Covalent organic frameworks (COFs) demonstrate great potential in regulating ion transport and stabilizing electrode/electrolyte interfaces due to their tunable pore structures and multifunctional groups. Compared to widely used neutral COFs, ionic COFs (iCOFs) selectively bind target ions through strong electrostatic interactions, thereby accelerating ion dissociation. Furthermore, the charged framework of iCOFs induces interlayer electrostatic repulsion, promoting spontaneous stripping and thereby enhancing ion transport kinetics.
This study in situ constructed a low-crystallinity iCOF interfacial film on the surface of a zinc anode. The guanidino groups within the framework fix water molecules via hydrogen bonding, effectively suppressing side reactions; while Coulombic interactions between the positively charged framework and SO₄²⁻ promote Zn²⁺ dissociation, enabling stable ion transport and uniform zinc deposition. Benefiting from the enhanced electrochemical stability of the modified zinc anode, the assembled zinc metal pouch battery exhibits a reversible capacity of ~0.35 Ah g⁻¹ with a capacity retention rate of 98.72% over extended cycling. This work provides a model for utilizing iCOFs to regulate Zn²⁺ transport kinetics for next-generation energy storage systems.
Aqueous zinc metal batteries emerge as strong candidates for safe, sustainable energy storage due to their high theoretical capacity (5855 mAh cm⁻³, 820 mAh g⁻¹), favorable redox potential (−0.762 V vs. SHE), and environmental friendliness. However, their practical application is constrained by uncontrollable side reactions and dendrite growth. Specifically, slow Zn²⁺ transport exacerbates concentration polarization at the electrode/electrolyte interface, promoting Zn atom migration toward surface protrusions and intensifying deposition inhomogeneity. Furthermore, the high energy barrier required for Zn²⁺ desolvation limits the release of free Zn²⁺ ions, while active water molecules within the solvation shell become the primary catalyst for the hydrogen evolution reaction (HER). These challenges necessitate the design of a bifunctional interface to simultaneously regulate Zn²⁺ diffusion pathways and immobilize water molecules. While in situ interface modification plays a crucial role in stabilizing zinc anodes, questions remain regarding coating material selection and the underlying reaction mechanisms.
Covalent organic frameworks (COFs) are organic porous crystalline materials featuring periodic skeletons and well-defined pore structures, providing ordered ion transport pathways. Their customizable functional groups selectively bind anions/cations and solvent molecules, promoting metal ion dissociation in electrolytes. This combination of structural precision and tunable multifunctionality offers novel insights for addressing zinc electrodeposition challenges. Within COF-based artificial interfaces, ion transport primarily follows a “hopping mechanism,” where ion migration is facilitated by electrostatic interactions or functional group coordination. To accelerate Zn²⁺ transport, two key design principles must be satisfied: (1) suppressing concentration polarization and lowering the desolvation energy barrier to stabilize Zn²⁺ supply; (2) providing sufficient binding sites to enhance ion mobility, achievable through precise control of COF crystallinity and interlayer spacing.
Based on charge characteristics, COFs can be categorized into electrically neutral COFs (nCOFs) and ionic COFs (iCOFs). iCOFs retain the inherent periodicity and porosity of COFs while introducing charged groups in the backbone or side chains, offering multiple advantages. On one hand, nCOFs promote metal ion release through polar interactions, but weak interactions result in insufficient Zn²⁺ desolvation; whereas the strong electrostatic interactions in iCOFs enable selective binding to anions or metal cations. Furthermore, solvated molecules or ions can permeate the iCOF framework via ion exchange effects. This dual selectivity based on molecular sieving and charge interactions allows precise regulation of molecular/ionic adsorption and separation, thereby promoting efficient dissociation of ion pairs in electrolytes. Conversely, nCOFs form tightly layered stacks due to strong π-π interactions, potentially lengthening ion transport pathways. In contrast, the charged framework of iCOFs induces interlayer electrostatic repulsion, promoting spontaneous exfoliation into few-layer two-dimensional nanosheets. This structural transformation is crucial for enhancing ion transport kinetics.
Covalent organic frameworks (COFs) demonstrate great potential in regulating ion transport and stabilizing electrode/electrolyte interfaces due to their tunable pore structures and multifunctional groups. Compared to widely used neutral COFs, ionic COFs (iCOFs) selectively bind target ions through strong electrostatic interactions, thereby accelerating ion dissociation. Furthermore, the charged framework of iCOFs induces interlayer electrostatic repulsion, promoting spontaneous stripping and thereby enhancing ion transport kinetics.
This study in situ constructed a low-crystallinity iCOF interfacial film on the surface of a zinc anode. The guanidino groups within the framework fix water molecules via hydrogen bonding, effectively suppressing side reactions; while Coulombic interactions between the positively charged framework and SO₄²⁻ promote Zn²⁺ dissociation, enabling stable ion transport and uniform zinc deposition. Benefiting from the enhanced electrochemical stability of the modified zinc anode, the assembled zinc metal pouch battery exhibits a reversible capacity of ~0.35 Ah g⁻¹ with a capacity retention rate of 98.72% over extended cycling. This work provides a model for utilizing iCOFs to regulate Zn²⁺ transport kinetics for next-generation energy storage systems.
Aqueous zinc metal batteries emerge as strong candidates for safe, sustainable energy storage due to their high theoretical capacity (5855 mAh cm⁻³, 820 mAh g⁻¹), favorable redox potential (−0.762 V vs. SHE), and environmental friendliness. However, their practical application is constrained by uncontrollable side reactions and dendrite growth. Specifically, slow Zn²⁺ transport exacerbates concentration polarization at the electrode/electrolyte interface, promoting Zn atom migration toward surface protrusions and intensifying deposition inhomogeneity. Furthermore, the high energy barrier required for Zn²⁺ desolvation limits the release of free Zn²⁺ ions, while active water molecules within the solvation shell become the primary catalyst for the hydrogen evolution reaction (HER). These challenges necessitate the design of a bifunctional interface to simultaneously regulate Zn²⁺ diffusion pathways and immobilize water molecules. While in situ interface modification plays a crucial role in stabilizing zinc anodes, questions remain regarding coating material selection and the underlying reaction mechanisms.
Covalent organic frameworks (COFs) are organic porous crystalline materials featuring periodic skeletons and well-defined pore structures, providing ordered ion transport pathways. Their customizable functional groups selectively bind anions/cations and solvent molecules, promoting metal ion dissociation in electrolytes. This combination of structural precision and tunable multifunctionality offers novel insights for addressing zinc electrodeposition challenges. Within COF-based artificial interfaces, ion transport primarily follows a “hopping mechanism,” where ion migration is facilitated by electrostatic interactions or functional group coordination. To accelerate Zn²⁺ transport, two key design principles must be satisfied: (1) suppressing concentration polarization and lowering the desolvation energy barrier to stabilize Zn²⁺ supply; (2) providing sufficient binding sites to enhance ion mobility, achievable through precise control of COF crystallinity and interlayer spacing.
Based on charge characteristics, COFs can be categorized into electrically neutral COFs (nCOFs) and ionic COFs (iCOFs). iCOFs retain the inherent periodicity and porosity of COFs while introducing charged groups in the backbone or side chains, offering multiple advantages. On one hand, nCOFs promote metal ion release through polar interactions, but weak interactions result in insufficient Zn²⁺ desolvation; whereas the strong electrostatic interactions in iCOFs enable selective binding to anions or metal cations. Furthermore, solvated molecules or ions can permeate the iCOF framework via ion exchange effects. This dual selectivity based on molecular sieving and charge interactions allows precise regulation of molecular/ionic adsorption and separation, thereby promoting efficient dissociation of ion pairs in electrolytes. Conversely, nCOFs form tightly layered stacks due to strong π-π interactions, potentially lengthening ion transport pathways. In contrast, the charged framework of iCOFs induces interlayer electrostatic repulsion, promoting spontaneous exfoliation into few-layer two-dimensional nanosheets. This structural transformation is crucial for enhancing ion transport kinetics.
Dictating Zn2+ Transport Kinetics via Versatile Ionic Covalent Organic Framework for Robust Zn Metal Anodes - Zou - 2025 - Angewandte Chemie International Edition - Wiley Online Library