Lithium-air battery attracts great attention because of its high energy density. However, due to the low solubility and diffusivity of oxygen in the electrolyte, oxygen transport to the reaction site of the positive electrode is limited. The aim of this study is to reduce the oxygen transport resistance and increase the power output by using thin solid electrolyte membranes (ionomer). It is thought that ionomers can form a thin solid electrolyte film, which is difficult with liquid electrolytes, and can reduce oxygen transport resistance. The ionomer produced by coating the cathode with lithiated Nafion solution and drying. In this study, the effect of ionomer coating was investigated by conducting discharge experiments using cathodes with and without ionomer coating, respectively. Experimental results showed that performance was improved by using ionomer. Additionally, it was also suggested that the water content of the ionomer can affect the discharge performance.