Radical polymer-wrapped SWNTs at a molecular level: high-rate redox mediation through a percolation network for a transparent charge-storage material

Formulating Interfacial Impedances for Designing High-Energy and High-Power All-Solid-State Battery Cathodes

All-solid-state batteries (ASSBs) are safe, high-energy-storage systems. However, despite the progress achieved in the development of high-ionic-conductivity solid electrolytes (SEs), the power performance of ASSBs remains low because of the high interfacial impedances in composite cathodes. Therefore, understanding the interfacial factors is crucial for obtaining high power ASSBs. This study provides a quantitative analysis of the influence of these factors using impedance spectroscopy measurements, which enables the elucidation of the interfacial impedance values of two key parameters, the grain-boundary resistance (ri,gb) and charge-transfer resistance (ri/e). Systematic investigation revealed an unexpected increase in the cathodic resistance with the decrease in the size of the cathode active material (CAM) particles, indicating that even high-reaction-surface-area CAMs yield low ri/e but high ri,gb values owing to their high porosity, resulting in a trade-off relationship. In contrast, this phenomenon is unlikely to occur in liquid-electrolyte-based batteries. Notably, we discuss how composite cathode design impacts performances of stable, high-power, and high-energy ASSBs.

Thermodynamic model for voltammetric responses in conducting redox polymers

Electroactive polymer materials are known to play important roles in a vast spectrum of modern applications such as in supercapacitors, fuel cells, batteries, medicine, and smart materials, etc. They are usually divided into two main groups: first, conducting π-conjugated organic polymers, which conduct electricity by cation-radicals delocalized over a polymer chain; second, redox polymers, which conduct electricity via an electron-hopping mechanism. Polymer materials belonging to these two main groups have been thoroughly studied and their thermodynamic and kinetic models have been built. However, in recent decades a lot of mixed-type materials have been discovered and investigated. To the best of our knowledge, a thermodynamic-based description of conducting redox polymers (CRPs) has not been provided yet. In this work, we present a thermodynamic model for voltammetric responses of conducting redox polymers. The derived model allows one to extract thermodynamic parameters of a CRP including the polaron delocalization degree and redox active groups interaction constant. The model was verified with voltammetric experiments on three recently synthesized CRPs and showed a satisfactory predictive ability. The simulated data are in good agreement with the experiment. We believe that developing theoretical descriptions for CRPs and other types of electroactive materials with the ability to simulate their electrochemical responses may help in future realization of new systems with superior characteristics for electrochemical energy storage, chemical sensors, pharmacological applications, etc.

Redox: Organic Robust Radicals and Their Polymers for Energy Conversion/Storage Devices

Persistent radicals can hold their unpaired electrons even under conditions where they accumulate, leading to the unique characteristics of radical ensembles with open-shell structures and their molecular properties, such as magneticity, radical trapping, catalysis, charge storage, and electrical conductivity. The molecules also display fast, reversible redox reactions, which have attracted particular attention for energy conversion and storage devices. This paper reviews the electrochemical aspects of persistent radicals and the corresponding macromolecules, radical polymers. Radical structures and their redox reactions are introduced, focusing on redox potentials, bistability, and kinetic constants for electrode reactions and electron self-exchange reactions. Unique charge transport and storage properties are also observed with the accumulated form of redox sites in radical polymers. The radical molecules have potential electrochemical applications, including in rechargeable batteries, redox flow cells, photovoltaics, diodes, and transistors, and in catalysts, which are reviewed in the last part of this paper.

FeIII Chelated with Humic Acid with Easy Synthesis Conditions and Good Performance as Anode Materials for Lithium-Ion Batteries

In this work, we prepared a green, cheap material by chelating humic acid with ferric ions (HA-Fe) and used it as an anode material in LIBs for the first time. From the SEM, TEM, XPS, XRD, and nitrogen adsorption-desorption experimental results, it was found that the ferric ion can chelate with humic acid successfully under mild conditions and can increase the surface area of materials. Taking advantage of the chelation between the ferric ions and HA, the capacity of HA-Fe is 586 mAh·g-1 at 0.1 A·g-1 after 1000 cycles. Moreover, benefitting from the chelation effect, the activation degree of HA-Fe (about 8 times) is seriously improved compared with pure HA material (about 2 times) during the change-discharge process. The capacity retention ratio of HA-Fe is 55.63% when the current density increased from 0.05 A·g-1 to 1 A·g-1, which is higher than that of HA (32.55%) and Fe (24.85%). In the end, the storage mechanism of HA-Fe was investigated with ex-situ XPS measurements, and it was found that the C=O and C=C bonds are the activation sites for storage Li ions but have different redox voltages.

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.

Electronic and Spintronic Open-Shell Macromolecules, Quo Vadis?

Open-shell macromolecules (i.e., polymers containing radical sites either along their backbones or at the pendant sites of repeat units) have attracted significant attention owing to their intriguing chemical and physical (e.g., redox, optoelectronic, and magnetic) properties, and they have been proposed and/or implemented in a wide range of potential applications (e.g., energy storage devices, electronic systems, and spintronic modules). These successes span multiple disciplines that range from advanced macromolecular chemistry through nanoscale structural characterization and on to next-generation solid-state physics and the associated devices. In turn, this has allowed different scientific communities to expand the palette of radical-containing polymers relatively quickly. However, critical gaps remain on many fronts, especially regarding the elucidation of key structure-property-function relationships that govern the underlying electrochemical, optoelectronic, and spin phenomena in these materials systems. Here, we highlight vital developments in the history of open-shell macromolecules to explain the current state of the art in the field. Moreover, we provide a critical review of the successes and bring forward open opportunities that, if solved, could propel this class of materials in a meaningful manner. Finally, we provide an outlook to address where it seems most likely that open-shell macromolecules will go in the coming years. Our considered view is that the future of radical-containing polymers is extremely bright and the addition of talented researchers with diverse skills to the field will allow these materials and their end-use devices to have a positive impact on the global science and technology enterprise in a relatively rapid manner.

Redox Potential Tuning of s-Tetrazine by Substitution of Electron-Withdrawing/Donating Groups for Organic Electrode Materials

Herein, we tune the redox potential of 3,6-diphenyl-1,2,4,5-tetrazine (DPT) by introducing various electron-donating/withdrawing groups (methoxy, t-butyl, H, F, and trifluoromethyl) into its two peripheral benzene rings for use as electrode material in a Li-ion cell. By both the theoretical DFT calculations and the practical cyclic voltammetry (CV) measurements, it is shown that the redox potentials (E_1/2) of the 1,2,4,5-tetrazines (s-tetrazines) have a strong correlation with the Hammett constant of the substituents. In Li-ion coin cells, the discharge voltages of the s-tetrazine electrodes are successfully tuned depending on the electron-donating/withdrawing capabilities of the substituents. Furthermore, it is found that the heterogeneous electron transfer rate (k₀) of the s-tetrazine molecules and Li-ion diffusivity (D_Li) in the s-tetrazine electrodes are much faster than conventional electrode active materials.

The Progress and Prospect of Tunable Organic Molecules for Organic Lithium-Ion Batteries

Compared to inorganic electrodes, organic materials are regarded as promising electrodes for lithium-ion batteries (LIBs) due to the attractive advantages of light elements, molecular-level structural design, fast electron/ion transferring, favorable environmental impacts, and flexible feature, etc. Not only specific capacities but also working potentials of organic electrodes are reasonably tuned by polymerization, electron-donating/withdrawing groups, and multifunctional groups as well as conductive additives, which have attracted intensive attention. However, organic LIBs (OLIBs) are also facing challenges on capacity loss, side reactions, electrode dissolution, low electronic conductivity, and short cycle life, etc. Many strategies have been applied to tackle those challenges, and many inspiring results have been achieved in the last few decades. In this review, we have introduced the basic concepts of LIBs and OLIBs, followed by the typical cathode and anode materials with various physicochemical properties, redox reaction mechanisms, and evolutions of functional groups. Typical charge-discharge behaviors and molecular structures of organic electrodes are displayed. Moreover, effective strategies on addressing problems of organic electrodes are summarized to give some guidance on the synthesis of optimized organic electrodes for practical applications of OLIBs.

Polymer-Based Batteries-Flexible and Thin Energy Storage Systems

Batteries have become an integral part of everyday life-from small coin cells to batteries for mobile phones, as well as batteries for electric vehicles and an increasing number of stationary energy storage applications. There is a large variety of standardized battery sizes (e.g., the familiar AA-battery or AAA-battery). Interestingly, all these battery systems are based on a huge number of different cell chemistries depending on the application and the corresponding requirements. There is not one single battery type fulfilling all demands for all imaginable applications. One battery class that has been gaining significant interest in recent years is polymer-based batteries. These batteries utilize organic materials as the active parts within the electrodes without utilizing metals (and their compounds) as the redox-active materials. Such polymer-based batteries feature a number of interesting properties, like high power densities and flexible batteries fabrication, among many more.

Mellitic Triimides Showing Three One-Electron Redox Reactions with Increased Redox Potential as New Electrode Materials for Li-Ion Batteries

The mellitic triimide (MTI) bearing three imide groups on a benzene core with C3 symmetry is proposed as a new building block for organic electrode materials in lithium-ion batteries. MTI was anticipated to deliver a higher theoretical specific capacity of up to 282 mAh g^-1 with increased reduction potentials compared with the well-known pyromellitic diimide building block bearing two imide groups because the additional imide group can accept one more electron and provide an electron-withdrawing effect. A model compound, ethyl-substituted mellitic triimide (ETTI), shows three well distinguished and reversible one-electron redox reactions at -0.97, -1.62, and -2.34 V versus Ag/Ag⁺ in 0.1 m tetrabutylammonium hexafluorophosphate electrolyte, but the redox potentials were increased in 2 m lithium bis(trifluoromethanesulfonyl)imide electrolyte: -0.60 V, -0.86 V, and -1.42 V vs. Ag/Ag⁺ . The DFT calculations revealed that the unique C3 symmetric structural design leads to the higher reduction potential of MTI in the Li-based electrolyte by formation of a stable 7-membered ring with a Li ion and the two carbonyl oxygen atoms from the adjacent imide groups. In a Li-ion coin cell, the ETTI electrode delivered a specific capacity of 176 mAh g^-1 , corresponding to 81 % of capacity utilization, with three clear voltage plateaus. The higher average discharge voltage (2.41 V vs. Li/Li⁺ ) of ETTI allows it to deliver one of the highest specific energies (421 Wh kg^-1 ) among reported diimide-based electrode materials. Finally, its redox mechanism was investigated by ex situ FTIR measurements and DFT calculations.

Flexible pressure sensors with a highly pressure- and strain-sensitive layer based on nitroxyl radical-grafted hollow carbon spheres

The spherical structure of hollow carbon spheres (HCSs) makes their contact resistance and tunnel resistance extremely sensitive to the distance between them, which can be used as a conductive filler for high-sensitivity pressure sensors. Compared with one- and two-dimensional carbon-based materials, HCSs require a higher filling concentration for constructing an effective conductive network due to their average conductivity, which affects the mechanical properties of the sensor. In a single-electron system, electrons are transferred by hopping between the nitroxyl radical monomers and when the distance between the monomers is shortened, the electron transfer rate of nitroxyl radical compounds can be increased, thus further improving their conductivity. In this work, a composite of nitroxyl radical-modified hollow carbon spheres (HCS-g-NO˙) and polydimethylsiloxane (PDMS) polymer is introduced, and the resistivity of HCS-g-NO˙ is about one magnitude lower than that of HCSs at the same filling concentration. A flexible piezoresistive sensor with HCS-g-NO˙@PDMS as the sensitive layer coated on the PET electrode is presented, in which the spacing between HCS-g-NO˙ changes, causing changes in the contact and tunnel resistances in the sensitive layer when mechanical stresses are applied. The sensor achieved a piezoresistive response of -0.55 kPa-1 and the tensile response of 211 , and a sensor array of nine pixels was successfully demonstrated; thus, it can be used as a high sensitivity pressure and strain sensor.

Organic Electrode Materials for Metal Ion Batteries

Organic and polymer materials have been extensively investigated as electrode materials for rechargeable batteries because of the low cost, abundance, environmental benignity, and high sustainability. To date, organic electrode materials have been applied in a large variety of energy storage devices, including nonaqueous Li-ion, Na-ion, K-ion, dual-ion, multivalent-metal, aqueous, all-solid-state, and redox flow batteries, because of the universal properties of organic electrode materials. Moreover, some organic materials enable the batteries to be operated in the extreme conditions, such as a wide temperature range (-70 to 150 °C), a wide pH range, and in the presence of O₂. As a guidance for the research in organic batteries, this Review focuses on the reaction mechanisms and applications of organic electrode materials. Six categories of reaction mechanisms and the applications of organic and polymer materials in various rechargeable batteries are discussed to provide an overview of the state-of-the-art organic batteries.

Recent Progress on Organic Electrodes Materials for Rechargeable Batteries and Supercapacitors

Rechargeable batteries are essential elements for many applications, ranging from portable use up to electric vehicles. Among them, lithium-ion batteries have taken an increasing importance in the day life. However, they suffer of several limitations: safety concerns and risks of thermal runaway, cost, and high carbon footprint, starting with the extraction of the transition metals in ores with low metal content. These limitations were the motivation for an intensive research to replace the inorganic electrodes by organic electrodes. Subsequently, the disadvantages that are mentioned above are overcome, but are replaced by new ones, including the solubility of the organic molecules in the electrolytes and lower operational voltage. However, recent progress has been made. The lower voltage, even though it is partly compensated by a larger capacity density, may preclude the use of organic electrodes for electric vehicles, but the very long cycling lives and the fast kinetics reached recently suggest their use in grid storage and regulation, and possibly in hybrid electric vehicles (HEVs). The purpose of this work is to review the different results and strategies that are currently being used to obtain organic electrodes that make them competitive with lithium-ion batteries for such applications.

Ultrathin and Stretchable Rechargeable Devices with Organic Polymer Nanosheets Conformable to Skin Surface

Ultrathin flexible electronic devices have been attracting substantial attention for biomonitoring, display, wireless communication, and many other ubiquitous applications. In this article, organic robust redox-active polymer/carbon nanotube hybrid nanosheets with thickness of just 100 nm are reported as power sources for ultrathin devices conformable to skin. Regardless of the extreme thinness of the electrodes, a moderately large current density of 0.4 mA cm^-2 is achieved due to the high output of the polymers (>10 A g^-1 ). For the first time, the use of mechanically robust yet intrinsically soft electrodes and polymer nanosheet sealing leads to the fabrication of rechargeable devices with only 1-µm thickness and even with stretchable properties.

s-Tetrazines as a New Electrode-Active Material for Secondary Batteries

Because of the limitations of conventional metal-oxide-based electrodes, studies on organic redox-active materials as alternative electrodes for secondary batteries are emerging. However, reported organic electrode materials are still limited to a few kinds of organic redox groups. Therefore, the development of new redox-active groups for high-performance electrode materials is indispensable. Here, we evaluate s-tetrazine derivatives as a new electrode material in Li-ion batteries and study their charge/discharge mechanisms by ex situ XPS measurements. The porous carbon CMK-3 was introduced to encapsulate the s-tetrazines, which allowed 100 % utilization of the theoretical capacity and stable cycle performance of the s-tetrazines by preventing dissolution of the molecules into the electrolytes. This new class of redox-active group can pave the way for the next-generation of energy storage systems.

High-capacity organic sodium ion batteries using a sustainable C4Q/CMK-3/SWCNT electrode

SWCNTs formed a three-dimensional conductive network between C4Q/CMK-3 nanocomposites, significantly improving the electrochemical performance of C4Q-SIBs.

Recent Progress in Organic Electrodes for Li and Na Rechargeable Batteries

Organic rechargeable batteries, which use organics as electrodes, are excellent candidates for next-generation energy storage systems because they offer design flexibility due to the rich chemistry of organics while being eco-friendly and potentially cost efficient. However, their widespread usage is limited by intrinsic problems such as poor electronic conductivity, easy dissolution into liquid electrolytes, and low volumetric energy density. New types of organic electrode materials with various redox centers or molecular structures have been developed over the past few decades. Moreover, research aimed at enhancing electrochemical properties via chemical tuning has been at the forefront of organic rechargeable batteries research in recent years, leading to significant progress in their performance. Here, an overview of the current developments of organic rechargeable batteries is presented, with a brief history of research in this field. Various strategies for improving organic electrode materials are discussed with respect to tuning intrinsic properties of organics using molecular modification and optimizing their properties at the electrode level. A comprehensive understanding of the progress in organic electrode materials is provided along with the fundamental science governing their performance in rechargeable batteries thus a guide is presented to the optimal design strategies to improve the electrochemical performance for next-generation battery systems.

Stable Radical Materials for Energy Applications

Although less studied than their closed-shell counterparts, materials containing stable open-shell chemistries have played a key role in many energy storage and energy conversion devices. In particular, the oxidation-reduction (redox) properties of these stable radicals have made them a substantial contributor to the progress of organic batteries. Moreover, the use of radical-based materials in photovoltaic devices and thermoelectric systems has allowed for these emerging molecules to have impacts in the energy conversion realm. Additionally, the unique doublet states of radical-based materials provide access to otherwise inaccessible spin states in optoelectronic devices, offering many new opportunities for efficient usage of energy in light-emitting devices. Here, we review the current state of the art regarding the molecular design, synthesis, and application of stable radicals in these energy-related applications. Finally, we point to fundamental and applied arenas of future promise for these designer open-shell molecules, which have only just begun to be evaluated in full.

An Ultrahigh Output Rechargeable Electrode of a Hydrophilic Radical Polymer/Nanocarbon Hybrid with an Exceptionally Large Current Density beyond 1 A cm-2

Facile charge transport by a hydrophilic organic radical-substituted polymer and the 3D current collection by a self-assembled mesh of single-walled carbon nanotube bundles lead to the operation of an ultrahigh-output rechargeable electrode. Exceptionally large current density beyond 1 A cm^-2 and high areal capacity around 3 mAh cm^-2 are achieved, which are 10^1-2 times larger than those of the previously reported so-called "ultrafast electrodes." A sub-millimeter-thick, flexible, highly safe organic redox polymer-based rechargeable device with an aqueous sodium chloride electrolyte is fabricated to demonstrate the superior performance.

Nitroxide radical polymers – a versatile material class for high-tech applications

A comprehensive summary of synthetic strategies for the preparation of nitroxide radical polymer materials and a state-of-the-art perspective on their latest and most exciting applications.

Molecular Engineering with Organic Carbonyl Electrode Materials for Advanced Stationary and Redox Flow Rechargeable Batteries

Organic carbonyl electrode materials that have the advantages of high capacity, low cost and being environmentally friendly, are regarded as powerful candidates for next-generation stationary and redox flow rechargeable batteries (RFBs). However, low carbonyl utilization, poor electronic conductivity and undesired dissolution in electrolyte are urgent issues to be solved. Here, we summarize a molecular engineering approach for tuning the capacity, working potential, concentration of active species, kinetics, and stability of stationary and redox flow batteries, which well resolves the problems of organic carbonyl electrode materials. As an example, in stationary batteries, 9,10-anthraquinone (AQ) with two carbonyls delivers a capacity of 257 mAh g^-1 (2.27 V vs Li⁺ /Li), while increasing the number of carbonyls to four with the formation of 5,7,12,14-pentacenetetrone results in a higher capacity of 317 mAh g^-1 (2.60 V vs Li⁺ /Li). In RFBs, AQ, which is less soluble in aqueous electrolyte, reaches 1 M by grafting -SO₃ H with the formation of 9,10-anthraquinone-2,7-disulphonic acid, resulting in a power density exceeding 0.6 W cm^-2 with long cycling life. Therefore, through regulating substituent groups, conjugated structures, Coulomb interactions, and the molecular weight, the electrochemical performance of carbonyl electrode materials can be rationally optimized. This review offers fundamental principles and insight into designing advanced carbonyl materials for the electrodes of next-generation rechargeable batteries.

Pyrene-Functionalized PTMA by NRC for Greater π-π Stacking with rGO and Enhanced Electrochemical Properties

Nitroxide radical polymers can undergo both excellent electrochemical redox reactions and a rapid "click" coupling reaction with carbon-centered radicals (i.e., nitroxide radical coupling (NRC) reaction). In this work, we report a strategy to functionalize poly(2,2,6,6,-tetramethylpiperidinyl-1-oxyl methacrylate) (PTMA) with pyrene side groups through a rapid and near quantitative NRC reaction. This resulted in P(TMA-co-PyMA) random copolymers with near quantitative amounts of pyrene along the PTMA chain for greater π-π interaction with rGO, while the nitroxide radicals on the polymer could simultaneously be used for energy storage. These copolymers can bind with reduced graphene oxide (rGO) and form layered composites through noncovalent π-π stacking, attaining molecular-level dispersion. Electrochemical performance of the composites with different polymer contents (24, 35, and 45 wt %), tested in lithium ion batteries, indicated that the layered structures consisting of P(TMA-co-PyMA) maintained greater capacities at high C-rates. This simple and efficient strategy to synthesize pyrene-functionalized polymers will provide new opportunities to fabricate many other polymer composite electrodes for desired electrochemical performance.

Uric Acid as an Electrochemically Active Compound for Sodium-Ion Batteries: Stepwise Na+-Storage Mechanisms of π-Conjugation and Stabilized Carbon Anion

Developing efficient sodium-ion-storage mechanisms to increase the energy capacity in organic electrodes is a critical issue even after this period of prolonged effort. Uric acid (UA), a simple organic compound with three carbonyl groups is demonstrated to be electrochemically active in the insertion/extraction of Na ions. Theoretical calculations and experimental characterizations reveal that the sodium-ion storage by UA is a result of the stepwise mechanisms of p-π conjugation and the carbon anion. Aside from C═O, the functional group C═C(NH-)₂ also provides an efficient Na-storage activated site in which the lone-pair electrons is stabilized through the planar-to-tetrahedral structural transition and low-energy orbital hybridization of N atoms. For further improvement of the electrochemical performance, a uric acid and carbon nanotube (UA@CNT) composite is prepared via a vacuum solution impregnation method. When employed as an anode material for sodium-ion batteries, the UA@CNT composite exhibits high specific capacity, excellent rate capability, and long cycling life even at high current densities. A reversible capacity of over 163 mA h g^-1 is maintained even after 150 cycles at a current density of 200 mA g^-1. The present study paves a way to develop reversible high-capacity organic electrode materials for sodium-ion batteries by a carbon-anion stabilization mechanism.

High Performance Poly(viologen)-Graphene Nanocomposite Battery Materials with Puff Paste Architecture

Four linear poly(viologens) (PV1, PV2: phenylic, PV3: benzylic, and PV4: aliphatic) in tight molecular contact with reduced graphene oxide (rGO), that is, PV@rGO, were prepared and used as anodic battery materials. These composites show exceptionally high, areal, volumetric, and current densities, for example, PV1@rGO composites (with 15 wt % rGO, corresponding to 137 mAh g^-1) show 13.3 mAh cm^-2 at 460 μm and 288 mAh cm^-3 with 98% Coulombic efficiency at current densities up to 1000 A g^-1, better than any reported organic materials. These remarkable performances are based on (i) molecular self-assembling of PVs on individual GO sheets yielding colloidal PV@GO and (ii) efficient GO/rGO transformation electrocatalyzed by PVs. Ion breathing during charging/discharging was studied by electrochemical quartz crystal microbalance and electrochemical atomic force microscopy revealing an absolute reversible and strongly anisotropic thickness oscillation of PV1@rGO at a right angle to the macroscopic current collector. It is proposed that such stress-free breathing is the key property for good cyclability of the battery material. The anisotropy is related to a puff paste architecture of rGO sheets parallel to the macroscopic current collector. A thin graphite sheet electrode with an areal capacity of 1.23 mAh cm^-2 is stable over 200 bending cycles, making the material applicable for wearable electronics. The polymer acts as a lubricant between the rGO layers if shearing forces are active.

Polymer-Based Organic Batteries

The storage of electric energy is of ever growing importance for our modern, technology-based society, and novel battery systems are in the focus of research. The substitution of conventional metals as redox-active material by organic materials offers a promising alternative for the next generation of rechargeable batteries since these organic batteries are excelling in charging speed and cycling stability. This review provides a comprehensive overview of these systems and discusses the numerous classes of organic, polymer-based active materials as well as auxiliary components of the battery, like additives or electrolytes. Moreover, a definition of important cell characteristics and an introduction to selected characterization techniques is provided, completed by the discussion of potential socio-economic impacts.

Covalently Functionalized Graphene by Radical Polymers for Graphene-Based High-Performance Cathode Materials

Polymer-functionalized graphene sheets play an important role in graphene-containing composite materials. Herein, functionalized graphene sheets covalently linked with radical polymer, graphene-graft-poly(2,2,6,6-tetramethylpiperidin-1-oxyl-4-yl methacrylate) (G-g-PTMA), were prepared via surface-initiated atom transfer radical polymerization (SI-ATRP). A composite cathode with G-g-PTMA as major active material and reduced graphene oxide (RGO) as conductive additive was fabricated via a simple dispersing-depositing process, and this composite cathode exhibited a relatively high specific capacity up to 466 mAh g(-1) based on the mass of PTMA, which is much higher than the theoretical capacity of PTMA. This extraordinary electrochemical performance is attributed to the fast one-electron redox reaction of G-g-PTMA and surface Faradaic reaction of RGO boosted by G-g-PTMA, which suggested that G-g-PTMA sheets play a dual role in the composite materials, that is, on the one hand provided the fast one-electron redox reaction of PTMA and on the other hand worked as nanofiller for facilitating the surface Faradaic reaction-based lithium storage of RGO.

Poly(TEMPO)/Zinc Hybrid-Flow Battery: A Novel, "Green," High Voltage, and Safe Energy Storage System

The combination of a polymer-based 2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO) catholyte and a zinc anode, together with a cost-efficient size-exclusion membrane, builds a new type of semi-organic, "green," hybrid-flow battery, which features a high potential range of up to 2 V, high efficiencies, and a long life time.

Electrochemical current rectification with cross reaction at a TEMPO/viologen-substituted polymer thin-layer heterojunction

The electrochemical large current rectification was achieved in the bilayer system composed of the TEMPO- and viologen-containing polymer thin layers.

Nitroxide radical polymer/carbon-nanotube-array electrodes with improved C-rate performance in organic radical batteries

The intimate connection between carbon nanotubes and the current collector reduces electron-transfer resistance of the cathode and enhances the C-rate performance of the batteries.

Humic acid as promising organic anodes for lithium/sodium ion batteries

As a representative natural polymer, humic acid was creatively explored as an anode material for lithium/sodium ion batteries.

Efficient charge transport of a radical polyether/SWCNT composite electrode for an organic radical battery with high charge-storage density

A fast and reversible charge storage capability was established for the radical polyether/SWCNT composite layer with a large layer thickness of several tens of micrometres despite the low SWCNT content of 10%.

A new design of organic radical batteries (ORBs): carbon nanotube buckypaper electrode functionalized by electrografting

A novel hybrid material displaying a fast and reversible charge storage capability is prepared by electrografting of an alkoxyamine-bearing acrylate onto a carbon nanotubes buckypaper.

Anionic Polymerization of 4-Methacryloyloxy-TEMPO Using an MMA-Capped Initiator

Anionic polymerization of 4-methacryloyloxy-TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidin-1-oxyl) was successfully carried out using methyl methacrylate-capped 1,1-diphenylhexyllithium (DPHLi/MMA), of which nucleophilicity is moderate enough to suppress the side reaction between the nitroxide radical of TEMPO moiety and the carbanion of DPHLi, to yield the radical polymer with well-controlled molecular weight, narrow polydispersity index (PDI < 1.10), high yield (>95%), and almost 1.0 radicals per monomer unit.

Hybrid supercapacitor-battery materials for fast electrochemical charge storage

High energy and high power electrochemical energy storage devices rely on different fundamental working principles--bulk vs. surface ion diffusion and electron conduction. Meeting both characteristics within a single or a pair of materials has been under intense investigations yet, severely hindered by intrinsic materials limitations. Here, we provide a solution to this issue and present an approach to design high energy and high power battery electrodes by hybridizing a nitroxide-polymer redox supercapacitor (PTMA) with a Li-ion battery material (LiFePO4). The PTMA constituent dominates the hybrid battery charge process and postpones the LiFePO4 voltage rise by virtue of its ultra-fast electrochemical response and higher working potential. We detail on a unique sequential charging mechanism in the hybrid electrode: PTMA undergoes oxidation to form high-potential redox species, which subsequently relax and charge the LiFePO4 by an internal charge transfer process. A rate capability equivalent to full battery recharge in less than 5 minutes is demonstrated. As a result of hybrid's components synergy, enhanced power and energy density as well as superior cycling stability are obtained, otherwise difficult to achieve from separate constituents.