Owing to its excellent ionic conductivity, 20 mol% samarium doped ceria (Ce0.8Sm0.2O2-δ, SDC) is considered a promising alternative as an electrolyte in solid oxide fuel cells (SOFCs). SDC electrolytes, however, require high sintering temperatures over 1,600 ℃ to attain sufficient density to be SOFC electrolytes. To lower the SDC sintering temperature, different amounts of Li2CO3 (0-12mol% of Li) were evaluated as a sintering aid for SDC electrolytes. The SDC electrolyte samples with Li were sintered at 1,400 ℃ and were compared with SDC electrolytes sintered at 1,600 ℃. The SDC electrolyte with 6mol% of Li sintered at 1,400 ℃ (Li6SDC1400) was densified to 97.495% of theoretical density (T.D.), which is similar to that achieved by the SDC electrolyte sintered at 1,600 ℃ (97.433% of T.D.). The improved formation of grain boundary in the Li6SDC1400 sample increased the density of the SDC, resulting in enhancement of ionic conductivity and cell performance. At 800 ℃, the maximum power density of the Li6SDC1400 electrolyte sample was 120.15mW/cm2.