COF

Summary ⚙️

A polymer electrolyte reinforced with a covalent organic framework (COF) has been developed to improve rapid sodium-ion transport, while enhancing electrode interface stability in solid-state sodium batteries. This technological innovation raises fast-charging efficiency and extends battery life by providing organized and integrated ionic conduction channels prepared for industrial conditions. Research has shown a significant improvement in ionic conductivity and electrochemical stability at standard operating temperatures, with high tolerance over long charging and discharging periods.

Introduction: Solid-State Sodium Batteries and Their Role in Energy 🔋

Solid-state sodium batteries (solid-state sodium batteries) are distinguished as a promising option for safe and low-cost energy storage, due to the abundance of sodium and its distinctive electrochemical properties. However, the main challenge lies in achieving rapid ionic conduction and chemical and mechanical stability at the battery’s electrode interfaces, especially during fast charging (fast charging) and long cycles.

The challenges of conventional batteries relate to the reduced mobility of sodium ions (Na⁺) inside polymers due to high polymer crystallinity (polymer crystallinity) and weak ion coordination, which lowers ionic conductivity. Previous attempts to use inorganic fillers have faced issues such as particle agglomeration and mechanical incompatibility, leading to the formation of destructive dendrites and interface degradation.

Innovative Solutions: The Polymer-Reinforced Covalent Organic Framework (COF/PNSE) 🔧

Design and Preparation of COF with Sulfonate Groups

A covalent organic framework known as TpPa-SO₃-Na was synthesized using a Schiff-base condensation reaction between 1,3,5-triformylphloroglucinol and 2,5-diaminobenzenesulfonic acid, then the protons were replaced with sodium ions through ion exchange with sodium acetate.

The result was a framework with organized hexagonal pores, densely covered with -SO₃^–Na⁺ groups that enhance the guidance and transport of sodium ions within the nanochannels.

Integrating COF into a Highly Insulating PNSE Polymer

The TpPa-SO₃-Na framework was integrated into a fluorinated polymer matrix (PNSE) containing polar groups (C–F, C–Cl) that enhance the polymer’s strength and help better ion dissociation, contributing to greater stability.

The result was a composite electrolyte that combines mechanical strength with pathways for transporting Na⁺ ions, allowing rapid and orderly ion transport through the electrolyte.

Electrical and Mechanical Performance Analysis of the New Design 🧪

Structural and Mechanical Verification

Structural inspection techniques such as XRD, SEM, and TEM showed that the framework has high crystallinity and well-defined nanopores, in addition to a uniform chemical distribution of sulfonate and sodium groups.

Molecular dynamics simulation (MD) showed that Na⁺ ions cluster and move in a directed manner inside COF channels near -SO₃^– groups, compared with the random distribution state in the COF-free polymer.

Electrical and Experimental Properties

• The ionic conductivity of the composite electrolyte reached 1.2 mS cm^-1 at 30 degrees Celsius, outperforming the single polymer.
• Symmetric batteries using the composite electrolyte were tested for more than 6750 hours at a current density of 0.1 mA cm^-2, with low electrical polarization (~85 mV).
• The critical current for decomposition reached 1.9 mA cm^-2.
• On the cathode side, the electrolyte contributed to the formation of a composite layer rich in fluorides NaF and Na₂O, which reduced transition-metal dissolution and protected against electrochemical decomposition.
• The Na||NNM mini-cell delivered a charging capacity of 82.5 mAh g^-1 at a charging current of 1 A g^-1, with 77.2% capacity retention after 1000 cycles and stable charging up to 4.2 volts.

Detailed Analysis of Electrode Interfaces 🏭

Advanced analysis tools such as XAS and XPS revealed the formation of graded layers of NaF and Na₂O materials as key components at the electrolyte-cathode interface.

These layers act as a barrier protecting the battery electrodes from cracking and unwanted metal deposition, ensuring electrical stability over long and fast charging periods.

Analysis of electrochemical response mismatch during operation (operando EIS and DRT) confirmed reduced interfacial resistance and faster ion movement within the composite system.

Practical Demonstration Test: 1 Amp-hour Battery Cells 🚗

To prove practical applicability, pouch cells with a capacity of 1 Ah were manufactured using hard carbon as the anode and NFM as the cathode.

The results showed notable capacity retention of 87.3% after 488 charge and discharge cycles, confirming the effectiveness of the composite electrolyte under real operating conditions.

Conclusion and Outlook 🔥

The new technology presented through the use of a functional covalent organic framework within a fluorinated polymer matrix has proven its ability to enhance sodium-ion transport and stabilize interfaces inside solid-state batteries.

The main advantages include:

• High ionic conductivity reaching 1.2 mS cm^-1.
• Excellent electrical and mechanical stability under fast and long-term charging conditions.
• Reduced dendrite growth and protection of active interfaces from degradation and charging difficulty.
• Practical achievements in manufacturing 1 Ah cells with high tolerance.

This study represents a major step toward developing solid batteries with long-life fast-charging speed and greater safety and cost-effectiveness in energy storage, while opening prospects for improving materials and technologies in the ecosystem of mechanical and electrical battery engineering.

📚 مقالات ذات صلة

Cordmark Miyota Mixed-Use Building Design by Aida Atelier: An Architectural and Engineering Study

2026/09/05

Lenovo Confirms Legion Go Problems After Reports of Devices Failing for Users

2026/09/05

Wire Arc 3D Printing Technology Strengthens Local Clean Energy Supply Chains in Mechanical Engineering

2026/09/05