In Situ 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 in situ 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- co -styrene] (P(OEGMA- co -S)) macromolecular chain transfer agent. Bicontinuous nanoscale domains of soft P(OEGMA- co -S)/propylene carbonate/lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) phase and hard poly[isobornyl acrylate- co -(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 (10 6 –10 7 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 0.8 Mn 0.1 Co 0.1 O 2 or LiFePO 4 positive electrodes, we further demonstrate that the in situ nanostructured QSPE exhibited better performances than the corresponding stacked battery.