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Compositional graphitic cathode investigation and structural characterization tests for Na-based dual-ion battery applications using ethylene carbonate:ethyl methyl carbonate-based electrolyte
As significant as the electrolyte selection is for dual-ion battery applications, the characteristics of the graphitic cathode can also be decisive for the resultant cell operation. During this work, in order to find a promising electrode-electrolyte combination for Na-based dual-ion batteries, CCCV cycling tests were applied to different positive electrode compositions to optimize the effects of carbon black and binder as well as to mitigate the irreversible charge losses, by utilizing 0.5 M NaPF6/EC:EMC electrolyte which was found to be the most promising mixture in our preceding study. Electrodes consisting of 90 wt% KS6 graphite, 2 wt% carbon black and 8 wt% binder was found to be the most promising combination, and proved its superiority over SLP 30 type graphite, delivering 86.2 mAh/g discharge capacity by means of its lower particle size and larger surface area. Moreover, structural characterization tests of Raman spectroscopy and X-ray diffraction were implemented by providing qualitative and quantitative insights so as to elucidate and characterize the PF6− intercalation/de-intercalation characteristics for our Na-based dual-ion battery. The results of the tests acknowledged that the surface and the bulk of the electrode behave differently.