Abstract: A lithium secondary battery is intended to suppress deterioration upon storage at high temperature of 50° C. or higher without deteriorating the output characteristics at a room temperature. The battery includes a positive electrode capable of occluding and releasing lithium ions, a negative electrode capable of occluding and releasing lithium ions, a separator disposed between the positive electrode and the negative electrode and an electrolyte, in which the electrolyte contains a compound represented by formula (1) (R?O)nSiR4-n??(Formula 1) where R? represents an alkyl group, R is selected from hydrogen, an alkyl group, an alicyclic group, and an aryl group, each of R? and R may be identical or different from each other, the alkyl group has a straight or branched chain having fewer than 10 carbon atoms, and n is an integer of 1 to 3, and a compound having a polymerizable group in the molecule.