A lithium secondary battery

摘要

A lithium secondary battery comprising a negative electrode containing an active material including carbon materials capable of electrochemically occluding and releasing lithium ions, a positive electrode containing an active material including lithium compounds capable of electrochemically occluding and releasing lithium ions, a separator interposed therebetween. The battery further includes an organic electrolyte prepared by dissolving lithium compounds as solute in an organic solvent. The organic solvent further includes at least one tetraalkyl phosphonium salt as an additive. As a result of the use of this additive, the lithium secondary battery has an improved charge and discharge efficiency, lowering of the capacity retention rate is suppressed and cycle life is prolonged, and also energy density of the battery is increased.