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In the solid oxide fuel cell field, heterogeneous ion doping is a common methodology to improve the ionic conductivity of electrolytes, but overwhelming grain boundary resistance is still the main obstacle for low‐temperature applications. According to previous reports, building rapid ion transport at the grain boundary through compositing methods was considered as a proposed design for electrolytes to decrease the grain boundary resistance and obtain high ionic conductivity. Herein, Ce0.9Gd0.1O2 − δ (GDC) is selected as the matrix material and composited with Na2CO3 and NdBa0.5Sr0.5Cu2O5 + δ (NBSCu) to form GDC‐Na2CO3 nanocomposite and GDC‐NBSCu composite. The grain boundary conductivity (σb) is delicately separated from the EIS results, demonstrating that the σb of GDC‐NBSCu and GDC‐Na2CO3 composite are both substantially higher than that of pure GDC. Therefore, the power density maximum of GDC‐NBSCu and GDC‐Na2CO3 electrolyte is 726 mW cm−2 at 600 °C and 797 mW cm−2 at 575 °C, respectively. Variety of characterization reveales that the proton contributes to the enhancement of σb in GDC‐Na2CO3, while the band energy alignment between GDC and NBSCu works as an accelerator to promote the ionic conduction for GDC‐NBSCu.

The preparation of electrolyte with excellent ionic conduction is an important development direction in the practical application of solid oxide fuel cell (SOFC). Traditional methods to improve ion conduction was structure doping to develop electrolyte materials. In this work, the ionic conductor Ce0.8Sm0.2O2‐δ (SDC) was modified by insulator Al2O3 to enhance ion conduction and apply as electrolytes for the SOFC. The transmission electron microscopy (TEM) characterization clearly clarified that a thin Al2O3 layer in the amorphous state coated on SDC to form the SDC@Al2O3 core−shell structure. The SDC@Al2O3 electrolyte with the core−shell structure possesses a super ionic conductivity of 0.096 S cm−1 and results in advanced cell performance of 1190 mW cm−2 at 550°C. The X‐ray photoelectron spectroscopy (XPS) analysis revealed that the concentration of oxygen vacancies in the SDC@Al2O3 core–shell structure significantly improved in comparison with pure SDC, the newly produced oxygen vacancies can promote the oxygen ion transport. Moreover, the interface between SDC and Al2O3 provides a fast channel for the proton transport. In addition, the SDC‐based SOFC was usually suffered from the reduction of the SDC electrolyte and the accompanying generated electron conduction should deteriorate the cell performance, this is the main challenge for the SDC electrolyte application. In our case, the Al2O3 shell on the SDC surface not only can avoid the contact between SDC and hydrogen to eliminate the reduction of SDC but also can restrain electron conduction due to the electron insulation characteristic of the Al2O3 shell. This work demonstrates an efficient approach to develop the advanced low‐temperature SOFC technology from material fundamentals.

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The α-NaFeO 2 structure-type oxides, such as LiNiO 2 , LiCoO 2 , and α-LiAlO 2, could not only provide channels for Li + conduction but also conduct protons through intercalation. However, the detailed conduction mechanism of protons in the layer structure oxide needs to be further distinguished. In this work, we prepared layered-oxide α-Li 0.88 AlO 2 and used it as an electrolyte to assemble a solid oxide fuel cell (SOFC), which delivered an output of 1046 mW cm −2 at 550 °C, a decent power output is ascribed to the excellent ion conductivity (0.2 S cm −1 ) and low activation energy (0.36 eV) of the α-Li 0.88 AlO 2 electrolyte. Moreover, the H/ D isotope experiments revealed that the proton dominated the ion conduction of α-Li 0.88 AlO 2. First-principles calculations indicate that the special structure-layered oxides provide channels that allow protons to transfer rapidly with low activation energy. This work indicates the possibility of using layered oxides as proton conductors in a low-temperature SOFC (LT-SOFC) and reveals the proton transport mechanism in oxides, it provides a new approach to exploit novel electrolytes for LT-SOFC.