Development of industrial-scale L-shaped dielectric barrier discharge reactor for improving capacity retention of graphite anode using plasma pretreatment

Abstract

Abstract Electrode slurry coatings on the current collector of a Li-ion battery suffer from high mass loading owing to the severe floating of the binder during solvent drying. Atmospheric plasma pretreatment of the Cu current collector forms a functional group on its surface, which forms a hydroxyl bond with the binder materials. However, the Cu foil transferred to a high-speed roll-to-roll machine undergoes displacement due to wrinkling. This foil displacement deteriorates the uniformity of the process results and the discharge stability. To overcome the above-mentioned limitations, in this study, we designed an L-shaped dielectric barrier discharge (DBD) reactor as a combination of the direct-type DBD reactor with high processing speed and a jet-type DBD reactor with high discharge stability for industrial-scale current collector pretreatment. Helium gas injected between a pair of L-shaped electrodes and an electrode with bipolar high-voltage power generated stable seed electrons, which led to a homogeneous discharge between the lower part of the L-shaped electrode and the high-speed moving Cu current-collector surface. The plasma-treated Cu current collector exhibited stronger solvent adhesion and improved surface tension. In addition, the graphite anode coated on the plasma-treated current collector showed high mechanical adhesion strength with the anode materials and high-capacity retention in the half-cell test.