Covalent Organic Framework Bipolar Pseudocapacitive Electrodes in an All‐Organic Symmetric Lithium‐Ion Battery

Abstract Covalent organic frameworks (COFs) have emerged as promising active materials for secondary‐ion battery electrodes, owing to their robust porous structure and the flexibility in selecting redox‐active building blocks. Here, a novel highly crystalline, electro‐active, bipolar‐type WTTF ‐COF, obtained by integrating p‐type N , N , N ′, N ′‐tetrakis(4‐aminophenyl)‐1,4‐phenylenediamine ( W ) and 4,4′,4″,4′″‐([2,2'‐bi(1,3‐dithiolylidene)]‐4,4′,5,5′‐tetrayl)tetrabenzaldehyde ( TTF ) molecular building blocks via n‐type imine linkages, is reported, serving as a Li‐ion battery electrode. In Li‐ion half cells, WTTF ‐COF as a cathode features 12‐electron dual‐ion redox chemistry per unit cell within a stable, unusually wide potential window of 0.1–3.6 V versus Li/Li ⁺ , corresponding to a high theoretical capacity of 315 mAh g ⁻¹ , with an experimental reversible specific capacity of 271 mAh g ⁻¹ at 0.1 A g ⁻¹ . The hybrid redox features coupled with the long‐range ordered nanostructure of WTTF ‐COF enable an efficient pseudo‐capacitive charge‐storage mechanism. Different diffusion pathways and diffusion coefficients for Li ⁺ and PF ₆ ⁻ transport are established through detailed diffusion measurements and theoretical modeling. Among hybrid storage electrodes, WTTF ‐COF is reported to offer the option to serve as both anode and cathode up to a high rate of 200 mV s ⁻¹ , as demonstrated in fully organic symmetric cell tests. Summarizing, judiciously designed COFs are suitably established for efficient bipolar electrode applications.