High Potential Organic Materials for Battery Applications

Investigation of new materials capable of undergoing reversible electrochemical oxidation at very high potentials (> 4 V vs. Li/Li+) is important for overcharge protection in conventional lithium ion batteries as well as for the development of new catholytes in nonaqueous redox flow batteries. We have employed several strategies to prepare novel organic heterocycles that exhibit such behavior. First, parent molecules were designed such that the molecular reorganization associated with oxidation to the radical cation is impeded, leading to a shift to more positive potentials without sacrificing stability. Second, numerous phenothiazine-5,5-dioxide derivatives were prepared and characterized. These latter materials display highly reversible electrochemical oxidation and very good solubility in carbonate solvents, making them particularly attractive for flow battery applications.