Understanding the Stability and Reactivity of Radical Cations for Improved Overcharge Protection in Lithium-Ion Batteries

The overall goal of this proposal is to improve the stability of radical cation forms aromatic molecules used as redox shuttle electrolyte additives for overcharge protection in lithium-ion batteries. To accomplish these objectives, we will generate the radical cations of a variety of aromatic compounds by electron transfer reactions using chemical oxidants. We will study the lifetimes of the radical cations in a variety of solvent environments, including carbonates used as battery electrolytes, to determine decomposition products upon oxidation. We will analyze the products to determine the following: (1) trends in radical cation stability in different solvent environments: polarity, nucleophilicity, (2) features that results in more stable radical cations, i.e. electron delocalization and (3) comparison of radical cation persistance vs. overcharge protection: is there a correlation? In addition to these sytematic studies, we will use this opportunity of studying the byproducts of radical cation formation to determine if we can develop new pathways to functionalize aromatic rings. Upon radical cation formation, an otherwise nucleophilic aromatic ring becomes an electrophile. Depending on the electron delocalization in the radical cation, we may be able to harness this reactive species to functionalize aromatic rings in unique positions compared to electrophilic aromatic substitution, or with more efficient routes that utilize nucleophiles in solution.