Machine Learning-Guided Solvation Engineering of Chiral Viologens for Durable Neutral Aqueous Organic Flow Batteries.

Journal: Angewandte Chemie (International ed. in English)
Published Date: Dec 30, 2025

Abstract

Conventional N-alkylated viologen electrolytes in neutral aqueous organic redox flow batteries (AORFBs) undergo irreversible nucleophilic SN2 dealkylation degradation. Moreover, trial-and-error molecular design often fails to resolve the solubility-stability trade-off in high-concentration systems. Here we report a machine learning (ML) strategy using large language models (LLMs) trained on over 1300 AORFB studies to predict chiral viologens with ortho-dihydroxy motifs. This bonding network forms a dynamic, pH-adaptive "solvation armor" that stabilizes the viologen structure. The R-/S-enantiomers (2.75/2.76 M) exhibit 1.66 times higher solubility versus RS-racemate. Molecular simulations and in situ spectroscopy confirm that the dihydroxy groups protect reactive C─N bonds via a solvation structure (unrelated to chiral effect), enhancing stability to pH 11. The 1 M R2+/R+• redox couple sets a new record by achieving 99.42% capacity retention over 3652 cycles. The 1 M R-based AORFB shows 100% retention over 533 cycles, outperforming quaternary ammonium- ([(NPr)2 V]Cl4, 94.92%) and sulfonate-modified viologen ((SPr)2 V), 65.49%). Stable cycling across 0.1 ∼ 2.5 M demonstrates decoupling of degradation from concentration. This strategy is validated by 2.5 kg-scale synthesis and Ah-class stack testing (98.65% retention over 77 cycles), demonstrating industrial scalability. This work establishes a generalizable, ML-enabled platform for electrolyte development, bridging molecular design and practical AORFB deployment.

Authors

  • Xu Liu
    School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore. [email protected].
  • HaiYan Yu
    Department of Food Science and Technology, Shanghai Institute of Technology, Shanghai 201418, China.
  • Xiaotong Deng
    Frontier Institute of Science and Technology, Interdisciplinary Research Center of Frontier science and technology, State Key Laboratory for Strength and Vibration of Mechanical Structures, Institute of New Concept Sensors and Molecular Materials, Shaanxi Key Laboratory of New Conceptual Sensors and Molecular Materials, Engineering Research Center of Key Materials for Efficient Utilization of Clean Energy of Shaanxi Province, National innovation Platform (Center) for Industry-Education Integration of Energy Storage Technology, Xi'an Key Laboratory of Electronic Devices and Material Chemistry, School of Physics, Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710049, China.
  • Jian-Yue He
    Frontier Institute of Science and Technology, Interdisciplinary Research Center of Frontier science and technology, State Key Laboratory for Strength and Vibration of Mechanical Structures, Institute of New Concept Sensors and Molecular Materials, Shaanxi Key Laboratory of New Conceptual Sensors and Molecular Materials, Engineering Research Center of Key Materials for Efficient Utilization of Clean Energy of Shaanxi Province, National innovation Platform (Center) for Industry-Education Integration of Energy Storage Technology, Xi'an Key Laboratory of Electronic Devices and Material Chemistry, School of Physics, Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710049, China.
  • Xuri Zhang
    Frontier Institute of Science and Technology, Interdisciplinary Research Center of Frontier science and technology, State Key Laboratory for Strength and Vibration of Mechanical Structures, Institute of New Concept Sensors and Molecular Materials, Shaanxi Key Laboratory of New Conceptual Sensors and Molecular Materials, Engineering Research Center of Key Materials for Efficient Utilization of Clean Energy of Shaanxi Province, National innovation Platform (Center) for Industry-Education Integration of Energy Storage Technology, Xi'an Key Laboratory of Electronic Devices and Material Chemistry, School of Physics, Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710049, China.
  • Junjie Huang
    Department of Surgery, Changxing People's Hospital, Huzhou, 313100, Zhejiang, China.
  • Zengrong Wang
    Frontier Institute of Science and Technology, Interdisciplinary Research Center of Frontier science and technology, State Key Laboratory for Strength and Vibration of Mechanical Structures, Institute of New Concept Sensors and Molecular Materials, Shaanxi Key Laboratory of New Conceptual Sensors and Molecular Materials, Engineering Research Center of Key Materials for Efficient Utilization of Clean Energy of Shaanxi Province, National innovation Platform (Center) for Industry-Education Integration of Energy Storage Technology, Xi'an Key Laboratory of Electronic Devices and Material Chemistry, School of Physics, Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710049, China.
  • Chenjing Liu
    Frontier Institute of Science and Technology, Interdisciplinary Research Center of Frontier science and technology, State Key Laboratory for Strength and Vibration of Mechanical Structures, Institute of New Concept Sensors and Molecular Materials, Shaanxi Key Laboratory of New Conceptual Sensors and Molecular Materials, Engineering Research Center of Key Materials for Efficient Utilization of Clean Energy of Shaanxi Province, National innovation Platform (Center) for Industry-Education Integration of Energy Storage Technology, Xi'an Key Laboratory of Electronic Devices and Material Chemistry, School of Physics, Xi'an Jiaotong University, Xi'an, Shaanxi Province, 710049, China.
  • Xin Zhang
    First Department of Infectious Diseases, The First Affiliated Hospital of China Medical University, Shenyang, China.
  • Gang He
    School of Economics and Management, Anhui University of Science and Technology, Huainan, China.

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