Redox-Bipolar Covalent Organic Framework Cathode for Advanced Sodium-Organic Batteries

Redox-active covalent organic frameworks (COFs) are promising candidates for sodium-ion batteries (SIBs). However, the construction of redox-bipolar COFs with the anions and cations co-storage feature for SIBs is rarely reported. Herein, redox-bipolar COF constructed from aniline-fused quinonoid units (TPAD-COF) is developed as the cathode material in SIBs for the first time. The unique integration of conductive aniline skeletons and quinone redox centers endows TPAD-COF with high ionic/electrical conductivity, abundant redox-active sites, and fascinating bipolar features. Consequently, the elaborately tailored TPAD-COF cathode exhibits higher specific capacity (186.4 mAh g^-1 at 0.05 A g^-1) and superior cycling performance (over 2000 cycles at 1.0 A g^-1 with 0.015% decay rate per cycle). Impressively, TPAD-COF also displays a high specific capacity of 101 mAh g^-1 even at -20 °C. As a proof of concept, all-organic SIBs (AOSIBs) are assembled using TPAD-COF cathode and disodium terephthalate anode, which also show impressive electrochemical properties, indicating the potential application of TPAD-COF cathode in AOSIBs. The work will pave the avenue toward advanced COFs cathode for rechargeable batteries through rational molecular design.