Preparation Of Fe-N-C Modified Graphene Sponge And Its Electrochemical Performance

With the development of portable electronic market and the improvement oftransportation electrification, energy storage attracts more and more attention these days.Even though lithium-ion batteries have been widely applied as energy storage devices, thelow energy density and power density of LIBs limited their application in electric vehicles.In recent years, the lithium air battery receives wide attention both at home and abroad asit has super high theoretical energy density(~11400Wh kg-1). A lithium air battery consistsof a lithium metal anode, a porous air electrode, catalysts which are usually supported bythe porous cathode and electrolytes. According to the electrolyte used and the structuredifference of the batteries, lithium air batteries can be devided into four types: aqueoussystem, organic system, hybrid system and solid-state lithium air batteries. Researches onthe lithium air batteries are mainly concentrating on cathode materials, electrocatalysts,and electrolytes, et al. In this paper, we put our attention on the non-aqueous batterysystem and research on the combination of cathode and catalyst. The preparation ofFe-N-C/Graphene sponge and the its electrochemical performance as a cathode for lithiumair batteries were investigated.Non-noble metal catalysts based on Fe-N-C categories have been studied aspromising oxygen reduction reaction(ORR) catalysts in proton exchange membrane fuelcells (PEMFCs). However, the catalytic performance for oxygen evolution reaction (OER)in lithium-oxygen batteries has not been noticed too much. In this study, we report an easyprocess to prepare Fe-N-C composite based on flexible three dimensional (3D) graphenesponge (GS) which was proved to be high conductive, flexible and ultra-light (Fe-N-GS).The graphene sponge was synthesized through a hydrothermal reaction followed by afreezing dry process and the Fe-N-GS hybrid was obtained through heat treatment of ironphthalocyanine supported on GS. TEM of the composite shows a uniform dispersion of Fe-N-C catalysts over graphene nanosheets. Besides, the3D interconnectedstructure of Fe-N-GS composites ensures not only effective electron conductivity in theGS but also good contact between graphene sponge and Fe-N-C catalyst. Theelectrochemical tests show that the as-formed hybrids exhibit high capacity and excellentcycling performance as an cathode compared with pure GS as air electrode forlithium-oxygen batteries. The Fe-N-GS cathode materials for lithium-oxygen batterieswere proved to have effective catalytic properties with specific capacity as high as6762mAh g-1by using0.1M LiTFSI/dimethyl sulfoxide (DMSO) as electrolyte. In addition,the cell containing Fe-N-GS air electrode exhibited stable cyclic performance andeffective reduction of charge potential plateau. The charge end potential can be remainedat4.35V even after50cycles with controlled discharge-charge depth and the dischargevoltage plateaus remain to be stable. The results indicate the great potential of Fe-N-GScomposite to be applied as electrocatalyst in rechargeable lithium air batteries.