Spatially Decoupled Ion Transport and Mechanical Robustness Enabled by a Molecular Scaffold Strap in Gel Polymer Electrolytes.

In situ gel polymer electrolytes (GPEs), which confine liquid electrolytes within a polymer matrix, are promising for realizing high-safety lithium (Li) metal batteries. However, the liquid phase and the polymer matrix act as reciprocal chokes: the liquid expedites ion transport but plasticizes the matrix and compromises its mechanical strength, whereas the matrix provides rigidity yet obstructs ionic conduction. In this study, we propose a molecular scaffold strap strategy that decouples the regulation of mechanical robustness and ion transport in GPEs. Specifically, six-arm monomers are employed to form a 3D polymer matrix, while ethylene glycol dibutyl ether, with a size-matched anchoring character, acts as a scaffold strap that strengthens adjacent polymer segments. Fluorinated carbonate cosolvents further facilitate Li+ transport and interfacial stability. The engineered GPE exhibits a high modulus of 8.9 MPa, ionic conductivity of 3.82 × 10-4 S cm-1, Li+ transference number of 0.68, and stable electrode interfaces. The Li||LiNi0.8Co0.1Mn0.1O2 pouch cell (2.7 Ah) achieves 87% capacity retention after 100 cycles and exhibits an elevated self-heating onset temperature of 160.7°C. Furthermore, a high energy density of 506 Wh kg-1 is demonstrated in the Cu||LiNi0.92Co0.03Mn0.05O2 pouch cell (3.5 Ah).