To provide a lithium ion secondary battery capable of suppressing insertion of lithium ion into a second negative electrode part of a negative electrode active material layer when charging, and suppressing degradation of a battery capacity, and to provide a vehicle with the lithium ion secondary battery and a battery-mounted device.

The lithium ion secondary battery 1 includes a positive electrode plate 30, a negative electrode plate 40 having the negative electrode active material layer 41, a separator 20, and an electrolyte solution 60. The negative electrode active material layer is composed of a first negative electrode part 42 opposed to the positive electrode material layer 31 with the separator interposed and a second negative electrode part 43 having no opposing positive electrode material layer. The separator includes a first separator part 22 which is opposed to the first negative electrode part and is porous and capable of permeating lithium ion in its own thickness direction DC and a second separator part 23 opposed to the second negative electrode part. Part of the second separator part is made to be more difficult to permeate lithium ion in the thickness direction DC than the first separator part.

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