Ester-Based Battery Solvents in Contact with Metallic Lithium: Effect of Water and Alcohol Impurities

Abstract

Organic ester-based battery solvents were examined with respect to their reactivity with water and alcohols in contact with metallic lithium. The investigation was focused on monohydric esters (n-propyl acetate, isopropyl acetate), dihydric esters (trimethylene diacetate, 1,2-propylene glycol diacetate), and trihydric esters (triacetin). Experiments with lithium metal, the respective ester and water, and the matching alcohol were done. The resulting reaction solutions were analyzed with 1H NMR spectroscopy and compared to spectra recorded with the anticipated reaction products that were synthesized separately. The study reveals a tandem reaction from ester saponification to a catalytic Claisen condensation. Thus, the products formed during the reaction showed early degradation in cyclic voltammetry measurements in both the anodic and cathodic regions. A reactivity trend could be examined whereupon the trihydric esters were the least reactive followed by the dihydric and monohydric esters. In the absence of water and alcohols, all investigated esters are stable against metallic lithium.