Electrochemical and Infrared Studies of the Reduction of Organic Carbonates

INTRODUCTION Electrolytes typically used in lithium batteries consist of a lithium salt dissolved in an organic solvent, or a mixture of these solvents. The solvents fall into two general classes: ethers or alkyl esters of carbonic acid. Because of lower volatility and higher flash point, the organic carbonates are the preferred solvent class in commercial batteries. Propylene carbonate (PC) has many advantages over other organic carbonates for use in the battery electrolyte, e.g. lower cost and better low temperature performance. Use of PC in Li-ion batteries has, however, been problematic due to co-intercalation of solvent molecules along with Li ion into the graphite and subsequent exfoliation . The electrolyte commonly used in commercial lithium-ion cells is based on ethylene carbonate (EC), even though these batteries have poorer low temperature performance. Research efforts have, with some success, pursued additives to PC to generate a SEI layer that prevents PC co-intercalation. The mechanism of functioning of these additives is, however, still uncertain.