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Open research questions in Aqueous and Flow Batteries

393 gap statements mined from Aqueous and Flow Batteries papers in our 7.9M-paper local library, which holds 6,563 papers on the topic — drawn mostly from each paper's own stated research gap, future-work, challenge and limitation notes, and its abstract. The ones listed below are a selection still marked open; each names the study that raised it, with a DOI link where the paper has one.

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What the literature leaves open

  • Future Work may focus on combining the complementary advantages of different polymer systems—for example, pairing the dendrite-suppressing properties of CSAM with a less proton-dependent cathode, or integrating PBI with an additional anti-dendrite protective layer on the zinc anode—may offer a viable route toward improved performance in next-generation flexible and wearable zinc-ion batteries.

    Towards Sustainable Energy Storage: Evaluating the Performance of Three Polymer Electrolytes for Zinc-Ion Batteries · 2026 · DOI

  • Due to their insufficient mechanical robustness, limited environmental adaptability, and difficulty in simultaneously achieving high ionic conductivity and long-term interfacial stability, the applicability of pristine PAM hydrogels in ZBBs is constrained.

    Emerging Polyacrylamide-Based Hydrogels as Electrolytes for Stable and Dendrite-Free Zn Anodes: Challenges, Strategies, and Perspectives · 2026 · DOI

  • Their value should be assessed from a system-level perspective rather than by cell-level energy density alone, because their main advantage lies in replacing passive structural mass, reducing redundant packaging, and enabling distributed energy storage within load-bearing components.

    Carbon-Fiber Structural Batteries: From Multifunctional Integration to Retained Reliability · 2026 · DOI

  • Further research into their derivatives, improved synthesis methods, and the development of multifunctional hybrid frameworks will be crucial for creating high-energy, durable, and cost-effective ZIBS.

    Critical Progress of Mn, Cu, Co, and V-MOFs and Their Derivatives as Promising Electrodes for Aqueous Zn-Ion Batteries · 2025 · DOI

  • Future research should consider optimizing the electrolyte composition and ratio design for electrolytes with different redox couples, aiming to enhance the energy conversion efficiency and extend the lifespan of redox flow batteries.

    Numerical Simulation of Impact of Different Redox Couples on Flow Characteristics and Electrochemical Performance of Deep Eutectic Solvent Electrolyte Flow Batteries · 2025 · DOI

  • As reviewed in this paper, the energy storage mechanism of manganese-based cathode materials remains highly debated, with no consensus reached to date.

    Advancing Zinc–Manganese Oxide Batteries: Mechanistic Insights, Anode Engineering, and Cathode Regulation · 2025 · DOI

  • Recent studies have identified the stripping process as a critical factor governing battery longevity, yet the underlying failure mechanisms remain poorly understood.

    In Situ Nanoscale Visualization of Stripping-Induced Failure Behavior in Aqueous Zinc Batteries · 2026 · DOI

  • Previously unexplored, the field of multi-metal alloying has been delved into with this work, filling a significant gap in the literature.

    Bimetal-Initiated Concerted Zn Regulation Enabling Highly Stable Aqueous Zn-Ion Batteries · 2024 · DOI

  • The cost, manufacturability, and scalability of additional multifunctional zinc-ion capacitor components (substrates, encapsulation layers) have not been systematically evaluated. Design strategies that minimize device costs while maintaining performance in these integrated systems require investigation toward grid-scale mass production.

    Multifunctional zinc-ion capacitors for energy storage · 2026 · DOI

  • The initial research on ZABs faced challenges due to poor chemical reactions on the zinc anode and slow oxygen reaction rates, - There is a need for innovative solutions to address the current challenges hindering the development of rechargeable Zn-air batteries.

    Sustainable zinc-air batteries: advances, challenges, and opportunities · 2026 · DOI

  • There is a need for more efficient and sustainable membranes for all-iron redox flow batteries (AIRFBs). Prior research has not fully addressed the issue of iron crossover through the membrane.

    All-Iron Redox Flow Batteries Using a DABCO-PPO Anion Exchange Membrane · 2026 · DOI

  • Summary of key advances HEs have emerged as a promising platform for addressing the two intertwined challenges in ZIBs: polyiodide shuttling at the cathode and Zn dendrite growth/corrosion at the anode. This review has systematically summarized the design principles and working mechanisms of HEs in ZIBs.

    Advances and challenges of hydrogel electrolytes for rechargeable zinc-iodine batteries · 2026 · DOI

  • The formation of irreversible discharge products limits the reversibility of Li||SOCl2 batteries. The lack of effective methods for creating localized high-concentration environments of molecular catalysts.

    Local-high-concentration molecular catalysts enabled by covalent organic frameworks for rechargeable Li | |SOCl2 battery · 2026 · DOI

  • The lack of effective methods for creating localized high-concentration environments of molecular catalysts.

    Local-high-concentration molecular catalysts enabled by covalent organic frameworks for rechargeable Li | |SOCl2 battery · 2026 · DOI

  • The lack of effective utilization of redox-active sites in covalent organic frameworks. The suboptimal electrochemical performance of covalent organic frameworks due to long-range AA-stacking structures.

    Formation Energy‐Dominated AB‐Stacking Structure Promotes Metal‐Covalent Organic Frameworks for High‐Performance Dual‐Ion Storage Potassium‐Ion Batteries · 2026 · DOI

  • This review has detailed the transition from fundamental mechanism discovery to advanced chemical strategies and practical system integration.

    Recent Advancements in Electrolytic Zn–MnO2 Batteries: Mechanistic Insights into Mn2+/MnO2 Deposition/Dissolution and Applications to Scalable Energy Storage · 2026 · DOI

  • Ionowaxes consisting of asymmetric tetraalkylammonium cations paired with long-chain organic acids have been demonstrated to form membranes with unique proton-selective conduction properties when deposited on porous polymer supports.

    Ionowaxes on Porous Polymer Supports Form Cheap, Robust and Exquisitely Selective Proton-Conducting Membranes · 2026 · DOI

  • The comparison was limited to the initial post-preconditioning state and the state after 50 cycles, and separate membrane-only and electrode-only replacement tests were not conducted.

    Condition-Dependent Open Circuit Voltage Behavior in Vanadium Redox Flow Batteries and Implications for State-of-Charge Estimation · 2026 · DOI

  • This term is used as a reliability-oriented umbrella concept rather than as a separate material property. Within this review, retained multifunctionality is defined as the preservation of electrochemical output, mechanical integrity, interfacial stability, and safety under coupled electrochemical, mechanical, thermal, and manufacturing-induced stresses.

    Carbon-Fiber Structural Batteries: From Multifunctional Integration to Retained Reliability · 2026 · DOI

  • First of all, the design of ionic conductivity and mechanical properties of the hydrogel electrolyte is still in need of further optimization.

    A Review of the Synthesis of Biopolymer Hydrogel Electrolytes for Improved Electrode–Electrolyte Interfaces in Zinc-Ion Batteries · 2024 · DOI

  • The rational design of well-matched positive electrode materials is crucial to fully unleash the potential of iron-ion batteries. Polyaniline positive electrodes for iron-ion batteries face limited redox-accessible groups and unstable −NH− sites.

    Phosphorus-activated carboxyl small molecule positive electrode for high specific capacity and long-life iron-organic batteries · 2026 · DOI

  • The energy density of ZICs, particularly areal and volumetric energy densities, requires further improvement. Multifunctional ZICs remain confined to the laboratory scale.

    Multifunctional zinc-ion capacitors for energy storage · 2026 · DOI

  • Optimization of the Zn: V electrolyte molar ratio. Investigation of the long-term stability of the modified electrode. Application of the surface modification strategy to other types of redox flow batteries.

    Regulating Zinc Nucleation via KOH-Etched and Cu-Coated Carbon Felt for Stable Zinc–Vanadium Redox Flow Batteries · 2026 · DOI

  • The investigation of the scalability and stability of the synthesised MnO₂/N–rGO nanocomposite. The exploration of other biogenic precursors for the synthesis of MnO₂/N–rGO nanocomposites. The development of more efficient bifunctional electrocatalysts for rZABs.

    Bifunctional Electrocatalytic Performance of Manganese Oxide/Nitrogen-Doped Reduced Graphene Oxide Nanocomposite for Rechargeable Zinc-Air Batteries · 2026 · DOI

  • The development of wearable AZIBs with improved electrochemical performance and mechanical flexibility. The exploration of new materials and architectures for wearable AZIBs. The integration of wearable AZIBs with other energy harvesting and sensing technologies.

    Integrated design of wearable aqueous zinc-ion batteries: From energy autonomy to intelligent sensing · 2026 · DOI

Most-cited papers in Aqueous and Flow Batteries

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Open questions raised by papers listed on this page include: (1) Recent studies have identified the stripping process as a critical factor governing battery longevity, yet the underlying failure mechanisms remain poorly understood (“In Situ Nanoscale Visualization of Stripping-Induced Failure Behavior in…”, 2026); (2) The cost, manufacturability, and scalability of additional multifunctional zinc-ion capacitor components (substrates, encapsulation layers) have not been systematically evaluated (“Multifunctional zinc-ion capacitors for energy storage”, 2026); (3) There is a need for more efficient and sustainable membranes for all-iron redox flow batteries (AIRFBs) (“All-Iron Redox Flow Batteries Using a DABCO-PPO Anion Exchange Membrane”, 2026); (4) The lack of effective methods for creating localized high-concentration environments of molecular catalysts (“Local-high-concentration molecular catalysts enabled by covalent organic…”, 2026); (5) The lack of effective utilization of redox-active sites in covalent organic frameworks (“Formation Energy‐Dominated AB‐Stacking Structure Promotes Metal‐Covalent…”, 2026). 393 gap statements have been mined from Aqueous and Flow Batteries papers in our 7.9M-paper local library, which holds 6,563 papers on the topic; the gaps come from whichever of those papers state one. They are mostly the research gaps the authors state and the papers' abstracts, plus future-work, limitations and challenges passages. The ones listed below are a selection still marked open; each names the study that raised it, with a DOI link where the paper has one, so you can read the original claim in context.

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