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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]

[Display omitted] • Redox-active binary eutectics with weak intermolecular interaction are synthesized. • Weakening intermolecular interaction leads to enhanced ionic conductivity. • The binary eutectic alone can be used as electrolyte that show good reversibility. Eutectics are emerging as promising candidate for electrochemical energy storage. However, the eutectics usually show high viscosity that usually arises from strong intermolecular interactions greatly limits their application. In this communication, we design and prepare two redox-active molecules that both are able to form binary eutectics with TBMA-TFSI. Combined experimental and computational studies indicate the intermolecular interaction is weakened after eutectic formation, resulting in decreased viscosity and enhanced ionization ratio of TBMA-TFSI without affecting the redox behaviors of the individual molecules. Further, the redox-active binary eutectic is used as solvent-free electrolyte for battery application. [ABSTRACT FROM AUTHOR]

Abstract Organic redox flow batteries receive increasing interest for large-scale electrical energy storage owing to the structural diversity and elemental abundance of organic compounds. However, their implementation is challenged by the cyclability, which is an order of magnitude lower than traditional redox flow batteries using inorganic redox couples. The unsatisfactory cyclability mainly arises from electrolyte contamination and irreversible losses of active material in the electrolyte. To address such issues, a highly water-soluble artificial bipolar molecule containing cathode-active ferrocene moiety and anode-active bipyridinium moiety is realized and used as the sole active material in a symmetric organic redox flow cell. Owing to the good reversibility, minimum electrolyte contamination, and stability of the synthesized molecule, the demonstrated cell boosts the cyclability to 4000 cycles with capacity retention of ca. 75% at 100% depth of discharge, which fills in the gap of cyclability between organic redox flow batteries and conventional redox flow batteries. Graphical abstract Image 1 Highlights • A highly water-soluble bipolar molecule is designed and synthesized for SORFB. • The demonstrated SORFB overcomes the technical constraints of traditional RFBs. • The SORFB shows stable cycling performance and round-trip efficiencies. [ABSTRACT FROM AUTHOR]