Taking advantage of Li-evaporation in LiCoO2 as cathode for proton-conducting solid oxide fuel cells

Abstract

LiCoO2, a widely used electrode material for Li-ion batteries, was found to be suitable as a cathode material for proton-conducting solid oxide fuel cells (H-SOFCs). Although the evaporation of Li in LiCoO2 was detrimental to the Li-ion battery performance, the Li-evaporation was found to be beneficial for the H-SOFCs. The partial evaporation of Li in the LiCoO2 material preparation procedure led to the in-situ formation of the LiCoO2+Co3O4 composite. Compared to the cell using the pure phase LiCoO2 cathode that only generated moderate fuel cell performance, the H-SOFCs using the LiCoO2+Co3O4 cathode showed a high fuel cell performance of 1160 mW·cm−2 at 700 °C, suggesting that the formation of Co3O4 was critical for enhancing the performance of the LiCoO2 cathode. The first-principles calculation gave insights into the performance improvements, indicating that the in-situ formation of Co3O4 due to the Li-evaporation in LiCoO2 could dramatically decrease the formation energy of oxygen vacancies that is essential for the high cathode performance. The evaporation of Li in LiCoO2, which is regarded as a drawback for the Li-ion batteries, is demonstrated to be advantageous for the H-SOFCs, offering new selections of cathode candidates for the H-SOFCs. [Figure not available: see fulltext.].