Optimization of Monomer Molecular Structure for Polymer Electrodes Fabricated through in‐situ Electro‐Polymerization Strategy

Abstract

In‐situ electro‐polymerization of redox‐active monomers has been proved to be a novel and facile strategy to prepare polymer electrodes with superior electrochemical performance. The monomer molecular structure would have a profound impact on electro‐polymerization behavior and thus electrochemical performance. However, this impact is poorly understood and has barely been investigated yet. Herein, three carbazole‐based monomers, 9‐phenylcarbazole (CB), 1,4‐bis(carbazol‐9‐yl)benzene (DCB), and 2,6‐bis(carbazol‐9‐yl)naphthalene (DCN), were applied to study the above issue systematically and achieve excellent long cycle performance. The monomers were rationally designed with different polymerizable sites and solubilities. It was found that a monomer with increased polymerizable sites and decreased solubility brought about enhanced electrochemical performance. This is because poor solubility could enhance utilization of the monomer for polymerization and more polymerizable sites could lead to a stable crosslinked polymer network after electro‐polymerization. DCN with four polymerizable sites and the poorest solubility displayed the best electrochemical performance, which showed stable cycling up to 5000 cycles with high capacity retention of 76.2 % (among the best cycle in the literature). Our work for the first time reveals the relationship between monomer structure and in‐situ electro‐polymerization behavior. This work could shed light on the structure design/optimization of monomers for high‐performance polymer electrodes prepared through in‐situ electro‐polymerization.

High‐Performance Poly(1‐naphthylamine)/Mesoporous Carbon Cathode for Lithium‐Ion Batteries with Ultralong Cycle Life of 45000 Cycles at ‐15 °C

“…The oxidation peaks at 3.1-3.7 V disappeared after the first cycle and were replaced by a broad peak, indicating the formation of polymer after the first charge. [36][37][38] Galvanostatic charge/discharge profiles of the NA/CMK-3 cathode were consistent with the CV results (Figure 2b). In the first charging process, after the appearance of several short voltage plateaus at 3.2-3.8 V, a long sloping voltage plateau was observed from ≈4.1 V. Thereafter, sloping voltage profiles without an obvious plateau were presented in subsequent cycles with good reversibility.…”

p‐Type Redox‐Active Organic Electrode Materials for Next‐Generation Rechargeable Batteries

“…Reproduced with permission. [ 134 ] Copyright 2021, Wiley‐VCH GmbH. c) Charge–discharge profiles of p‐DPICZ‐O at a current density of 1C.…”

“…Subsequently, a comparative study to find optimal molecular design of the Cbz monomer was reported to improve the performance. [ 134 ] Three monomers—9‐phenylcarbazole (CB), 1,4‐bis(carbazol‐9‐yl)benzene (DCB), and 2,6‐bis(carbazol‐9yl)naphthalene (DCN)—were prepared, which had different core sizes and the number of polymerizable sites (see Figure 6c for the molecular structures). The cycling stability of CB was notably lower than the other monomers even after polymerization ( Figure b), which was attributed to that CB could form only a linear polymer with good solubility.…”

“…As displayed in Figure 23b, most polymeric p‐type ROMs (i.e., both linear and network polymers) exhibited outstanding capacity retention (>85%) except the Cbz‐based ROMs cross‐linked by the in situ electrochemical method. [ 131,134 ] Most impressively, an exceptionally stable cyclability was shown by a PNZ‐based network polymer TzPz, which retained 99% of the initial capacity even after 10 000 cycles. [ 158 ] In contrast, several PTZ polymers also showed high cycle stability over ultra‐long cycles (>1000–10 000 cycles); but they mostly delivered low specific capacities below 50 mAh g −1 .…”

“…b) Long-term cycling test of 9-phenylcarbazole (CB), 1,4-bis(carbazol-9-yl)benzene (DCB), and 2,6-bis(carbazol-9yl)naphthalene (DCN) at a current density of 2 A g À1 after in situ electropolymerization. Reproduced with permission [134]. Copyright 2021, Wiley-VCH GmbH.…”