Synthesis of flexible pure graphene papers and utilization as free standing cathodes for lithium-air batteries

• Free-standing flexible graphene papers were produced with different thicknesses.
• Synthesized graphene papers were used as air breathing cathodes in Li-air battery.
• Graphene paper cathodes coded as 10G, 30G and 50G.
• Best results were observed from 50G which has 497 mAhg−1 capacity.
• Graphene cathodes exhibited good cyclability and continued up to 85 cycles.

In Lithium-air cathode, graphene containing materials have been reported as ideal cathode materials due to their large theoretical specific surface area, chemical stability, high electrical conductivity and charge capacity. In this study; three free-standing flexible graphene cathodes were produced with different thickness by vacuum filtration technique. For preparation of the graphene electrodes, graphene oxide (GO) papers were chemically reduced. Surface morphology of the produced graphene cathodes were characterized using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) was conducted to understand elemental composition of the GO paper. X-ray diffraction (XRD) technique and Raman spectroscopy were carried out to investigate the structure of the GO paper electrode. Moreover, specific surface area and porosity distribution of the GO paper was performed using Brunauer–Emmett–Teller (BET) method from N2 adsorption and desorption isotherms and the pore size were calculated using the Barrett–Joyner–Halenda (BJH) algorithm on the desorption branch. Electrochemical performance of the free-standing graphene electrodes were assessed in ECC-Air test cell from 1.5 V to 4.5 V at a constant current density.