Abstract: An organic electrolyte for use in a lithium secondary battery comprising a lithium salt dissolved in an organic solvent mixture is disclosed. The lithium salt can be LiClO.sub.4, LiPF.sub.6, LiBF.sub.4, LiCF.sub.3 SO.sub.3, LiAsF.sub.6, or other lithium salt, and the organic solvent mixture contains a carbonate and an acetate. The carbonate is ethylene carbonate, and the acetate can be either methyl acetate or ethyl acetate. The carbonate and the acetate are provided in a ratio of carbonate/acetate ranging from 80/20 to 20/80, or preferably from 40/60 to 60/40, and said lithium salt has a concentration of between 0.6 and 1.5M, or preferably at about 1M. The electrolyte exhibits excellent stability in a lithium secondary battery having a cathode which contains either LiCoO.sub.2 or LiMn.sub.2 O.sub.4, and can withstand charge/discharge voltages of at least as high as 5 V (vs. Li/Li.sup.+), with excellent service life.