Self‐Polarized Organic–Inorganic Hybrid Ferroelectric Cathode Coatings Assisted High Performance All‐Solid‐State Lithium Battery

Abstract Ferroelectrics can significantly boost electrochemical performances of all‐solid‐state batteries by constructing built‐in electric field to reduce the space charge layer at cathode/solid‐state electrolyte interface. However, the construction mechanism of ferroelectric built‐in electric field is poorly understood. Herein, the guanidinium perchlorate (GClO 4 ) ferroelectrics as the cathode coatings in the LiCoO 2 ‐based all‐solid‐state lithium battery are reported, which has state‐of‐the‐art specific capacity of 210.6 mAh g −1 (91.6% of the liquid battery). Systematic studies reveal that the flexoelectric effect originating from the lattice mismatch between GClO 4 and LiCoO 2 gives GClO 4 coatings the single‐domain state and upward self‐polarization. Consequently, a vertically downward built‐in electric field is generated relative to the cathode, which transports the lithium ions inside the electrolyte to the three‐phase interface to alleviate the space charge layer. These findings highlight that the microstructural characteristics of ferroelectric and electrode materials are the primary concern for building an effective built‐in electric field.