© 2020 Elsevier B.V. Li metal battery with garnet-type Li7La3Zr2O12 (LLZ) as a solid electrolyte has attracted attentions as a promising candidate for high-energy batteries. However, the interfacial resistance between LLZ and Li is huge due to a point-point contact, leading to poor battery performances such as rate capability and cycleability. Here, we have studied the hybrid-electrolyte structure using the liquid electrolyte interlayer containing LiBH4 between LLZ and Li at high operating temperature of 120 °C. This hybrid-electrolyte structure offers high current density usage and a long-term cycleability. The Li|LLZ|Li symmetric cell shows high critical current density of 13 mA cm−2 and a long term cycle. The liquid electrolyte interlayer containing LiBH4 provides an improved coulombic efficiency of Li striping/plating due to an excellent reductive stability. Our findings suggest that the interfacial conditions on LLZ|Li could be effectively improved by using the modified liquid electrolyte interlayer.