Homogeneous polymer-ionic solvate electrolyte with weak dipole-dipole interaction enabling long cycling pouch lithium metal battery

Abstract

Solid polymer electrolytes (SPEs) are considered as promising electrolytes for high-voltage lithium metal batteries. Whereas, the strong dipole-dipole interaction in polymer electrolytes limits the enhancement of the ionic conductivity. Here, we propose the 1,1,2,2-Tetrafluoroethyl-2,2,3,3-Tetrafluoropropylether (TTE) diluent to significantly regulate the dipole-dipole interaction in polymer-ionic solvate electrolytes (TPISEs). The TTE encapsulates ionic solvate to reduce the dipole-dipole interaction of ionic solvate with the polymer matrix, which promotes their homogeneous distribution, creating a continuous ion percolating network among the polymer matrix. The ion conductivity of TPISEs is therefore enhanced to 1.27×10−3 S cm−1 at 25 °C. Meanwhile, the TTE induces the ionic solvate to transform from contact ion pairs to aggregates, contributing to a stable lithium/electrolyte interface with exchange current density 190 times larger than that without TTE. The Li||LiNi0.8Co0.1Mn0.1O2 full cells exhibit good cycling stability from −30 °C to 60 °C. The practical pouch cells consisting of a thin Li metal foil (50 μm) and a high-areal-capacity positive electrode (3.58 mAh cm−2) achieve a high specific energy of 354.4 Wh·kg−1 and maintain 78.1% capacity after 450 cycles at 54 mA g−1 and 25 °C. This work provides a design strategy for SPEs beyond the bottleneck of ionic conductivity for practical solid-state batteries.