Wet Chemical Method ZnF2 Interlayer for High Critical Current Density Lithium Metal Batteries Utilizing Ba and Ta–Doped Li7La3Zr2O12 Garnet Solid Electrolyte

Li metal batteries with garnet-type solid electrolytes have the potential to increase specific energy and power densities of current Li-ion batteries. Li metal batteries have been hampered by the poor wettability of solid electrolyte with elemental lithium. Here, to resolve the solid garnet electrolyte/Li interface issue, a scalable, cost-effective, and efficient surfactant-assisted wet-chemical strategy is developed. A ZnF2 interlayer coating is applied on Ba and Ta -co-doped Li7La2.75Ba0.25Zr1.75Ta0.25O12 that formed LiF and Li-Zn alloy upon contact with molten Li. Conformal contact applying a homogenous surfactant-assisted ZnF2 coating reduced the interfacial resistance from 87 to 15.5 𝛀 cm2 which enhanced critical current density to a record high value of 5 mA cm−2 at room temperature. Dense and Li2CO3 free garnet solid electrolyte assisted in achieving long-term stability for 1000 cycles at 1 mA cm−2. Interface stabilized Li/ZnF2- solid electrolyte/liquid electrolyte/LiFePO4 cell displayed a 90% capacity retention over 800 cycles at 0.2 C, with Coulombic efficiency of 99% as well as excellent cycle stability at 1 C, with ≈91% of capacity retention for 500 cycles. Using a new design principle for Li anode interfaces, next-generation power-intensive and stable solid-state Li metal batteries can be developed.