Polyamine-Mediated Proton/TFSI^- Dual Capture Enables High-Voltage PEO-Based All-Solid-State Li Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) in all-solid-state lithium batteries (ASSLBs) degrade at high voltages (>3.8 V vs. Li+/Li).
• This degradation is caused by corrosive acids, primarily bis(trifluoromethanesulfonyl)imide (HTFSI), limiting ASSLB energy density.
• Current passive strategies fail to inhibit HTFSI generation effectively.

Purpose of the Study:

• To develop a proactive strategy for mitigating degradation in high-voltage ASSLBs.
• To inhibit the formation of corrosive acids (HTFSI) within the PEO matrix.
• To enhance the cycling stability and energy density of ASSLBs.

Main Methods:

• A polyamine-based agent was designed for dual capture of protons (H+) and TFSI- anions.
• The agent utilizes Brønsted-base sites and H-bond donors for electrostatic and H-bonding interactions.
• The agent was implemented in 4.2 V LiCoO2-based ASSLBs.

Main Results:

• The polyamine agent effectively captured H+ and TFSI- ions, suppressing HTFSI formation.
• ASSLBs with the agent showed exceptional cycling stability (>600 cycles at 1.0 C, 65°C).
• 95.5% capacity retention was achieved, outperforming existing high-voltage polymer-based ASSLBs.

Conclusions:

• A dual capture active strategy effectively mitigates both interfacial and bulk degradation in high-voltage ASSLBs.
• This approach significantly suppresses acid-catalyzed chain scission in the PEO matrix.
• The findings offer new insights for designing high-energy-density ASSLBs.