Ultrathin Aramid/COF Heterolayered Membrane for Solid-State Li-Metal Batteries

Abstract

Ultrathin, ultrastrong, and highly conductive solid-state polymer-based composite electrolytes have long been exploited for the next-generation lithium-based batteries. In particular, the lightweight membranes that are less than tens of microns are strongly desired, aiming to maximize the energy densities of solid-state batteries. However, building such ideal membranes are challenging when using traditional materials and fabrication technologies. Here we reported a 7.1 μm thick heterolayered Kevlar/covalent organic framework (COF) composite membrane fabricated via a bottom-up spin layer-by-layer assembly technology that allows for precise control over the structure and thickness of the obtained membrane. Much stronger chemical/mechanical interactions between cross-linked Kevlar and conductive 2D-COF building blocks were designed, resulting in a highly strong and Li⁺ conductive (1.62 × 10^–4 S cm^–1 at 30 °C and 4.6 × 10^–4 S cm^–1 at 70 °C) electrolyte membrane that can prevent solid-state batteries from short-circuiting after over 500 h of cycling. All-solid-state lithium batteries using this membrane enable a significantly improved energy density.