Polymer-in-Ceramic Nanocomposite Solid Electrolyte for Lithium Metal Batteries Encompassing PEO-Grafted TiO2 Nanocrystals

Lithium Metal Batteries (LMB) require solid or quasi-solid electrolytes able to block dendrites formation during cell cycling. Polymer-in-ceramic nanocomposites with the ceramic fraction exceeding the one normally used as the filler (>10 divided by 15 wt%) are among the most interesting options on the table. Here, we report on a new hybrid material encompassing brush-like TiO2 nanocrystals functionalized with low molecular weight poly(ethylene oxide) (PEO). The nanocomposite electrolyte membranes are then obtained by blending the brush-like nanocrystals with high molecular weight PEO and LiTFSI. The intrinsic chemical compatibility among the PEO moieties allows a TiO2 content as high as similar to 39 wt% (90:10 w/w functionalized nanocrystals/PEOLiTFSI), while maintaining good processability and mechanical resistance. The 50:50 w/w nanocomposite electrolyte (18.8 wt% functionalized TiO2) displays ionic conductivity of 3 x 10(-4) S cm(-1) at 70 degrees C. Stripping/plating experiments show an excellent long-term behavior even at relatively high currents of 200 mu A cm(-2) . Upon testing in a lab-scale Li/electrolyte/LiFePO4 cell, the material delivers 130 mAh g(-1) and 120 mAh g(-1) after 40 and 50 cycles at 0.05 and 0.1 mA, respectively, with Coulombic efficiency exceeding 99.5%, which demonstrates the very promising prospects of these newly developed nanocomposite solid electrolyte for future development of LMBs. (C) 2020 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.