Organic Active Materials Research Articles

Organic Cathode for Lithium Batteries, Enabled by Solid-State LLZO Separator

Small organic molecule quinones are promising as cathode active materials for Li batteries. They have high theoretical capacity (up to ~500 mAh/g) at moderate voltage (2 to 3V vs. Li/Li+). However, in conventional Li-ion batteries with liquid electrolyte, they dissolve and cross through the membrane, leading to reaction with the Li anode. To solve this issue, we employ a dense lithium garnet solid electrolyte (LLZO) as the separator to block transport of the organic cathode material. This work demonstrates solid electrolyte/liquid catholyte hybrid battery cells with metallic Li alloy as the anode and lawsone, a biologically-derived quinone, as the cathode. LLZO is used as a separator and effectively prevents dissolved cathode material from meeting the anode. Lawsone LLZO hybrid cells reached cathode utilization of up to 67% based on lithiation of both carbonyl groups, and had little self-discharge compared to liquid cells. A side-reaction at low voltage is identified as the main source of capacity fade. Nevertheless, use of a solid electrolyte is shown to be a promising approach to enable use of soluble organic cathode active materials.

Application of Naphthoquinone Derivatives Non‐Covalently Modified Graphene Nanosheets in Asymmetric Supercapacitors

AbstractAs an organic pseudocapacitive active material, 2, 3‐Dichloro‐1, 4‐naphthoquinone (DNQ) was used in supercapacitors. Graphene with unique structures and high electrical conductivity acts as substrate. DNQ non‐covalently modified graphene composite material (DNQ@rGO) was synthesized through the simple solvothermal synthesis. The redox reaction between naphthol and naphthoquinone occurs on reduced graphene oxide(rGO), which forms an ideal pseudocapacitance without destroying its sp2 network. The optimal DNQ@rGO electrode material obtained the specific capacitance of 361.2 Fg−1 at 5 mV s−1 in 1 mol L−1 H2SO4 and exhibited excellent rate capability (capacitance retention of 87.5 % at 100 mV s−1) in the three‐electrode system. We also prepared holey layered oxygen‐rich graphene hydrogels (HLGH) material, whose electrochemical performance is superior to traditional three‐dimensional (3D) graphene hydrogels (GH). Finally, two asymmetric supercapacitors (ASCs) were assembled by using the DNQ@rGO (positive electrode), the HLGH and GH (negative electrode). The results show that the ASC with HLGH as negative electrode achieved the high energy and power densities due to the perfect matching of capacitance and kinetics between the positive and negative electrodes. The specific capacitance was almost no loss after 4700 cycles, showing the excellent stability.

Exploration of Organic Cathode Active Materials with High Energy Densities for Li-Ion Batteries via First-Principles Calculations

Exploration of Organic Cathode Active Materials with High Energy Densities for Li-Ion Batteries via First-Principles Calculations

A Shapeshifting Roadmap for Polycyclic Skeletal Evolution.

Polycyclic ring systems are ubiquitous three-dimensional (3D) structural motifs central to the function of many biologically active small molecules and organic materials. Indeed, subtle changes to the overall molecular shape and connectivity of atoms in a polycyclic framework (i.e., isomerism) can drastically alter its function and properties. Unfortunately, direct evaluation of these structure-function relationships typically requires the development of distinct synthetic strategies toward a specific isomer. Dynamic, "shapeshifting" carbon cages present a promising approach for sampling isomeric chemical space but are often difficult to control and are largely limited to thermodynamic mixtures of positional isomers about a single core scaffold. Here, we describe the development of a new shapeshifting C9-chemotype and a chemical blueprint for its evolution into structurally and energetically diverse isomeric ring systems. By leveraging the unique molecular topology of π-orbitals interacting through-space (homoconjugation), a common skeletal ancestor evolved into a complex network of valence isomers. This unusual system represents an exceedingly rare small molecule capable of undergoing controllable and continuous isomerization processes through the iterative use of just two chemical steps (light and organic base). Computational and photophysical studies of the isomer network provide fundamental insight into the reactivity, mechanism, and role of homoconjugative interactions. Importantly, these insights may inform the rational design and synthesis of new dynamic, shapeshifting systems. We anticipate this process could be a powerful tool for the synthesis of structurally diverse, isomeric polycycles central to many bioactive small molecules and functional organic materials.

Weakening solvent polarity enables shuttle-effect-free and temperature-independent lithium-organic batteries

Lithium-organic batteries feature transition-metal-free cathode, resource sustainability and low cost, showing great potential to be substitutes for lithium-ion batteries that greatly depend on scarce natural resources. However, lithium-organic batteries are plagued by the shuttle effect and unstable Li metal anodes, especially under extreme operating conditions. High-concentration or localized high-concentration electrolytes may mitigate these problems, but at the expense of high-cost and environmental concerns. Herein, we propose a standard-concentration electrolyte that shows excellent compatibility with both organic active materials (shuttle-effect-free) and Li metal anodes (Coulombic efficiency ∼ 99.52%) by weakening the solvent polarity. It demonstrates that the introduction of the nonpolar n-heptane can simultaneously inhibit the dissolution of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) and restrain side reactions between electrolyte solvents and Li metal, as well as weaken the affinity between solvents and Li+. The PTCDA|Li batteries retain 98.2% capacity after 200 cycles with an average Coulombic efficiency of 99.97%, and also show high cycling stability from −40 to +60 °C. With the replacement of traditional electrolyte by our electrolyte, the energy density of PTCDA|Li pouch-cells increases by 13.9% under identical conditions. Furthermore, our electrolyte can be extended to other (Li-sulfur, Li-FeS) batteries encountering the dilemma of the shuttle effect and unstable Li anodes.

Nanorod-Like Organic Active Materials Directly Grown on the Carbon Cloth for Aqueous Zn-Ion Batteries

Organic active materials are regarded as a promising candidate to replace inorganic counterparts owing to their tunable redox activity, mild synthesis condition, and multi-electron reactions. However, these organic materials are limited by their dissolution in the aqueous electrolyte and low electrical conductivity. Herein, we synthesized self-assembled nanorods of perylene-3,4,9,10-tetracarboxylic dianhydride (NRPTCDA) grown on carbon cloth for high-performance Zn-ion storage. The vertical orientation and length of nanorods were controlled through optimizing the synthesis condition, which can facilitate Zn-ion insertion–deinsertion. For an aqueous Zn-ion battery, the NRPTCDA cathode achieved a high capacity of 127.5 mAh g–1 at a current density of 1 A g–1, which retained 82.10 mAh g–1 even at a high current rate of 50 A g–1. Additionally, structure-controlled NRPTCDA exhibited 90.1% of rate capability at 100 mV s–1 and 78.91% capacity retention over 10 000 galvanostatic charge–discharge cycles at 10 A g–1 of current density. Additionally, ex situ X-ray diffraction, attenuated total reflectance–Fourier transform infrared spectroscopy, and field emission scanning electron microscopy measurements were performed and confirmed structural, chemical, and morphological stability and reversibility of NRPTCDA electrodes for Zn2+ ion storage.

Lithium-Conducting Organic Solid Electrolyte for Organic Rechargeable Batteries: Boronated Benzoimidazole-Linked Polymer

Some of the Benzimidazole-linked polymers (BILPs) are a class of porous organic polymers that have high porosities, large specific surface areas, and high thermal and chemical stability. Owing to these properties, BILPs can be used in various applications including solid electrolytes for renewable energy utilization. In this study, we carried out the boran-modification of a kind of BILPs, in order to increase the Li ion conductivity by decreases the interaction between lithium ions and the anion backbone. The resulting B-TFB-HAB-BILP materials have an ionic conductivity of 2.9 × 10−6 S cm−1 at 30 °C, which increases to 1.4 × 10−4 S cm−1 at room temperature with the addition of the ionic liquid, PP13[TFSA]. This can be attributed to the suppression of resistance at the grain boundary. A coin cell with an organic cathode active material, B-TFB-HAB-BILP/PP13[TFSA] as the quasi-solid electrolyte, and Li foil as the anode exhibited an initial discharge capacity of 223 mAh g−1 (76 % of theoretical capacity). Our study can aid in the realization of organic rechargeable batteries with high gravimetric energy density.

Rational design of composite supporting electrolyte required for achieving high performance aqueous organic redox flow battery

Although aqueous organic redox flow batteries (AORFBs) have many benefits, their organic active materials have the limitations in solubility and chemical instability. To overcome the problems, efforts to develop new organic active materials is usually made. However, these efforts have still limitations in some prospects. Thus, in this study, instead of developing new organic active materials, a rationally designed composite supporting electrolyte is suggested to improve energy density, power density, life-cycle, and efficiency of AORFB using 2-hydroxy-1,4-naphthoquinone (Lawsone) and potassium ferrocyanide as redox couple. The composite supporting electrolyte consists of potassium hydroxide (KOH) and potassium sulfite and is optimized by density functional theory (DFT). DFT predicts that sulfite anions help the solubility and stability of Lawson to improve, while hydroxide anions promote reactivity. The predictions are proved by electrochemical evaluations. With that, when the optimal composite supporting electrolyte is used, high capacity and excellent retention of AORFB (90 % at 100th cycle (from 20.27 to 18.42 Ah·L−1)) are achieved, while high power of 12.4 W is produced by AORFB short stack.

Non-aqueous organic redox active materials for a bicontinuous microemulsion-based redox flow battery

To mitigate fluctuations in renewable energy sources, redox flow batteries (RFBs) attract much attention for stationary energy storage applications by taking advantage of decoupling power and energy. However, there are still some limitations for conventional RFBs, including low energy density, a narrow electrochemical window (∼1.23 V) for an aqueous electrolyte, and low ionic conductivity for a non-aqueous electrolyte. Herein, we demonstrate a bicontinuous microemulsion-based RFB using methyl-p-benzoquinone and 2,2,6,6-Tetramethyl-1-piperidinyloxy as anolyte and catholyte redox active materials, respectively. By stabilizing an aqueous and organic medium at a nanometer scale through a surfactant, the microemulsion electrolyte exhibits a wider electrochemical window and good ionic conductivity, a promising alternative to increase the energy density by applying non-aqueous redox species with high solubility and high redox potential. The resulting cell exhibits Coulombic efficiency of 80%–85% and capacity retention of 50% over 30 cycles. We provide a systemic analysis of performance limitation and capacity decay and proposed a possible dimerization mechanism for an anolyte through a density functional theorycalculation, ending with a discussion of the efforts needed to realize the application of microemulsion-based RFBs.

Extended Conjugation Acceptors Increase Specific Energy Densities in π-Conjugated Redox Polymers

Organic materials are a sustainable alternative to replace inorganic transition metal-based cathodes in rechargeable intercalation batteries. Among the possible redox active organic materials, conjugated polymers with multiple redox sites per repeat unit are expected to afford high energy and power densities while being resistant to dissolution when in contact with battery electrolytes. However, accessing the full capacity of polymeric electrodes while ensuring electrochemical reversibility has been challenging. Using diketopyrrolopyrrole (DPP)-based donor–acceptor (D–A) polymers as model systems and complementary electrochemical experiments and first-principles calculations, we show that conjugated backbone moieties that minimize charge localization on the electron accepting repeat units lead to near theoretical discharge capacities. Further, the capacity enhancement is associated with better rate performance and improved electrochemical stability of the polymer over prolonged cycling. Our work suggests that charge density on the electron accepting moiety is a potential descriptor for rationally designing redox-active polymer electrodes that afford high discharge capacities along with a long cycle life.

Development and Characterization of Electrospun Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Biopapers Containing Cerium Oxide Nanoparticles for Active Food Packaging Applications

Food quality is mainly affected by oxygen through oxidative reactions and the proliferation of microorganisms, generating changes in its taste, odor, and color. The work presented here describes the generation and further characterization of films with active oxygen scavenging properties made of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) loaded with cerium oxide nanoparticles (CeO2NPs) obtained by electrospinning coupled to a subsequent annealing process, which could be used as coating or interlayer in a multilayer concept for food packaging applications. The aim of this work is to explore the capacities of these novel biopolymeric composites in terms of O2 scavenging capacity, as well as antioxidant, antimicrobial, barrier, thermal, and mechanical properties. To obtain such biopapers, different ratios of CeO2NPs were incorporated into a PHBV solution with hexadecyltrimethylammonium bromide (CTAB) as a surfactant. The produced films were analyzed in terms of antioxidant, thermal, antioxidant, antimicrobial, optical, morphological and barrier properties, and oxygen scavenging activity. According to the results, the nanofiller showed some reduction of the thermal stability of the biopolyester but exhibited antimicrobial and antioxidant properties. In terms of passive barrier properties, the CeO2NPs decreased the permeability to water vapor but increased the limonene and oxygen permeability of the biopolymer matrix slightly. Nevertheless, the oxygen scavenging activity of the nanocomposites showed significant results and improved further by incorporating the surfactant CTAB. The PHBV nanocomposite biopapers developed in this study appear as very interesting constituents for the potential design of new active organic recyclable packaging materials.

Li–S battery cathode anchoring polysulfides by interaction between redox-active imide and carbon nanotube

Providing high energy density and theoretical capacity, lithium-sulfur (Li–S) battery technologies emerged as a suitable alternative to the existing lithium-ion batteries (LIBs) at low cost. However, insulating nature of sulfur, dissolution of polysulfides into the aprotic electrolyte solvent as well as volume changes upon cycling cause rapid capacity decay. One of the effective strategies is the usage of redox active functional organic materials to trap polysulfides or utilization of conductive carbon materials to overcome lower electronic conductivity of the sulfur active material. In this work, N–N′-diphenyl-1,4,5,8-naphtalene-tetra-carboxylic-diimide (DP-NTCDI) is efficiently synthesized and mixed with single-walled carbon nanotube (SWCNT) to both serve as polysulfide adsorbent and conductive agent role. After the detailed structural characterization, density functional theory (DFT) analysis as well as adsorption tests, the electrochemical performances of the Li–S cell performances are evaluated in which the discharge value over 330 mAh/g at C/5 after 150 cycle is achieved with 85 wt% sulfur containing electrode.

Additive-Free Organic Radical Batteries Prepared through Electrochemical Polymerization of TEMPO-Decorated Terthiophene

Batteries based on organic active materials offer a promising alternative to traditional metal-based systems due to environmental issues as well as high possible charging and discharging rates. However, the established organic materials suffer from a very low intrinsic electrical conductivity, requiring the addition of conductive materials. Herein, we present an approach to overcome this problem through the application of a conductive polythiophene decorated with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) units through electrochemical polymerization of suitable monomers directly onto the battery electrode. We demonstrate that a terthiophene linked to one TEMPO moiety not only allows successful electropolymerization but also the construction of additive-free organic batteries. Based on electrochemical investigations in combination with quantum chemical simulations, we can evaluate the underlying redox processes at the molecular level. Cell tests demonstrate the principle functionality of the system with rate capabilities of up to 20% capacity retention at 50C and a good long-term stability with a capacity loss of only 0.03% per cycle.

Capacity-prediction models for organic anode-active materials of lithium-ion batteries: advances in predictors using small data

A capacity prediction model for organic anode active materials was constructed using sparse modeling for small data. The new model was validated in terms of the prediction accuracy, validity of the descriptors, and amount of the training data.

Organic Anode Materials for Lithium-Ion Batteries: Recent Progress and Challenges.

In the search for novel anode materials for lithium-ion batteries (LIBs), organic electrode materials have recently attracted substantial attention and seem to be the next preferred candidates for use as high-performance anode materials in rechargeable LIBs due to their low cost, high theoretical capacity, structural diversity, environmental friendliness, and facile synthesis. Up to now, the electrochemical properties of numerous organic compounds with different functional groups (carbonyl, azo, sulfur, imine, etc.) have been thoroughly explored as anode materials for LIBs, dividing organic anode materials into four main classes: organic carbonyl compounds, covalent organic frameworks (COFs), metal-organic frameworks (MOFs), and organic compounds with nitrogen-containing groups. In this review, an overview of the recent progress in organic anodes is provided. The electrochemical performances of different organic anode materials are compared, revealing the advantages and disadvantages of each class of organic materials in both research and commercial applications. Afterward, the practical applications of some organic anode materials in full cells of LIBs are provided. Finally, some techniques to address significant issues, such as poor electronic conductivity, low discharge voltage, and undesired dissolution of active organic anode material into typical organic electrolytes, are discussed. This paper will guide the study of more efficient organic compounds that can be employed as high-performance anode materials in LIBs.

Longer cycle life and higher discharge voltage of a small molecular indanthrone resulting from the extended conjugated framework

Organic cathodes have attracted wide attentions owing to their worthful advantages including higher capacity, abundant reserves and designable structure. However, significant dissolution of active organic materials hinders their practical applications in lithium-ion batteries (LIBs). Extending the conjugated framework in which intermolecular interactions play a crucial role, is an efficient strategy to inhibit the dissolution. Herein, an organic molecule with extended conjugated framework, indanthrone (IDT), is reported for LIBs. The rich carboxyl groups (CO) ensure the high capacity for redox reactions, which is hence utilized as cathodic active centers. Moreover, the presence of CO and amidogen resulted in plentiful intermolecular interactions, leading to insolubility and high stability. The rich functional groups also promote the chelation of oxygen and nitrogen with Li-ion and hence benefit their storage. A specific capacity of 238 mAh g−1 has been achieved for IDT-based cathodes at 0.2C, and a capacity of over 200 mAh g−1 is retained after 1000 cycles with a decay rate of only ∼0.014% per-cycle. It is worth mentioning that there is a visible increase in voltage platform during cycling. The structure design of extending the conjugated framework endows the battery performance with longer cycle life and higher energy density.

Recent Advances in Selenophene-Based Materials for Organic Solar Cells.

Due to the low cost, light weight, semitransparency, good flexibility, and large manufacturing area of organic solar cells (OSCs), OSCs have the opportunity to become the next generation of solar cells in some specific applications. So far, the efficiency of the OSC device has been improved by more than 20%. The optical band gap between the lowest unoccupied molecular orbital (LUMO) level and the highest occupied molecular orbital (HOMO) level is an important factor affecting the performance of the device. Selenophene, a derivative of aromatic pentacyclic thiophene, is easy to polarize, its LUMO energy level is very low, and hence the optical band gap can be reduced. In addition, the selenium atoms in selenophene and other oxygen atoms or sulfur atoms can form an intermolecular interaction, so as to improve the stacking order of the active layer blend film and improve the carrier transport efficiency. This paper introduces the organic solar active layer materials containing selenium benzene in recent years, which can be simply divided into donor materials and acceptor materials. Replacing sulfur atoms with selenium atoms in these materials can effectively reduce the corresponding optical band gap of materials, improve the mutual solubility of donor recipient materials, and ultimately improve the device efficiency. Therefore, the sulfur in thiophene can be completely replaced by selenium or oxygen of the same family, which can be used in the active layer materials of organic solar cells. This article mainly describes the application of selenium instead of sulfur in OSCs.

Nonconfinement growth of edge-curved molecular crystals for self-focused microlasers.

Synthesis of single-crystalline micro/nanostructures with curved shapes is essential for developing extraordinary types of optoelectronic devices. Here, we use the strategy of liquid-phase nonconfinement growth to controllably synthesize edge-curved molecular microcrystals on a large scale. By varying the molecular substituents on linear organic conjugated molecules, it is found that the steric hindrance effect could minimize the intrinsic anisotropy of molecular stacking, allowing for the exposure of high-index crystal planes. The growth rate of high-index crystal planes can be further regulated by increasing the molecular supersaturation, which is conducive to the cogrowth of these crystal planes to form continuously curved-shape microcrystals. Assisted by nonrotationally symmetric geometry and optically smooth curvature, edge-curved microcrystals can support low-threshold lasing, and self-focusing directional emission. These results contribute to gaining an insightful understanding of the design and growth of functional molecular crystals and promoting the applications of organic active materials in integrated photonic devices and circuits.

Title: Static Cell and Porous Electrode Model for Cycling Behavior of Aqueous Organic Redox Active Materials

Aqueous Organic Redox Flow Batteries (AORBs) have shown growing potential as a stationary energy storage technology for regulating intermittent renewable sources. For long charge/discharge duration systems, the capital cost of a redox flow battery asymptotically approaches the cost of the electroactive material.[i] Therefore, for commercialization of this technology, proper evaluation of the redox active electrolytes is needed. The capacity retention over time and over cycling is one of the most vital criteria for evaluation. For very stable electrolytes with fade rates less than about 10% per year, disentangling cycle-denominated and time-denominated fade can be very difficult for flow batteries due to longer cycle time and noise due to pumping and splashing. Thus, we have used a sealed, static, non-flow cell to achieve capacity measurements with greater cycling frequency and reduced noise, as shown in Figure 1. To isolate decomposition from crossover through the membrane or apparent capacity fade due to changes in the resistance of the cell, we use volumetrically unbalanced, compositionally symmetric cells with potentiostatic cycling.[iii] For proper capacity fade rate evaluation, material properties of the electrode and electrolyte should be considered when setting up cycling protocols because the amount of accessed charge depends on these properties. Thus, simulations from porous electrode models that consider these material properties can inform appropriate cycling conditions.Using Newman’s porous electrode theory[iv] to model our static cell, we have simulated the spatial distribution of ions and potentials over time in response to time-varying applied potentials. From the transient behavior, we simulated the potentiostatic cycling of these cells. The simulations show how the physics inside porous electrodes and cycling performance depend on material properties. For example, the diffusivities can affect the spatial distributions of ions across a porous electrode, as shown in Figure 2 (left), as well as the minimum acceptable time for cycling and the accessed capacity for given cycling parameters, as shown in Figure 2 (right). Using the same porous electrode model for simulations, we aim to show differences between apparent and real capacity fade. [i] F. R. Brushett, M. J. Aziz, and K. E. Rodby. ACS Energy Lett. 2020, 5, 879−884 [ii] D. G. Kwabi, Y. Ji, and M. J. Aziz. C hem. Rev. 2020, 120, 14, 6467–6489 [iii] M.A. Goulet and M. J. Aziz, “Flow Battery Molecular Reactant Stability Determined by Symmetric Cell Cycling Methods”. Journal of The Electrochemical Society, 165 (7) A1466-A1477 (2018) [iv] J. Newman and C. W. Tobias, J. Electrochem. Soc., 1962, 109, 1183 Figure 1

(Invited) Artistic: An AI and Modeling-Supported Digital Infrastructure for Battery Manufacturing Optimization

Energy, power, lifetime and safety of Lithium ion batteries (LIBs) are determined in part by the internal microstructure of the electrodes. That microstructure is characterized by the spatial location and the resulting interfaces between the active material particles, the conductive additive, the binder and the pores. The microstructure is determined by the manufacturing process of the electrodes, which encompasses, in its traditional wet form, multiple steps and numerous parameters. Therefore, its optimization is difficult and can be time consuming and costly if carried out only on the basis of a trial and error approach.In this lecture I discuss a digital infrastructure for accelerated optimization of the manufacturing process of LIBs that we are developing since few years: ARTISTIC.1 Such digital infrastructure is supported on a hybrid approach encompassing a physics-based multiscale modeling workflow, Artificial Intelligence (AI)/machine learning models and high throughput experimental characterizations.2 ARTISTIC simulates different steps along the battery cells manufacturing process, such as the electrode slurry preparation, the coating, the drying, the calendering and the electrolyte infiltration. For that purpose, it uses a combination of sequentially-coupled 3D-resolved physical models based on experimentally-validated Coarse Grained Molecular Dynamics, Discrete Element Method and Lattice Boltzmann Method. This allows predicting the impact of the manufacturing process parameters on the final electrode microstructure in three dimensions. The predicted electrode microstructures are then injected in a continuum performance simulator capturing the influence of the electrode microstructure on the solid electrolyte interphase formation (for anodes) and the electrochemical response (of anodes vs. lithium, cathodes vs. lithium and the full cells). Machine learning models are used to unravel manufacturing parameters interdependencies from the physical models’ predictions and experimental data, and to suggest manufacturing process optimizations. The predictive capabilities and chemistry-neutrality of the ARTISTIC digital infrastructure are illustrated with results for different LIB electrode formulations and chemistries (NMC, LFP, graphite, silicon/graphite blends) and also for organic active materials for sodium ion batteries. Finally, I discuss the free online battery manufacturing simulation services (online caculator and associated databases) offered by our project and that you can use interactively from your Internet Browser.3