Single-Ion Lithium Conducting Polymers with High Ionic Conductivity Based on Borate Pendant Groups.

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Developing advanced electrolytes is crucial for improving lithium battery performance and safety.
• Single-ion conducting polymer electrolytes offer advantages over traditional liquid electrolytes, such as reduced leakage and improved safety.
• Borate-based polymers are being explored for their potential in creating highly conductive and stable lithium electrolytes.

Purpose of the Study:

• To synthesize and characterize a novel family of single-ion lithium conducting polymer electrolytes based on delocalized borate groups.
• To investigate the impact of substituents on the boron atom on the ionic conductivity of methacrylic polymers.
• To evaluate the potential of these electrolytes for lithium battery applications.

Main Methods:

• Synthesis of methacrylic polymers incorporating delocalized borate groups with varying substituents.
• Ionic conductivity measurements using electrochemical impedance spectroscopy.
• Determination of lithium transference number and electrochemical stability window.
• Fabrication and testing of lithium symmetrical cells using a gel polymer electrolyte.

Main Results:

• The synthesized lithium borate polymers exhibited high ionic conductivity, reaching 1.65×10^-4 S/cm at 60°C.
• Polymers with flexible and electron-withdrawing substituents showed the highest ionic conductivity among single-ion conducting homopolymers.
• A high lithium transference number (t<0xC2><0x80><0x8E>=0.93) and a wide electrochemical stability window (4.2 V) were achieved.
• A lithium symmetrical cell integrated with a gel polymer electrolyte demonstrated good performance, with low overpotential.

Conclusions:

• The developed lithium borate polymers represent a promising class of single-ion conductors for lithium batteries.
• The ability to tune ionic conductivity through substituent modification offers a pathway for optimizing electrolyte performance.
• These electrolytes show potential for enhancing the safety and efficiency of next-generation lithium battery technologies.