Redox‐Active Organic Compounds for Future Sustainable Energy Storage System

Abstract

to be promising for rechargeable battery chemistries that emit low carbon footprints during production. [4-8] Redox-active organic compounds, that is, chemicals composed of unlimited resources such as carbon, hydrogen, oxygen, nitrogen, and sulfur, among them have exhibited the great potential as a carbon-neutral option, possibly exploiting the bio-derived materials and not relying on the scarce transition metal resources, in all organic-based LIBs, owing to their chemical diversity and functional versatility. [6-8] Despite their promising potential and intensive research efforts to date, replacing the commercial electrodes in LIBs with these new electrode materials remains a great challenge due to the short cycle life and the low energy density in the electrode-and system-level. However, recent alternative approaches have demonstrated that the utilization of redox-active organic compounds in battery systems other than LIBs can be more promising, taking advantage of their chemical and functional flexibilities in diverse electrochemical configurations. In this essay, we highlight the progressive shift in exploiting the redox-active organic compounds in new battery platforms for future ESSs, as well as offer an overview of the advancements achieved during the past decade. 2. Basic Operating Mechanisms of Organic Electrode Materials The working principle of the redox-active organic compounds as active materials in electrodes can be classified into three categories, that is, n-type, [9] p-type, [10] and bipolar-type, [11] based on their capabilities to receive or release electrons in their neutral state during the electrochemical reaction. Figure 1 schematically illustrates the three types of redox reaction with the molecular structures of the representative redox-active compounds. [6,8,12] Most of the known redox-active organic compounds follow one or more of these redox mechanisms in rechargeable batteries. The n-type electrochemical reaction represents the reduction of the neutral-state organic compound electrodes, forming negatively charged molecular states, which can be reversed during the oxidation reaction. In lithium batteries, the n-type "cathodes" readily accept electrons and the corresponding number of Li-ions during the discharge process, thus generally require Li-containing anodes. Contrarily, the n-type "anodes" can be paired with the conventional LIB cathodes, such as LiMeO 2 (Menickel, cobalt, manganese, aluminum, etc.), LiFePO 4 , or LiMn 2 O 4 , which intrinsically Utilizing redox-active organic compounds for future energy storage system (ESS) has attracted great attention owing to potential cost efficiency and environmental sustainability. Beyond enriching the pool of organic electrode materials with molecular tailoring, recent scientific efforts demonstrate the innovations in various cell chemistries and configurations. Herein, recent major strategies to build better organic batteries, are highlighted: diversifying charge-carrying ions, modifying electrolytes, and utilizing liquid-type organic el...

In-situ electropolymerized bipolar organic cathode for stable and high-rate lithium-ion batteries

“…Organic electrode materials are mainly categorized into three types based on the redox reaction mechanism: ntype, p-type, and bipolar [10][11][12][13]. The n-type materials react with Li + cations, and the positive charges are compensated by the uptake of the same number of electrons, leading to a reduction reaction.…”

RedDB, a Computational Database of Electroactive Molecules for Aqueous Redox Flow Batteries

“…RedDB, a computational database of electroactive molecules for aqueous redox flow batteries Elif Sorkun 1,2 , Qi Zhang 1,2,3 , Abhishek Khetan 1,2 , Murat Cihan Sorkun 1,2,3 , and Süleyman Er 1,2 S1: Explanation of the data columns that are present in RedDB's additional data tables. Descriptions of data columns have been provided alongside the units, whenever applicable, for the different data types.…”

Carbonyl‐rich Poly(pyrene‐4,5,9,10‐tetraone Sulfide) as Anode Materials for High‐Performance Li and Na‐Ion Batteries

“…Organic materials have gained much attention for ESSs in terms of the beneficial characteristics: natural abundance, environmental friendliness, produces in minimal waste, high specific capacity and system security. [4] Among these organic materials, carbonyl-containing conjugated compounds have been developed by researchers for ESSs due to their high theoretical capacity and multiple active sites. [5] Unfortunately, the inevitable existence solubility and weak conductivity of small-molecule organic compounds limit their further development in ESSs.…”