Cross-linked Single-Ion Solid Polymer Electrolytes with Alternately Distributed Lithium Sources and Ion-Conducting Segments for Lithium Metal Batteries

Solid polymer electrolytes (SPEs), with improved energy densities and operational safety, have replaced liquid electrolytes in next-generation Li metal batteries (LMBs). However, the detrimental effect of anion polarization associated with a conventional dual-ion SPE caused by a relatively low Li-ion transference number prohibits its use in devices that require high power densities. Herein, an alternating copolymer slightly cross-linked by diamino polyethylene glycol (NH2-PEG-NH2) containing ethylene glycol oligomers associated with immobilized 4-styrenesulfonyl(4-(trifluoromethoxy)benzenesulfonyl)imide (SSTFMBSI-) anions (cross-linked-P[SSTFMBSILi-alt-(MA-g-mPEG8-NH2)]) was prepared. The homogeneous distribution of Li+ sources and conducting segments within the prepared single-ion SPE (SSPE) facilitated Li+ migration, with the slightly cross-linked structure reducing the crystallinity and providing mechanical strength for film formation. The SSPE exhibited an improved ionic conductivity at 30 degrees C (1.96 x 10(-5) S/cm) and a wide electrochemical window with Li metal contact. Compared to LMBs with traditional poly(ethylene oxide)-based SPEs, LMBs with the prepared SSPE exhibited good rate capability and cycling life, indicating potential for applications in next-generation safe LMBs.