Constructing Donor–Acceptor-Linked COFs Electrolytes to Regulate Electron Density and Accelerate the Li⁺ Migration in Quasi-Solid-State Battery

Regulation the electronic density of solid-state electrolyte by donor–acceptor (D–A) system can achieve highly-selective Li⁺ transportation and conduction in solid-state Li metal batteries. This study reports a high-performance solid-state electrolyte thorough D–A-linked covalent organic frameworks (COFs) based on intramolecular charge transfer interactions. Unlike other reported COF-based solid-state electrolyte, the developed concept with D–A-linked COFs not only achieves electronic modulation to promote highly-selective Li⁺ migration and inhibit Li dendrite, but also offers a crucial opportunity to understand the role of electronic density in solid-state Li metal batteries. The introduced strong electronegativity F-based ligand in COF electrolyte results in highly-selective Li⁺ (transference number 0.83), high ionic conductivity (6.7 × 10^–4 S cm⁻¹), excellent cyclic ability (1000 h) in Li metal symmetric cell and high-capacity retention in Li/LiFePO₄ cell (90.8% for 300 cycles at 5C) than substituted C- and N-based ligands. This is ascribed to outstanding D–A interaction between donor porphyrin and acceptor F atoms, which effectively expedites electron transferring from porphyrin to F-based ligand and enhances Li⁺ kinetics. Consequently, we anticipate that this work creates insight into the strategy for accelerating Li⁺ conduction in high-performance solid-state Li metal batteries through D–A system.