Lithium Ion Secondary Battery and Method for Producing Lithium Ion Secondary Battery

Abstract

Provided are a lithium ion secondary battery that prevents short circuit of a battery in which energy density, cycle characteristics, and safety are all balanced at high levels; and a method for producing the lithium ion secondary battery. The lithium ion secondary battery according to the present invention has a positive electrode, a negative electrode, and a separator provided between the positive electrode and the negative electrode, in which the negative electrode contains a negative electrode active material containing silicon, the hardness of the negative electrode active material is 10 GPa or more and 20 GPa or less, and the separator has a constitution in which a resin layer and a porous layer are laminated, the thickness of the porous layer is 2 μm or more and 10 μm or less when the thickness of the resin layer is 25 μm or more and 30 μm or less, and the thickness of the porous layer is 5 μm or more and 20 μm or less when the thickness of the resin layer is 15 μm or more but less than 25 μm.

Dependencies are inferred from the claim text.