Abstract: It is of great significance to enhance mass transfer and improve active surface area in cathodes for zinc–air batteries (ZABs), which promote oxygen reduction reaction (ORR) efficiency and power outputs. Nature has endowed some tissues with special structures to have efficient mass transfer properties and high active surface area. As an important mass transfer part of trees, xylem contains massive long and partially aligned channels, which provides numerous “passageway” and high active surface area for plants to facilitate the efficient transport of oxygen and inorganic salts. The multi-channel structures give an important insight to develop high efficient air cathode. Herein, 3D-printed bio-inspired multi-channel cathodes (BMCs), inspired by xylem structures, have been developed for high-performance ZABs via 3D printing. Channels of bionic cathode contribute to forming a continuous supply of oxygen from air. As a result, massive tri-phase boundary regions, where ORR happens, are formed inside of cathode. Moreover, the 3D-printed metal-based framework can facilitate electron transfer during ORR process. Benefiting from the multi-channel framework, the assembled ZABs with BMC-600 show excellent electrochemical performances in terms of the high power density of 170.1 mW cm?2 and a high open-circuit voltage of 1.51 V. Therefore, BMCs provide a potential alternative as promising cathode for metal–air batteries.

Key words: Zinc–air battery , · Bio-inspired , · 3D printing , · Mass transfer