Capacitance Optimization of Planar Carbon-based Supercapacitor

Abstract

By offering high power density and a long cycle life, electrochemical double-layer capacitor (EDLC) or ‘supercapacitor’ becomes a great candidate for energy storage device. Supercapacitors store charge through the electric field at the interface between porous electrode and electrolyte. Activated carbon and other carbon-based materials are typically used as electrode due to its high surface area. On the other hand, dimension of the electrode is also a crucial parameter regardless of material characteristic. Here, six electrode architectures with different array ratio (active area: gap space) were studied. The focus is to design electrode arrangement of planar supercapacitor to enhance its performance beyond a conventional sandwich structure. All cells were fabricated with the same procedures where each side of a copper foil was coated with carbon-based material and a separator soaked with 3M aqueous sodium nitrate was used as electrolyte. In case of low charging current of 5mA, all planar designs provide a higher specific capacitance than the conventional sandwich supercapacitor. Maximum yielded is 23.3 F/g (array ratio of 4:1) which is around 30% enhancement from that of conventional design (17.9 F/g) at 0.8V. Upon increasing the charging current, the specific capacitance of the cells with large gap space decreases dramatically while the cells with narrow gap space still provide a good performance relative to the conventional structure. This behavior indicates how electrode arrangement plays an important role on ions movement. Optimization of electrode pattern will give an opportunity for enhancing the capacitance of planar supercapacitor for real application of energy storage device.