Electrochemically oxidized electronic and ionic conducting nanostructured block copolymers for lithium battery...

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Block copolymers offer dual electronic and ionic conductivity for advanced battery materials.
• Poly(3-hexylthiophene)-b-poly(ethylene oxide) (P3HT-PEO) is investigated as a conductive binder for solid-state batteries.
• Electrochemical doping with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt is key to tuning conductivity.

Purpose of the Study:

• To investigate the electronic charge transport properties of P3HT-PEO copolymers during lithium battery charge/discharge cycles.
• To evaluate the performance of P3HT-PEO as a conductive binder in LiFePO4-based electrodes.
• To explore the potential of conductivity switching for battery protection mechanisms.

Main Methods:

• Utilized a solid-state three-terminal electrochemical cell for simultaneous conductivity measurements and doping control.
• Measured electronic conductivity (σe,ox) of P3HT-PEO at various electrochemical oxidation levels.
• Incorporated P3HT-PEO as a binder in LiFePO4 positive electrodes for cycling tests.

Main Results:

• Electronic conductivity of P3HT-PEO increased from 10⁻⁷ S/cm to 10⁻² S/cm with increasing oxidation.
• Binder conductivity ranged from 10⁻⁴ to 10⁻² S/cm during most of the charge/discharge cycle, enabling high capacities.
• Conductivity sharply dropped to 10⁻⁷ S/cm at the end of discharge, indicating a transition to an insulating state.

Conclusions:

• P3HT-PEO functions as an effective conductive binder, facilitating efficient charge transport in solid-state batteries.
• The binder's ability to switch between conducting and insulating states offers a novel method for automatic overdischarge protection.
• This dynamic conductivity switching presents a promising strategy for enhancing battery safety and performance.