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

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journal contribution
posted on 04.01.2021, 16:07 by Marta Alvarez Tirado, Laurent Castro, Gregorio Guzmán-González, Luca Porcarelli, David Mecerreyes
Lithium–O2 batteries represent one of the most appealing candidates for battery electric vehicles because of their remarkable theoretical high energy density, similar to fossil fuels. Solid polymer electrolytes represent a plausible solution to tackle some of the challenges associated with conventional liquid-based Li–O2 batteries, including safety concerns. Herein, cross-linked robust gel polymer electrolytes (GPEs) based on poly­(ethylene glycol) dimethacrylate and tetraethylene glycol dimethyl ether as a plasticizer are prepared by rapid UV-photopolymerization. Both types of robust GPEs presented high ionic conductivity at room temperature (1.6 × 10–4 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 outstanding behavior where the overpotential was <0.2 V versus Li0/Li+ for more than 40 h at a current density as high as ±1 mA·cm–2. On the other hand, in the full Li–O2 configuration, the single-ion GPE cell showed superior discharge capacity, up to 2.38 mA·h·cm–2. Here, a dynamic discharge characterization technique is proposed as a method for evaluating the polarization effect in electrolytes during discharge in an easy, quantifiable, and reproducible manner.