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Organic compounds are promising candidates as battery materials because they can be sourced from sustainable resources, have tunable structures, and are cheap. However, the working voltage of battery cells containing organic compounds as positive electrodes is relatively lower than that of those containing an inorganic counterpart. In this work, a strategy was developed to increase the discharge voltage of battery cells by diluting the electron density of N‐based redox centers in conjugated organic materials. In electron‐rich heterocyclic compounds that utilize N as the redox center, pentatomic rings such as carbazole derivatives exhibited a higher atomic‐dipole‐moment‐corrected Hirshfeld charge population compared with hexatomic rings, which led to a significant increase in the oxidation potential. As a result, polymeric indolocarbazole derivatives showed a high discharge voltage of 3.7–4.3 V vs. Li+/Li and good cycling performance. Such a strategy can be used to design high‐voltage organic electrode materials containing other redox centers. [ABSTRACT FROM AUTHOR]

Symmetric batteries received an increasing research interest in the past few years because of their simplified fabrication process and reduced manufacturing cost. In this study, we propose the first dual‐ion organic symmetric cell based on a molecular anion of 4,4′‐(phenazine‐5,10‐diyl)dibenzoate. The alkali salt of 4,4′‐(phenazine‐5,10‐diyl)dibenzoate allows a facile transport of cations and large anions, and remains stable in both oxidized and reduced states. The large potential difference between phenazine and benzoate results in a high cell voltage of 2.5 V and an energy density of 127 Wh kg−1 at a current rate of 1 C. The introduction of bipolar organic materials may further consolidate the development of symmetric batteries that are fabricated from abundant elements and environmentally friendly materials. [ABSTRACT FROM AUTHOR]

Efficient energy storage systems impact profoundly the renewable energy future. The performance of current electrical energy storage technologies falls well short of requirements for using electrical energy efficiently in transportation, commercial, and residential applications. This paper explores the possibility by using transition-metal-based complexes as active materials in a Li-ion battery full cell that synergizes the concept of both lithium-ion batteries and redox flow batteries. A cathode made from transition metal complex, [Fe(bpy)3](BF4)2, exhibits high discharge voltage approaching 4 V (vs Li/Li+). When coupled with a Li4Ti5O12 anode, the Li-ion full battery exhibits a cell voltage exceeding 2.2 V and decent cycling efficiencies with Coulombic efficiency and energy/voltage efficiencies above 99% and 92%/93%, respectively. Such a Li-ion battery full cell offers distinct features such as low cost and flexibility in molecular structure design. The result reveals a generic design route toward iron-based complexes as cathode materials with good electrochemical performances. [ABSTRACT FROM AUTHOR]

Cover Feature: Dilution of the Electron Density in the -Conjugated Skeleton of Organic Cathode Materials Improves the Discharge Voltage (ChemSusChem 9/2020) Keywords: aromaticity; electron delocalization; high voltage; indolocarbazole; organic batteries EN aromaticity electron delocalization high voltage indolocarbazole organic batteries 2103 2103 1 05/08/20 20200508 NES 200508 B The Cover Feature b shows that the discharge voltage of conjugated organic battery cathode materials could be increased by diluting the electron density in the -conjugated skeleton. The smoke rings represent the diluted electron density of the molecule, and their size is correlated to the degree of dilution. [Extracted from the article]