Efficient electrocatalysts for biomass quasi-solid-state Li–O2 batteries: porous nanocages with nickel–cobalt-N/C active species†

Abstract

Ordered porous materials can offer more accessible catalytic sites and large buffer space for discharge products, thus improving cell performance. In this paper, a simple down-top solution-precipitation method followed by pyrolysis was proposed to disperse active nickel–cobalt-NC sites in ZIF-derived porous carbon nanocages. It was found that these metal nanoparticles were confined in the N-enriched carbon nanocage with a total metal loading of about 8.74 at%. As expected, this porous structure not only enhances electron conductivity, but also provides a sufficient surface area to facilitate the triphasic cell reaction and create more space for the storage of discharge products. Experimental findings confirm that this interesting nanostructure manifests an increase in capacity (6682.6 mA h g⁻¹), coulombic efficiency (∼100%) and cycling performance (∼80 cycles) over the control group for quasi-solid-state cells. Benefitting from the addition of Ni to modify the porous structure, the O₂/ion diffusion pathway and accessible active sites are enriched, yielding faster redox kinetics and lower overpotential (high reversibility). Thus, our work demonstrates that this type of porous bimetallic nanocage is promising for fabricating efficient biomass quasi-solid-state Li–O₂ batteries.