Lithium-ion batteries are increasingly used for energy storage today due to their excellent energy capacity and voltage characteristics. However, the limited window of electrochemical stability for conventional carbonate-based lithium-ion battery electrolytes constrains the development of devices with higher voltages and longer lifetimes. One method used to achieve desirable electrolyte performance is through mixing multiple electrolyte solvents with different properties; however, increasing solution complexity can lead to unexpected synergies and an inadequate functional understanding of the solution components. Therefore, innovating electrolyte systems with increased thermal and electrochemical stability, and understanding the nature of solvent behavior in mixed electrolytes, are relevant issues in battery development. Organosilicon solvents for battery electrolytes, developed by Silatronix, Inc. with the University of Wisconsin-Madison, have demonstrated improved oxidative stability, reduced gassing, and increased thermal stability. This dissertation investigates the mechanisms and structure-function relationships between organosilicon solvents for lithium-ion batteries and their superior thermal and electrochemical stability, in addition to quantifying competitive solvation in mixed organosilicon-carbonate electrolytes. We studied a series of organosilicon electrolytes with differing nitrile, glycol, and fluorine functional substituents to understand the structural origins of thermal 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 Nuclear Magnetic Resonance (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. Next, we investigated organosilicon nitrile-based electrolytes for lithium-ion batteries at highly anodic potentials to gain a mechanistic understanding of electrochemical stability. Voltammetry shows superior intrinsic oxidative stability of electrolytes with organosilicon nitrile solvents compared to carbonate solvents against inert platinum electrodes. Studies on a series of nonfluorinated to trifluorinated organosilicon nitriles demonstrate that fluorination at the silicon atom decreases the electrolyte oxidation potential. Density functional theory (DFT) calculations, NMR spectroscopy, and x-ray photoelectron spectroscopy (XPS) analyses were used to determine the mechanisms of stability and understand the trend of fluorination and oxidation potential. DFT and NMR showed that the preferred oxidation pathway is a coupled fluorination-oxidation resulting in Si-C bond cleavage to form a fluorosilane in solution, and XPS showed that a thin (<4 nm) nitrogen-containing surface film forms simultaneously. Our results suggest a self-limited surface film forms at moderate oxidizing potentials in organosilicon nitriles that inhibits further oxidation and enables high-potential stability. Finally, we investigated the nature of lithium solvation in organosilicon (OSN) and mixed OSN-ethylene carbonate (EC) and OSN-diethyl carbonate (DEC) electrolytes. DFT, FTIR, and NMR were used to analyze how the degree of lithium coordination of each solvent changes with the addition of a second solvent species, and to begin to quantitate the degree of lithium solvation and percentage of each solvent component involved in the solvent shell. The relative degree of ionic dissociation in different electrolyte mixtures was also calculated through diffusion NMR measurements. The FTIR and NMR results agreed that the carbonate composes a greater fraction of the solvation shell than the organosilicon in binary electrolytes, with EC a strong majority in the solvation shell (63% in 1:1 mol:mol EC:OSN) and DEC sharing the solvation shell more with OSN (57% DEC in 1:1 mol:mol DEC:OSN). Despite a lower solvation shell contribution, OSN is still present in the solvation shell (5-8%) even when only 9 mol% of the solution composition. Furthermore, addition of OSN to the carbonate electrolytes increases ionic dissociation and decreases the solvation number, showing that OSN has a significant impact on the solvation properties. These studies unveil the subtleties of analyzing even simple electrolyte solutions and provide a foundation of techniques and solvation structure that can be used in understanding electrolyte systems of greater complexity and application. This work advances the fundamental understanding of novel organosilicon-containing lithium-ion electrolytes, to enable their use in high-performance batteries, and the rational design of future ultra-stable functional organosilicon solvents and additives.