Model systems for electrochemical impedance spectroscopy (EIS) studies of solid-state electrolytes based on ceramic lithium ion conductor Li₇La₃Zr₂O₁₂ (LLZO) and polymer electrolyte P(EO)₂₀-LiClO₄ are investigated for the first time. The aim of the present study is to identify and quantify the lithium ion transition resistance of the ceramic/polymer interface. Symmetrical model systems consisting of LLZO pellets with sheets of P(EO)₂₀-LiClO₄ are manufactured and investigated in detail. In such symmetric model systems we observed an additional ion-transfer process, which we attributed to the interface processes (i.e. distributed Li⁺ transition across the interface). Based on the EIS measurement data obtained above the polymer electrolyte's melting temperature, at 70°C the interface resistance of the lithium ion transition is estimated to be ∼9 kΩ cm² and the capacitance of the process is in the order of 0.1 μF/cm². According to our investigations, it is possible to predict interface resistivity of lithium ion transport for different polymer/ceramic composite electrolytes for solid state lithium battery applications.