A self-healing plastic ceramic electrolyte by an aprotic dynamic polymer network for lithium metal batteries

Abstract

Oxide ceramic electrolytes (OCEs) have great potential for solid-state lithium metal (Li⁰) battery applications because, in theory, their high elastic modulus provides better resistance to Li⁰ dendrite growth. However, in practice, OCEs can hardly survive critical current densities higher than 1 mA/cm². Key issues that contribute to the breakdown of OCEs include Li⁰ penetration promoted by grain boundaries (GBs), uncontrolled side reactions at electrode-OCE interfaces, and, equally importantly, defects evolution (e.g., void growth and crack propagation) that leads to local current concentration and mechanical failure inside and on OCEs. Here, taking advantage of a dynamically crosslinked aprotic polymer with non-covalent –CH₃⋯CF₃ bonds, we developed a plastic ceramic electrolyte (PCE) by hybridizing the polymer framework with ionically conductive ceramics. Using in-situ synchrotron X-ray technique and Cryogenic transmission electron microscopy (Cryo-TEM), we uncover that the PCE exhibits self-healing/repairing capability through a two-step dynamic defects removal mechanism. This significantly suppresses the generation of hotspots for Li⁰ penetration and chemomechanical degradations, resulting in durability beyond 2000 hours in Li⁰-Li⁰ cells at 1 mA/cm². Furthermore, by introducing a polyacrylate buffer layer between PCE and Li⁰-anode, long cycle life >3600 cycles was achieved when paired with a 4.2 V zero-strain cathode, all under near-zero stack pressure.