Ion-Dipole Interaction Regulation Enables High-Performance Single-Ion Polymer Conductors for Solid-State Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Solid-state batteries require electrolytes with high ionic conductivity, transference numbers, and electrode compatibility.
• Traditional dual-ion polymer conductors suffer from polarization and side reactions, limiting their use.

Purpose of the Study:

• To develop novel single-ion polymer conductors (SIPCs) for advanced solid-state batteries.
• To overcome limitations of dual-ion conductors by enhancing ion selectivity and stability.

Main Methods:

• Precisely regulating ion-dipole interactions between Li+ ions and polymer functional groups (carbonyl/cyano).
• Synthesizing single-ion polymer conductors (SIPCs) with tailored properties.
• Fabricating and testing LiFePO4-based solid-state cells with the developed SIPCs.

Main Results:

• Achieved exceptional Li-ion transference numbers (up to 0.93) and high room-temperature ionic conductivity (~10^-4 S cm^-1).
• Demonstrated a wide electrochemical stability window (>4.5 V vs Li/Li+) and excellent stability with Li metal.
• Observed good rate and cycling performance in LiFePO4 cells across a wide temperature range (-20 to 90 °C).
• Successfully prepared sodium- and potassium-based SIPCs with similar high performance.

Conclusions:

• The developed SIPCs provide a promising pathway for high-performance, safe solid-state batteries.
• Regulating ion-dipole interactions is a key strategy for designing advanced ion conductors.
• The findings extend to the development of other metal-ion systems beyond lithium.