Comprehensive study on lithium-ion battery cathode LiNixCoyMn1-x-yO2 as an air electrode for protonic ceramic fuel cells

The protonic ceramic fuel cells (PCFCs) exhibits a remarkable high-energy conversion efficiency and significant application potential at low temperatures. In this context, the layered ternary lithium-ion batteries (LIB) material, LiNi_xCo_yMn_1-x-yO₂ (LNCM), is explored as a potential cathode for PCFCs. Utilizing density functional theory (DFT) calculations, we have conducted a comprehensive analysis of oxygen vacancies, hydration energy, density of states, and other pertinent properties to evaluate these ternary materials. Both theoretical and experimental findings suggest that LiNi_0.5Co_0.2Mn_0.3O₂ (LNCM523) may offer the optimal performance as a PCFCs cathode. Notably, after calcination in air at 700 °C for 100 h, LNCM523 displayed no phase transition or the emergence of new phases. The impedance of LNCM523, measured on a BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-δ (BZCYYb) electrolyte, is 0.225 Ω cm² at 650 °C. At this temperature, the peak power density of the single cell reaches 355 mW cm⁻². Moreover, during a 100-h stability test conducted at 550 °C, the output performance of the single cell remained unaltered. In electrolysis mode, at 650 °C and 1.3 V, the current density for electrolysis water attained 1.75 A cm⁻². Based on these promising results, LNCM emerges as a viable cathode candidate for PCFCs.