Tuning Redox Behavior of Pyrene–Benzothiadiazole/TTF–Based Covalent Organic Framework Electrodes in Dual‐Ion Batteries

Abstract

ABSTRACT Covalent organic frameworks (COFs) have emerged as promising electrode materials for secondary‐ion batteries, where redox‐active building blocks and linkages enable tunable redox properties, while ordered pores serve as nanochannels for fast ion transport. We report a novel highly crystalline 2D PyTTF‐COF, synthesized by integrating n ‐type pyrene–benzothiadiazole (PyBT) and p ‐type tetrathiafulvalene (TTF) subunits via an n ‐type imine linkage, yielding a bipolar electrode capable of reversible 16 e − dual cation–anion storage. Initially, the dual‐ion, redox synergy was tested in a Li‐ion half‐cell, where PyTTF served as cathode, and 1 м LiPF 6 or LiTFSI electrolytes were employed to probe anion‐dependent electrochemical behavior. Electrochemical evaluation in Li‐ion half cells revealed a wide electrochemical window of 0.1−3.6 V vs. Li/Li + , with markedly enhanced charge‐storage kinetics and ion diffusion with LiTFSI relative to LiPF 6 electrolytes. The PyTTF electrode delivered specific capacities of 286 mAh g −1 (LiTFSI) and 184 mAh g −1 (LiPF 6 ) at 0.3 A g −1 , highlighting the strong influence of anion identity. Systematic variation of LiTFSI salt concentration (1−3 м) revealed strong correlations between electrolyte composition, ion storage dynamics, and interfacial charge‐transfer resistance. This study highlights, for the first time, the critical importance of tailoring both charge‐carrier identity and electrolyte concentration to unlock the full potential of bipolar COF electrodes for dual‐ion batteries.