ZHANG Shuangshuang ¹, LUO Linghong ¹, WANG Leying ¹, CHENG Liang ²,

XU Xu ¹, DING Liping ¹, CAO Xiwen ¹

(1. School of Materials Science and Engineering, Jingdezhen Ceramic University, Jingdezhen 333403, Jiangxi, China;

2. National Engineering Research Center for Domestic & Building Ceramics Jingdezhen Ceramic University,

Jingdezhen 333001, Jiangxi, China)

Extended abstract:[Significance] Solid oxide fuel cell (SOFC) has garnered significant attention due to the clean and efficient energy conversion characteristics, with the performance of cathode materials playing a decisive role in the overall efficiency and lifetime of the device. However, the commercialization of SOFC in the intermediate- to low-temperature range (500–800 ℃) faces two major challenges: insufficient electrocatalytic activity for the oxygen reduction reaction (ORR) at the electrodes and poor long-term operational stability. Although traditional perovskite cathode materials (such as La_1–xSr_xCoO_3–δ, LSC, etc.) exhibit excellent catalytic activity for ORR, they still suffer from issues, such as element segregation, thermal expansion coefficient mismatch, inadequate high-temperature stability, and susceptibility to CO₂/Cr poisoning. In recent years, high-entropy perovskite oxide (HEPO) materials have emerged as a significant research direction for overcoming the limitations of traditional cathode materials by introducing multi-element lattice distortion effects, which demonstrate unique structural stability and performance regulation potential. The high configurational entropy of HEPO materials effectively inhibits cation segregation, enhances phase structural stability, and optimizes oxygen reduction reaction kinetics through the synergistic effect of multiple active sites. Furthermore, high-entropy design can improve the anti-poisoning capability and electronic/ionic conductivity of materials by adjusting the d–band center or oxygen vacancy concentration, providing new insights for the practical application of intermediate- and low-temperature SOFC.[Progress] Compared with conventional doping methods, the high-entropy strategy exhibits greater flexibility in component regulation, enabling precise adjustments of the chemical composition, defect characteristics and the disordered/ordered structures of materials, thereby achieving targeted optimization of material properties. In contrast to traditional perovskite materials, the introduction of multiple ions within specific lattices through the high-entropy strategy significantly expands the design space and customization potential of cathode materials, owing to the highly uniform distribution of various elements in the lattice. The preparation methods for high-entropy perovskite materials are relatively diverse, with liquid-phase methods currently being predominantly used to synthesize the high-performance high-entropy perovskite cathode materials. The A-site in the lattice is typically occupied by rare earth or alkaline earth metal cations with larger ionic radii, while the B-site is filled by transition metal cations with relatively smaller ionic radius. HEPO materials exhibit the novel functional characteristics and infinite possibilities, due to the extensive selectivity in elemental composition and content. Depending on the doping elements, they are primarily categorized into ABO₃-type A-site, ABO₃-type B-site, AA'BB'O₆-type and other types of high-entropy perovskite cathode materials. This approach significantly improves the catalytic activity of cathodes, enhances oxygen ion transport capabilities and increases stability, providing new perspectives and solutions to the numerous challenges faced by the traditional SOFC cathode materials, thereby demonstrating cutting-edge and innovative features.[Conclusions and prospects] Starting from the design and preparation of high-entropy perovskite materials, the application of high-entropy perovskite cathode materials was focused on, as an emerging and highly potential material system in SOFC. The performance breakthroughs and the mechanism of action are discussed in detail. The high-entropy perovskite material system demonstrates significant enhancement in oxygen reduction activity under medium- and low- temperature operating conditions, effectively suppresses element segregation and simultaneously exhibits excellent CO₂ tolerance, resistance to Cr poisoning and long-term operational stability. The high-entropy strategy has opened new avenues for innovation of SOFC cathode materials. However, current research primarily focuses on the performance enhancement of HEPO, while the elucidation of their mechanisms and theoretical studies still face challenges, mainly manifested in the three aspects. (1) It is necessary to systematically analyze the synergistic mechanisms of multiple elements and quantify the correlation between entropy value and performance through a combination of experimental and theoretical computational methods. (2) It is essential to establish a multi-dimensional evaluation system encompassing electrochemical catalytic activity, oxygen ion transport, chemical compatibility and durability to systematically verify the universality of the four core effects of high entropy under actual SOFC operating conditions. (3) It is crucial to systematically reveal the dynamic regulatory mechanisms of configurational entropy on crystal structure, oxygen vacancy distribution and oxygen reduction kinetics, thereby elucidating the multi-scale correlation laws of entropy-structure-performance.

Key words: high-entropy perovskite; solid oxide fuel cell; cathode; oxygen reduction reaction; the entropy stabilized effect