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 LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode, the cells can be operated at 1 C with superior capacity retention over 88% after 300 cycles.