High-Power-Density Organic Radical Batteries

A high-spin s-triazine linked fluorenyl radical polymer

The syntheses of high-spin organic polymers have been a daunting task due to the highly reactive nature of organic radicals, especially when they are ferromagnetically coupled. In this paper, we report our approach to obtain high-spin organic polymers, in which a reasonably stable fluorenyl radical was employed as the primary radical unit, and s-triazine serves as the connector that facilitates ferromagnetic coupling between them. Initially, the diamagnetic polymer precursor was synthesized by cyclotrimerization of a cyano-monomer. Subsequently, the high-spin polymers were obtained by oxidizing corresponding anionic polymers using O2 (6) or I2 (7). The temperature-dependent magnetic moments, and field-dependent magnetization data obtained from SQUID measurements revealed ferromagnetic couplings between primary radical units, with coupling J = 7.5 cm-1 and 38.6 cm-1. The percentages of primary unit in the radical form are 29%, and 47% for 6 and 7, respectively. Notably, this marks the first reported instance of a high-spin fluorenyl radical polymer exhibiting ferromagnetic coupling.

Versatile Nitrogen-Centered Organic Redox-Active Materials for Alkali Metal-Ion Batteries

Versatile nitrogen-centered organic redox-active molecules have gained significant attention in alkali metal-ion batteries (AMIBs) due to their low cost, low toxicity, and ease of preparation. Specially, their multiple reaction categories (anion/cation insertion types of reaction) and higher operating voltage, when compared to traditional conjugated carbonyl materials, underscore their promising prospects. However, the high solubility of nitrogen-centered redox active materials in organic electrolyte and their low electronic conductivity contribute to inferior cycling performance, sluggish reaction kinetics, and limited rate capability. This review provides a detailed overview of nitrogen-centered redox-active materials, encompassing their redox chemistry, solutions to overcome shortcomings, characterization of charge storage mechanisms, and recent progress. Additionally, prospects and directions are proposed for future investigations. It is anticipated that this review will stimulate further exploration of underlying mechanisms and interface chemistry through in situ characterization techniques, thereby promoting the practical application of nitrogen-centered redox-active materials in AMIBs.

Harmonizing Energies: The Interplay Between a Nonplanar SalEn-Type Molecule and a TEMPO Moiety in a New Hybrid Energy-Storing Redox-Conducting Polymer

Redox-conducting polymers based on SalEn-type complexes have attracted considerable attention due to their potential applications in electrochemical devices. However, their charge transfer mechanisms, physical and electrochemical properties remain unclear, hindering their rational design and optimization. This study aims to establish the influence of monomer geometry on the polymer's properties by investigating the properties of novel nonplanar SalEn-type complexes, poly[N,N'-bis(salicylidene)propylene-2-(hydroxy)diaminonickel(II)], and its analog with 2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO)-substituted bridge (MTS). To elucidate the charge transfer mechanism, operando UV-Vis spectroelectrochemical analysis, electrochemical impedance spectroscopy, and electron paramagnetic resonance are employed. Introducing TEMPO into the bridge moiety enhanced the specific capacity of the poly(MTS) material to 95 mA h g-1, attributed to TEMPO's and conductive backbone's charge storage capabilities. Replacement of the ethylenediimino-bridge with a 1,3-propylenediimino- bridge induced significant changes in the complex geometry and material's morphology, electrochemical, and spectral properties. At nearly the same potential, polaron and bipolaron particles emerged, suggesting intriguing features at the overlap point of the electroactivity potentials ranges of polaron-bipolaron and TEMPO, such as a disruption in the connection between TEMPO and the conjugation chain or intramolecular charge transfer. These results offer valuable insights for optimizing strategies to create organic materials with tailored properties for use in catalysis and battery applications.

Modulation of Radical Intermediates in Rechargeable Organic Batteries

Organic materials have been considered as promising electrodes for next-generation rechargeable batteries in view of their sustainability, structural flexibility, and potential recyclability. The radical intermediates generated during the redox process of organic electrodes have profound effect on the reversible capacity, operation voltage, rate performance, and cycling stability. However, the radicals are highly reactive and have very short lifetime during the redox of organic materials. Great efforts have been devoted to capturing and investigating the radical intermediates in organic electrodes. Herein, this review summarizes the importance, history, structures, and working principles of organic radicals in rechargeable batteries. More importantly, challenges and strategies to track and regulate the radicals in organic batteries are highlighted. Finally, further perspectives of organic radicals are proposed for the development of next-generation high-performance rechargeable organic batteries.

The Biomimetic Synthesis of Polyarylated Fluorenes, Relevant to Selaginellaceae Polyphenols, Leading to the Spontaneous Formation of Stable Radicals

This work reports a biomimetic synthesis of polyarylated fluorene derivatives. The molecules are formed via intramolecular electrophilic aromatic substitution, resembling a cyclization leading towards the natural selaginpulvilins from selaginellins. The scope of the reaction was investigated, and the products were obtained in 60-95 % yields. Some of the compounds decompose to a stable radical. We investigated the nature and the origin of the radical using experimental methods, including EPR or electrochemical measurements, as well as theoretical methods, such as DFT calculations. Based on our observations, we hypothesize, that phenoxy radicals are formed in the first instance, which however undergo internal rearrangement to thermodynamically more stable carbon-centered radicals. The preliminary data also show the cytotoxic properties of some of the molecules.

Organic electrodes based on redox-active covalent organic frameworks for lithium batteries

Electroactive organic materials have received much attention as alternative electrodes for metal-ion batteries due to their high theoretical capacity, resource availability, and environmental friendliness. In particular, redox-active covalent organic frameworks (COFs) have recently emerged as promising electrodes due to their tunable electrochemical properties, insolubility in electrolytes, and structural versatility. In this Highlight, we review some recent strategies to improve the energy density and power density of COF electrodes for lithium batteries from the perspective of molecular design and electrode optimisation. Some other aspects such as stability and scalability are also discussed. Finally, the main challenges to improve their performance and future prospects for COF-based organic batteries are highlighted.

Influencing ionic conductivity and mechanical properties of ionic liquid polymer electrolytes by designing the chemical monomer structure

Polymeric single chloride-ion conductor networks based on acrylic imidazolium chloride ionic liquid monomers AACXImCYCl as reported previously are prepared. The chemical structure of the polymers is varied with respect to the acrylic substituents (alkyl spacer and alkyl substituent in the imidazolium ring). The networks are examined in detail with respect to the influence of the chemical structure on the resulting properties including thermal behavior, rheological behavior, swelling behavior, and ionic conductivity. The ionic conductivities increase (by two orders of magnitude from 10-6 to 10-4 S·cm-1 with increasing temperature), while the complex viscosities of the polymer networks decrease simultaneously. After swelling in water for 1 week the ionic conductivity reaches values of 10-2 S·cm-1. A clear influence of the spacer and the crosslinker content on the glass transition temperature was shown for the first time in these investigations. With increasing crosslinker content, the Tg values and the viscosities of the networks increase. With increasing spacer length, the Tg values decrease, but the viscosities increase with increasing temperature. The results reveal that the materials represent promising electrolytes for batteries, as proven by successful charging/discharging of a p(TEMPO-MA)/zinc battery over 350 cycles.

Discovery of lead quinone cathode materials for Li-ion batteries

Organic cathode materials are attractive candidates for the development of high-performance Li-ion batteries (LIBs). The chemical space of candidate molecules is too vast to be explored solely by experiments; however, it can be systematically explored by a high-throughput computational search that incorporates a spectrum of screening techniques. Here, we present a time- and resource-efficient computational scheme that incorporates machine learning and semi-empirical quantum mechanical methods to study the chemical space of approximately 200 000 quinone-based molecules for use as cathode materials in LIBs. By performing an automated search on a commercial vendor database, computing battery-relevant properties such as redox potential, gravimetric charge capacity, gravimetric energy density, and synthetic complexity score, and evaluating the structural integrity upon the lithiation process, a total of 349 molecules were identified as potentially high-performing cathode materials for LIBs. The chemical space of the screened candidates was visualized using dimensionality reduction methods with the aim of further downselecting the best candidates for experimental validation. One such directly purchasable candidate, 1,4,9,10-anthracenetetraone, was analyzed through cyclic voltammetry experiments. The measured redox potentials of the two lithiation steps, , of 3.3 and 2.4 V, were in good agreement with the predicted redox potentials, , of 3.2 and 2.3 V vs. Li/Li+, respectively. Lastly, to lay out the principles for rational design of quinone-based cathode materials beyond the current work, we constructed and discussed the quantitative structure property relationships of quinones based on the data generated from the calculations.

Ambipolar Charge Transport in Organic Semiconductors: How Intramolecular Reorganization Energy Is Controlled by Diradical Character

The charged forms of π-conjugated chromophores are relevant in the field of organic electronics as charge carriers in optoelectronic devices, but also as energy storage substrates in organic batteries. In this context, intramolecular reorganization energy plays an important role in controlling material efficiency. In this work, we investigate how the diradical character influences the reorganization energies of holes and electrons by considering a library of diradicaloid chromophores. We determine the reorganization energies with the four-point adiabatic potential method using quantum-chemical calculations at density functional theory (DFT) level. To assess the role of diradical character, we compare the results obtained, assuming both closed-shell and open-shell representations of the neutral species. The study shows how the diradical character impacts the geometrical and electronic structure of neutral species, which in turn control the magnitude of reorganization energies for both charge carriers. Based on computed geometries of neutral and charged species, we propose a simple scheme to rationalize the small, computed reorganization energies for both n-type and p-type charge transport. The study is supplemented with the calculation of intermolecular electronic couplings governing charge transport for selected diradicals, further supporting the ambipolar character of the investigated diradicals.

3-Substituted Blatter Radicals: Cyclization of N-Arylguanidines and N-Arylamidines to Benzo[e][1,2,4]triazines and PhLi Addition

A series of 3-amino- and 3-alkyl-substituted 1-phenyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yls was prepared in four steps involving N-arylation, cyclization of N-arylguanidines and N-arylamidines, reduction of the resulting N-oxides to benzo[e][1,2,4]triazines, and subsequent addition of PhLi followed by aerial oxidation. The resulting seven C(3)-substituted benzo[e][1,2,4]triazin-4-yls were analyzed by spectroscopic and electrochemical methods augmented with density functional theory (DFT) methods. Electrochemical data were compared to DFT results and correlated with substituent parameters.

Polynitrosoarene Radical as an Efficient Cathode Material for Lithium-Ion Batteries

Organic radical batteries (ORBs) with radical-branched polymers as cathode materials represent a valuable alternative to meet the continuously increasing demand on energy storage. However, the low theoretical capacities of current radical-contained compounds strongly hamper their practical applications. To address this issue, a chemically robust polynitrosoarene (tris(4-nitrosophenyl)amine) with a pronounced radical property is rationally designed as an efficient cathode for ORBs. Its unique multi-nitroso structure displays remarkably reversible charge/discharge capability and a superior capacity up to 300 mA h g-1 (93% theoretical capacity) after 100 cycles at 100 mA g-1 within a broad potential window of 1.3-4.3 V (vs Li+/Li). Moreover, the ultra-long cycle life is also achieved at 1000 mA g-1 with 85% preservation of the capacity after 1000 cycles, making it the best-reported organic radical cathode material for lithium-ion batteries.

Blatter Radical-Decorated Silica as a Prospective Adsorbent for Selective NO Capture from Air

Nitrogen oxides are adverse poisonous gases present in the atmosphere and having detrimental effects on the human health and environment. In this work, we propose a new type of mesoporous materials capable of capturing nitrogen monoxide (NO) from air. The designed material combines the robust Santa Barbara Amorphous-15 silica scaffold and ultrastable Blatter-type radicals acting as NO traps. Using in situ electron paramagnetic resonance spectroscopy, we demonstrate that NO capture from air is selective and reversible at practical conditions, thus making Blatter radical-decorated silica highly promising for environmental applications.

Tailored Charge Transfer Kinetics in Precursors for Organic Radical Batteries: A Joint Synthetic-Theoretical Approach

The development of sustainable energy storage devices is crucial for the transformation of our energy management. In this scope, organic batteries attracted considerable attention. To overcome the shortcomings of typically applied materials from the classes of redox-active conjugated polymers (i. e., unstable cell voltages) and soft matter-embedded stable organic radicals (i. e., low conductivity), a novel design concept was introduced, integrating such stable radicals within a conductive polymer backbone. In the present theory-driven design approach, redox-active (2,2,6,6-tetramethylpiperidin-1-yl)oxyls (TEMPOs) were incorporated in thiophene-based polymer model systems, while structure-property relationships governing the thermodynamic properties as well as the charge transfer kinetics underlying the charging and discharging processes were investigated in a systematical approach. Thereby, the impact of the substitution pattern, the length as well as the nature of the chemical linker, and the ratio of TEMPO and thiophene units was studied using state-of-the-art quantum chemical and quantum dynamical simulations for a set of six molecular model systems. Finally, two promising candidates were synthesized and electrochemically characterized, paving the way to applications in the frame of novel organic radical batteries.

Tethered Blatter Radical for Molecular Grafting: Synthesis of 6-Hydroxyhexyloxy, Hydroxymethyl, and Bis(hydroxymethyl) Derivatives and Their Functionalization

Synthetic access to 7-CF₃-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl radicals containing 4-(6-hydroxyhexyloxy)phenyl, 4-hydroxymethylphenyl or 3,5-bis(hydroxymethyl)phenyl groups at the C(3) position and their conversion to tosylates and phosphates are described. The tosylates were used to obtain disulfides and an azide with good yields. The Blatter radical containing the azido group underwent a copper(I)-catalyzed azide-alkyne cycloaddition with phenylacetylene under mild conditions, giving the [1,2,3]triazole product in 84% yield. This indicates the suitability of the azido derivative for grafting Blatter radical onto other molecular objects via the CuAAC "click" reaction. The presented derivatives are promising for accessing surfaces and macromolecules spin-labeled with the Blatter radical.

The synthesis and magnetic properties of carboxylic acid-derived 1,2,4-benzotriazinyl radicals and their coordination particles

Stable magnetic coordination particles based on π-conjugated 1,2,4-benzotriazinyl radical ligands were synthesized using a sonochemical method.

High Capacity and Energy Density Organic Lithium-Ion Battery Based on Buckypaper with Stable π-Radical

Owing to an increasing demand on high performance and rare-metal free energy storage systems, organic rechargeable battery has attracted much attention. To increase the capacity of the whole battery, we have fabricated coin-type buckypaper cells composed of a trioxotriangulene neutral radical derivative (H₃ TOT) and single-walled carbon nanotubes as a cathode and lithium metal plate as an anode without current collector. The cells exhibited a stable charge-discharge behavior even at a 90 wt % H₃ TOT content with a high-rate performance of 10 C originating from high electrical conductivity of H₃ TOT. Furthermore, based on the four-stage redox ability of H₃ TOT, the H₃ TOT 90 wt % cathode showed a high capacity of approximately 260 mAh g^-1 and a high energy density of 546 Wh g^-1 . In view of the simple fabrication of the cathode and excellent performance, TOT-based buckypaper will open a new strategy for the flexible cells for next-generation energy storages.

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.

Covalent functionalization of carbon materials with redox-active organic molecules for energy storage

Carbon-based materials (CBMs) have shown great versatility because they can be chemically combined with other materials for various applications. Chemical modification of CBMs can be achieved via covalent or non-covalent interactions. Non-covalent interactions are weak and fragile, causing structural change and molecule dissociation. Therefore, in this review, we summarize the covalent modification of CBMs via organic chemistry techniques, aiming at forming more robust and stable CBMs. Besides, their application as electrode materials in energy storage systems is also within the scope of this review. Covalent binding of redox-active organic molecules with CBMs improves the transfer rate of electrons and prevents the dissolution of redox-active molecules, resulting in good conductivity and cycle life. Numerous papers on the functionalization of CBMs have been published to date, but some of them lack scientific evidence and are unable to understand from chemistry viewpoint. Reliable articles with adequate evidence are summarized in this review from a synthetic chemistry viewpoint.

Design Strategies for High-Performance Aqueous Zn/Organic Batteries

Organic electroactive compounds are attractive to serve as the cathode materials of aqueous zinc-ion batteries (ZIBs) because of their resource renewability, environmentally friendliness and structural diversity. Up to now, various organic electrode materials have been developed and different redox mechanisms are observed in aqueous Zn/organic battery systems. In this Minireview, we present the recent developments in the energy storage mechanisms and design of the organic electrode materials of aqueous ZIBs, including carbonyl compounds, imine compounds, conductive polymers, nitronyl nitroxides, organosulfur polymers and triphenylamine derivatives. Furthermore, we highlight the design strategies to improve their electrochemical performance in the aspects of specific capacity, output voltage, cycle life and rate capability. Finally, we discuss the challenges and future perspectives of aqueous Zn/organic batteries.

Air-Stable Organic Radicals: New-Generation Materials for Flexible Electronics?

In the last few years, air-stable organic radicals and radical polymers have attracted tremendous attention due to their outstanding performance in flexible electronic devices, including transistors, batteries, light-emitting diodes, thermoelectric and photothermal conversion devices, and among many others. The main issue of radicals from laboratory studies to real-world applications is that the number of known air-stable radicals is very limited, and the radicals that have been used as materials are even less. Here, the known and newly developed air-stable organic radicals are summarized, generalizing the way of observing air-stable radicals. The special electric and photophysical properties of organic radicals and radical polymers are interpreted, which give radicals a wide scope for various of potential applications. Finally, the exciting applications of radicals that have been achieved in flexible electronic devices are summarized. The aim herein is to highlight the recent achievements in radicals in chemistry, materials science, and flexible electronics, and further bridge the gap between these three disciplines.

2D Coordination Network of Trioxotriangulene with Multiple Redox Abilities and Its Rechargeable Battery Performance

A three-fold symmetric trioxotriangulene derivative with three pyridyl groups as coordinating sites was designed and synthesized. In a cyclic voltammetry measurement, the trioxotriangulene skeleton exhibited a multi-stage redox ability from neutral radical to radical tetra-anion species. In the zinc complex of monoanion species, three pyridyl groups coordinated to the zinc ion to build up a two-dimensional coordination network with a cavity larger than 12 Å in diameter. This complex was utilized as a cathode active material of a lithium ion battery, and it exhibited a capacity of ca. 60 mAh g^-1 per the weight of the active material with a stable cycling performance up to 1000 cycles. This work shows that the coordination network formed by the trioxotriangulene-based ligand was effective in the improvement of cycle performance of the organic rechargeable battery.

Structure-properties relationship for energy storage redox polymers: a review

Redox-active polymers among the energy storage materials (ESMs) are very attractive due to their exceptional advantages such as high stability and processability as well as their simple manufacturing. Their applications are found to useful in electric vehicle, ultraright computers, intelligent electric gadgets, mobile sensor systems, and portable intelligent clothing. They are found to be more efficient and advantageous in terms of superior processing capacity, quick loading unloading, stronger security, lengthy life cycle, versatility, adjustment to various scales, excellent fabrication process capabilities, light weight, flexible, most significantly cost efficiency, and non-toxicity in order to satisfy the requirement for the usage of these potential applications. The redox-active polymers are produced through organic synthesis, which allows the design and free modification of chemical constructions, which allow for the structure of organic compounds. The redox-active polymers can be finely tuned for the desired ESMs applications with their chemical structures and electrochemical properties. The redox-active polymers synthesis also offers the benefits of high-scale, relatively low reaction, and a low demand for energy. In this review we discussed the relationship between structural properties of different polymers for solar energy and their energy storage applications.

Pairing Cross-Linked Polyviologen with Aromatic Amine Host Structure for Anion Shuttle Rechargeable Batteries

Electroactive organic compounds could bring new chemical opportunities to further improve existing electrochemical energy-storage technologies as they can be prepared from less-limited resources and potentially at low environmental footprint. Among the current explored research fields, the anion-ion cell configuration appears poorly investigated although quite promising to promote the fabrication of molecular (metal-free) rechargeable batteries. Herein, we report the synthesis and the electrochemical behavior of both Mg/Li salts of 2,5-(dianilino)terephthalate (MgDAnT and Li₂ DAnT) and cross-linked polyviologen (c-PV²⁺ ) that can reversibly uptake/extract anions at different working potentials, enabling the assembly of full anionic organic batteries. The reversible anion ingress in MgDAnT is however accompanied by solvent co-insertion from the electrolyte that provokes an overpotential effect during the first charge. Full anionic batteries pairing Li₂ DAnT with c-PV²⁺ were assembled giving rise to 0.7 V as output voltage with a specific capacity of 50 mAh per gram of Li₂ DAnT.

Sustainable Energy Storage: Recent Trends and Developments toward Fully Organic Batteries

In times of spreading mobile devices, organic batteries represent a promising approach to replace the well-established lithium-ion technology to fulfill the growing demand for small, flexible, safe, as well as sustainable energy storage solutions. In the last years, large efforts have been made regarding the investigation and development of batteries that use organic active materials since they feature superior properties compared to metal-based, in particular lithium-based, energy-storage systems in terms of flexibility and safety as well as with regard to resource availability and disposal. This Review compiles an overview over the most recent studies on the topic. It focuses on the different types of applied active materials, covering both known systems that are optimized and novel structures that aim at being established.

Practical use of polymer brushes in sustainable energy applications: interfacial nanoarchitectonics for high-efficiency devices

The discovery and development of novel approaches, materials and manufacturing processes in the field of energy are compelling increasing recognition as a major challenge for contemporary societies. The performance and lifetime of energy devices are critically dependent on nanoscale interfacial phenomena. From the viewpoint of materials design, the improvement of current technologies inevitably relies on gaining control over the complex interface between dissimilar materials. In this sense, interfacial nanoarchitectonics with polymer brushes has seen growing interest due to its potential to overcome many of the limitations of energy storage and conversion devices. Polymer brushes offer a broad variety of resources to manipulate interfacial properties and gain molecular control over the synergistic combination of materials. Many recent examples show that the rational integration of polymer brushes in hybrid nanoarchitectures greatly improves the performance of energy devices in terms of power density, lifetime and stability. Seen in this light, polymer brushes provide a new perspective from which to consider the development of hybrid materials and devices with improved functionalities. The aim of this review is therefore to focus on what polymer brush-based solutions can offer and to show how the practical use of surface-grafted polymer layers can improve the performance and efficiency of fuel cells, lithium-ion batteries, organic radical batteries, supercapacitors, photoelectrochemical cells and photovoltaic devices.

Raising the redox potential in carboxyphenolate-based positive organic materials via cation substitution

Meeting the ever-growing demand for electrical storage devices requires both superior and “greener” battery technologies. Nearly 40 years after the discovery of conductive polymers, long cycling stability in lithium organic batteries has now been achieved. However, the synthesis of high-voltage lithiated organic cathode materials is rather challenging, so very few examples of all-organic lithium-ion cells currently exist. Herein, we present an inventive chemical approach leading to a significant increase of the redox potential of lithiated organic electrode materials. This is achieved by tuning the electronic effects in the redox-active organic skeleton thanks to the permanent presence of a spectator cation in the host structure exhibiting a high ionic potential (or electronegativity). Thus, substituting magnesium (2,5-dilithium-oxy)-terephthalate for lithium (2,5-dilithium-oxy)-terephthalate enables a voltage gain of nearly +800 mV. This compound being also able to act as negative electrode via the carboxylate functional groups, an all-organic symmetric lithium-ion cell exhibiting an output voltage of 2.5 V is demonstrated.

Organic electrode materials could enable novelty chemistry required by the new generation of batteries. Here the authors show the synthesis and electrochemical performance of Mg(Li₂)-p-DHT as a lithiated cathode material that cycles at 3.4 V due to the presence of a spectator cation in the host structure.

Tuning Spin-Spin Interactions in Radical Dendrimers

Two generations of polyphosphorhydrazone (PPH) dendrimers were synthesized and fully functionalized with TEMPO radicals via acrylamido or imino group linkers to evaluate the impact of the linker substitution on the radical-radical interactions. A drastic change in the way that the radicals interacted among them was observed by EPR and CV studies: while radicals in Gn -imino-TEMPO dendrimers presented a strong spin-spin interaction, in the Gn -acrylamido-TEMPO ones they acted mainly as independent radicals. This shows that these interactions could be tuned by the solely substitution of the radical linker, opening the perspective of controlling and modulating the extension of these interactions depending on each application. The chemical properties of the linker strongly influence the spin-spin exchange between pendant radicals.

A nonconjugated radical polymer glass with high electrical conductivity

Solid-state conducting polymers usually have highly conjugated macromolecular backbones and require intentional doping in order to achieve high electrical conductivities. Conversely, single-component, charge-neutral macromolecules could be synthetically simpler and have improved processibility and ambient stability. We show that poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl), a nonconjugated radical polymer with a subambient glass transition temperature, underwent rapid solid-state charge transfer reactions and had an electrical conductivity of up to 28 siemens per meter over channel lengths up to 0.6 micrometers. The charge transport through the radical polymer film was enabled with thermal annealing at 80°C, which allowed for the formation of a percolating network of open-shell sites in electronic communication with one another. The electrical conductivity was not enhanced by intentional doping, and thin films of this material showed high optical transparency.

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.