###### Abstract  
The lithium oxygen battery is a promising energy storage system due to its high theoretical energy density and ability to use oxygen from air as a \"fuel\". Although various carbonaceous materials have been widely used as a cathode material due to their high electronic conductivity and facial processability, previous studies mainly focused on the electrochemical properties associated with the materials (such as graphene and carbon nanotubes) and the electrode configuration. Recent reports demonstrated that the polarization associated with cycling could be significantly increased by lithium carbonates generated from the reaction between the carbon cathode and an electrolyte, which indicates that the physicochemical properties of the carbon cathode could play an important role on the electrochemical performances. However, there is no systematic study to understand these phenomena. Here, we systematically explore the electrochemical properties of carbon nanofibers (CNF) webs with different graphitization degree as a cathode for Li oxygen batteries. The physicochemical properties and electrochemical properties of CNF webs were carefully monitored before and after cycling. CNF webs are prepared at 1000, 1200 and 1400 \({}^{\circ}\)C. CNF web pyrolyzed at 1400 \({}^{\circ}\)C shows lowered polarization and improved cycle retention compared to those of CNF webs pyrolyzed at 1000 and 1200 \({}^{\circ}\)C.  
carbon nanofibers; electrospinning; lithium oxygen batteries 2018  
this reaction results in the formation of lithium carbonates film on the surface of carbon cathode, which significantly increases the charge polarization [3; 17; 18; 19; 20; 21]. To decrease polarization associated with formation/decomposition of Li\({}_{2}\)O\({}_{2}\), various transition metal oxides and novel metals have been explored as a catalyst [5; 22; 23; 24]. Although it is generally accepted that the electrocataly could enhance the kinetics associated with formation/decomposition of Li\({}_{2}\)O\({}_{2}\), their catalytic activity should be investigated in the stable electrolyte system to understand their substantive effectiveness and underlying mechanism. Regarding the catalytic effect of carbonaceous materials itself during the cycling, it is certain that carbon materials play an important role in electrochemical performances. Therefore, it is expected that the physicochemical properties and geometry of carbon based cathode could significantly affect upon the electrochemical performances. However, there is no systematic study to understand the effect of physicochemical properties of carbon cathode on the electrochemical performances, which is critical to improve the performances of Li-oxygen batteries.  
Here, we systematically study the electrochemical properties of carbon nanofibers (CNF) webs with different graphitization degree as a cathode for Li oxygen batteries. CNF webs are simply prepared using electrospinning method, and its graphitization degree was controlled by adjusting pyrolysis temperature [25; 26]. The three dimensional network structure of CNF web enables an efficient electron transport along one dimensional geometry and provides uniform pore structure [27]. The geometrical advantages of CNF webs allow us to investigate the influence of graphitization degree on the electrochemical performances without its degradation caused by the pore clogging associated with Li\({}_{2}\)O\({}_{2}\). The physicochemical properties and electrochemical properties of CNF webs were carefully monitored before and after cycling. The CNF web shows different electrochemical properties as a function of the graphitization degree. The CNF web with high graphitization degree exhibits the low polarization during OER/ORR reactions and improved cycle performance compared to those of the CNF webs with lower graphitization degree. These improvements could be attributed to the enhanced chemical stability came from the high graphitization degree.