A lithium-ion secondary battery and related preparation method thereof, battery module, battery pack and apparatus. The lithium-ion secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator, wherein the positive electrode plate includes a positive electrode current collector and a first positive electrode active material layer and a second positive electrode active material layer sequentially disposed on at least one side of the positive electrode current collector; the lithium-ion secondary battery satisfies: −1≤log10(u/v)×w≤15.5, wherein, u is a thickness of the first positive electrode active material layer in microns, v is a thickness of the second positive electrode active material layer in microns, w is a conductivity of the electrolyte at a temperature of 25° C. in mS·cm−1. The lithium-ion secondary battery has excellent performance such as low discharge resistance at low SOC and low gas production at high temperature.