The release of gases through electrolyte decomposition is a problem of prominent concern in the Li-ion battery industry, due to the negative impact of gassing on cell safety and performance. The development of new electrolytes and additives is essential in enabling low-gassing batteries. Organosilicon (OS) molecules, which merge a silane with a Li+ coordinating functionality, have been developed by Silatronix® as additions to conventional carbonate electrolytes, demonstrating critical high thermal and voltage stability to enable next-generation Li-ion batteries. In this study we report performance testing and fundamental mechanistic studies to investigate gassing phenomena in advanced Li-ion chemistries under storage test conditions. Novel organosilicon nitriles developed by Silatronix® as well as common gas reducing additives (i.e. 1,3-propanesultone, succinonitrile) were evaluated in a 4.35 V Graphite/NMC622 (LiNi0.6Mn0.2Co0.2O2) multi-layer pouch cell. Potential synergies between OS materials and these additives were investigated. The dependence of gassing on electrolyte composition and test conditions was investigated, and connections between gassing behavior and electrode surface chemistry are also reported. Key experimental results show that all OS concentrations reduce gas generation during 60 °C storage, and higher OS content provides greater benefit. Overall, we show that organosilicon additives substantially reduce gassing from carbonate-based electrolytes while maintaining cell performance.

Syntheses and structural study of the new compounds bis[2-(1H-benzimidazol-2-yl)phenyl]disulfide (1) and bis[2-(3H-benzimidazol-1-ium-2-yl)-phenyl]disulfide sulfate (2), and their corresponding bis-hydrogen sulfate (3), bis-dihydrogen-phosphate (4), bis-tetrafluoroborate (5) and bis-perchlorate (6), are reported. X-ray diffraction analyses of 2-6 and three pseudo-polymorphs of 1 have shown that the conformation of 1 is the result of sulfur weak N f S intramolecular interactions, where the sulfur atom is acting as a Lewis acid. Nitrogen protonation changes the elongated conformation of 1 into a folded conformation for 2-4 and a semifolded conformation in compounds 5 and 6 with the assistance of intramolecular π-π stacking and hydrogen bonds, which bridge the two halves of the molecules. All disulfides adopt chiral conformations in the solid state; the ensemble of these chiral conformations is racemic. They present polymeric arrays with multiple cooperative stabilizing intermolecular and intramolecular interactions like π-interactions, O f S, C(π) f S, N(π) f S, F f S, and H-bonds.

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The high flammability and thermal instability of conventional carbonate electrolytes limit the safety and performance of lithium-ion batteries (LIBs) and other electrochemical energy storage devices. Organosilicon solvents have shown promise due to their reduced flammability and greater chemical stability at high temperatures. A series of organosilicon electrolytes with different functional substituents were studied to understand the structural origins of this enhanced stability. The thermal and hydrolytic stability of organosilicon and carbonate solvents with LiPF6 was probed by storage at high temperatures and with added water. Quantitative monitoring of organosilicon and carbonate electrolyte decomposition products over time using NMR spectroscopy revealed mechanisms of degradation and led to the discovery of a key PF5-complex that forms in organosilicon electrolytes to inhibit further salt breakdown. Increased knowledge of specific structural contributions to electrolyte stability informs the development of future electrolyte solvents to enable the safer operation of high-performing lithium-ion batteries.