materials research society

UK-MRS Seminars

UK-MRS Seminars

June 12. 2017, 10:00-11:00 am

C226 OHR (Oliver H. Raymond Civil Engineering Building)

 

“Anode Surface Evolution in Aqueous Sodium-Ion Batteries”

Xiaowen Zhan, Department of Chemical and Materials Engineering 

Aqueous sodium-ion batteries may solve the cost and safety issues associated with the energy storage systems for the fluctuating supply of electricity based on solar and wind power. Compared to their lithium counterparts, aqueous sodium-ion batteries offer multiple advantages including more earth abundant sodium, cheaper electrode materials and electrolyte solutions as well as less costly manufacturing conditions. However, poor overall performance and low electrode utilization (much of the electrode material ends up being electrochemically inactive) are the main barriers implementing them in (micro) grid systems. Here we characterize the surface reactions on NASICON-type phosphate anode materials and rationalize their close associations with capacity fading upon slow cycling of aqueous sodium-ion batteries. The surface reactions result in the formation of an electrically insulating surface layer causing the failure of electrochemical performance and the precipitation of surface particles that blocks the pores thereby leading to poor electrode utilization. These findings provide insights into new possibilities of improving the electrochemical performance of aqueous sodium-ion batteries by designing protective layers through surface modifications that prevent the formation of insulating surface layers and insoluble precipitates. 

 

“Stable, High-Capacity Electrolytes for Non-Aqueous Redox Flow Batteries”

Harsha Attanayake, Department of Chemistry University of Kentucky

Redox flow batteries (RFBs) are one of the promising electrochemical devices for stationary energy storage applications due to their decoupled energy and power, long service life, and simple manufacturing. Despite advances of commercially available aqueous RFBs, they suffer from lower energy densities due to narrow electrochemical window of water (~1.5 V). Transitioning from aqueous to non-aqueous chemistry offers a wider and stable electrochemical window (>4 V), a greater selection of redox materials, a wider range of working temperatures, high cell voltage, and potentially high energy density. So far, only a limited number of highly soluble and stable organic compounds have been reported for non- aq RFBs applications as catholytes. It is crucial that the design of organic electro-active materials does not compromise any of the following characteristics: high solubility (charged and neutral states), higher oxidation potential (for electron donors), and enabling a high molecular capacity for electron donation (or acceptance). Our studies mainly focus on development of high capacity catholytes for non-aqueous redox flow batteries with stable neutral and oxidized states. This presentation will focus on molecular designing strategies to increase the solubility of phenothiazine derivatives in their charged states and neutral states, stabilization of one and two electron donation, and a new approach to raise the oxidation potential, along with their synthesis and electrochemical analysis. 

 

 

 

Date:
-
Location:
OHR C226

UK MRS Seminar - Modeling in Li-ion Batteries

SEMINAR 

"Modeling of the Interface and Interphases in Li-ion Batteries"

Prof. Yue Qi, Ph.D. 

Department of Chemical Engineering & Materials Science Michigan State University, East Lansing, Michigan 

April 11, 2016 at 3:30 P.M., 112 OHR (Oliver H. Raymond Civil Engineering Building) 

 

Abstract

One of the most significant challenges for current and future lithium ion batteries is the smart structure design at the nanoscale and the control of electron and ion transport at the electrode/electrolyte interface. This issue is further complicated by the existence of ultrathin interphase layers (IL) covering the electrode, forming a complex heterogeneous electrode/IL/electrolyte interface. New computational methods are being developed to critically examine the different pathways of electrons and ions crossing this complex interface, that are critical to charge transfer, degradation mechanisms, and interphase design. The electrochemical reactions responsible for electrolyte degradation are examined using Density functional theory (DFT)-based methods. Examples are rigorous voltage calibration in DFT calculations and estimation of irreversible capacity loss agreeing well with experimental measurements. In order to understand how to design interphase materials with higher ionic conductivity, the dominating diffusing carriers and their diffusion pathways are predicted, as a function of the voltage of the electrode. The chemical-mechanical degradation at the artificial coatings is further investigated by molecular dynamics simulations with ReaxFF. The insights gained from these simulations have enhanced our understanding on battery degradation mechanisms and inspired new designs across various length scales (nano to vehicle applications). 

Biography

Dr. Yue Qi is an associate professor in the Chemical Engineering and Materials Science Department at Michigan State University. She received her dual-B.S. degrees in Materials Science and Engineering and Computer Sciences from Tsinghua University in 1996 and her Ph.D. in Materials Science from California Institute of Technology in 2001. She was a co-recipient of 1999 Feynman Prize in Nanotechnology for Theoretical Work during her PhD study. After receiving her Ph.D. degree, she spent 12 years working in the Chemical Sciences and Materials Systems Lab, General Motors R&D Center. She led a multi-scale modeling research effort to solve problems related to forming and machining of lightweight alloys, and developing energy materials for batteries and fuel cells. She won three GM Campbell awards for outstanding research on various topics and a TMS Young Leader Professional Development Award. 

This seminar is hosted by the students of MRS-UK.

 

Date:
-
Location:
Oliver H Raymond Building Room 112
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