Development of high-performance bipolar plates by electrode integration for vanadium redox flow batteries
Topic(s) : Industrial applications
Co-authors :
Amanpreet KAUR , Jun Woo LIM (KOREA, REPUBLIC OF)Abstract :
The bipolar plate is a key core component of the energy conversion system, such as fuel cell and vanadium redox flow battery (VRFB) [1]. Generally, the graphite material is used as the bipolar material in the VRFB due to good electrical conductivity. However, high handling cost and difficulty in assembly due to its brittle nature are main disadvantages. The ideal bipolar plate should provide high electrical conductivity, high mechanical properties, and good chemical stability. The carbon/epoxy composite provides high mechanical properties. However, the high electrical resistance is the big issue due to the resin-rich area formed on the surface of the bipolar plate [2].
In this study, the electrode integrated bipolar plate structure is developed from the single carbon felt (CF). The electrode integrated bipolar plate structure decreases the electrical contact resistance (ICR) between the carbon felt electrode and the bipolar plate. The electrode integrated bipolar plate assembly should be fabricated with a single carbon felt to effectively remove the ICR between the carbon felt electrode and the bipolar plate. Therefore, a single carbon felt is used separately as two different portions for the bipolar plate and the electrode. The carbon felt should undergo high pressure during the fabrication process of the bipolar plate portion to achieve low electrical resistance. However, the carbon felt has a relatively lower compressive strength compare to the curing pressure. Therefore, the electrode portion of the carbon felt is impregnated with soluble resin to increase the compressive strength and prevent the epoxy impregnation while the bipolar plate curing process. Polyvinylpyrrolidone (PVP K30, Sigma-Aldrich, MO, USA) and epoxy (YD-114F, KUKDO Chemical Co., Ltd., Republic of Korea) are used for the electrode and bipolar plate portion, respectively. Polyethylene and polypropylene sheets are used as a soft layer to fabricate the bipolar plate. After the bipolar plate is fully cured, the PVP of electrode portion is removed by placing the structure into hot water. Experimental results reveal that the total resistance of the electrode integrated bipolar plate structure is dramatically lowered compare to than of the conventional bipolar plate as shown in Fig. 1. The electrode integrated bipolar plate structure developed in this study showed 28% reduction in the total resistance and a 175% increment in mechanical property. Acid aging and gas permeability test verified the durability of the electrode-integrated BP with zero gas permeability. Finally, a two-cell charge/discharge test verified that the developed structure exhibited a 6.3% enhancement in energy efficiency. Therefore, the developed bipolar plate can be an excellent alternative for the conventional bipolar plates of VRFB.
In this study, the electrode integrated bipolar plate structure is developed from the single carbon felt (CF). The electrode integrated bipolar plate structure decreases the electrical contact resistance (ICR) between the carbon felt electrode and the bipolar plate. The electrode integrated bipolar plate assembly should be fabricated with a single carbon felt to effectively remove the ICR between the carbon felt electrode and the bipolar plate. Therefore, a single carbon felt is used separately as two different portions for the bipolar plate and the electrode. The carbon felt should undergo high pressure during the fabrication process of the bipolar plate portion to achieve low electrical resistance. However, the carbon felt has a relatively lower compressive strength compare to the curing pressure. Therefore, the electrode portion of the carbon felt is impregnated with soluble resin to increase the compressive strength and prevent the epoxy impregnation while the bipolar plate curing process. Polyvinylpyrrolidone (PVP K30, Sigma-Aldrich, MO, USA) and epoxy (YD-114F, KUKDO Chemical Co., Ltd., Republic of Korea) are used for the electrode and bipolar plate portion, respectively. Polyethylene and polypropylene sheets are used as a soft layer to fabricate the bipolar plate. After the bipolar plate is fully cured, the PVP of electrode portion is removed by placing the structure into hot water. Experimental results reveal that the total resistance of the electrode integrated bipolar plate structure is dramatically lowered compare to than of the conventional bipolar plate as shown in Fig. 1. The electrode integrated bipolar plate structure developed in this study showed 28% reduction in the total resistance and a 175% increment in mechanical property. Acid aging and gas permeability test verified the durability of the electrode-integrated BP with zero gas permeability. Finally, a two-cell charge/discharge test verified that the developed structure exhibited a 6.3% enhancement in energy efficiency. Therefore, the developed bipolar plate can be an excellent alternative for the conventional bipolar plates of VRFB.