Solid oxide fuel cells (SOFC) can be made to last longer and perform better if their operating temperatures are lowered. Traditional SOFCs, however, have poor performance at low temperatures due to significant Ohmic and polarization losses. Regarding ionic conductivity, doped ceria excels as a lowtemperature SOFC catalyst. In this study, Bi-doped CeO 2 (Bi 0.1 Ce 0.9 O 2 ) has been used to function as an electrolyte in lowtemperature solid oxide fuel cells (LT-SOFCs). The Bi−CeO 2 is prepared as a functional electrolyte layer placed between two symmetrical porous electrodes NCAL (Ni 0.8 Co 0.15 Al 0.05 LiO 2−δ ) by a wet chemical coprecipitation process. Using Na 2 Co 3 as a precipitating agent enhances the performance of the produced Bi−CeO 2 particles by enhancing their surface characteristics. The synthesized Bi−CeO 2 electrolyte demonstrates an impressive fuel cell performance with a high ionic conductivity of 0.192 S/cm at a low temperature of 520 °C. Additionally, Bi-doped CeO 2 demonstrates remarkable proton performance, with 660 mW/cm 2 and an activation energy of only 0.456 eV at 520 °C. The mechanism of high conduction was proposed in great detail. The findings demonstrate that high ionic and proton conductivity in fuel cells is possible at low temperatures. In addition, the suggested work hints at the possibility of designing well-functioning electrolytes for advancing low-temperature fuel-cell technology.