LITHIUM-ION SECONDARY BATTERY

A lithium-ion secondary battery comprises a positive electrode plate, a negative electrode plate, and an electrolyte, and has a charge cut-off voltage of ≥4.48 V. The positive electrode plate comprises a positive electrode active coating layer comprising lithium cobalt oxide, wherein the lithium cobalt oxide contains the element Al, and the mass content c1 of the element Al in the positive electrode active coating layer is 6000-15000 ppm. The negative electrode plate comprises a negative electrode active coating layer comprising a silicon-carbon material, wherein the mass content c2 of the element Si is 1.5-16%; and the silicon-carbon material comprises primary spherical particles with an average particle size of 1-6 μm. The electrolyte comprises 1,3,6-hexanetricarbonitrile, with the mass content c3 of 1,3,6-hexanetricarbonitrile in the electrolyte and the mass content c2 of the element Si in the negative electrode active coating layer satisfying: 0.63≤c2/c3≤15.