Polyether‐b‐Amide Based Solid Electrolytes with Well‐Adhered Interface and Fast Kinetics for Ultralow Temperature Solid‐State Lithium Metal Batteries

Abstract Solid‐state lithium metal batteries (SSLMBs) are highly desirable for energy storage because of the urgent need for higher energy density and safer batteries. However, it remains a critical challenge for stable cycling of SSLMBs at low temperature. Here, a highly viscoelastic polyether‐ b ‐amide (PEO‐ b ‐PA) based composite solid‐state electrolyte is proposed through a one‐pot melt processing without solvent to address this key process. By adjusting the molar ratio of PEO‐ b ‐PA to lithium bis(trifluoromethanesulphonyl)imide (ethylene oxide:Li = 6:1) and adding 20 wt.% succinonitrile, fast Li + transport channel is conducted within the homogeneous polymer electrolyte, which enables its application at ultra‐low temperature (−20 to 25 °C). The composite solid‐state electrolyte utilizes dynamic hydrogen‐bonding domains and ion‐conducting domains to achieve a low interfacial charge transfer resistance (<600 Ω) at −20 °C and high ionic conductivity (25 °C, 3.7 × 10 −4 S cm −1 ). As a result, the LiFePO 4 |Li battery based on composite electrolyte exhibits outstanding electrochemical performance with 81.5% capacity retention after 1200 cycles at −20 °C and high discharge specific capacities of 141.1 mAh g −1 with high loading (16.1 mg cm −2 ) at 25 °C. Moreover, the solid‐state SNCM811|Li cell achieves excellent safety performance under nail penetration test, showing great promise for practical application.