[CCoE Notice] Nano Seminar: Understanding the Role of Electrolyte Solubility in Limiting the Energy Density of Electrochemical Cells

[Grayson, Audrey A]

***** Seminar *****
Department of Electrical and Computer Engineering
Center for Integrated Bio and Nano Systems
     Friday, March 9, 2018
11:15 a.m., Room: CBB 122
Understanding the Role of Electrolyte Solubility in Limiting the Energy Density of Electrochemical Cells
Dr. Jim P. Zheng
Sprint Eminent Scholar Chair
Department of Electrical and Computer Engineering
A&M University and Florida State University
Abstract: All electrochemical energy storage systems are constructed with cathode and anode electrodes and electrolyte. The electrolyte is a chemical medium that allows the flow of ions between the cathode and anode. In some electrochemical systems, the electrolyte solubility can be a limitation factor for the maximum energy density such as supercapacitors, flow batteries, and lithium (Li)-sulfur (S) batteries. In this talk, we will provide the following two examples that energy densities are limited by the electrolyte and novel or improved systems which overcome the bottleneck of electrolyte solubility.
(1)        The supercapacitor is a promising energy storage device due to its superior characteristics of high power density and extremely long cycle life. The supercapacitor is comprised with a pair of symmetrical activated carbon electrodes which have no self-carried charge. The electric double-layer build up is accompanied by consumption of the salt in the electrolyte; therefore, the ultimate energy density is limited by the concentration of the salt in the electrolyte. The new high energy density of Li-ion capacitors benefits from the high concentration of Li pre-doped into the anode vs. low concentration ion source available in liquid electrolytes. Therefore, much less electrolyte is needed in our Li-ion capacitors than conventional supercapacitor.
(2)        The Li-S battery has attracted much attention recently due to potential high energy density. However, we have recently found the significant affect of Li polysulfide (LiPS) solubility on both the performance and the theoretical energy density of Li-S batteries, because the maximum amount of sulfur that can be reduced is hindered by the finite LiPS solubility. The operation of Li-S batteries under lean electrolyte conditions can be challenging, because the solubility LiPS sets an upper bound for polysulfide dissolution and limits the maximum amount of sulfur in the cathode that can be reduced. However, when cathode starts with solid Li2S4 which is the end of series of soluble LiPS, the solid Li2S4 will continue to dissolve with liquid Li2S4 reduced to solid Li2S2 and/or Li2S during the discharge process continues, and all the Li2S4 will be able to be reduced to the final product of Li2S.
Bio: Dr. Jim P. Zheng is a Professor and Sprint Eminent Scholar Chair at the Department of Electrical and Computer Engineering of Florida A&M University and Florida State University. He is the recipient of National Academy of Inventors Fellow, National Research Council Fellow, Army Research & Development Achievement Award, NASA Faculty Research Award, and Progress Energy Professional Development Award. He has published more than 140 articles in scholarly journals, and 130 papers in conference proceedings in the fields of energy storage, fuel cells, nano-sensors, photonics, and thin film growth, and been awarded 18 patents, and 5 patents have been licensed by a private companies. He is the founder of General Capacitor LLC and a co-founder of Bing Energy International Inc.
Contact Prof. Yan Yao (yyao4 at central.uh.edu<mailto:yyao4 at central.uh.edu>) if you would like to arrange for a time to meet with Dr. Zheng.
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