Highly Concentrated Alcohol-based Solutions as Novel Electrolytes for Safe Li-ion Batteries

Overview

ARL Fellow Marshall A. Schroeder, Ph.D. Project Advisor Electrochemistry Branch, U.S. Army Research Laboratory Highly concentrated electrolytes have gained attention for their unusual behaviors in improving ion transport, safety, and electrochemical stability. In this work, a series of super concentrated alcohol-based solutions— isopropanol (IPA), ethanol, and methanol—were evaluated for the first time using lithium bis(trifluoromethane sulfonyl)imide (LiN(SO2CF3)2, LiTFSI) as the salt. Despite the flammability of each individual solvent, at high concentrations, none of the solutions are flammable due to intensified ion-solvent interaction. ¹H NMR and FTIR data reveal the desired suppression of the active proton on the -OH group of each of the alcohols, suggesting Li⁺ is the preferred ion for transport. Ionic conductivity data confirms this claim. Most importantly, the electrochemical stability window of these electrolytes is significantly expanded from ~1.6 Vof diluted electrolytes to ~2.7 V, raising the possibility of supporting meaningful battery chemistries at high rates and non-flammability. The “methanol-in-salt” electrolyte (MiSE), 18 m LiTFSI in methanol, outperformed both IPA and ethanol electrolytes in conductivity and LiTFSI solubility, suggesting a new frontier for practical material design of safe liquid electrolytes. The results presented provide an interesting system for a fundamental understanding of how solvent molecules and ions interact in protic solvents in general. A Novel Approach to Determining Cost-Effective Federal Spending On Urban Homelessness Zadan P. Mason University School of Milwaukee Milwaukee, WI Supervising Scientist: Dr. Scott Adams PhD University of Wisconsin-Milwaukee Background: The federal government spends $5 billion annually on homelessness. Prior approaches to studying effectiveness of programs have relied on analyzing data from a single city, region, or funding source. Because of a lack of data, a national approach hasn’t previously been attempted. In 2007, Housing & Urban Development (HUD) started collecting Point-in-Time (PIT) homelessness counts through continuum of care (CoC) organizations. As such, there is now a decade of publically available accurate data. Hypothesis: When controlling for total spending, of the four categories of HUD spending, investment in permanent housing will yield the greatest decrease in homelessness numbers in urban settings. Methodology: A merged database was created from documents obtained from HUD for individual CoCs (2007- 2017). Merging this database with other publically available data allowed per capita normalization. Difference-in- difference (DID) statistical analysis was used to compare a treatment group (effect of HUD spending on homelessness) and a control group (baseline change in homelessness independent of HUD spending). Results: - A regression of total homelessness counts on total spending showed where the homeless problem is bigger, more money is spent. - DID analysis showed that all categories of spending, across all grouping of homelessness, are statistically significant (p<0.01), suggesting a collinearity problem. - Multivariable regression was used to address collinearity, and showed some types of spending caused increases in homelessness, suggesting potential data heterogeneity. - CoCs were cohorted into ‘large’ and ‘small’ based on size. Key Finding: Spending on ‘supportive services’ has the biggest impact on decreasing homelessness counts for ‘large’ urban CoCs.