Enhanced performance of lithiated cathode materials of <scp> LiCo ₀ </scp> _. <scp> ₆ X ₀ </scp> _. <scp> ₄ O ₂ </scp> (X = Mn, Sr, Zn) for proton‐conducting solid oxide fuel cell applications

Abstract

LiCoO2-based materials are well-known cathode materials used in lithium ion batteries. Moreover, these materials are currently utilized in low-temperature proton-conducting solid oxide fuel cells (SOFCs). Various dopants, such as Mn, Sr, and Zn, are introduced into LiCo2-based materials to improve their properties and performance for proton-conducting SOFC applications. In this regard, Mn-, Sr-, and Zn-doped LiCoO2 and LiCo0.6X0.4O2 (X = Mn, Sr, or Zn) powders are synthesized via the glycine-nitrate combustion method. Their properties are characterized using different techniques. The precursor cathode powder is dried at 100°C and subjected to thermogravimetric analysis (TGA). The phase formation and morphology of calcined LiCo0.6Mn0.4O2 (LCMO), LiCo0.6Sr0.4O2 (LCSO), and LiCo0.6Zn0.4O2 (LCZO) powders at 600°C to 700°C are examined via X-ray diffraction. At 600°C, both calcined LCSO and LCZO powders show few secondary phases, but these phases greatly decrease as calcination temperature increases to 700°C. By contrast, calcined LCMO powders exhibit a single phase structure at both calcination temperatures of 600°C and 700°C. The measured crystallite sizes of LCMO, LCSO, and LCZO powders are 23.32 ± 0.20, 21.08 ± 0.72, and 21.24 ± 0.32 nm, respectively. TEM images indicate that the particles in LCMO and LCZO powders highly agglomerate compared with those in LCZO powders. This result confirms that LCSO cathodes have the highest electrical conductivity (356.66 S cm−1) and the lowest area specific resistance (0.29 Ω cm2 in humidified [3%] air) at 700°C. In conclusion, LCSO materials are the best cathodes with high potential for proton-conducting SOFC applications.

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