Three‐dimensional interconnected graphene network‐based high‐performance air electrode for rechargeable zinc‒air batteries

Abstract

Abstract Although zinc‒air batteries (ZABs) are regarded as one of the most prospective energy storage devices, their practical application has been restricted by poor air electrode performance. Herein, we developed a free‐standing air electrode that is fabricated on the basis of a multifunctional three‐dimensional interconnected graphene network. Specifically, a three‐dimensional interconnected graphene network with fast mass and electron transport ability, prepared by catalyzing growth of graphene foam on nickel foam and then filling reduced graphene oxide into the pores of graphene foam, is used to anchor iron phthalocyanine molecules with atomic Fe‒N4 sites for boosting the oxygen reduction during discharging and nanosized FeNi hydroxides for accelerating the oxygen evolution during charging. As a result, the obtained air electrode exhibited an ultra‐small electrocatalytic overpotential of 0.603 V for oxygen reactions, a high peak power density of 220.2 mW cm‒2, and a small and stable charge‒discharge voltage gap of 0.70 V at 10 mA cm‒2 after 1136 cycles. Furthermore, in situ Raman spectroscopy together with theoretical calculations confirmed that phase transformation of FeNi hydroxides takes place from α‐Ni(OH)x to β‐Ni(OH)x to γ‐Ni(3+δ)+OOH for the oxygen evolution reaction and Ni is the active center while Fe enhances the activity of Ni active sites.

Keywords

• in situ Raman
• interconnected graphene network
• iron phthalocyanine
• NiFe hydroxide
• zinc‒air battery