Hydroperoxide-Mediated Degradation of Acetonitrile in the Lithium–Air Battery

摘要

Understanding and eliminating degradation of the electrolyte solution isarguably the major challenge in the development of high energy densitylithium-air batteries. The use of acetonitrile provides cycle stabilitycomparable to current state-of-the-art glyme ethers and, while solventdegradation has been extensively studied, no mechanism for acetonitriledegradation has been proposed. Through the application of in situ pressuremeasurements and ex situ characterization to monitor the degradation ofacetonitrile in the lithium-air battery, a correlation between H_2Oconcentration within the cell and deviation from the idealized electron/oxygenratio is revealed. Characterization of the cycled electrolyte solution identifiesacetamide as the major degradation product under both cell and modelconditions. A new degradation pathway is proposed that rationalizes theformation of acetamide, identifies the role of H_2O in the degradation process,and confirms lithium hydroperoxide as a critical antagonistic species inlithium-air cells for the first time. These studies highlight the importance ofconsidering the impact of atmospheric gases when exploring lithium-air cellchemistry and suggest that further exploration of the impact of hydroperoxidespecies on the degradation in lithium-air cells may lead to identification ofmore effective electrolyte solvents.