Hydroxyl on the filler surface promotes Li+ conduction in PEO all-solid-state electrolyte

In this paper, the phenolic resin nano-spherical fillers (RFS) were added to PEO all-solid-state electrolytes, and the effect of surface groups (phenolic hydroxyl) of fillers on lithium ion conduction in PEO solid-state electrolyte was studied. It was found by AC impedance that the ion conductivity increased after adding 6% RFS (from 8.85 × 10 −5 to 2.88 × 10 −4 S cm −1 at 60 °C). It was unexpectedly found by DSC that RFS was different from traditional inert ceramics. It did not reduce the crystallinity of PEO in the matrix but lowered its the glass transition temperature, thereby increasing the ion conductivity. Infrared spectroscopy showed that the degree of complexation between Li + and ether oxygen segment in PEO decreased after RFS was added. It is speculated that the lithium ion partly complexed with the oxygen atom of the hydroxyl group to form Li + channels on the surface of RFS, and the effect of the hydrogen bond between the phenolic hydroxyl group and PEO can be ignored. The difference between the strength of this interaction is proved by theoretical calculation of its binding energy. Based on this, we propose that the hydroxyl group on the filler surface enhances lithium ion conduction mainly because the oxygen atoms in the hydroxyl group participate in the construction of lithium ion channels. • RFS filler can improve the conductivity of PEO solid-state electrolyte. • RFS filler reduces the degree of complexation between PEO and Li+. • Oxygen atoms in the hydroxyl groups on the RFS surface can complex with Li+ to form lithium ion transport channels.