A Bridge between Ceramics Electrolyte and Interface Layer to Fast Li+ Transfer for Low Interface Impedance Solid‐State Batteries

Abstract Solid‐state batteries (SSBs) are regarded as next generation advanced energy storage technology to provide higher safety and energy density. However, a practical application is plagued by large interfacial resistance, owing to solid‐solid interface contact between ceramics electrolytes and Li anode. Introducing polymer‐based coating between electrolytes and Li anode is a feasible strategy to solve this issue. Unfortunately, current polymer is hard to achieve intimate contact at the atomic scale and lacks of a bridge to transfer Li + quickly between electrolytes and polymer coating. This gives rise to sluggish Li + transfer dynamics, huge interface impedance and greatly limits the effectiveness of this strategy. Herein, Poly(lithium 4‐styrenesulfonate)(PLSS) is introduced between Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZTO) electrolyte and Li anode. The theories and experiments prove the existence of strong coordinating interaction between SO 3 Li in PLSS and atoms on LLZTO surface. This interaction structures a bridge to migrate Li + fast across LLZTO/PLSS interface and hence interface impedance is as low as 9 Ω cm 2 . Moreover, the electron‐blocking feature of PLSS can prevent electrons from tunneling the LLZTO/PLSS interface and combining with Li + to form dendrite within LLZTO. PLSS‐base cells show improved long‐life cycling for 4700 h at 0.1 mA cm −2 at room temperature.