Lithium-ion batteries are increasingly used as energy storage devices today due to their excellent energy capacity and voltage characteristics. However, the limited window of electrochemical stability for lithium-ion battery electrolytes constrains the development of devices with higher voltages and longer lifetimes. Conventional carbonate electrolytes degrade under conditions of high heat or voltage to form electrode surface films, leading to capacity fade, impedance increase, and reduced performance over time. Additionally, these electrolytes present a safety risk due to degradation at high temperatures. Therefore, the development of electrolyte systems with increased thermal and electrochemical stability is a relevant issue 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. Our work characterizes the thermal and electrochemical behavior of these organosilicon electrolytes by accelerated aging with high heat and extreme potentials. We show evidence of inhibited thermal degradation and propose mechanisms for protection of the lithium salt in organosilicon electrolytes. We identify mechanisms of electrochemical stability and degradation at high voltages against model platinum electrodes. Electroanalytical voltammetry shows increased oxidative stability of the organosilicon electrolytes compared with carbonates. Multinuclear NMR is used to identify and quantify the soluble post-mortem electrochemical products. Voltage and electrolyte composition dependence of surface film product are tracked by x-ray photoelectron spectroscopy. These investigations of solvent-mediated mechanisms of enhanced electrochemical stability enable the future development of advanced high stability electrolytes.