Ionic Conducting Properties and Fuel Cell Performance Developed by Band Structures

The layer-structure transition-metal oxides have good triple H⁺/O^2–/e^– charge transport which can promote redox reactions and enhance fuel cell performance. This work has developed ionic transport property based on the layer-structure LiCoO₂ (LCO) by tuning the energy band structure with Mg doping also applied for the electrolyte in high-performance low-temperature solid oxide fuel cells (LT-SOFCs). Mg-doped LiCoO₂ exhibited a hexagonal-layered structure with the R3m space group. By doping LiCoO₂, its band gap was reduced from 2.65 to 2.24 eV. Electrochemical impedance analysis revealed that Mg-doped LCO (LMCO) significantly reduces the polarization loss (charge-transfer resistance) from 0.85 to 0.5 Ω cm² at 600 °C; the power output of the fuel cell devices improved from 0.5 to 0.7 W/cm², resulting also in better operation durability. Various characterizations on structural and electrochemical properties were conducted. The mechanism was further discussed in relation with the band structure.