NOVELTY - Flat nonaqueous secondary battery (10) comprises a positive electrode including a positive electrode substrate having a surface with a positive electrode active material layer formed; a negative electrode including a negative electrode substrate having a surface with a negative electrode active material layer formed; a positive electrode tab (12) connected to the positive electrode substrate; a negative electrode tab (13) connected to the negative electrode substrate; and a separator.    USE - In nonaqueous secondary battery pack (claimed); and used as power supplies for powering portable electronic equipment, such as cell phones, portable personal computers and portable music players, and power supplies for hybrid electric vehicles and electric vehicles.    ADVANTAGE - The flat nonaqueous secondary battery is extremely safe; and is unlikely to emit smoke or explode even when a nail penetrates the battery in a charged state.    DETAILED DESCRIPTION - A flat nonaqueous secondary battery comprises a positive electrode including a positive electrode substrate having a surface with a positive electrode active material layer formed; a negative electrode including a negative electrode substrate having a surface with a negative electrode active material layer formed; a positive electrode tab connected to the positive electrode substrate; a negative electrode tab connected to the negative electrode substrate; and a separator, where an electrode assembly is formed by stacking or winding the positive electrode and the negative electrode with the separator interposed between them being sealed in a laminated outer body (11) together with a nonaqueous electrolyte, the positive electrode tab and the negative electrode tab are led out from the laminated outer body. The separator has a rupture elongation of greater than or equal to 50% in at least transverse direction (TD) or machine direction (MD). A metal plate (14) connected to the positive electrode tab is placed on an outer principal surface (15) of the laminated outer body. An INDEPENDENT CLAIM is included for a nonaqueous secondary battery pack comprising the flat nonaqueous secondary batteries stacked and integrated to form the battery pack, where each of the flat nonaqueous secondary batteries comprise a metal plate being placed on an outer principal surface of the laminated outer body of at least one flat nonaqueous secondary battery, and the metal plate is connected to the positive electrode tab of at least one flat nonaqueous secondary battery.    DESCRIPTION OF DRAWING(S) - The figure shows an exploded perspective view of a nonaqueous secondary battery using a laminated outer body.    Nonaqueous secondary battery (10)    Laminated outer body (11)    Positive electrode tab (12)    Negative electrode tab (13)    Metal plate (14)    Outer principal surface (15)