-density of 5.4 mA cm⁻² is achieved, effectively preventing lithium-metal penetration into the bulk electrolyte. The Li symmetric cell with the SA artificial SEI layer cycles stably for 8700 h without dendrite formation, significantly outperforming the SnO₂ modified layer (only 1350 h) and most interface modification layers reported in literature, demonstrating its excellent interfacial-stability. Additionally, full cells with LiFePO₄ and LiNi_0.8Co_0.1Mn_0.1O₂ cathodes exhibit stable cycling performance (LiFePO₄: 88.95% capacity retention at the 400^th cycle at 0.5 C; LiNi_0.8Co_0.1Mn_0.1O₂: 89.16% capacity retention at the 200^th cycle at 0.5 C). This work underscores the significant potential of the plasma magnetron co-sputtering method for creating artificial SEI layers, paving the way for the practical application of garnet-type solid-state batteries.