Spins at work: probing charging and discharging of organic radical batteries by electron paramagnetic resonance spectroscopy

15 April 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Organic radical batteries (ORBs) are a promising class of electrochemical power sources employing organic radicals as redox-active groups. This article reports on the development of a versatile on-substrate electrode setup for spectroelectrochemical Electron Paramagnetic Resonance (EPR) measurements on redox conductive polymers for ORBs. Quantitative in-operando EPR experiments performed on electrochemical cells with a di-TEMPO Ni-Salen polymer as active electrode material demonstrate a strong decrease in the number of paramagnetic centers upon oxidizing the film. The distinct EPR signatures of the TEMPO-containing polymer and its fragments in different molecular environments are used to study its degradation upon repeated cycling. A comparison between the number of EPR-active sites and the number of electrochemically active charges, as measured by cyclic voltammetry, provides information on the nature of the degradation process. Low-temperature ex-situ pulse EPR measurements on the oxidized polymer film reveal the spectrum of dilute nitroxide species, which may be associated with electrochemically inactive islands. These experiments pave the way for advanced EPR techniques for accurately determining distances between adjacent paramagnetic centers and thus for identifying performance-limiting loss mechanisms, which can eventually help develop strategies for making ORBs powerful contenders on the path towards sustainable electrochemical power sources.


Organic Radical Batteries
Redox Polymers
Film Electrochemistry
Organic Cathode Materials

Supplementary materials

Electronic Supplementary Information
Experimental section, Q-factors and cwEPR spectra for p-DiTS in standard and modified tube, Sample information, p-DiTS in-operando redox series, p-DiTS degradation series, p-DiTS ex-situ oxidation series, p-NiMeOS ex-situ oxidation series, Transfer of charge to the p-DiTS film during the degradation study


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