Abstract: A lithium ion secondary battery includes a positive electrode, a negative electrode, and an electrolyte. The negative electrode has a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector. The negative electrode current collector satisfies: (D2/D1)?0.968??(1), D2?21.947*(X/100)?24.643??(2), 110?X?125??(3), and where D1 is a first displacement amount in a first piercing test at a first piercing speed of 0.1 mm/min or more; D2 is a second displacement amount in a second piercing test at a second piercing speed of less than 0.1 mm/min; and X is an expansion coefficient (%) of the negative electrode active material layer.

Abstract: Disclosed is a secondary battery in which a negative electrode has a covered portion covered with a negative electrode active material covering portion and a negative electrode active material non-covered portion on a strip-shaped negative electrode foil, the negative electrode active material non-covered portion is joined to a negative electrode current collector plate at the other end portion of the electrode winding body, the electrode winding body has a flat surface formed by bending any one or both of a positive electrode active material non-covered portion and the negative electrode active material non-covered portion toward a central axis of the wound structure and overlapping the positive electrode active material non-covered portion and the negative electrode active material non-covered portion, and a first groove formed in the flat surface, at least one C-shaped second groove is included in a can bottom of a battery can.

Abstract: Provided is a secondary battery, in the secondary battery, the positive electrode has a covered portion covered with a positive electrode active material layer and a positive electrode active material non-covered portion on a strip-shaped positive electrode foil, the negative electrode has a covered portion covered with a negative electrode active material layer and a negative electrode active material non-covered portion on a strip-shaped negative electrode foil, the positive electrode active material non-covered portion are joined to the positive electrode current collector plate at one end portion of the electrode winding body, the negative electrode active material non-covered portion is joined to the negative electrode current collector plate at the other end portion of the electrode winding body, the electrode winding body has a flat surface formed by bending any one or both of the positive electrode active material non-covered portion and the negative electrode active material non-covered portion.

Abstract: A lithium ion secondary battery includes a positive electrode, a negative electrode, and an electrolyte. The negative electrode has a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector. The negative electrode current collector satisfies: (D2/D1)?0.968 ??(1), D2?21.947*(X/100)?24.643 ??(2), 110?X?125 ??(3), and where D1 is a first displacement amount in a first piercing test at a first piercing speed of 0.1 mm/min or more; D2 is a second displacement amount in a second piercing test at a second piercing speed of less than 0.1 mm/min; and X is an expansion coefficient (%) of the negative electrode active material layer.

Abstract: A cathode includes a lithium transition metal complex compound including lithium, one, or two or more transition metals, magnesium, and oxygen as constituent elements. In a standardized X-ray absorption spectrum of the lithium transition metal complex compound measured by an X-ray absorption spectroscopic method, a first absorption edge having absorption edge energy E1 in X-ray absorption intensity of about 0.5 exits in a range where X-ray energy is from about 1303 eV to about 1313 eV both inclusive, in a discharged state in which a discharge voltage is about 3.0 V, and a second absorption edge having absorption edge energy E2 in X-ray absorption intensity of about 0.5 exits, in a charged state in which a charge voltage V is from about 4.3 V to about 4.5 V both inclusive. The absorption edge energies E1 and E2 and the charge voltage V satisfy a relation of E2?E1?(V?4.25)×4.

Abstract: A cathode includes a lithium transition metal complex compound including lithium, one, or two or more transition metals, magnesium, and oxygen as constituent elements. In a standardized X-ray absorption spectrum of the lithium transition metal complex compound measured by an X-ray absorption spectroscopic method, a first absorption edge having absorption edge energy E1 in X-ray absorption intensity of about 0.5 exits in a range where X-ray energy is from about 1303 eV to about 1313 eV both inclusive, in a discharged state in which a discharge voltage is about 3.0 V, and a second absorption edge having absorption edge energy E2 in X-ray absorption intensity of about 0.5 exits, in a charged state in which a charge voltage V is from about 4.3 V to about 4.5 V both inclusive. The absorption edge energies E1 and E2 and the charge voltage V satisfy a relation of E2?E1?(V?4.25)×4.