The development of sustainable, high-performance energy storage systems has driven significant interest in all-organic proton batteries. These systems leverage redox-active organic materials and proton-conducting electrolytes to enable environmentally friendly and cost-effective energy storage. This study presents a novel approach using conducting redox polymers (CRPs) functionalized with quinone-based pendant groups and paired with nonstoichiometric protic ionic liquids (PILs) as the electrolyte. The CRPs are synthesized via postdeposition polymerization (PDP), allowing precise control over molecular architecture and enabling full utilization of starting materials. By optimizing the polymerization conditions, both quinizarin (Qz) and naphthoquinone (NQ)-based CRPs achieve their theoretical capacities. When combined into a rocking-chair configuration—Qz-CRP as cathode and NQ-CRP as anode—the system delivers a stable 0.8 V voltage output in a nonstoichiometric MeTriHTFSI-based PIL electrolyte. The resulting all-organic battery exhibits a discharge capacity of 62 mAh/g and retains 80% of its initial capacity after 500 cycles under rapid potentiostatic charging and galvanostatic discharge at 4.5 C. Notably, the design eliminates the need for conductive additives, relying solely on the intrinsic conductivity of the polymer backbone. This work demonstrates a scalable, eco-friendly pathway toward high-capacity, long-cycle-life proton batteries.
The growing demand for large-scale energy storage in electric vehicles and renewable grid integration necessitates alternatives to conventional lithium-ion batteries. These rely on scarce metals and pose environmental challenges due to high CO₂ footprints and complex recycling processes. Organic electrode materials offer a promising solution: they are derived from abundant elements, exhibit low toxicity, and can be processed under mild conditions. Among them, quinones stand out due to their high theoretical capacity, fast two-electron redox kinetics, and tunable redox potentials through chemical substitution.EphB6 Antibody medchemexpress However, their practical application is hindered by poor electrical conductivity and solubility in aqueous electrolytes. To overcome these issues, conducting redox polymers have been developed by covalently attaching redox-active moieties to conjugated polymer backbones. Such materials provide electronic percolation pathways while immobilizing active sites, preventing dissolution. In this work, thiophene-based ethynylpentiptycenylethynylene (EPE) units serve as the conductive backbone, functionalized with Qz and NQ pendants to form the cathode and anode materials, respectively. The use of a nonstoichiometric protic ionic liquid—1-methyl-1,2,4-triazole-based with partially protonated heterocycles—further enhances performance by enabling proton-coupled redox reactions, offering a wider electrochemical window than water (>1.23 V), and improving wettability for hydrophobic organic components.
Postdeposition polymerization (PDP) was employed to synthesize the CRPs.TSG101 Antibody MedChemExpress A pre-deposited trimer film of EPE-Qz or EPE-NQ was immersed in a mixed solvent electrolyte containing 0.PMID:34990596 1 M MeTriHTFSI/MeCN/H₂O. The neutral trimer remained insoluble, preserving structural integrity. Upon oxidation, radical cations formed transiently and exhibited partial solubility in the MeCN-rich medium. This controlled dissolution enables intermolecular coupling and chain growth without material loss. Cyclic voltammetry confirmed the formation of poly(QzH₂-EPE) and poly(NQ-EPE), showing well-defined redox peaks at 0.45 V and -0.35 V (vs Fc⁺/⁰), corresponding to Qz/QzH₂ and NQ/NQH₂ conversions. In situ EQCM measurements revealed a substantial mass increase during polymerization, primarily due to solvent uptake and TFSI⁻ anion doping. Estimated solvent content reached up to 49 wt%, indicating significant swelling. Conductance measurements showed a steady rise with potential, peaking at ~0.2 V, followed by a broad plateau—indicative of continuous doping across a wide potential range. This behavior confirms that the polymer backbone provides efficient electron transport pathways essential for redox conversion.
Optimization of the polymerization solvent composition was crucial. Pure MeCN caused excessive dissolution of the neutral trimer, leading to irreversible material loss. Pure H₂O prevented necessary intermediate dissolution, limiting chain growth. By tuning the MeCN volume fraction, an optimal balance was achieved. Maximum discharge capacities of 78 mAh/g (poly(NQ-EPE)) and 68 mAh/g (poly(QzH₂-EPE)) were obtained at 67% and 75% MeCN, respectively—matching theoretical values. SEM imaging revealed progressive morphological evolution: increasing MeCN content led to rougher, more porous films, culminating in a highly interconnected nanowire network at 100% MeCN. This suggests that solvent composition governs the rearrangement dynamics of radical intermediates during PDP. Polymer length analysis indicated average chain lengths of 14 and 9 thiophene units for poly(NQ-EPE) and poly(QzH₂-EPE), respectively, consistent with effective chain propagation. IR spectroscopy confirmed retention of key vibrational modes, verifying chemical fidelity.
When assembled into a full cell, the Qz-CRP cathode and NQ-CRP anode delivered a stable 0.8 V output. Galvanostatic discharge produced a clear voltage plateau near 0.8 V, with peak capacity observed at 0.78 V—consistent with the formal potential difference between the two redox couples. Rapid charging at 1 V (anode-limited) achieved full charge within 150 s, with an initial current density of 26 A/g. After 500 cycles, the cell retained 80% of its initial capacity, with minimal shift in dQ/dV peaks, indicating excellent cycling stability. Self-discharge experiments revealed that the cathode suffered from irreversible oxidation, leading to lower Coulombic efficiency in cathode-limited configurations. However, by limiting the oxidation potential, the anode-limited design suppressed these side reactions, achieving near-100% efficiency. The battery successfully powered a red LED when three cells were connected in series, demonstrating practical applicability.
In conclusion, this study establishes a robust framework for designing high-performance all-organic proton batteries. The synergy between PDP-synthesized CRPs and nonstoichiometric protic ionic liquids enables full access to theoretical capacity, exceptional cycle life, and fast kinetics. The elimination of conductive additives and reliance on earth-abundant materials underscores the sustainability of this approach. This work paves the way for next-generation energy storage systems that are not only efficient and durable but also environmentally responsible.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com
