LITHIUM ION SECONDARY BATTERY

A purpose of the present invention is to provide a lithium ion secondary battery having more improved life characteristics while suppressing gelation of an electrode mixture slurry in a manufacturing process. The lithium ion secondary battery according to the present invention comprises a positive electrode having a positive electrode mixture layer comprising a layered lithium-nickel composite oxide in which a proportion of nickel in metals other than lithium is 80 mol % or more; LiOH; LiCO; and a chlorine-containing polyvinylidene fluoride-based polymer, wherein a content of LiOH in the positive electrode mixture layer and a content of LiCOin the positive electrode mixture layer are each 0.1 weight % or more and 2.1 weight % or less, a total content of LiOH and LiCOin the positive electrode mixture layer is 0.2 weight % or more and 4.2 weight % or less, and a content of chlorine in the positive electrode mixture layer is 30 μg/g or more and 120 μg/g or less.