Decoupling Ionic Conductivity from Structural Rigidity Constraints of Solid Polymer Electrolytes through Microphase Separation Regulation

Solid polymer electrolytes (SPEs) are pivotal for solid-state batteries due to their high safety, structural versatility, and processability. However, the inherent trade-off between ionic conductivity and mechanical strength, arising from insufficient segmental relaxation and excessive chain flexibility, remains a fundamental challenge. To overcome this limitation, we engineered a bicontinuous microphase separated poly(ether-urethane) electrolyte by leveraging the equilibrium between thermodynamic driving forces and intermolecular interactions to decouple segmental relaxation from chain rigidity. Bicontinuous microphase structure facilitates rapid ion transport (1.1 × 10–3 S·cm–1) through continuous amorphous soft domains, while the hard segments ensure mechanical integrity (789% elongation at break, 13 MPa tensile strength). Consequently, the Li||Li symmetric cell demonstrates stable plating/stripping for 2,500 h and the Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) full cell retains 81% capacity over 300 cycles at 0.5 C. Our work establishes explicit microphase structure-electrochemical property correlations, providing a scalable design paradigm to break the conductivity-rigidity compromise in SPEs.