## 3 Results and Discussion
Figure 3 shows the voltage profiles and cycle performances for CNF 1000, CNF 1200 and CNF 1400 electrodes. The electrochemical properties were evaluated with a limited capacity of 1000 mAh/g at a current density of 50 mA/g\({}_{\rm c}\) using 1 M LiPF\({}_{6}\)/tetra(ethylene glycol)dimethyl ether (TEGDME) as an electrolyte. As shown in Figure 3a, the CNF electrodes show the different shape in the voltage profiles depending on the pyrolysis temperature. The CNF 1000 electrode has the discharge plateau at the voltage of \(\sim\)2.63 V and the charge plateau at the voltage of \(\sim\)4.19 V at 1 st cycle, respectively, resulting in a large polarization of \(\sim\)1.56 V. It is observed that the steep potential drop during the ORR and the significant increase in the ORR potential after the first cycle. Although the CNF 1200 electrode shows the consistent voltage profile during the cycling, it exhibits also large polarization. On the  
Figure 2: Analysis of CNF 1000, 1200 and 1400 of (**a**) XRD patterns, (**b**) Raman results, XPS analysis (**c**) C1s and (**d**) O1s. other hand, the CNF 1400 electrode has small polarization of \(\sim\)1.16 V with OER potential under 4 V, which leads to the improvement in cycle performance. The CNF electrodes exhibit markedly different cycle performances. (Figure 3d-f) The CNF 1000 electrode works only for 5 cycles. Even though the CNF 1200 electrode exhibits slightly enhanced cycle performance compared to that of the CNF 1000 electrode, it also shows fast degradation after 9 cycles. On the other hand, the CNF 1400 electrode exhibits the stable cyclability for 50 cycles. The enhanced cyclability of the CNF 1400 electrode is attributed to the high graphitization degree, confirmed by the TEM in Figure 1, and reduced defects on the surface. In Table 1, the Li-O\({}_{2}\) batteries performances of various carbon electrodes are summarized. The charge and discharge voltage (V) difference of CNF webs pyrolyzed at 1000, 1200, and 1400 \({}^{\circ}\)C are lower than the other carbon electrodes [7; 13; 32; 33; 34; 35; 36; 37; 38; 39]. The morphological changes of the CNF webs were carefully monitored after the discharging and charging within a limited capacity of 1000 mAh/g. As shown in Figure 4a,b,e,f,i,j, the discharging products were homogeneously formed on the surfaces of all CNF electrodes without any blocking and clogging. In the case of the CNF 1000 electrode, the diameter of discharging product is several \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Carbon Materials (for Oxygen Electrode)**} & \multicolumn{3}{c}{**Differences of**} & \multirow{2}{*}{
\begin{tabular}{c} **Capacity** \\ **Change and** \\ **Discharge Village (V)** \\ \end{tabular} } & \multirow{2}{*}{**Ref.**} \\  & & & & \\ \hline Super P carbon + \(\alpha\)-MnO\({}_{2}\) & LiPF\({}_{6}\)-PC & 1.3 & 70 mAhg-c\({}^{-1}\) & 1000 & [32] \\ Cheylon carbon + & & & 0.1 mAcm\({}^{-2}\) (discharge) & 520 & [33] \\ Co-phthalocyanine & LiPF\({}_{6}\)-PC-EC-PAN & 0.92 & 0.05 mAcm\({}^{-2}\) (charge) & 520 & [33] \\ Super P carbon + MnO\({}_{2}\) & LiTFSi-PC & 1.8 & 0.02 mAhg-c\({}^{-1}\) & 800 & [34] \\ BP2000 carbon + MnO\({}_{2}\) & LiPF\({}_{6}\)-TEGDME & 1.4 & 0.13 mAhg-c\({}^{-1}\) & 800 & [35] \\ Super P carbon & LiPF\({}_{6}\)-TEGDME & 1.8 & 70 mAhg-c\({}^{-1}\) & 3000 & [36] \\ Carbon on carbon paper & LiCF\({}_{6}\)-TEGME & 1.7 & 500 mAhg-c\({}^{-1}\) & 3000 & [37] \\ CNT fibril & TEGME & 1.6 & 2000 mAhg-c\({}^{-1}\) & 1000 & [38] \\ All carbon-nanofiber & LiPF\({}_{6}\)-EC-DMC & \(\sim\)1.55 & 43 mAhg-c\({}^{-1}\) & \(-\)5000 & [7] \\ Graphene nanosheets & LiClO\({}_{4}\)-PC & 1.22 & 0.1 mAhg-c\({}^{-1}\) & 2332 & [13] \\ Porous graphene & DMSO & 1.579 & 200 mAhg-c\({}^{-1}\) & 29,375 & [39] \\ nanoarchitectures & CHF 1000 (this work) & LiTFSi-TEGEME & 1.58 & 50 mAhg-c\({}^{-1}\) & 1000 \\ CHF 1000 (this work) & LiTFSi-TEGEME & 1.42 & 50 mAhg-c\({}^{-1}\) & 1000 \\ CHF 1000 (this work) & LiTFSi-TEGEME & 1.16 & 50 mAhg-c\({}^{-1}\) & 1000 \\ \hline \hline \end{tabular}
\end{table}