Poly(catechol)s As Universal Electrode Materials for Advanced Organic Batteries
Authors: Patil Nagaraj , Marcilla Rebeca 
Published: July 2021

This decade has been witnessing the resurgence of redox-active polymer (RAP) based organic electrode materials in the quest of building large-scale, safe, economical, and sustainable electrochemical energy storage technologies (EESTs) after their brief silence. [1] Most of these RAPs mainly fall under the category of quinone, imide, organosulfur or radical polymers that have demonstrated admirable electrochemical performances. However, it is further necessary to design novel electrode materials with outstanding properties for the development of “next-generation” “high-performance” advanced organic batteries.
Here, I present the macromolecular engineering of RAPs bearing catechol pendants of different functionality/composition that dictate their overall electrochemical performances in different battery technologies.
Firstly, electrochemical performance of poly(catechol) cathodes in lithium-ion batteries will be presented. By tuning the pendant catechol structure, specific capacity of the homopolymer was boosted from 217 [for P(DA)] to 350 [for P(4VC)] mAh g‒1.[2] Furthermore, incorporation of cation conducting styrene sulfonates within the polymer chain in P(4VC-stat-LiSS) drastically improved the rate capability compared to P(4VC). Moreover, a voltage gain of +350 mV was demonstrated when catechol pendants were confined to an electron-withdrawing poly(ionic liquid) backbone, compared to the same redox groups groups in neutral poly(acrylamide) backbone.[3]
Secondly, the application of poly(catechol) as organic cathodes for aqueous Zinc-ion batteries will be presented.[4] The Zn||P(4VC86-stat-SS14) cell in the optimized Zn(TFSI)2-H2O electrolyte simultaneously delivered high gravimetric capacity (324 mAh g‒1), high areal capacity (5.5 mAh cm‒2) at 1C, with remarkable capacity of 98 mAh g‒1 at 450C, extremely low capacity fading rate of 0.00035% per cycle over 48 000 cycles at 30 C rate and low temperature operativity (178 mAh g‒1 at –35 °C).
Finally, all-polymer aqueous battery comprising poly(catechol) cathode and poly(imide) anode will be presented.[5] Interestingly, full cell exhibited tunable cell voltage depending on the salt used in the aqueous electrolyte, i.e., 0.58, 0.74, 0.89, and 0.95 V, respectively, when Li+, Zn2+, Al3+, and Li+/H+ were utilized as charge carriers. The full-cell delivered best rate performance (a sub-second charge/discharge) and cycling stability (80% capacity retention over 1000 cycles at 5 A g‒1) in Li+. Furthermore, maximum energy/power density of 80.6 Wh kganode+cathode
‒1/348 kW kganode+cathode
‒1 was achieved in Li+/H+, superior than most of the previously reported aqueous all–polymer batteries.
Taking together, by the applicability of poly(catechol) as organic electrode material in different battery technologies, the following general conclusions can be drawn. They are quite universal- and accommodate reversibly numerous cations, ranging from H+, and Li+ to Al3+. This unprecedented approach is based on a simple catecholato–cation complex charge storage mechanism (n-type redox molecules). Development of such universal organic electrodes is particularly intriguing, and gaining popularity among the battery community due to the fact that it demands minimal electrode/device engineering efforts.

References:

1 S. Muench, A. Wild, C. Friebe, B. Häupler, T. Janoschka and U. S. Schubert, Chem. Rev., 2016, 116, 9438–9484.
2 N. Patil, A. Aqil, F. Ouhib, S. Admassie, O. Inganäs, C. Jérôme and C. Detrembleur, Adv. Mater., 2017, 29, 1703373.
3 N. Patil, M. Aqil, A. Aqil, F. Ouhib, R. Marcilla, A. Minoia, R. Lazzaroni, C. Jérôme and C. Detrembleur, Chem. Mater., 2018, 30, 5831–5835.
4 N. Patil, et al., Adv Energy Mater, Submitted.
5 N. Patil, A. Mavrandonakis, C. Jérôme, C. Detrembleur, N. Casado, D. Mecerreyes, J. Palma and R. Marcilla, J. Mater. Chem. A, , DOI:10.1039/D0TA09404H.

Figure 1