Design of High‐Entropy Tape Electrolytes for Compression‐Free Solid‐State Batteries

Abstract Advanced solid electrolytes with strong adhesion to other components are the key for the successes of solid‐state batteries. Unfortunately, traditional solid electrolytes have to work under high compression to maintain the contact inside owing to their poor adhesion. Here, a concept of high‐entropy tape electrolyte (HETE) is proposed to simultaneously achieve tape‐like adhesion, liquid‐like ion conduction, and separator‐like mechanical properties. This HETE is designed with adhesive skin layer on both sides and robust skeleton layer in the middle. The significant properties of the three layers are enabled by high‐entropy microstructures which are realized by harnessing polymer–ion interactions. As a result, the HETE shows high ionic conductivity (3.50 ± 0.53 × 10 −4 S cm −1 at room temperature), good mechanical properties (toughness 11.28 ± 1.12 MJ m −3 , strength 8.18 ± 0.28 MPa), and importantly, tape‐like adhesion (interfacial toughness 231.6 ± 9.6 J m −2 ). Moreover, a compression‐free solid‐state tape battery is finally demonstrated by adhesion‐based assembling, which shows good interfacial and electrochemical stability even under harsh mechanical conditions, such as twisting and bending. The concept of HETE and compression‐free solid‐state tape batteries may bring promising solutions and inspiration to conquer the interface challenges in solid‐state batteries and their manufacturing.