Synergistic Combination of Ether-Linkage and Polymer-in-Salt for Electrolytes with Facile Li+ Conducting and High Stability in Solid-State Lithium Batteries

In developing solid polymer electrolytes (SPEs), networked SPE (NSPE) and polymer-in-salt (PiS) configurations are effective strategies to achieve high ionic conductivity. The ether linkage of poly(ethylene oxide) (PEO) effectively dissociates salts, among which salt Li[N(SO2F)2] (LiFSI) exhibits excellent Li+-conductive characteristics. The present study synthesizes a PiS-NSPE comprising 55 wt% LiFSI and 45 wt% PEO-based NSPE. The PiS configuration creates aggregated Li+n-FSI−m domains for Li+ transport through the decoupling ion-conductive mechanism and the NSPE, with high-voltage tolerance, dissociates LiFSI and segregates the Li+n-FSI−m domains into interconnected clusters for Li+ percolation. With such a synergistic combination, the PiS-NSPE exhibits an ionic conductivity of 2.3×10−3 S cm−1 and a Li+-transference number of 0.69 at 30 ℃. Protected by LiFSI, the PiS-NSPE is electrochemically stable until 4.6 V (vs. Li/Li+). The elastic feature enables the PiS-NSPE to withstand the Li-anode volume change and the lithiophilic FSI−-derived interlayer facilitates smooth Li deposition. The high compatibility between the PiS-NSPE and electrode materials results in the excellent performance of commercial-scale cathodes (∼10 mg cm−2 in active mass) in batteries. The synergy between PEO-based NSPEs and high-content LiFSI is promising in realizing the practical application of SPEs in all-solid-state batteries.