Organic Electrode Materials Research Articles

Molecular Engineering and Microstructure Modulation of High‐Performance Organic Batteries

Organic electrode materials (OEMs) featuring high abundance, structural designability, and eco‐friendliness, are considered promising candidates for rechargeable metal‐ion batteries. Nevertheless, the realization of efficient metal‐ion batteries based on OEMs is plagued by the poor intrinsic electronic conductivity and low insolubility of OEMs in common organic electrolytes. Herein, we present a systematic discussion of advancements in the design of OEMs from the perspective of molecular engineering and microstructure modulation, aiming at tuning the electrochemical, physical, and chemical properties of OEMs. Additionally, we elucidate the reaction mechanism of regulation strategies and provide new design directions for OEMs. This review offers essential concepts and perspectives on the development of advanced OEMs for rechargeable batteries.

Quasi-Solid-State Conversion with Fast Redox Kinetics Enabled by a Sulfonamide-Based Electrolyte in Li-Organic Batteries.

The serious dissolution of organic electrode materials (e.g., perylene-3,4,9,10-tetracarboxylic dianhydride, PTCDA) in electrolytes is a major challenge, deteriorating their electrochemical performances and hindering the interpretation of the fundamental redox reaction mechanisms including the intrinsic kinetics and the solvent cointercalation. To address these issues, we propose a rationally designed sulfonamide-based electrolyte to enable a quasi-solid-state conversion (QSSC) of the PTCDA cathode by effectively suppressing its dissolution in the electrolyte. Benefiting from the QSSC, the Li||PTCDA cells can retain ∼95.8% of the original capacity after 300 cycles with both high and stable energy efficiencies >95%, even comparable to the layered transition-metal oxide cathodes, greatly outperforming an ether-based electrolyte with a high PTCDA solubility. The high energy efficiencies indicate that the QSSC of PTCDA has intrinsic fast redox kinetics. Furthermore, the solvent cointercalation mechanism was investigated by density functional theory/molecular dynamic calculations. This work develops a strategy for designing electrolytes for highly stable and efficient Li-organic batteries.

Zero-Shot Discovery of High-Performance, Low-Cost Organic Battery Materials Using Machine Learning.

Organic electrode materials (OEMs), composed of abundant elements such as carbon, nitrogen, and oxygen, offer sustainable alternatives to conventional electrode materials that depend on finite metal resources. The vast structural diversity of organic compounds provides a virtually unlimited design space; however, exploring this space through Edisonian trial-and-error approaches is costly and time-consuming. In this work, we develop a new framework, SPARKLE, that combines computational chemistry, molecular generation, and machine learning to achieve zero-shot predictions of OEMs that simultaneously balance reward (specific energy), risk (solubility), and cost (synthesizability). We demonstrate that SPARKLE significantly outperforms alternative black-box machine learning algorithms on interpolation and extrapolation tasks. By deploying SPARKLE over a design space of more than 670,000 organic compounds, we identified ≈5000 novel OEM candidates. Twenty-seven of them were synthesized and fabricated into coin-cell batteries for experimental testing. Among SPARKLE-discovered OEMs, 62.9% exceeded benchmark performance metrics, representing a 3-fold improvement over OEMs selected by human intuition alone (20.8% based on six years of prior lab experience). The top-performing OEMs among the 27 candidates exhibit specific energy and cycling stability that surpass the state-of-the-art while being synthesizable at a fraction of the cost.

Solvation structure manipulation of ester-based electrolyte by acetonitrile additive enables high-capacity and stable K-storage for phenazine-based anode

Potassium ion batteries configured with organic electrode materials show promising applications due to the advantages of low cost and high theoretical capacity. Nevertheless, the design of electrolytes compatible with organic anodes and the resolution of the issue of uniform deposition of highly active potassium remain significant challenges. In this study, an engineering strategy was proposed to employ additives with electron-rich nitrile group in order to modulate the properties of ester-based electrolytes. It was found that acetonitrile (AN) can change the cation solvation structure, which determines the interfacial behavior of the K-solvent at the electrode interface, and effectively guides the homogeneous plating/stripping of K as well as suppresses dendritic growth. Therefore, a high reversible capacity of 200 mAh/g(composite) with the coulombic efficiency of 99.1 % at 50 mA/g was produced by the K-storage system of the novel phenazine anode with carbon nanotubes supported (PhAz/CNTs) and AN-containing electrolyte. The cyano-based additive strategy may offer novel insights into the tuning of electrolyte properties for the development of high-performance potassium ion battery systems.

Close‐packed One‐dimensional Coordination Polymer Cathode with Fast Kinetics for Sodium‐ion Batteries

Sustainable sodium‐ion batteries (SIBs) have gained tremendous attention; however, the large‐sized Na+ poses serious challenges on the development of inorganic‐based cathodes. To overcome the issues, metal–organic electrode materials are appealing because they combine attractive characteristics of organic redox centers (e.g., flexibility, highly reversible redox properties, fast kinetics (regardless of size and charge of guest ions), structural/redox tunability, and resource abundance) with structural stability arising from metal‐ligand coordination. Herein, a one‐dimensional copper‒benzoquinoid coordination polymer (CP), [CuL(Py)2]n, (LH4 = 1,4‐dicyano‐2,3,5,6‐tetrahydroxybenzene, Py = pyridine) is investigated as cathode for SIBs. As opposed to most CPs reported for SIBs which possess high porosity and surface area, this close‐packed CP can deliver discharge capacity as high as 277 mAh g‒1 at 2C (~523 mA g‒1), and at extremely high rates of 50C and 300C (~13 and 78 A g‒1), reversible capacities of 131 and 74 mAh g‒1 still can be delivered, respectively. The transport kinetics of Na+ in [CuL(Py)2]n is found to be even faster than that of Li+ despite the close‐packed structure. The mechanistic and kinetic studies have been performed. The findings gained in this work undoubtedly unravel a potential design strategy for high‐performance metal–organic electrode materials for emerging post‐Li‐ion batteries.

An Organic Small Molecule Electrode with Intermolecular Intercalation and Synergistic Effects for High‐Rate Alkali Metal‐Ion Batteries

AbstractDesignable molecular structures, unique ion‐coordination charge storage mechanisms, and resource sustainability enable organic electrode materials to become potential candidates for alkali metal‐ion batteries (AMIBs). Herein, integrating the excellent π–π stacking ability of Hexaazatriphenylene units and strong electron‐withdrawing properties of cyano (C≡N) groups into one moleuce, a π‐conjugated organic compound 1,4,5,8,9,11‐Hexaazatriphenylenehexacarbonitrile (HAT‐CN) is synthesized and systematically investigated as electrodes in Li/Na/K‐ion batteries. Explored by mechanism characterizations and density functional theory calculations, HAT‐CN can provide nine redox‐active sites for Na/K‐ions to intercalate/de‐intercalate, among which six Na/K‐ions are distributed evenly to both sides of conjugated skeletons through intermolecular intercalation and three Na/K‐ions are stored with the synergistic effect of C≡N groups. Employing HAT‐CN as electrodes, AMIBs are found to exhibit high reversible capacities, excellent rate capabilities, and stable cycle performances. After 100 cycles at the current density of 100 mA g−1, Na‐ion batteries present 415.6 mAh g−1 with a capacity fading rate of 1.2% per cycle. Meanwhile, K‐ion batteries maintain 345 mAh g−1 with a coulombic efficiency ≈100%. Li‐ion batteries display superlithiation performances with ultra‐high reversible capacity. This work emphasizes the necessity of comprehensively studying the electrochemical performance of organic electrodes in different secondary battery systems and is conducive to maximizing electrode functionality.

Azopyridine Aqueous Electrochemistry Enables Superior Organic AZIBs.

Azo compounds (AZO), such as azobenzene, are classic organic electrode materials featuring a redox potential close to Zn/Zn2+. Recent studies show that azobenzene could work as a cathode in aqueous zinc-ion batteries (AZIBs), providing a voltage output of around 0.7 V. However, the energy storage mechanism of AZO cathodes in AZIBs remains unclear, and their practical usage in AZIBs is hindered by the low voltage. In this study, azopyridine isomers, the hydrophilic analogues of azobenzene, were adopted as cathodes for AZIBs, and the energy storage mechanism was unveiled through aqueous electrochemical studies. Through in situ electrochemical characterizations and theoretical computations, we reveal that both the electron-withdrawing effect of the pyridyl group and the H+-involved -N = N-/-NH-NH- redox reaction uplift the redox potential of the azopyridine cathodes. These findings led to the first AZO-based AZIB, providing a voltage output of 1.4 V. The proposed air-stable AZIBs deliver a high energy/power density and a capacity of around 200 mAh g-1. This work discovers different azopyridine electrochemistry in aqueous and organic electrolytes and enabling AZIBs to outperform its competitors from the AZO family.

A Review on the Role of Hydrogen Bonds in Organic Electrode Materials

AbstractOrganic electrode materials (OEMs) hold significant development potential in the field of batteries and are regarded as excellent complementary materials to resource‐limited inorganic electrode materials, which have recently been the subject of extensive research. As research deepens, an increasing number of scholars recognize the influence of weak bond interactions on the properties of OEMs. Generally, weak bond interactions have more pronounced effects on organic materials compared to inorganic ones. Among various weak interactions, hydrogen bonds are particularly noteworthy, having been proven to play crucial roles in adjusting electrode charge distribution, stabilizing crystal structures, and inhibiting cyclic dissolution. The studies of hydrogen bonds in OEMs are therefore of paramount importance for guiding their future development. In this review, we primarily summarize the research progress in hydrogen bond science within OEMs and discuss future research directions and development prospects in this area. Hoping to provide valuable references for the advancement of OEMs.

Organometallic Polymer Constructed by Active Fe-C12N8 Centers for Boosting Sodium-Ion Storage.

Organic-metal coordination materials with rich structural diversity are considered as promising electrode materials for rechargeable sodium-ion batteries. However, the electrochemical performance can be constrained by the limited number of active sites and structural instability under the discharge/charge process. Herein, organometallic polymer microspheres (Fe-PDA-220) with a unique d-π conjugated structure was designed and successfully constructed through a simple synchronous polymerization and coordination reactions. Polymerization of phenylenediamine was initiated by Fe3+ and Fe2+ ions generated synchronously during the polymerization integrated with poly-aminoquinone chains to form Fe-C12N8 active centers. Used as electrode materials for sodium-ion batteries, the distinctive Fe-C bond significantly boosts the structural stability, and the π-d conjugation system could facilitate electron transfer. A high reversible capacity of 345 mAh g-1 was delivered at 0.1 A g-1 and a capacity of 106 mAh g-1 was maintained even after discharged/charged at 1.0 A g-1 for 5000 cycles, outperforming most reported coordination materials. Spectroscopic and electronic analyses revealed that a two-electron reaction occurred per active unit, accompanied by the reversible redox evolution of the C=N groups and Fe ions during the sodiation/desodiation. This work provides a promising and efficient strategy for boosting the electrochemical performance of organic electrode materials by the design of organometallic polymers.

Organometallic Polymer Constructed by Active Fe−C12N8 Centers for Boosting Sodium‐Ion Storage

AbstractOrganic‐metal coordination materials with rich structural diversity are considered as promising electrode materials for rechargeable sodium‐ion batteries. However, the electrochemical performance can be constrained by the limited number of active sites and structural instability under the discharge/charge process. Herein, organometallic polymer microspheres (Fe‐PDA‐220) with a unique d‐π conjugated structure was designed and successfully constructed through a simple synchronous polymerization and coordination reactions. Polymerization of phenylenediamine was initiated by Fe3+ and Fe2+ ions generated synchronously during the polymerization integrated with poly‐aminoquinone chains to form Fe−C12N8 active centers. Used as electrode materials for sodium‐ion batteries, the distinctive Fe−C bond significantly boosts the structural stability, and the π‐d conjugation system could facilitate electron transfer. A high reversible capacity of 345 mAh g−1 was delivered at 0.1 A g−1 and a capacity of 106 mAh g−1 was maintained even after discharged/charged at 1.0 A g−1 for 5000 cycles, outperforming most reported coordination materials. Spectroscopic and electronic analyses revealed that a two‐electron reaction occurred per active unit, accompanied by the reversible redox evolution of the C=N groups and Fe ions during the sodiation/desodiation. This work provides a promising and efficient strategy for boosting the electrochemical performance of organic electrode materials by the design of organometallic polymers.

Nano-organic polymers with rich redox sites as anode materials for dual-ion batteries

Organic electrode materials (OEMs) are considered one of the potential electroactive materials used in rechargeable batteries due to their high availability, low price, and sustainability. Nevertheless, the high solubility of their organic small molecules and their low electrical conductivity limit their practical applications. In this study, porous nanorods organic conjugated polymer were successfully prepared by a solvothermal method using 1,4,5,8-naphthalenetetracarboxylic anhydride and azodicarbonamide as precursors for dual-ion battery anodes. The successful synthesis of polymer extends the π-conjugated structure, effectively reducing its solubility in organic electrolytes. Moreover, the azo group (NN) in the polymer was easily conjugated with the adjacent aromatic ring, increasing the utilization of the active site, thereby improving the conductivity of the material so that the polymer has a high discharge capacity (90.5 mAh g−1 at 2 C, up to 96 % capacity retention). Even with a high rate of 10 C, the polymer still exhibits excellent electrochemical performance (50.0 mAh g−1 at 270 cycles). Moreover, reaction kinetics tests show that the electrode material was based on a pseudocapacitive storage mechanism influenced by diffusion and double-layer control. Therefore, the design strategy of such a material paves the way for the application of dual-ion batteries.

Electrolyte-triggered in-situ polymerization of multi-site organic cathodes for superior-longevity cation-anion co-storage secondary batteries

Organic electrodes are promising as next-generation energy storage materials owing to their diverse structures, low mass, and environmental friendliness. Nevertheless, the dissolution and degradation of organic active species in electrolytes are remaining obstacles to their authentic commercialization. Herein, we report an instantaneous in-situ upgrading strategy to convert multi-site organic cathode materials, e.g., 1-aminoanthraquinone (1-AAQ) and 1,5-diaminoanthraquinone (1,5-DAAQ), into poly(1-aminoanthraquinone) (PAAQ) and poly(1,5-diaminoanthraquinone) (PDAAQ) simply by dropping the electrolyte during battery assembly without extra operations. The remarkable chemistry is essentially a chemical polymerization process of redox-active organic monomers triggered by the electrolyte containing magnesium bis(hexamethyldisilazide) (Mg(HMDS)2) as an initiator. Notably, due to the π-conjugated polymer chain with inhibited dissolution, high conductivity, and improved stability, the as-obtained PDAAQ cathode delivered a high specific capacity (254 mAh/g at 100 mA/g), superior rate performance (83 mAh/g at 2000 mA/g), and excellent cycling stability for over 8000 cycles accompanied by an average capacity decay of only 0.0026 % per cycle. Detailed characterizations further explore the kinetic behaviors and verify a reversible hybrid cation–anion co-redox mechanism of PDDAQ cathode, which involves reversible Mg2+ cation insertion/extraction on AQ units and anion doping/de-doping reactions on the PANI backbones. Density functional theory (DFT) computations demonstrate the optimized structure of the discharged products and indicate that Mg2+ preferably interact with two carbonyls oxygen atoms and nitrogen atom for both PAAQ and PDAAQ. This study demonstrates an intriguing in-situ chemical-polymerization synthetic approach for preparing multi-site organic electrode materials that compromise structure optimization and synthetic efforts, offering great promise for high-performance and sustainable secondary batteries.

A Porphyrin-Phenylalkynyl-Based Conjugated Organic Polymer as a High-Performance Cathode for Rechargeable Organic Batteries.

Organic electrode materials (OEMs) have attracted much attention for rechargeable batteries due to their low cost, environment friendliness, flexibility, and structural versatility. Despite the above advantages, high solubility in electrolyte and low electronic conductivity remain critical limitations for the application of OEMs. In this work, the conjugated organic polymer (COP) poly([5,10,15,20-tetrakis(4-phenylalkynyl)porphyrin]Cu(II)) (PCuTPEP) is proposed as a cathode for high performance in organic lithium batteries. The polymerization inhibits the dissolution of the organic electrodes in the electrolyte, and the porphyrin and ethynyl-phenyl groups greatly expand the conjugated system and result in a high average discharge plateau at 4.0 V (vs Li+/Li). The PCuTPEP cathode exhibits a reversible discharge capacity of 119 mAh g-1 at a current of 50 mA g-1. Even at a high current density of 2.0 A g-1, excellent cycling stability up to 1000 cycles is achieved with capacity retentions of 88.5 and 90.4% at operating temperatures of 25 and 50 °C in organic lithium batteries, respectively. This study provides the approach for the development of organic cathodes for electrochemical energy storage.

Naphthalene Diimide-Based Cyanovinylene-Containing Conjugated Organic Polymers for Efficient Lithium-Ion Battery Electrodes.

The pursuit of innovative organic materials and the examination of the "structure-function" correlation in lithium-ion batteries (LIBs) are crucial and highly desirable. Current research focuses on the creation of novel conjugated organic polymers with polycarbonyl groups and examining the impact of electrode structure on the function of lithium-ion batteries. In this paper, two novel cyanovinylene-based conjugated organic polymers, NBA-TFB and NBA-TFPB, are synthesized using a Knoevenagel condensation reaction with naphthalene diimide as the integral unit. The performance of NBA-TFB and NBA-TFPB as cathodes in lithium-ion batteries is investigated. Improved conductivity and increased active site density in NBA-TFPB resulted in superior electrochemistry compared to NBA-TFB. Specifically, NBA-TFPB exhibited a larger reversible capacity (87.58 mAh g-1 at 0.2C and 88.34% retention after 100 cycles), exceptional rate capability (66.13 mAh g-1 at 5C), and robust cycling stability (99.58% coulombic efficiency at 1C and 60.71% retention after 2000 cycles). This study expands the family of diimide-based naphthalene polymers and provides a strategy for enhancing the performance of organic electrode materials containing polycarbonyl structure.

Research progress in benzoylpyridinium-based organic electrode materials

Research progress in benzoylpyridinium-based organic electrode materials

Free-Standing Poly(vinyl benzoquinone)/Reduced Graphene Oxide Composite Films as a Cathode for Lithium-Ion Batteries.

Quinones with a rapid reduction-oxidation rate are promising high-capacity cathodes for lithium-ion batteries. However, the high solubility of quinone molecules in polar organic electrolytes results in low cycle stability, while their low electric conductivity causes low utilization of electrode materials. In this article, a new p-benzoquinone derivative, poly(vinyl benzoquinone) (PVBQ), is designed and synthesized, and a solution-based method of preparing free-standing PVBQ/reduced graphene oxide (RGO) composite films is developed. PVBQ has a high theoretical specific capacity (400 mA h g-1) because of its low dead moiety mass. In the produced composite films, PVBQ nanoparticles are uniformly dispersed on RGO sheets, which endows the composite films with high electric conductivity and inhibits the dissolution of PVBQ through strong adsorption. As a result, the composite films show a high active material utilization, high practical specific capacity, and excellent cycling stability. PVBQ in the composite membrane containing 60.2 wt % RGO deliver 244 mA h g-1 capacity after 200 charge-discharge cycles at a current density of 300 mA g-1. At a current density of 1500 mA g-1, the reversible specific capacity is still 170 mA h g-1. This work provides a high-performance cathode material for lithium-ion batteries, and the molecular structure and electrode structure design ideas are also instructive for developing other organic electrode materials.

A low redox potential and long life organic anode material for sodium-ion batteries

Sodium-ion batteries (SIBs) with organic electrodes are an emerging research direction due to the sustainability of organic materials based on elements like C, H, O, and sodium ions. Currently, organic electrode materials for SIBs are mainly used as cathodes because of their relatively high redox potentials (>1 V). Organic electrodes with low redox potential that can be used as anode are rare. Herein, a novel organic anode material (tetrasodium 1,4,5,8-naphthalenetetracarboxylate, Na4TDC) has been developed with low redox potential (<0.7 V) and excellent cyclic stability. Its three-sodium storage mechanism was demonstrated with various in-situ/ex-situ spectroscopy and theoretical calculations, showing a high capacity of 208 mAh/g and an average decay rate of merely 0.022% per cycle. Moreover, the Na4TDC-hard carbon composite can further acquire improved capacity and cycling stability for 1200 cycles even with a high mass loading of up to 20 mg cm−2. By pairing with a thick Na3V2(PO4)3 cathode (20.6 mg cm−2), the as-fabricated full cell exhibited high operating voltage (2.8 V), excellent rate performance and cycling stability with a high capacity retention of 88.7% after 200 cycles, well highlighting the Na4TDC anode material for SIBs.

P/n-Type Polyimide Covalent Organic Frameworks for High-Performance Cathodes in Sodium-Ion Batteries.

Covalent organic frameworks (COFs) are viewed as promising organic electrode materials for metal-ion batteries due to their structural diversity and tailoring capabilities. In this work, firstly using the monomers N,N,N',N'-tetrakis(4-aminophenyl)-1,4-phenylenediamine (TPDA) and terephthaldehyde (TA), p-type phenylenediamine-based imine-linked TPDA-TA-COF is synthesized. To construct a bipolar redox-active, porous and highly crystalline polyimide-linked COF, i.e., TPDA-NDI-COF, n-type 1,4,5,8-naphthalene tetracarboxylic dianhydride (NDA) molecules are incorporated into p-type TPDA-TA-COF structure via postsynthetic linker exchange method. This tailored COF demonstrated a wide potential window (1.03.6 V vs Na+/Na) with dual redox-active centers, positioning it as a favorable cathode material for sodium-ion batteries (SIBs). Owing to the inheritance of multiple redox functionalities, TPDA-NDI-COF can deliver a specific capacity of 67 mAh g-1 at 0.05 A g-1, which is double the capacity of TPDA-TA-COF (28 mAh g-1). The incorporation of carbon nanotube (CNT) into the TPDA-NDI-COF matrix resulted in an enhancement of specific capacity to 120 mAh g-1 at 0.02 A g-1. TPDA-NDI-50%CNT demonstrated robust cyclic stability and retained a capacity of 92 mAh g-1 even after 10 000 cycles at 1.0 A g-1. Furthermore, the COF cathode exhibited an average discharge voltage of 2.1 V, surpassing the performance of most reported COF as a host material.

Insights into Mechanistic Aspect of Organic Materials for Aluminum-Ion Batteries.

Rechargeable aluminum-ion batteries (AIBs) with organic electrode materials have garnered significant attention due to their excellent safety profile, cost-effectiveness, and eco-friendly nature. This review delves into the intrinsic attributes of organic compounds and their impact on battery performance, mainly focusing on the alteration of ion interactions and charge storage mechanisms at the active sites. The ultimate aim is to propose innovative design approaches for AIBs that overcome the constraints associated with various types of organic materials. The review also discusses the application of advanced analytical tools, providing insights to better understand the electrochemical process of AIBs.

Novel metal-organic anode material by in-situ chelating Ni2+ with tannic acid on carbon nanotube for high-performance Li storage

Lithium-ion batteries (LIBs) with natural organic anode are attracting intensive interest for application owing to their structural diversity, cost-effectiveness, eco-friendliness, and high specific capacity. However, directly usage of natural organic materials as anode materials usually encounters poor electrochemical properties such as low reversible capacity and short cycling life. Thus, developing high-performance organic electrode materials for LIBs remains a great challenge. Herein, we present a rational design and fabrication of TA-Ni@CNTs by in-situ coating TA-Ni polymers onto the surface of carbon nanotubes (CNTs) as a superior anode material for LIBs. Specifically, the highly conductive CNTs can effectively relieve the aggregation of TA-Ni and improve the electronic conductivity. Meanwhile, the strong chelation among nickel irons and catechol groups enhances the structure stability and inhibits the dissolving property. Consequently, as an anode material for LIBs, the resulting TA-Ni@CNTs achieves a high reversible capacity of 1418.8 mAh·g−1 at 0.1 A·g−1 after 216 cycles and an outstanding cycling stability with 951.1 mAh·g−1 at 0.5 A·g−1 after 323 cycles. The presented design strategy holds great promise for developing more-efficient electrode materials for LIBs.