In-situ cobalt-nickel alloy catalyzed nitrogen-doped carbon nanotube arrays as superior freestanding air electrodes for flexible zinc-air and aluminum-air batteries.

A flexible air electrode with excellent activity and outstanding stability is highly desirable for metal-air batteries. Herein, the rational design of CoNi alloys derived intertwined N-doped carbon nanotube arrays onto carbon cloth (CoNi@NCNTs/CC) is reported, as self-supported air electrodes for flexible zinc-air and aluminum-air batteries. CoNi@NCNTs/CC exhibits a low potential of 1.56 V at 10 mA cm−2 in OER, along with a half-wave potential of 0.82 V in ORR, which is attributed to abundant active sites including CoNi alloys with optimized adsorption energy, Co/Ni-N x and N-doped CNTs. The well-designed nanotube array construction with substantial channels on carbon cloth facilitates the mass diffusion and electron delivery, and improves mechanical flexibility. Combining excellent activity and promising flexibility, CoNi@NCNTs/CC based liquid- and all-solid-state zinc-air batteries exhibit excellent charge/discharge capability and long-term stability. And the liquid- and all-solid-state aluminum-air batteries deliver promising discharge property with a high open circuit voltage as well as commendable flexibility. [Display omitted] • CoNi alloys derived N-doped carbon nanotube arrays on carbon cloth as freestanding flexible air electrodes. • The freestanding catalysts exhibit excellent bifunctional catalytic activity and stability for OER and ORR. • The air electrode enables excellent performance for liquid- and solid-state zinc-air and aluminum-air batteries. [ABSTRACT FROM AUTHOR]