SECONDARY BATTERY AND DEVICE CONTAINING SAME

The application relates to a secondary battery comprising a package bag and a battery core arranged in the package bag, the battery core comprising a positive electrode plate, a negative electrode plate and a separator, the positive electrode plate comprising a positive current collector and a positive electrode film disposed on at least one surface of the positive electrode current collector and comprising a positive active material; and the negative electrode plate comprising a negative electrode current collector and a negative electrode film provided on at least one surface of the negative electrode current collector and comprising a negative active material, characterized in that the positive active material comprises one or more of lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide, and at least a part of the positive active material comprises a single crystal particle; the negative active material comprises a silicon-based material and a graphite material; and the package bag has a sealing width of 3 mm to 8 mm.