Single- Versus Dual-Ion UV-Cross-Linked Gel Polymer Electrolytes for Li–O2 Batteries

Abstract

Lithium-O2 batteries represent one of the most appealing candidates for battery electric vehicles (BEV) due to its remarkable theoretical high energy density, similar to fossil fuels. Solid polymer electrolytes represent a plausible solution to tackle some of the challenges associated to conventional liquid-based Li-O2 batteries, including safety concerns. Herein, cross-linked robust gel polymer electrolytes (GPE) based on poly(ethylene glycol) dimethacrylate (PEGDM) and tetraethylene glycol dimethyl ether (TEGDME) as plasticizer are prepared by rapid UV-photopolymerization. Both types of robust GPEs presented high ionic conductivity at room temperature (1.6·10−4 S·cm−1 and 1.4·10−3 S·cm−1 for single ion or dual ion, respectively). Both types of GPEs, single ion and dual ion lithium conductors, have been compared for the first time on Li-O2 cells. First, their performance was investigated in symmetrical Li|Li cells. In this case, the dual-ion GPE showed an outstanding behavior where the overpotential was <0.2 V vs Li0/Li+ for more than 40 hours at a current density as highs as ±1 mA·cm−2. On the other hand, in full Li-O2 configuration, the single ion GPE cell showed superior discharge capacity, up to 2.38 mAh·cm−2. A dynamic discharge characterization technique is proposed here as a method for evaluating the polarization effect in electrolytes during discharge in an easy, quantifiable and reproducible manner.