High-Performance Quasi-Solid-State Calcium-Ion Batteries from Redox-Active Covalent Organic Framework Electrolytes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Calcium ion batteries (CIBs) offer high volumetric capacity and earth abundance, but face challenges from sluggish ion transport and anode passivation.
• Developing stable and efficient electrolytes is crucial for high-performance CIBs.

Purpose of the Study:

• To synthesize redox covalent organic frameworks (COFs) as quasi-solid-state electrolytes (QSSEs) for CIBs.
• To address challenges of ion transport and cycling stability in CIBs.

Main Methods:

• Preparation of two types of redox COFs (PT-COFs and PQ-COFs) with varying carbonyl group densities.
• Characterization of ionic conductivity, Ca2+ transference number, and electrochemical performance in full calcium ion cells.

Main Results:

• PT-COFs exhibited ionic conductivity of 0.46 mS cm-1 at room temperature and 5.05 mS cm-1 at 80 °C, with a Ca2+ transference number of 0.532.
• The full calcium ion cell using PT-COFs achieved a reversible specific capacity of 155.9 mAh g-1 at 0.15 A g-1 and maintained over 74.6% capacity after 1000 cycles at 1 A g-1.

Conclusions:

• Redox COFs, particularly PT-COFs, are effective QSSEs for high-performance CIBs.
• This study highlights the potential of redox COFs in advancing solid-state electrolyte technology for next-generation energy storage.