Study On The Engineering Characteristics Of Electrode Coating Process For Electronic Double Layer Capactior

Electronic Double Layer Capactiors (EDLCs) have attracted great interest in many areas due to their high power density and long cycle life, which is able to charge and discharge with large electricity in short time. The performance of EDLC is not only related with the kinds of electrode material, but also the manufacture conditions and amount of electrode material added to electrod paste or film thickness.At present, the electrode manufacturing process of the SuperCapacitor is lack of systematic research on production process.Hence, it is of important theoretical and practical significance to optimizethe process conditions for the electrode coating process.In this paper, a series of carbon based double layer capacitors were prepared by changing the formula of the electrode paste and the thickness of the coated wet film. The solid content concentration of electrode slurry, type of binder, the binder added amount and the thickness of the coated wet film were optimized according to the electrochemical performance evaluated by cyclic voltammetry, electrochemicalimpedance spectroscopy and galvanostatic charge/discharge. The variation law of the electrode performance with the production process conditions was established. The results are summaried as following.(1) The slurry concentration was optimized by evaluating its rheological behavior. The results showed that the viscosity of the slurry decreased with the increase of the shear rate, and increased with the increase of the solid concentration. At 25℃, when the shear rate is constant, the viscosity of the slurry did not change with time, indicating that the stability of the system is stable. When the slurry concentration is higher than 0.25 g/mL, it is difficult to obtain a uniform dispersion of the electrode paste.When the electrode slurry concentration is 0.225 g/mL, the as-prepared electrode could delivers good electrochemical performance with the specific capacitance of 34.3 F/g and good capacitance retention of 94.4% after 2000 cycles.(2) Three kinds of binders, including PVDF, CMC/SBR, and LA133were compared to prepare the optimized electrodes.When PVDF or CMC/SBR used as binder, the slurry had good flow and leveling properties with the viscosity of 2000-3000 mPa·s, making them easy to control the thickness of the electrode. On the other hand, the electrode paste viscosity is only 20-350 mPa/s using LA133 as binder. Furthermore, the optimized amount of PVDF and CMC/SBR were both 8 wt.%. In these cases, the specific capacitances were39.2 F/g and 34.7 F/g at 1 A/g for PVDF and CMC/SBR, respectively.(3)The optimized film thickness of the electrode was determined to be 60-90μm. For the electrode with the film thickness of 90μm, it could deliver the specific capacitance of 34.3 F/g at 1 A/gand a high retention of 94.4% after 2000 cycles.