Hybridizing polymer electrolyte with poly(ethylene glycol) grafted polymer-like quantum dots for all-solid-state lithium batteries

Abstract

Solid-state polymer electrolytes (SPEs) show great potential owing to inherent flexibility and safety but limited by the low ionic conductivity. Herein, poly (ethylene glycol) grafted polymer-like quantum dots (PPQDs) with average diameter of ~2.5 nm and abundant conduction groups are synthesized as nanofillers for hybrid polymer electrolytes. The functionalization of poly (ethylene glycol) provides abundant Li+ transfer sites and meanwhile enhances the compatibility between PPQDs and poly (ethylene oxide) (PEO). Accordingly, these PPQDs uniformly disperse and form rich networks with PEO chains to effectively reduce the crystallinity of PEO and promote the dissociation of lithium salts, different from large-size or inorganic fillers. Consequently, efficient ion-conductive networks are constructed by PPQDs and PEO for vertical Li+ conduction: 5.53 × 10−5 S cm−1 at 30 °C, 16 times higher than that of PEO electrolyte. Furthermore, the hydrogen-bonding interactions at PPQD-PEO interfaces afford excellent stability and flexibility to electrolytes. And superior cycling performance of ~146 mAh g−1 after 150 cycles at 1.0C with capacity decay of 0.046% per cycle is therefore achieved. Compared with traditional fillers, PPQDs with inherent advantages, i.e., molecular-level size and designable groups, endow hybrid electrolytes with dramatically enhanced ion conduction and stability, manifesting great potential for all-solid-state lithium batteries.