Presentation on theme: "Leah Douglas 1,3, Michael Bright 1, Doug Aaron 1, Alexander B. Papandrew 1, and Thomas A. Zawodzinski, Jr. 1,2 1 Department of Chemical and Biomolecular."— Presentation transcript:
Leah Douglas 1,3, Michael Bright 1, Doug Aaron 1, Alexander B. Papandrew 1, and Thomas A. Zawodzinski, Jr. 1,2 1 Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN 2 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN ³The University of Memphis, Memphis, TN OBJECTIVE Flow batteries are a potential technology for energy storage because they allow for large amounts of energy to be stored and flexibility in size. Energy and power capacity can be independently scaled. One type of flow battery is the vanadium redox battery (VRB). An advantage of the VRB is that crossover only results in loss of charge, not cross contamination and all charge is stored in the electrolyte. MOTIVATION The objective of this experiment was to increase electrode surface area and reduce the contact resistance between the membrane and the electrode. This was done by attaching a microporous electrode directly to the membrane. Variations of carbon inks, amounts of ink and types of carbon paper were considered in this effort. Electrolyte: 2M vanadium in 5M SO ⁴⁻ Flow rate: 20mL/min Potentiostat: Biologic HCP-803 up to 80 amps Membrane: N117 for thickness Carbon paper electrodes (SGL group) Setup Polarization curves allow for the determination of the dominant loss mechanisms in a battery. Activation loss is the result of slow reaction kinetics at low current. Ohmic loss is attributed to charge transport in the battery. Mass transport limitation is the inability to increase rate of electrolyte delivery to match increase in current. Electrode Mass6.8 mg (5 layer), 17.4 mg (10 layer) Carbon:Ionomer2:1 C:I, 50:1 C:I Carbon Paper5% treated, untreated, none Electrode Configuration Current flowing in electrochemical cells experiences intrinsic resistance (iR). To correct for this resistance, the high frequency resistance (HFR) is found Finding the areal specific resistance (ASR) allows for the calculation of an iR- free polarization curve. This is done by taking the HFR and multiplying it with the area of the membrane. Different compositions of carbon and ionomer ink were considered. The goal here was to increase electrode surface area and improve the electrical conductivity of the electrode. Different layers of ink were tested to see if, by adding more ink, performance would improve. Increased electrode surface area could result in better performance. However, the thicker electrode did not exhibit better performance. Different types of carbon paper were tested to determine the effect on the battery. There was no discernable difference between the different carbon papers. Electrode:5 layers, 50:1 C:I ink Electrode:10 layers, 2:1 C:I ink Summary Increased carbon content in the electrode resulted in improved performance. No great performance improvement was observed when doubling the number of layers of ink used to make the electrodes. Wet-proofed carbon paper performed similarly to non-wet-proofed carbon paper. Lack of carbon paper resulted in noticeably greater activation loss. Gold Current Collector Graphite Plate Membrane CathodeAnode 10 layer decal 2:1 C:I composition N117 membrane 2:1 C:I composition N117 membrane No carbon paper present Acknowledments to NSF grant #1004083 for making this research possible.