A secondary battery, comprising a positive electrode plate, a negative electrode plate, a separator and an electrolyte, wherein: the positive electrode plate comprises a positive electrode current collector and a positive electrode film disposed on at least one surface of the positive electrode current collector, comprising a positive active material, and the negative electrode plate comprises a negative electrode current collector and a negative electrode film disposed on at least one surface of the negative electrode current collector, comprising a negative active material; wherein: the positive active material comprises one or more of layered lithium nickel cobalt manganese oxide and layered lithium nickel cobalt aluminum oxide; the negative active material comprises graphite and silicon-oxygen compound SiO x, in which 0 < x < 2; the delithiation capacity A of the negative electrode film in the voltage range of 0.005V to the delithiation platform voltage and the delithiation capacity B of the negative electrode film in the voltage range of the delithiation platform voltage to 1.2V satisfy: 1≤A/B≤2; when the secondary battery is discharged to a voltage of 2.5V, a voltage U of the negative electrode plate relative to a lithium metal reference electrode satisfies: 0.5V ≤ U ≤ 0.7V, measured according to the methods as described in the description; and wherein a mass percentage ω of the silicon-oxygen compound in the negative active material satisfies 5%≤ω≤40%. the positive electrode plate comprises a positive electrode current collector and a positive electrode film disposed on at least one surface of the positive electrode current collector, comprising a positive active material, and the negative electrode plate comprises a negative electrode current collector and a negative electrode film disposed on at least one surface of the negative electrode current collector, comprising a negative active material; wherein: the positive active material comprises one or more of layered lithium nickel cobalt manganese oxide and layered lithium nickel cobalt aluminum oxide; the negative active material comprises graphite and silicon-oxygen compound SiO x, in which 0 < x < 2; the delithiation capacity A of the negative electrode film in the voltage range of 0.005V to the delithiation platform voltage and the delithiation capacity B of the negative electrode film in the voltage range of the delithiation platform voltage to 1.2V satisfy: 1≤A/B≤2; when the secondary battery is discharged to a voltage of 2.5V, a voltage U of the negative electrode plate relative to a lithium metal reference electrode satisfies: 0.5V ≤ U ≤ 0.7V, measured according to the methods as described in the description; and wherein a mass percentage ω of the silicon-oxygen compound in the negative active material satisfies 5%≤ω≤40%. the positive active material comprises one or more of layered lithium nickel cobalt manganese oxide and layered lithium nickel cobalt aluminum oxide; the negative active material comprises graphite and silicon-oxygen compound SiO x, in which 0 < x < 2; the delithiation capacity A of the negative electrode film in the voltage range of 0.005V to the delithiation platform voltage and the delithiation capacity B of the negative electrode film in the voltage range of the delithiation platform voltage to 1.2V satisfy: 1≤A/B≤2; when the secondary battery is discharged to a voltage of 2.5V, a voltage U of the negative electrode plate relative to a lithium metal reference electrode satisfies: 0.5V ≤ U ≤ 0.7V, measured according to the methods as described in the description; and wherein a mass percentage ω of the silicon-oxygen compound in the negative active material satisfies 5%≤ω≤40%.