Enhancing Lithium‐Oxygen Battery Performance by Optimizing the Interaction of Cathode Materials and Soluble FePc Redox Mediator

Abstract Macrocyclic redox mediators (RMs) such as iron(II) phthalocyanine (FePc) can improve lithium–oxygen (Li─O 2 ) battery performance by shuttling electrons and oxygen. However, their low solubility in electrolytes due to strong π–π interaction with carbon‐based cathodes (e.g., 3D graphene) limits practical applications. Herein, non‐sp 2 ‐carbon materials (MoN, TiN, and Ti 3 C 2 T x ) are employed as cathodes to regulate cathode‐FePc interactions, thereby increasing FePc solubility and improving Li─O 2 battery performance. For cathode‐FePc coupling catalysts, the solubility of FePc rises as its adsorption strength on cathodes (3DG, MoN, TiN, and Ti 3 C 2 T x ) decreases, creating a “volcano‐shaped” correlation with cathode‐FePc@battery performances. Correspondingly, the total resistance ( R ESR = R s + R ct ) of the batteries after charging exhibits an “inverted‐volcano” trend. The optimized TiN‐FePc catalyst achieves the highest cycling stability (392 cycles). Control experiments and density functional theory (DFT) calculations demonstrate that TiN‐FePc catalyst maintains high FePc concentration in electrolyte while facilitating electron transfer and oxygen shuttling, significantly enhancing catalytic activity. This work provides an efficient strategy for designing high‐performance Li─O 2 batteries by optimizing RMs‐cathode interactions.