Robust Interface Enabled by Bicontinuous‐Structured Electrolyte Elastomers for Solid‐State Battery Applications

Abstract Solid‐state electrolytes (SSEs) with high ionic conductivity, superior electrochemical stability, and mechanical durability are safe and reliable for solid‐state lithium (Li) batteries. However, most existing SSEs suffer from limited mechanical resilience and poor interface contact, impeding their practical deployment. Here, an in situ phase separation strategy is proposed to construct a class of elastomeric solid‐state electrolytes with bicontinuous architecture. The rigid phase ensures high ionic conductivity (7.8 × 10 −4 S cm −1 at 25 °C), while the elastic phase provides excellent elastic restorability (82%) and strong interface contact (adhesion energy ≈43.9 J m −2 ). This bicontinuous structure endows the material with superior stretchability (1800%), fatigue resistance, and puncture strength, while maintaining interface contact, keeping mechanical integrity of the battery structure during cycling, and restraining the dendrite growth. Consequently, symmetric batteries exhibit no short‐circuiting even after 2000 h of operation, and Li–metal batteries demonstrate high specific capacity. Solid‐state Li–O 2 batteries fabricated with the P(BA‐SN)‐IL electrolyte also exhibit good cycling performance (500 cycles), and the Li–O 2 pouch cell achieves stable cycling and superior feasibility under various abuse tests, including bending and squeezing. The bicontinuous‐structured elastomer electrolytes present a highly promising strategy for enabling safe operation of high‐energy solid‐state batteries.