KNi_0.8Co_0.2F₃ as an Efficient Electrocatalyst for Nonaqueous Li–O₂ Batteries

The rechargeable nonaqueous Li–O2 battery provides an ultrahigh theoretical energy density for energy storage application. However, its electrochemical performance is significantly hindered by numerous challenges including short cycle life, lower round-trip efficiency, and insulation caused by lithium peroxide (Li2O2) that results in a large overpotential. Utilizing known merits of fluoride perovskite structures and building on previous studies in an aqueous electrolyte, KNi0.8Co0.2F3 (KNCF82), shows promise as a Li–O2 battery electrocatalyst. When placed in a nonaqueous rechargeable Li–O2 battery, the KNCF82 cathode demonstrates an improved specific capacity of ∼9600 mA h g–1 at a current density of 175 mA g–1. The battery shows a cycling stability for 85 cycles with a narrow charge–discharge voltage difference of 1.41 V when the capacity was regulated at 500 mA g–1 and a round-trip efficiency of 63%. Further, despite a slight increase in overpotential, the cell exhibited good stability for 145 cycles and cycled over 835 h

DataSheet1_Synthesis of perovskite-type high-entropy oxides as potential candidates for oxygen evolution.docx

High-entropy materials offer a wide range of possibilities for synthesizing new functional ceramics for different applications. Many synthesis methods have been explored to achieve a single-phase structure incorporating several different elements, yet a comparison between the synthesis methods is crucial to identify the new dimension such complex ceramics bring to material properties. As known for ceramic materials, the synthesis procedure usually has a significant influence on powder morphology, elemental distribution, particle size and powder processability. Properties that need to be tailored according to specific applications. Therefore, in this study perovskite-type high-entropy materials (Gd0.2La0.2–xSrxNd0.2Sm0.2Y0.2) (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 (x = 0 and x = 0.2) are synthesized for the first time using mechanochemical synthesis and a modified Pechini method. The comparison of different syntheses allows, not only tailoring of the constituent elements of high-entropy materials, but also to optimize the synthesis method as needed to overcome limitations of conventional ceramics. To exploit the novel materials for a variety of energy applications, their catalytic activity for oxygen evolution reaction was characterized. This paves the way for their integration into, e.g., regenerative fuel cells and metal air batteries.</p