Carbon electrodes supported with nickel oxide derived from olive pits for Li O2 air cathode

A hybrid carbon composite material comprising bio-derived activated carbon and nickel oxide (AC/NiO) has been designed to decrease charge overpotential and enhance cyclability of lithium-oxygen batteries (LOBs). The activated carbon products have been synthesized from olive seeds (S) via a physical activation process at different carbonization and activation temperatures. Activation reaction time and the effect of one-step and two-step physical activation processes were investigated to determine their effects on porosity, particle size, surface area, and yield % of AC products. The results demonstrated that the activated carbon produced in 3 h using one-step activation at 900 degrees C gave the highest surface area of 1048 m(2)/g. The electrochemical performance of products was further evaluated in LOB system. As a result, AC exhibited a low specific capacity of 3510 mAh g(-1) at a current density of 100 mAh g(-1) due to its poor catalytic activity and formation of parasite residues (such as Li2CO3). With this regard, flower-like nickel oxide was grown on the surface of AC to improve the catalytic activity of cathode materials. The AC particles provide numerous micro/meso/macropores that act as active sites (or nucleation sites) for the discharge reaction, while NiO on the AC surface forms a flower-like structure with good catalytic activity with its high adsorption behaviors in AC/NiO and enhances a higher specific capacity of 8870 mAh g(-1).