New Interpretation of the Performance of Nickel-Based Air Electrodes for Rechargeable Zinc–Air Batteries

Abstract

Rechargeable zinc−air batteries with high energy density, cycle life, and calendar life require corrosion-resistant support materials in the air electrode. Nickel-based air electrodes have shown promise in this regard as a substitute for conventional carbon-based air electrodes, but their performance in zinc−air batteries has not been studied in-depth. Specifically, the effect of the nickel (oxy)hydroxide passivating film on the electrode's catalytic performance and durability requires investigation. To fill this research gap, a method involving electrochemical estimation of the nickel (oxy)hydroxide film capacity was used to link the growth of the film to performance losses experienced on the air electrode after battery cycling. The main cause of voltage loss was the nickel (oxy)hydroxide film growing overtop of and inside the catalyst-coated nickel aggregates. This resulted in significant activation and mass transfer losses, where the latter losses were caused by the film growing overtop of the catalyst and accounted for at least 65% of the total voltage degradation at 10 mA cm −2 . Potential modifications to the electrode structure which could mitigate these voltage losses are discussed, including reducing the nickel particle aggregate size, using high-aspect ratio catalysts, and physically separating the catalyst and nickel particles with nonfilm-forming conductive additives.

Controlled Synthesis of Bifunctional NiCo2O4@FeNi LDH Core–Shell Nanoarray Air Electrodes for Rechargeable Zinc–Air Batteries

“…Furthermore, a curve with an arc shape (1.7−1.9 V) was observed in the charging process owing to metal nickel oxidation of Ni−O → Ni−O−OH, and the curve (1.8−1.6 V) in the discharging process appeared because of cation reduction of Ni−O−OH → Ni−O. 46,47 The unique core−shell structure makes this NiCo 2 O 4 @FeNi LDH bifunctional air electrode a promising candidate for rechargeable ZABs with high energy efficiency and ultralong stability.…”

(Co,Fe)3O4 Decorated Nitrogen‐Doped Carbon Nanotubes in Nano‐Composite Gas Diffusion Layers as Highly Stable Bifunctional Catalysts for Rechargeable Zinc‐Air Batteries

“…For instance, NiCo 2 O 4s catalysts on a Ni‐based GDL were prepared by Cano et al. and were cycled in a ZAB (6 M KOH) at 10 mA cm −2 . However, significant performance losses were reported after 50 h (∼55.6 % efficiency at 50 h).…”

Spinel Type Mn−Co Oxide Coated Carbon Fibers as Efficient Bifunctional Electrocatalysts for Zinc‐Air Batteries

“…Another example is the work by Cano et al, where NiCo 2 O 4 catalysts on a Ni-based GDL were prepared and cycled in 6 M KOH at 10 mA cm À 2 . [46] However, significant performance losses were reported after 50 h of cycling (~55.6 % efficiency). Performance then declined more rapidly until 100 h with a final discharge potential of ~0.1 V vs. Zn/ZnO.…”