A secondary battery, comprising a negative electrode plate, wherein the negative electrode plate comprises a composite current collector and a negative electrode active material layer disposed on at least one surface of the composite current collector, the negative electrode active material layer comprises a silicon-based active material, and the silicon-based active material accounts for 0.5 wt% to 50 wt% of total mass of the negative electrode active material layer; the composite current collector comprises a polymer support layer and a metal conductive layer disposed on at least one surface of the polymer support layer, and brittleness parameter C of the composite current collector ranges from 0.03 to 0.5, wherein C = T 1 × D 1 / T 2 × D 2 T 1 is tensile strength of the metal conductive layer, in MPa; D 1 is thickness of the metal conductive layer, in μm; T 2 is tensile strength of the polymer support layer, in MPa, D 2 is thickness of the polymer support layer, in μm; wherein T 1 and T 2 are measured at 25°C; and the tensile strength is measured by cutting a sample cut with a width of 15 mm and a length of 150 mm, then loading between an upper clamp and a lower clamp of American INSTRON 3365 universal tensile tester with an initial length set to 50 mm, and then performing a tensile test at a tensile rate of 5 mm/min until the sample broke. the negative electrode plate comprises a composite current collector and a negative electrode active material layer disposed on at least one surface of the composite current collector, the negative electrode active material layer comprises a silicon-based active material, and the silicon-based active material accounts for 0.5 wt% to 50 wt% of total mass of the negative electrode active material layer; the composite current collector comprises a polymer support layer and a metal conductive layer disposed on at least one surface of the polymer support layer, and brittleness parameter C of the composite current collector ranges from 0.03 to 0.5, wherein C = T 1 × D 1 / T 2 × D 2 T 1 is tensile strength of the metal conductive layer, in MPa; D 1 is thickness of the metal conductive layer, in μm; T 2 is tensile strength of the polymer support layer, in MPa, D 2 is thickness of the polymer support layer, in μm; wherein T 1 and T 2 are measured at 25°C; and the tensile strength is measured by cutting a sample cut with a width of 15 mm and a length of 150 mm, then loading between an upper clamp and a lower clamp of American INSTRON 3365 universal tensile tester with an initial length set to 50 mm, and then performing a tensile test at a tensile rate of 5 mm/min until the sample broke. T 1 is tensile strength of the metal conductive layer, in MPa; D 1 is thickness of the metal conductive layer, in μm; T 2 is tensile strength of the polymer support layer, in MPa, D 2 is thickness of the polymer support layer, in μm; wherein T 1 and T 2 are measured at 25°C; and the tensile strength is measured by cutting a sample cut with a width of 15 mm and a length of 150 mm, then loading between an upper clamp and a lower clamp of American INSTRON 3365 universal tensile tester with an initial length set to 50 mm, and then performing a tensile test at a tensile rate of 5 mm/min until the sample broke.