Lithium-ion secondary battery and method of manufacture thereof

A lithium-ion secondary battery that includes an electricity-generating unit that includes: a positive electrode having a positive electrode collector, and a positive electrode mixture layer formed on a surface of the positive electrode collector; a negative electrode having a negative electrode collector, and a negative electrode mixture layer formed on a surface of the negative electrode collector; and a separator disposed between the positive electrode and the negative electrode. At least one of the positive electrode mixture layer and the negative electrode mixture layer has a high-density portion of high mixture density, and a low-density portion having a lower mixture density than the high-density portion and being in contact with the high-density portion. The low-density portion has a smaller area than the high-density portion when viewed in plan.