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

The photopolymerization-induced microphase separation (photo-PIMS) process involving a reactive polymer block was implemented to fabricate nanostructured quasi-solid polymer electrolytes (QSPEs) for use in lithium metal batteries (LMBs). This innovative one-pot fabrication enhances interfacial properties in LMBs by enabling <i>in situ</i> nanostructuring of QSPE directly onto the electrodes. This process also allows for customization of QSPE structural dimensions by tweaking the architecture and molar mass of poly[(oligo ethylene glycol) methyl ether methacrylate-<i>co</i>-styrene] (P(OEGMA-<i>co</i>-S)) macromolecular chain transfer agent. Bicontinuous nanoscale domains of soft P(OEGMA-<i>co</i>-S)/propylene carbonate/lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) phase and hard poly[isobornyl acrylate-<i>co</i>-(oligo ethylene glycol)diacrylate] phase furnished the QSPEs with respectively high ionic conductivity (0.34 mS cm^-1 at 30 °C) and interesting level of mechanical strength (10⁶-10⁷ Pa at 30 °C). The as-prepared QSPE showed decent electrochemical properties and an electrochemical stability window of about 4.2 V vs Li⁺/Li. This electrolyte enables the Li||SPE||Li symmetric cell to cycle over 350 h at 0.1 mA cm^-2 without evidence of dendrite formation. By means of galvanostatic cycling studies on a prototype lithium metal battery with LiNi_0.8Mn_0.1Co_0.1O₂ or LiFePO₄ positive electrodes, we further demonstrate that the <i>in situ</i> nanostructured QSPE exhibited better performances than the corresponding stacked battery.