An ionic liquid- and PEO-based ternary polymer electrolyte for lithium metal batteries: an advanced processing solvent-free approach for solid electrolyte processing

Abstract

A processing solvent-free manufacturing process for cross-linked ternary solid polymer electrolytes (TSPEs) is presented. Ternary electrolytes (PEODA, Pyr₁₄TFSI, LiTFSI) with high ionic conductivities of >1 mS cm⁻¹ are obtained. It is shown that an increased LiTFSI content in the formulation (10 wt% to 30 wt%) decreases the risk of short-circuits by HSAL significantly. The practical areal capacity increases by more than a factor of 20 from 0.42 mA h cm⁻² to 8.80 mA h cm⁻² before a short-circuit occurs. With increasing Pyr₁₄TFSI content, the temperature dependency of the ionic conductivity changes from Vogel–Fulcher–Tammann to Arrhenius behavior, leading to activation energies for the ion conduction of 0.23 eV. In addition, high Coulombic efficiencies of 93% in Cu‖Li cells and limiting current densities of 0.46 mA cm⁻² in Li‖Li cells were obtained. Due to a temperature stability of >300 °C the electrolyte guarantees high safety in a broad window of conditions. In LFP‖Li cells, a high discharge capacity of 150 mA h g⁻¹ after 100 cycles at 60 °C was achieved.