The most widely used liquid non-aqueous electrolytes for lithium-ion cells used in electronic consumer and automotive applications consist of lithium hexafluorophosphate (LiPF6) as conductive salt dissolved in a mixture of carbonate esters (cyclic and linear) with the structural unit RO-CO–OR. The separator is a second safety related component in lithium-ion cells, which can be classified into three groups according to the structure: microporous polymer membranes (MPM), non-woven fabric mats (FM) and inorganic composite membranes (ICM). Both non-active components can take part at calendar and cyclic ageing in lithium-ion cells. In this work we report investigations of long-term decomposition reaction mechanisms of a binary electrolyte system. Furthermore, the mutual interaction ageing behavior of both components are investigated.