<i>In Situ</i> Fabrication of Quasi-Solid\nPolymer Electrolytes for Lithium Metal Battery via Photopolymerization-Induced\nMicrophase Separation

The photopolymerization-induced microphase separation\n(photo-PIMS)\nprocess involving a reactive polymer block was implemented to fabricate\nnanostructured quasi-solid polymer electrolytes (QSPEs) for use in\nlithium metal batteries (LMBs). This innovative one-pot fabrication\nenhances interfacial properties in LMBs by enabling <i>in situ</i> nanostructuring of QSPE directly onto the electrodes. This process\nalso allows for customization of QSPE structural dimensions by tweaking\nthe architecture and molar mass of poly[(oligo ethylene glycol) methyl\nether methacrylate-<i>co</i>-styrene] (P(OEGMA-<i>co</i>-S)) macromolecular chain transfer agent. Bicontinuous nanoscale\ndomains of soft P(OEGMA-<i>co</i>-S)/propylene carbonate/lithium\nbis(trifluoromethanesulfonyl)imide (LiTFSI) phase and hard poly[isobornyl\nacrylate-<i>co</i>-(oligo ethylene glycol)diacrylate] phase\nfurnished the QSPEs with respectively high ionic conductivity (0.34\nmS cm<sup>–1</sup> at 30 °C) and interesting level of\nmechanical strength (10<sup>6</sup>–10<sup>7</sup> Pa at 30\n°C). The as-prepared QSPE showed decent electrochemical properties\nand an electrochemical stability window of about 4.2 V vs Li<sup>+</sup>/Li. This electrolyte enables the Li||SPE||Li symmetric cell to cycle\nover 350 h at 0.1 mA cm<sup>–2</sup> without evidence of dendrite\nformation. By means of galvanostatic cycling studies on a prototype\nlithium metal battery with LiNi<sub>0.8</sub>Mn<sub>0.1</sub>Co<sub>0.1</sub>O<sub>2</sub> or LiFePO<sub>4</sub> positive electrodes,\nwe further demonstrate that the <i>in situ</i> nanostructured\nQSPE exhibited better performances than the corresponding stacked\nbattery.