Self‐Reinforced Inductive Effect of Symmetric Bipolar Organic Molecule for High‐Performance Rechargeable Batteries

Abstract Herein, the self‐reinforced inductive effect derived from coexistence of both p‐ and n‐type redox‐active motifs in a single organic molecule is presented. Molecular orbital energy levels of each motif are dramatically tuned, which leads to the higher oxidation and the lower reduction potentials. The self‐reinforced inductive effect of the symmetric bipolar organic molecule, N,N’‐dimethylquinacridone (DMQA), is corroborated, by both experimental and theoretical methods. Furthermore, its redox mechanism and reaction pathway in the Li+‐battery system are scrutinized. DMQA shows excellent capacity retention at the operating voltage of 3.85 and 2.09 V (vs Li+/Li) when used as the cathode and anode, respectively. Successful operation of DMQA electrodes in a symmetric all‐organic battery is also demonstrated. The comprehensive insight into the energy storage capability of the symmetric bipolar organic molecule and its self‐reinforced inductive effect is provided. Thus, a new class of organic electrode materials for symmetric all‐organic batteries as well as conventional rechargeable batteries can be conceived

Cooperative Conformational Change of a Single Organic Molecule for Ultrafast Rechargeable Batteries

We unveil that the conformational change of a single organic molecule during the redox reaction leads to impressive battery performance for the first time. We propose the model material, a phenoxazin-3-one derivative, as a new redox-active bioinspired single molecule for the Li-ion rechargeable battery. The phenoxazin-3-one cathode delivered a high discharge capacity (298 mAh g(-1)) and fast rate capability (65% capacity retention at 10 C). We elaborate the redox mechanism and reaction pathway of phenoxazin-3-one during Li+-coupled redox reaction. The molecular structure alteration of phenoxazin-3-one during the lithium-coupled electron transfer reaction enables strong pi-pi interaction between 2Li-phenoxazin-3-one and carbon, which was evidenced by operando Raman spectroscopy and density functional theory calculation. Our work provides in-depth understanding about the conformational molecular switch of the single molecule during Li+-coupled redox reaction and insight into the design of a new class of organic electrode materials.N

Multi-redox phenazine/non-oxidized graphene/cellulose nanohybrids as ultrathick cathodes for high-energy organic batteries

Various redox-active organic molecules can serve as ideal electrode materials to realize sustainable energy storage systems. Yet, to be more appropriate for practical use, considerable architectural engineering of an ultrathick, high-loaded organic electrode with reliable electrochemical performance is of crucial importance. Here, by utilizing the synergetic effect of the non-covalent functionalization of highly conductive non-oxidized graphene flakes (NOGFs) and introduction of mechanically robust cellulose nanofiber (CNF)-intermingled structure, a very thick (approximate to 1 mm), freestanding organic nanohybrid electrode which ensures the superiority in cycle stability and areal capacity is reported. The well-developed ion/electron pathways throughout the entire thickness and the enhanced kinetics of electrochemical reactions in the ultrathick 5,10-dihydro-5,10-dimethylphenazine/NOGF/CNF (DMPZ-NC) cathodes lead to the high areal energy of 9.4 mWh center dot cm(-2) (= 864 Wh center dot kg(-1) at 158 W center dot kg(-1)). This novel ultrathick electrode architecture provides a general platform for the development of the high-performance organic battery electrodes.

Effects of Photochemical Oxidation of the Carbonaceous Additives on Li-S Cell Performance

We introduce a simple and easy way to functionalize the surface of various carbonaceous materials through the ultraviolet light/ozone (UV/O-3) plasma where we utilize the zero-, one-, and two-dimensional carbon frameworks. In a general manner, the lamps of a UV/O-3 generator create two different wavelengths (lambda = 185 and 254 nm); the shorter wavelength (lambda = 185 nm) dissociates the oxygen (O-2) in air and the longer wavelength (lambda = 254 nm) dissociates the O-3 and creates the reactive and monoatomic oxygen radical, which tends to incorporate onto the defects of the carbons. By tailoring the association and dissociation of the oxygen with various forms, carbon black, carbon nanofibers, and graphite flakes, chosen as representative models for the zero-, one-, and two-dimensional carbon frameworks, their structure can be oxidized, respectively, which is known as photochemical oxidation. Various carbons have their own distinctive morphology and electron transport properties, which are applicable for the lithium-sulfur (Li-S) cell. We, here, report on the improvement of electrochemical performance of the lithium/sulfur cell through such an efficient functionalization approach.N