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2.3.2 Cathode current collector and its requirements The cathode current collector is required to have good electronic conductivity, good chemical and electrochemical stability, a large surface area (more active sites), and cost-competitiveness to be used in the seawater cell described in Section 2.3.1. Among several candidates, a commercially available carbon felt was selected and tested in this work because it meets those requirements and has been extensively used in fuel cells and redox flow batteries 81, 82. However, the surface of carbon felts is typically hydrophobic due to the presence of sizing agents for mechanical reinforcement; thus, aqueous electrolytes, including seawater, are not wetted well on pristine carbon felts. We performed heat treatment of carbon felts at 500 °C in ambient air 81 and analyzed the surface wettability by measuring their contact angles before and after the heat treatment. Figure 27 (a) shows the contact angles of a seawater droplet on the pristine carbon felt (PCF) and HCF. The PCF did not allow complete wetting even after 5 min; the contact angle was measured as 135°. On the other hand, the HCF allowed the penetration of the water droplet within 1 s. Thus, the contact angle could not be measured, indicating that the air-heating process makes the surface of the carbon felts hydrophilic. We compared the electrochemical performance of PCF and HCF as cathode current collectors for seawater batteries. Figure 27. (b) exhibits the initial charge-discharge voltage curves of seawater cells using the PCF and HCF air-electrodes at a current rate of 0.025 mA cm-2 for 5 h at each step (OFF state). The PCF cell showed the charge and discharge voltages of 4.1 V and 2.5 V, respectively, resulting in a large voltage gap between the charge and discharge curves (ΔV) of ~1.6 V. On the contrary, the cell using HCF showed a relatively low ΔV of ~1.4 V. This result indicates that the improvement in the surface wettability of cathode current collector (here, carbon felts) enhances the reaction kinetics during charge/discharge processes by reducing ΔV. We performed XPS and N2 sorption isotherm measurements to analyze the changes in the surface chemistry and the area of carbon felts by heat treatment. The heat treatment in air resulted in an increase in the C–O bond-to-C=O bond ratio and in the specific surface area of carbon (Figure 27. (c) and (d)). For the O 1s spectra, the surface of HCF had a large ratio of the C–O bond (phenolic, at 533 eV)-to-C=O bond (carbonyl, at 531 eV), compared to that of the PCF surface 83-85. The specific surface area (SBET) increased from ~0.62 m2/g to ~2.23 m2/g by about 3.6 times after the heat treatment (the inset in Figure 27. (c) and (d)). Therefore, the increased surface area and changes in the functional groups on the surface, as a result of the air-heating process, were responsible for the improved surface wettability and the reduced ΔV, which could improve the energy efficiency of seawater batteries. 45PDF Image | China solar seawater battery
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Product and Development Focus for Salgenx
Redox Flow Battery Technology: With the advent of the new USA tax credits for producing and selling batteries ($35/kW) we are focussing on a simple flow battery using shipping containers as the modular electrolyte storage units with tax credits up to $140,000 per system. Our main focus is on the salt battery. This battery can be used for both thermal and electrical storage applications. We call it the Cogeneration Battery or Cogen Battery. One project is converting salt (brine) based water conditioners to simultaneously produce power. In addition, there are many opportunities to extract Lithium from brine (salt lakes, groundwater, and producer water).Salt water or brine are huge sources for lithium. Most of the worlds lithium is acquired from a brine source. It's even in seawater in a low concentration. Brine is also a byproduct of huge powerplants, which can now use that as an electrolyte and a huge flow battery (which allows storage at the source).We welcome any business and equipment inquiries, as well as licensing our flow battery manufacturing.CONTACT TEL: 608-238-6001 Email: greg@salgenx.com (Standard Web Page)