The Proton Trap Technology—Toward High Potential Quinone‐Based Organic Energy Storage

Abstract

An organic cathode material based on a copolymer of poly(3,4‐ethylenedioxythiophene) containing pyridine and hydroquinone functionalities is described as a proton trap technology. Utilizing the quinone to hydroquinone redox conversion, this technology leads to electrode materials compatible with lithium and sodium cycling chemistries. These materials have high inherent potentials that in combination with lithium give a reversible output voltage of above 3.5 V (vs Li0/+) without relying on lithiation of the material, something that is not showed for quinones previously. Key to success stems from coupling an intrapolymeric proton transfer, realized by an incorporated pyridine proton donor/acceptor functionality, with the hydroquinone redox reactions. Trapping of protons in the cathode material effectively decouples the quinone redox chemistry from the cycling chemistry of the anode, which makes the material insensitive to the nature of the electrolyte cation and hence compatible with several anode materials. Furthermore, the conducting polymer backbone allows assembly without any additives for electronic conductivity. The concept is demonstrated by electrochemical characterization in several electrolytes and finally by employing the proton trap material as the cathode in lithium and sodium batteries. These findings represent a new concept for enabling high potential organic materials for the next generation of energy storage systems.

In situ Investigations of a Proton Trap Material: A PEDOT-Based Copolymer with Hydroquinone and Pyridine Side Groups Having Robust Cyclability in Organic Electrolytes and Ionic Liquids

“…The capacity is reaching a plateau with extended cycling (79% capacity retention after 100 cycles), and we hypothesize that the proton loss during the first 30 cycles originates from the random structure of the copolymer with ∼20% of the quinones being at too far a distance from the traps. This constitutes a significant improvement as compared to the proton trap material presented in ref . In the preceding study, we found that the instability was due to breakage of the ester link between the polymer backbone and the pendant groups.…”

“…Recently, we designed a conducting redox polymer, based on PEDOT as the backbone with hydroquinone units and pyridine proton acceptors as pendant groups. 20 We call this a proton trap material as, upon oxidation of hydroquinone to quinone, the pyridine units extract the resulting protons, thus trapping them in the material and hence preventing diffusion into the electrolyte. Similarly, when the quinone is reduced the same protons are available to reform the hydroquinone species.…”

Reversible Hydrogen Fixation and Release under Mild Conditions by Poly(vinylquinoxaline)

“…GBL was selected to swell poly­(vinylquinoxaline) and poly­(vinyltetrahydroquinoxaline), on the basis of its solvophilicity for both of the polymers, high boiling point, and the results of reversible hydrogenation for monomeric quinoxaline (see Scheme and Table S3). GBL has been often utilized as the solvent for the electrolyte of batteries due to its wide potential window, high thermal stability, and less toxic properties. − …”

Opportunities and challenges for aqueous metal-proton batteries

“…A copolymer of PEDOT involving pyridine and hydroquinone has been designed to serve as a proton-trap cathode (Figure 3E). 33 The incorporated pyridine serves as a proton donor/acceptor, and the hydroquinone part is a redox center. This copolymer coupled with the Li anode provides a working potential of $3.5 V, and the potential decreases to $3.3 V when combined with a Na anode.…”