Negative Effect of\nthe Calendering Process on the\nInterphase Formation and Electrochemical Behavior of Reduced Graphene\nOxide Electrodes

Many studies on electrode material development for rechargeable\nbatteries have focused on improving the intrinsic physicochemical\nand electrochemical properties of active materials, but the electrochemical\nperformances of batteries are exhibited by the overall electrode unit\nconsisting of active materials, conductive additives, and a binder.\nAdditionally, the electrodes have undergone an essential calendering\nprocess to enhance the physical contact between those components.\nTherefore, the electrochemical behavior and performance of a cell\nshould be analyzed at the electrode level, as the inherent properties\nof active materials might be changed in electrode preparation, including\nthe calendaring process and real-operating environments. In this study,\nwe aimed to understand the electrochemical properties of the reduced\ngraphene oxide (RGO)-containing electrodes rather than the RGO-active\nmaterials by studying the changes in the RGO electrode before and\nafter the calendering process. Specifically, the study investigates\nthe effect of the calendering process on the electrochemically active\ninterphase formation and electrochemical properties of the RGO electrode.\nWe found that the calendering process deteriorates the electrochemical\nproperties of RGO electrodes by impeding enough electrolyte wetting,\nlimiting the formation of thin and stable solid–electrolyte\ninterphase, and leaving unreacted RGO sheets. Additional experiments\nwith carbon-coated silicon/RGO composite electrodes demonstrate that\nafter the calendering process, the sequential participation of Si/C\nparticles in the electrochemical reaction resulted in much more severe\ncapacity degradation over repeated cycling processes. The studies\nsuggest that fine-controlling the number of RGO sheets and maintaining\nenough distance between those sheets even after the calendering process\nare required for the utilization of RGO in rechargeable batteries.