Abstract
Is it possible to exceed the lithium redox potential in electrochemical systems? It seems impossible to exceed the lithium potential because the redox potential of the elemental lithium is the lowest among all the elements, which contributes to the high voltage characteristics of the widely used lithium ion battery. However, it should be possible when we use a molecule-based ion which is not reduced even at the lithium potential in principle. Here we propose a new model system using a molecular electrolyte salt with polymer-based active materials in order to verify whether a molecular ion species serves as a charge carrier. Although the potential of the negative-electrode is not yet lower than that of lithium at present, this study reveals that a molecular ion can work as a charge carrier in a battery and the system is certainly a molecular ion-based “rocking chair” type battery.
Highlights
Is it possible to exceed the lithium redox potential in electrochemical systems? It seems impossible to exceed the lithium potential because the redox potential of the elemental lithium is the lowest among all the elements, which contributes to the high voltage characteristics of the widely used lithium ion battery
To realize such a molecular ion battery, the first requirement is to demonstrate that a rechargeable system is viable in which a single molecular ion species serves as a charge carrier
As for the negative electrode active material, we focused on a 4,4’-bipyridinium moiety, known as the viologen unit, and synthesized a polymer bearing the bipyridinium units by polymerization through the quaternization reaction[22,23] of the nitrogen atoms of 4,4’-bipyridine with dibromopentane, followed by the ion exchange from Br− to PF6− to yield poly(1, 1’-pentyl-4,4’-bipyridinium dihexafluorophosphate): PBPy (Fig. 1b)
Summary
Is it possible to exceed the lithium redox potential in electrochemical systems? It seems impossible to exceed the lithium potential because the redox potential of the elemental lithium is the lowest among all the elements, which contributes to the high voltage characteristics of the widely used lithium ion battery. If we can find a molecule-based ion which is not reduced even at the lithium potential, we will be able to overcome the limit of the lithium potential and develop a very high voltage battery To realize such a molecular ion battery, the first requirement is to demonstrate that a rechargeable system is viable in which a single molecular ion species serves as a charge carrier. Polyaniline, polypyrrole and polythiophene, known as classical π -conjugated conductive polymers, are the representatives, and have been studied since the 1980’s13,14 This kind of redox properties have been applied to a positive electrode reaction in rechargeable lithium batteries[14,17,18,19,20,21]. This paper describes a concept and preliminary performance of our molecular ion battery system and its further prospects
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
