Gas Analysis Formed in Dual Carbon Battery Using LiPF₆ in EC-Dmc

Lithium ion rechargeable battery has been used in various field including mobile device and the power source for electric cars. Because of the limited capacity and rate property, advanced type new battery with large energy density as well as rate property are required at present. Dual carbon battery consists of graphitic carbon for both anode and cathode, and charge and discharge is performed by intercalation of Li and PF6 for both cathode and anode. This battery has an advantage of high discharge potential like 5V and superior rate property and expecting as an advance type battery. However, this battery has disadvantage of low coulomb efficiency and this may be related with decomposition of electrolyte. In this study, gas formation during charge and discharge in dual carbon battery was investigated by using mass spectrometry. Formation of gas from anode and cathode was analyzed by using H-type cell and for cathode and anode, graphitic carbon of KS-6 (TIMCAL) and MAG-D(Hitachi Kase) was used and stainless mesh was used for current corrector. Ar gas was used for carrier gas and part of carrier gas was introduced to vacuum line and analyzed with quadrupole mass spectrometer (MS). From the result of MS analysis of the gases in DCB during charge and discharge, it was found that the formed gas in charge was mainly observed at potential lower than 4.5 V from anode and higher than 4.5 V from cathode in charging process. The formed gas was mainly assigned to C2H6, C2H4, and CO2 for both anode and cathode. Considering the potential, gas from anode seems to be assigned to formation of SEI layer and that from cathode was decomposition of electrolyte. Comparing with Li ion battery, gas formation amount is little larger in DCB and this mainly assigned to gas formation from cathode at higher potential. On the other hand, the amount of gas was strongly affected by conducting binder and electrolyte. Among the examined carbon binder, it was found that carbon black shows the smallest gas formation and so by using the carbon black, the amount of gas from cathode was suppressed. After second cycles, the amount of gas was greatly decreased and so this study revealed that gas formation is mainly observed at initial charge process.