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Chen et al. Energy Mater. 2025, 5, 500045 https://dx.doi.org/10.20517/energymater.2024.144 Page 17 of 27

Figure 9. (A) Oxidation processes of Ni-YSZ and Ni-GDC in H O and CO . Reproduced with permission from Ref. [137] . Copyright 2022,
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[6]
Elsevier. (B) Microstructural changes at the LSM/YSZ interface in SOEC mode. Reproduced with permission from Ref. . Copyright
2023, Elsevier. (C) SEM image of the electrode/electrolyte interface after anodic polarization of the LSM for 20 h in the presence of
borosilicate glass. Reproduced with permission from Ref. [141] . Copyright 2016, Elsevier. (D) Schematic of inhibiting Sr diffusion after
adding GDC barrier layer. Reproduced with permission from Ref. [143] . Copyright 2021, American Chemical Society. (E) SEM image of
YSZ electrolyte rupture. Reproduced with permission from Ref. [147] . Copyright 2011, Elsevier.
In LSCF-based materials, cation diffusion and segregation of Sr represent the primary causes of degradation.
As shown in Figure 9D, the addition of a GDC barrier layer between the Zr-based solid-state electrolyte and
the LSCF can prevent the diffusion of Sr and inhibit the formation of deleterious phases, such as SrZrO or
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La Zr O . However, this approach was unable to inhibit the degradation of the LSCF . Laurencin et al.
[143]
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concluded that electrolysis results in the depletion of oxygen vacancies in the LSCF, thereby segregation of
Sr from the anode and consequently leading to LSCF degradation . However, Ai et al. concluded that the
[144]
direct assembly of LSCF on YSZ without a blocking layer also results in the production of high-performance
SOEC anodes . It was found that anode polarization has the effect of reducing the concentration of
[145]
oxygen vacancies and inhibiting the segregation of Sr and the generation of SrZrO , thereby enhancing the
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stability of the anode/electrolyte interface. The development of innovative material systems and a deeper
understanding of the degradation process represent promising avenues for enhancing the stability of
SOECs.
Electrolyte degradation
YSZ may exhibit delamination, fracture, and evolution of metallic elements when subjected to prolonged
operation in a reducing atmosphere. Moreover, this material requires high temperatures to sustain its high
level of activity, which can result in its degradation and the accelerated aging of sealants. The ohmic
resistance in SOECs is attributable to the electrolyte. A reduction in temperature results in a decline of
oxygen ion conductivity, which in turn elevates the ohmic resistance and gives rise to fractures at the
junctions between electrolyte particles . In SOEC mode, Tietz et al. found that the electrolyte layer
[146]
exhibited distinct degradation, with voids forming a clear distribution and horizontally aligned pores at the
edges of the electrolyte grains . The diffusion of the two elements, Y and Zr, and the crystallization on the
[65]
electrode surface will result in an increase in the overpotential during the reaction. Laguna-Bercero et al.