Fluorinated covalent organic framework with accelerated oxygen transfer nano-channels for high performance zinc-air batteries.

The establishment of abundant three-phase interfaces with accelerated mass transfer in air cathodes is highly desirable for the development of high-rate and long-cycling rechargeable zinc-air batteries (ZABs). Covalent Organic Frameworks (COFs) exhibits tailored nano-pore structures, facilitating the rational tuning of their specific properties. Here, by finely tuning the fluoridated nanopores of COF, we unprecedentedly designed and synthesized a novel high-performance air cathode for rechargeable ZABs. COF nanosheets were decorated with fluoridated alkyl chains, which shows high affinity to O 2 , in its nanopores (fluorinated COF). The fluorinated COF nanosheets are stacked into well-defined O 2 transport channels, which were then assembled into aerophilic "nano-islands" on the hydrophilic FeNi layered-double-hydroxide (FeNi LDH) electro-catalyst surface. Therefore, the mass transport "highway" for O 2 and water are segregated on the nanoscale, which significantly enlarges the area of three-phase boundaries and greatly promotes the mass-transfer therein. ZABs based on the COF modified air cathode deliver a small charge/discharge voltage gap (0.64 V at 5 mA cm -2 ), a peak power density (118 mW cm -2 ), and a stable cyclability, far exceeding the conventional FeNi LDH air cathode. This work provides a feasible approach for the design of the air cathodes for high performance ZABs, and will expand the new application of COF. This article is protected by copyright. All rights reserved.