Understanding How Nitriles Stabilize Electrolyte/Electrode Interface at High Voltage.

Nitriles have received extensive attention for their unique ability in stabilizing electrolytes against oxidation at high voltages. It was generally believed that their anodic stability originates from a monolayer of chemisorbed nitrile molecules on transition-metal oxide surface, which physically expels carbonate molecules and prevents their oxidative decomposition. We overturn this belief based on calculation and experimental results and demonstrate that, like many high voltage film-forming electrolyte additives, nitriles also experience an oxidative decomposition at high voltages, and the high oxidation stability of nitrile-containing electrolytes is merely the consequence of a new interphasial chemistry. This important mechanistic correction would be of high significance in guiding the design of new electrolytes and interphases for the future battery chemistries.