Taking advantage of Li-evaporation in LiCoO_(2) as cathode for proton-conducting solid oxide fuel cells

LiCoO_(2),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 LiCoO_(2) 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 LiCoO_(2) material preparation procedure led to the in-situ formation of the LiCoO_(2)+Co_(3)O_(4) composite.Compared to the cell using the pure phase LiCoO_(2) cathode that only generated moderate fuel cell performance,the H-SOFCs using the LiCoO_(2)+Co_(3)O_(4) cathode showed a high fuel cell performance of 1160 mW·cm^(-2) at 700℃,suggesting that the formation of Co_(3)O_(4) was critical for enhancing the performance of the LiCoO_(2) cathode.The first-principles calculation gave insights into the performance improvements,indicating that the in-situ formation of Co_(3)O_(4) due to the Li-evaporation in LiCoO_(2) could dramatically decrease the formation energy of oxygen vacancies that is essential for the high cathode performance.The evaporation of Li in LiCoO_(2),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.