Designing porous and stable Au-coated Ni nanosheets on Ni foam for quasi-symmetrical polymer Li–air batteries

Abstract

Li–air cells have aroused intense interest because of their ultra-high specific energies, but their practical application is still hindered by many problems, such as the slurry reaction kinetics and serious parasitic reactions at the cathode, obvious liquid electrolyte decomposition/leakage, and passivation/pulverization issues at the anode. Herein, Au-nanoparticle-coated Ni nanosheets grown on Ni foam (Au/NNS-NF) were first fabricated and then reacted with molten Li to form Li-based Au/NNS-NF (Li@Au/NNS-NF), which was applied as an electrode in quasi-symmetrical Li–air cells in which a poly(methyl methacrylate)-based electrolyte is used. Due to the porous/stable framework, good conductivity, and uniform Au coating layer, Au/NNS-NF cathodes possess excellent ORR/OER properties and inhibit parasitic reactions in Li–air batteries, while the Li@Au/NNS-NF anodes exhibit superior lithiophilicity, reducing dendritic Li formation and electrode dimension changes. A Li@Au/NNS-NF-based symmetric battery exhibits an excellent lifespan beyond 1100 cycles at 1 mA cm⁻² and small overpotentials (∼20 mV), while the Au/NNS-NF cathode also shows better performance than a carbon electrode. Additionally, the polymer electrolyte possesses good stability and is leakproof, offering superior anode protection. Therefore, a quasi-symmetrical Au/NNS-NF-based polymer Li–air battery shows a large capacity of 13 764.2 mA h g⁻¹ at 500 mA g⁻¹ and long cycling life (150 cycles) with low overpotentials (<2 V), and corresponding soft-package cells also present excellent properties under bending and can even drive many devices.