Weakly Coordinating Single-Ion Conductors Integrated with High-Dielectric Zwitterions for Accelerated Lithium-Ion Transport

Abstract

Single-ion conductors with immobile anions can suppress concentration polarization during the cycling in lithium metal batteries (LMBs), thereby inhibiting lithium (Li) dendrite formation. However, strong binding interactions between the anion and Li⁺ cation can hinder ion dissociation and transport within polymer electrolytes. Herein, weak-binding single-ion gel polymer electrolytes (WSGPE) are designed to enable fast ion transport while maintaining a high electrochemical stability window. The unique delocalized charge distribution of the weakly binding cyanamide-containing monomer, combined with the high dipole moment of the zwitterionic monomer as a decoupling agent, facilitates Li⁺ ion dissociation and reduces the activation energy for ion hopping. Consequently, the optimized WSGPE exhibits an ionic conductivity of 0.87 mS cm^-1, a near-unity transference number of 0.79, and a shear storage modulus of 0.27 MPa at room temperature. These exceptional ion transport and mechanical properties enable stable Li plating/stripping for over 500 h at 0.1 mA cm^-2 in Li symmetric cells, effectively suppressing dendrite growth. The design of weakly coordinating structures and the optimization process between ionic conductivity and the modulus is believed to facilitate the design of single-ion polymer electrolytes and the achievement of high-performance LMBs.

Keywords: lithium binding energies; lithium metal batteries; polymer electrolytes; single‐ion conductors; zwitterion.