Electrochemical Behavior of PEDOT/Lignin in Ionic Liquid Electrolytes: Suitable Cathode/Electrolyte System for Sodium Batteries

Electrochemical Characteristics of Lignin in CTMP for Paper Battery Electrodes

Lignin has been extensively researched as a cathode active material in secondary batteries. In the present work, the energy storage potential of lignin naturally present in papers made of softwood chemi-thermomechanical pulp (CTMP) is explored. More specifically, effects from softwood CTMP fines on the electrochemical characteristics have been studied. Compared to pulp fibers, fines are higher in lignin content and have higher specific surface area. It was expected that this would be positive for the electrode performance; however, the result points to the opposite. The fines do not significantly contribute to a higher lignin specific capacity, and they deteriorate the cycling stability. Higher fines content was found to result in a higher oxidative activity as well as more abundant competing reactions. These competing reactions are believed to be linked to the cycle stability. Therefore, we hypothesize that the electrochemical stability of lignin can be better understood by studying differences between fines and fiber lignin. As the theoretical specific capacity of this material is about 20 times larger than obtained here, identification of the reasons for this capacity discrepancy is needed to realize the full potential of lignin-based paper batteries.

Review on the oxidative catalysis methods of converting lignin into vanillin

Vanillin plays an important role not only in food and flavouring, but also as a platform compound for the synthesis of other valuable products, mainly derived from the oxidative decarboxylation of petroleum-based guaiacol production. In order to alleviate the problem of collapsing oil resources, the preparation of vanillin from lignin has become a good option from the perspective of environmental sustainability, but it is still not optimistic in terms of vanillin production. Currently, catalytic oxidative depolymerization of lignin for the preparation of vanillin is the main development trend. This paper mainly reviews four ways of preparing vanillin from lignin base: alkaline (catalytic) oxidation, electrochemical (catalytic) oxidation, Fenton (catalytic) oxidation and photo (catalytic) oxidative degradation of lignin. In this work, the working principles, influencing factors, vanillin yields obtained, respective advantages and disadvantages and the development trends of the four methods are systematically summarized, and finally, several methods for the separation and purification of lignin-based vanillin are briefly reviewed.

Electrolytes in Organic Batteries

Organic batteries using redox-active polymers and small organic compounds have become promising candidates for next-generation energy storage devices due to the abundance, environmental benignity, and diverse nature of organic resources. To date, tremendous research efforts have been devoted to developing advanced organic electrode materials and understanding the material structure-performance correlation in organic batteries. In contrast, less attention was paid to the correlation between electrolyte structure and battery performance, despite the critical roles of electrolytes for the dissolution of organic electrode materials, the formation of the electrode-electrolyte interphase, and the solvation/desolvation of charge carriers. In this review, we discuss the prospects and challenges of organic batteries with an emphasis on electrolytes. The differences between organic and inorganic batteries in terms of electrolyte property requirements and charge storage mechanisms are elucidated. To provide a comprehensive and thorough overview of the electrolyte development in organic batteries, the electrolytes are divided into four categories including organic liquid electrolytes, aqueous electrolytes, inorganic solid electrolytes, and polymer-based electrolytes, to introduce different components, concentrations, additives, and applications in various organic batteries with different charge carriers, interphases, and separators. The perspectives and outlook for the future development of advanced electrolytes are also discussed to provide a guidance for the electrolyte design and optimization in organic batteries. We believe that this review will stimulate an in-depth study of electrolytes and accelerate the commercialization of organic batteries.

Lignin-Based Materials for Sustainable Rechargeable Batteries

This review discusses important scientific progress, problems, and prospects of lignin-based materials in the field of rechargeable batteries. Lignin, a component of the secondary cell wall, is considered a promising source of biomass. Compared to cellulose, which is the most extensively studied biomass material, lignin has a competitive price and a variety of functional groups leading to broad utilization such as adhesive, emulsifier, pesticides, polymer composite, carbon precursor, etc. The lignin-based materials can also be applied to various components in rechargeable batteries such as the binder, separator, electrolyte, anode, and cathode. This review describes how lignin-based materials are adopted in these five components with specific examples and explains why lignin is attractive in each case. The electrochemical behaviors including charge–discharge profiles, cyclability, and rate performance are discussed between lignin-based materials and materials without lignin. Finally, current limitations and future prospects are categorized to provide design guidelines for advanced lignin-based materials.

Multifunctional lignin-based nanocomposites and nanohybrids

Significant progress in lignins valorization and development of high-performance sustainable materials have been achieved in recent years. Reports related to lignin utilization indicate excellent prospects considering green chemistry, chemical engineering, energy, materials and polymer science, physical chemistry, biochemistry, among others. To fully realize such potential, one of the most promising routes involves lignin uses in nanocomposites and nanohybrid assemblies, where synergistic interactions are highly beneficial. This review first discusses the interfacial assembly of lignins with polysaccharides, proteins and other biopolymers, for instance, in the synthesis of nanocomposites. To give a wide perspective, we consider the subject of hybridization with metal and metal oxide nanoparticles, as well as uses as precursor of carbon materials and the assembly with other biobased nanoparticles, for instance to form nanohybrids. We provide cues to understand the fundamental aspects related to lignins, their self-assembly and supramolecular organization, all of which are critical in nanocomposites and nanohybrids. We highlight the possibilities of lignin in the fields of flame retardancy, food packaging, plant protection, electroactive materials, energy storage and health sciences. The most recent outcomes are evaluated given the importance of lignin extraction, within established and emerging biorefineries. We consider the benefit of lignin compared to synthetic counterparts. Bridging the gap between fundamental and application-driven research, this account offers critical insights as far as the potential of lignin as one of the frontrunners in the uptake of bioeconomy concepts and its application in value-added products.

Electrochemical Activity of Lignin Based Composite Membranes

Our society’s most pressing challenges, like high CO₂ emission and the constant battle against energy poverty, require a clean and easier solution to store and utilize the renewable energy resources. However, recent electrochemical components are expensive and harmful to the environment, which restricts their widespread deployment. This study proposes an easy method to synthesize and fabricate composite membranes with abundantly found biomass lignin polymer to replace conventional costly and toxic electrode materials. Easier manipulation of lignin within the polymeric matrix could provide the improved composite to enhance its electrochemical activity. Our major focus is to activate the quinone moiety via oxidation in the polymeric mixture using a strong ionic acid. The physico-chemical and electrochemical characterizations of two different lignins within varied polymeric mixture compositions have been carried out to confirm that the redox properties of pure unmodified lignin could be achieved via intrinsic mutual sharing of the structural properties and intercross linkage leading to improved integrity and redox activity/conductivity.

Revealing better organic sodium battery performance in ionic liquid electrolytes

Ionic liquid (IL) electrolyte conduced to better sodium storage performance for organic electrode materials.

Symmetric All-Organic Battery Containing a Dual Redox-Active Polymer as Cathode and Anode Material

All-organic batteries are a promising sustainable energy storage technology owing to the wide availability, flexibility, and recyclability of organic/polymeric compounds. The development of all-organic or polymer batteries is still a challenge, as both electrode materials need to be carefully optimized to have a wide difference of redox potential and compatibility with the electrolyte. Herein, dual redox-active polyimides based on phenothiazine and naphthalene tetracarboxylic dianhydride units are presented. After only one optimization step, the electrodes based on these dual redox polymers can be applied simultaneously as anode and cathode in a symmetric all-organic battery. The phenothiazine functional polyimide shows two redox active voltages at around 2.5 and 3.7 V (vs. Li/Li⁺ ) with high discharge capacities of 160 mAh g^-1 . Moreover, the symmetric full battery delivers high power density up to 1542 W kg^-1 with stable cyclability for 1000 cycles. This work demonstrates an efficient strategy to develop dual redox active polymer electrodes for next generation all-polymer batteries.

Flexible and Stretchable PEDOT-Embedded Hybrid Substrates for Bioengineering and Sensory Applications

Herein, we introduce a flexible, biocompatible, robust and conductive electrospun fiber mat as a substrate for flexible and stretchable electronic devices for various biomedical applications. To impart the electrospun fiber mats with electrical conductivity, poly(3,4-ethylenedioxythiophene) (PEDOT), a conductive polymer, was interpenetrated into nitrile butadiene rubber (NBR) and poly(ethylene glycol) dimethacrylate (PEGDM) crosslinked electrospun fiber mats. The mats were fabricated with tunable fiber orientation, random and aligned, and displayed elastomeric mechanical properties and high conductivity. In addition, bending the mats caused a reversible change in their resistance. The cytotoxicity studies confirmed that the elastomeric and conductive electrospun fiber mats support cardiac cell growth, and thus are adaptable to a wide range of applications, including tissue engineering, implantable sensors and wearable bioelectronics.

Development of Acidic Imidazolium Ionic Liquids for Activation of Kraft Lignin by Controlled Oxidation: Comprehensive Evaluation and Practical Utility

A novel, eco-friendly method for the activation of lignin by controlled oxidation was studied. The results obtained for six acidic imidazolium ionic liquids containing the hydrogen sulfate anion were compared. The key goal of this research was to increase the content of carbonyl groups in the lignin structure because these may play the main role in the transport of protons and electrons in active materials for electrochemical applications. By means of a variety of analytical techniques (FTIR, ¹³ C CP/MAS NMR, and X-ray photoelectron spectroscopy; selected reactions to determine the presence of carbonyl groups; SEM; zeta-potential analysis; thermogravimetric analysis/differential thermogravimetric analysis; and porous structure analysis), it was determined that the product obtained after treatment with 3-cyclohexyloxymethy-1-methylimidazolium hydrogen sulfate had favorable properties, in terms of the target application. Electrochemical tests proved that the obtained materials could be used as anodes in lithium batteries. The results show that the activation of lignin with ionic liquids can increase its capacity and maintain stability.

Confinement of aqueous mixtures of ionic liquids between amorphous TiO2 slit nanopores: electrostatic field induction

Electrostatic potential in the vicinity of the surface is induced when aqueous mixtures of hydrophobic and hydrophilic ionic liquids (ILs) are confined between a slit nanopore of amorphous but not crystalline TiO₂ semiconductors.