SECONDARY BATTERY, BATTERY PACK, AND VEHICLE

According to one approach, a secondary battery (100) including a positive electrode (5), a negative electrode (3), an insulating layer, and a nonaqueous electrolyte is provided. The positive electrode (5) includes a positive electrode active material-containing layer (b) which contains a lithium nickel cobalt manganese composite oxide. The negative electrode (3) includes a negative electrode active material-containing layer (5b) that has a first surface (13) . The insulating layer includes a solid electrolyte layer (4b) that has a second surface (14) that is at least partly opposed to or partly in contact with the first surface (13) . The solid electrolyte layer contains a Li ion conductive oxide. At least part of the second surface (14) or the first and second surfaces (13, 14) includes a Mn-containing substance. An abundance ratio of Mn on the second surface (14) is higher than an abundance ratio of Mn on the first surface (13).