Porous NiCo2O4 nanotubes as a noble-metal-free effective bifunctional catalyst for rechargeable LiO2 batteries

Porous NiCo2O4 nanotubes have been successfully synthesized using a facile and cost-effective electrospinning method and used as a noble-metal-free catalyst for rechargeable Li-O-2 batteries. The as-synthesized NiCo2O4 nanotubes possess hollow cavities and porous walls, and were found to significantly improve the electrochemical performance of Li-O-2 batteries, by endowing them with a high initial discharge capacity, reduced overpotential as well as good rate capability. Excellent cycling stability over 110 cycles with a highly discharged voltage platform of 2.4 V at 200 mA g(c)(-1) was achieved. By means of FESEM, XRD, Raman spectroscopy and GITT analysis, toroidal-shaped Li2O2 particles were identified as the dominant discharge product and it was revealed that the Li2O2 can be completely decomposed during the charging process, indicating its superior reversibility as an effective bifunctional catalyst for Li-O-2 batteries. All the results indicated that the porous NiCo2O4 nanotubes expressed intriguing properties and great potential applications as a noble-metal-free effective bifunctional catalyst for rechargeable Li-O-2 batteries.