Lithiated Copper Polyphthalocyanine with Extended π‐Conjugation Induces LiF‐Rich Solid Electrolyte Interphase toward Long‐Life Solid‐State Lithium‐Metal Batteries

Abstract The composition of the solid electrolyte interphase (SEI) is crucial to stably operate solid‐state batteries based on lithium‐metal anodes. In this work, the redox state of the PVDF‐b‐PTFE (PVT) solid polymer electrolyte is regulated by introducing fully conjugated copper polyphthalocyanine metal (CuPcLi), improving the electron transfer kinetics to accelerate the decomposition of fluorinated ingredients. As a result, an effective SEI with enriched lithium fluoride forms in situ at the Li/electrolyte interface, which enhances the Li‐ion transport kinetics and regulates the lithium deposition behavior, delivering ultra‐stable lithium plating/stripping performance over 2000 h in the Li//Li half‐cell. In addition, the chemisorption between Cu²⁺ and O atoms from TFSI⁻ restrains the movement of anions in the electrolyte, and the CuPcLi improves the lithium ion release, exhibiting a high lithium‐ion conductivity of 0.8 mS cm⁻¹ and a high lithium‐ion transference number of 0.74. As a result, the solid polymer electrolyte of PVT‐10CuPcLi paired with LiFePO₄ delivers fantastic cyclic performance with a capacity retention of 92% even after 1000 cycles at 1 C at room temperature. When paired with high‐voltage LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) cathode, the cells can be operated at 1 C with superior capacity retention over 88% after 300 cycles.