The impact of vertical π-extension on redox mechanisms of aromatic diimide dyes

Aromatic diimide dyes are an attractive class of redox-active organic molecules for lithium-ion batteries,whose battery performances(stabilities,conductivities and cyclicities) are strongly dependent on the sizes of their π-systems.However,due to the different Clar’s structures possessed,three vertically7 r-extended aromatic diimides,namely,naphthalene diimide(two one-electron reductions),perylene diimide and terrylene diimide(two one-electron reductions),exhibit different electronic redox mechanisms when served as cathode materials in organic lithium-ion batteries.Herein,we have studied carefully the different electrochemical characteristics of the three aromatic diimides through experimental and theoretical calculations.Their battery present different shape of charge/discharge curves resulting from stability of their reduction state during charge/discharge process.Terrylene diimide shows better cycle and rate capacities than those of naphthalene diimide and perylene diimide,which could be attributed to the more energies released during terrylene diimide combining with lithium ions than those of other two diimides.

THE STUDY OF PHARMACEUTICALS BY THIN-LAYER SPECTROELECTROCHEMISTRY(I)——THE REDOX MECHANISM OF NITROFURAZONE

The electrochemical behavior of nitrofurazone in dimethylformamide has been studied by cyclic voltammetry and in-situ thin-layer spectroelectrochemistry.The redox reactions are complicated at platinium electrode,and a possible electrochemical mechanism of nitrofurazone is proposed.

In situ Fourier Transform Infrared Spectroscopy Diagnostic for Characterization and Performance Test of Catalysts

The present work establishes a systematic approach based on the application of in-situ Fourier transform infrared spectroscopy （FTIR） for the investigation of the crystal structure, thermal stability, redox behavior （temperature-programmed reduction/temperatureprogrammed re-oxidation） as well as the catalytic properties of Co3O4 thin films. The syntheses of Co3O4 were achieved by chemical vapor deposition in the temperature range of 400-500℃. The structure analysis of the as-prepared material revealed the presence of two prominent IR bands peaking at 544 cm-1 （υ1） and 650 cm-1 （υ2） respectively, which originate from the stretching vibrations of the Co-O bond, characteristic of the Co3O4 spinel. The lattice stability limit of Co3O4 was estimated to be above 650℃. The redox properties of the spinel structure were determined by integrating the area under the emission bands υ1 and υ2 as a function of the temperature. Moreover, Co3O4 has been successfully tested as a catalyst towards complete oxidation of dimethyl ether below 340 ℃. The exhaust gas analysis during the catalytic process by in situ absorption FTIR revealed that only CO2 and H2O were detected as the final products in the catalytic reaction. The redox behavior suggests that the oxidation of dimethyl ether over Co3O4 follows a Mars-van Krevelen type mechanism. The comprehensive application of in situ FTIR provides a novel diagnostic tool in characterization and performance test of catalysts.

The study of electrochemical cycle for LiCoO_(2) by dual-mode EPR

Dual-mode electron paramagnetic resonance(EPR)spectroscopy was employed to analyze redox mechanisms in lithium cobalt oxide LiCoO_(2)(LCO)cathode material during delithiation and lithiation.It was found that the O_(3)-II could not fully convert back to the pristine O_(3) -I phase while oxygen vacancies quickly generate and accumulate during the cycling.Our study paves the way for better understanding the doping effects of different elements on LiCoO_(2) in the future.

Li-rich layered oxides:Structure,capacity and voltage fading mechanisms and solving strategies

Lithium rich layered oxides(LLOs)are attractive cathode materials for Li-ion batteries owing to their high capacity(>250 mA h g^(-1))and suitable voltage(∼3.6 V).However,they suffer from serious voltage and capacity fading,which is focused in this review.First,an overview of crystal structure,band structure and electrochemical performances of LLOs is provided.After that,current understanding on oxygen loss,capacity fading and voltage fading is summarized.Finally,five strategies to mitigate capacity and voltage fading are reviewed.It is believed that these understandings can help solve the fading problems of LLOs.

Development of organic redox-active materials in aqueous flow batteries: Current strategies and future perspectives

Aqueous redox flow batteries,by using redox-active molecules dissolved in nonflammable water solutions as electrolytes,are a promising technology for grid-scale energy storage.Organic redox-active materials offer a new opportunity for the construction of advanced flow batteries due to their advantages of potentially low cost,extensive structural diversity,tunable electrochemical properties,and high natural abundance.In this review,we present the emergence and development of organic redox-active materials for aqueous organic redox flow batteries(AORFBs),in particular,molecular engineering concepts and strategies of organic redox-active molecules.The typical design strategies based on organic redox species for high-capacity,high-stability,and high-voltage AORFBs are outlined and discussed.Molecular engineering of organic redox-active molecules for high aqueous solubility,high chemical/electrochemical stability,and multiple electron numbers as well as satisfactory redox potential gap between the redox pair is essential to realizing high-performance AORFBs.Beyond molecular engineering,the redoxtargeting strategy is an effective way to obtain high-capacity AORFBs.We further discuss and analyze the redox reaction mechanisms of organic redox species based on a series of electrochemical and spectroscopic approaches,and succinctly summarize the capacity degradation mechanisms of AORFBs.Furthermore,the current challenges,opportunities,and future directions of organic redox-active materials for AORFBs are presented in detail.

Recent Progress and Design Principles for Rechargeable Lithium Organic Batteries

The most commonly used electrode materials in lithium organic batteries(LOBs)are redox-active organic materials,which have the advantages of low cost,environmental safety,and adjustable structures.Although the use of organic materials as electrodes in LOBs has been reported,these materials have not attained the same recognition as inorganic electrode materials,mainly due to their slight electronic conductivity and possible solubility in organic electrolytes,resulting in a low reversible capacity.However,over the past 10 years,organic materials have achieved outstanding results when used as battery electrodes,and an increasing number of researchers have realized their significance.This review summarizes the recent progress in organic electrodes for use in rechargeable LOBs.By classifying Li-storage mechanisms with various functional organic groups and designing molecules for next-generation advanced lithium organic systems,we attempt to analyze the working principle and the effect of various organic functionalities on electrochemical performance,to reveal the advantages and disadvantages of various organic molecules and to propose possible design principles and development trends for future LOBs.In addition,we highlight the recently reported two-dimensional covalent organic framework that is unique in its extensiveπconjugated structure and Li-storage mechanisms based on benzene and N-containing rings;this framework is considered to be the most promising alternative to metal-based electrode materials with comparable large reversible capacities and long cycle lives.