Cross-linked Single-Ion Solid Polymer Electrolytes with Alternately Distributed Lithium Sources and Ion-Conducting Segments for Lithium Metal Batteries
Shaoshan Chen, Yu Li, Yong Wang, Zeyu Li, Cong Peng, Yiyu Feng, Wei Feng
Abstract
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 °C (1.96 × 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.