Cell Voltage Efficiency Research Articles

Temperature adaptability of the lead methanesulfonate flow battery: Optimization of electrolytic composition based on solubility, conductivity, viscosity and cycle performance of battery

Optimizing the electrolytic composition is of practical interest to evaluate the flow battery's weatherability. In this work, the electrolytic composition is optimized for different temperature ranges according to the physicochemical characteristics of electrolyte from −30 °C to 50 °C. The solubility curves of lead methanesulfonate are obtained in methanesulfonic acid, and an equation is proposed among lead methanesulfonate's content, methanesulfonic acid's content and temperature. The conductivity and dynamic viscosity of electrolytes with different compositions can be enhanced by increasing temperature. The voltage efficiency of cell is improved with increasing temperature, but the coulombic efficiency has the maximum value around 30 °C. The high energy efficiency can be achieved by increasing the concentration of H+ below 0 °C or increasing the concentration of Pb2+ above 30 °C. The electrolytic composition of 1.5 M Pb2+ and 1.0 M H+ is suitable for the temperature range of −20 °C − 50 °C. It is also found that the concentration of H+ is demanded at least 0.17 mol/L for charging the battery.

Design Principles of Bipolar Electrochemical Co-Electrolysis Cells for Efficient Reduction of Carbon Dioxide from Gas Phase at Low Temperature

Cell designs for the electrochemical reduction of CO2 from gas phase were developed and investigated, and the critical elements for an efficient process were identified. Various types of polymeric membrane were used to build membrane electrode assembly adapted for CO2 reduction in gas phase: protonic and anion exchange membrane (AEM), bipolar membrane and a modified bipolar like membrane configuration. Configurations using anion exchange ionomer in the cathodic catalytic layer in contact with an AEM allow for a great enhancement of the cathode reaction selectivity toward CO. However, a severe problem was identified when co-electrolysis is performed using only an AEM: this type of membrane acts as a CO2 “pump” meaning that for each molecule of CO2 reduced at the cathode, one or two CO2 molecules are produced at the anode by oxidation of the carbonate/bicarbonate anion transported in the membrane. A bipolar membrane system was shown to soften this problem, but only a newly developed cell design was able to fully prevent the parasitic CO2 pumping. Using this new cell configuration, the faradaic efficiency of an alkaline environment is maintained, the parasitic CO2 pumping to the anode side is completely suppressed, and the overall cell voltage efficiency is highly improved.

고고도 무인기용 수전해 셀 및 스택의 제작 및 성능 평가

The experiments related on structure and water electrolysis performance of HALE UAV stack were conducted in this study. Anode catalyst <TEX>$IrRuO_2$</TEX> was prepared by Adam's fusion methods as 2~3 nm nano sized particles, and the cathode catalyst was used as commercial product of Premetek. The MEA (membrane electrode assembly) was manufactured by decal methods, anode and anode catalytic layers were prepared by electro-spray. HALE stack was composed of 5 multi-cells as <TEX>$0.2Nm^3/hr$</TEX> hydrogen production rate with hydrogen pressure as 10 bar. The water electrolysis performance was investigated at atmospheric pressure and temperature of <TEX>$55^{\circ}C$</TEX>. Best performance of HALE UAV stack was recorded as cell voltage efficiency as 86%.

Optimized Anion Exchange Membranes for Vanadium Redox Flow Batteries

In order to understand the properties of low vanadium permeability anion exchange membranes for vanadium redox flow batteries (VRFBs), quaternary ammonium functionalized Radel (QA-Radel) membranes with three ion exchange capacities (IECs) from 1.7 to 2.4 mequiv g(-1) were synthesized and 55-60 μm thick membrane samples were evaluated for their transport properties and in-cell battery performance. The ionic conductivity and vanadium permeability of the membranes were investigated and correlated to the battery performance through measurements of Coulombic efficiency, voltage efficiency and energy efficiency in single cell tests, and capacity fade during cycling. Increasing the IEC of the QA-Radel membranes increased both the ionic conductivity and VO(2+) permeability. The 1.7 mequiv g(-1) IEC QA-Radel had the highest Coulombic efficiency and best cycling capacity maintenance in the VRFB, while the cell's voltage efficiency was limited by the membrane's low ionic conductivity. Increasing the IEC resulted in higher voltage efficiency for the 2.0 and 2.4 mequiv g(-1) samples, but the cells with these membranes displayed reduced Coulombic efficiency and faster capacity fade. The QA-Radel with an IEC of 2.0 mequiv g(-1) had the best balance of ionic conductivity and VO(2+) permeability, achieving a maximum power density of 218 mW cm(-2) which was higher than the maximum power density of a VRFB assembled with a Nafion N212 membrane in our system. While anion exchange membranes are under study for a variety of VRFB applications, this work demonstrates that the material parameters must be optimized to obtain the maximum cell performance.

Nickel foam and carbon felt applications for sodium polysulfide/bromine redox flow battery electrodes

The first use of nickel foam (NF) as electrocatalytic negative electrode in a polysulfide/bromine battery (PSB) is described. The performance of a PSB employing NF and polyacrylonitrile (PAN)-based carbon felt (CF) as negative and positive electrode materials, respectively, was evaluated by constant current charge-discharge tests in a single cell. Charge/discharge curves of the cell, positive and negative electrodes show that the rapid fall in cell voltage is due to the drop of positive potential caused by depletion of Br2 dissolved in the catholyte at the end of discharge. Cell voltage efficiency was limited by the relatively high internal ohmic resistance drop (iR drop). Polarization curves indicated that both NF and CF have excellent catalytic activity for the positive and negative redox reactions of PSB. The average energy efficiency of the single cell designed in this work could be as high as 77.2% at 40mAcm−2 during 48 charge-discharge cycles.