Comparison of the Reaction of Li[sub x]Si or Li[sub 0.81]C[sub 6] with 1 M LiPF[sub 6] EC:DEC Electrolyte at High Temperature

Abstract

The reaction of lithiated silicon with ethylene carbonate–diethyl carbonate(EC:DEC) electrolyte was compared with that of and the same electrolyte using accelerating rate calorimetry (ARC). In the presence of -containing electrolyte, and showed similar ARC response in cases where the same number of moles of lithium atoms and the same amount of electrolyte were involved. X-ray diffraction results indicate that the major reaction product is comprised primarily of for both and . Apparently, the reaction product reduces the reactivity with electrolyte of both and . The self-heating rate of reacting with electrolyte was less than that of even though the specific surface area was about twice as large. This suggests composite electrodes using powdered Si-based electrode materials will be as safe as or safer than corresponding graphite electrodes in full-scale Li-ion cells. The reason that the lithiated silicon is safer than is because silicon stores more Li per unit volume than graphite, leading to thicker surface layers that slow the reaction with electrolyte.