All-Polymer Nanocomposite as Salt-Free Solid Electrolyte for Lithium Metal Batteries
Jorge L. Olmedo‐Martínez, Rafael Del Olmo, Antonela Gallastegui, Irune Villaluenga, Maria Forsyth, Alejandro J. Müller, David Mecerreyes
Abstract
High Resolution Image Download MS PowerPoint Slide Solid polymer electrolytes that combine both a high lithium-ion transference number and mechanical properties at high temperatures are searched for improving the performance of batteries. Here, we show a salt-free all-polymer nanocomposite solid electrolyte for lithium metal batteries that improves the mechanical properties and shows a high lithium-ion transference number. For this purpose, lithium sulfonamide-functionalized poly(methyl methacrylate) nanoparticles (LiNPs) of very small size (20–30 nm) were mixed with poly(ethylene oxide) (PEO). The morphology of all-polymer nanocomposites was first investigated by transmission electron microscopy (TEM), showing a good distribution of nanoparticles (NPs) even at high contents (50 LiNP wt %). The crystallinity of PEO was investigated in detail and decreased with the increasing concentration of LiNPs. The highest ionic conductivity value for the PEO 50 wt % LiNP nanocomposite at 80 °C is 1.1 × 10 –5 S cm –1, showing a lithium-ion transference number of 0.68. Using dynamic mechanic thermal analysis (DMTA), it was shown that LiNPs strengthen PEO, and a modulus of ≈10 8 Pa was obtained at 80 °C for the polymer nanocomposite. The nanocomposite solid electrolyte was stable with respect to lithium in a Li||Li symmetrical cell for 1000 h. In addition, in a full solid-state battery using LiFePO 4 as the cathode and lithium metal as the anode, a specific capacity of 150 mAhg –1 with a current density of 0.05 mA cm –2 was achieved.