The most prominent advantages of rechargeable Lithium Ion Batteries (LIBs) are: high specific and volumetric energy, excellent charge-discharge cycle life, little or no memory effect, low maintenance and potential for battery reconditioning. However, there are still some safety concerns, often related to the danger presented by the inability of lithium-ion cells to tolerate recharging to potentials above the manufacturer’s recommended end of charge potential, i.e., overcharge. One way to overcome this drawback is to incorporate chemical compounds known as redox shuttles. These additives are generally organic compounds that undergo reversible electrochemical oxidation at potentials near the maximum design value. However, many of the compounds studied to date are either too expensive or not sufficiently durable for commercial applications. Figure 1. Novel Carbazole and Phenothiazine Derivatives with Potential Applications in LIBs and ORFBs In this presentation, we describe ongoing efforts to develop organic materials capable of undergoing reversible electrochemical oxidation at specific potentials for use in overcharge protection of lithium ion batteries as well as for the development of new catholytes in nonaqueous, organic redox flow batteries (ORFBs) (Figure 1). 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 carbazoles and phenothiazine-5,5-dioxide derivatives were prepared and characterized chemical and electrochemically. These latter materials display highly reversible electrochemical oxidation and very good solubility in carbonate solvents, making them attractive candidates in organic redox flow batteries ORFBs for inexpensive grid-level energy storage.

Redox-active organic substrates with potential applications in lithium ion and flow batteries

2019 Fall National Meeting

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