LITHIUM-ION SECONDARY BATTERY AND PREPARATION METHOD THEREFOR, BATTERY MODULE, BATTERY PACK, AND DEVICE

Disclosed are a lithium-ion secondary battery and a preparation method therefor, a battery module, a battery pack, and a device. The lithium-ion secondary battery comprises a positive electrode pole piece, a negative electrode pole piece and an electrolyte solution. The positive electrode pole piece comprises a positive electrode active material and a positive electrode lithium supplementing material. The positive electrode lithium supplementing material comprises a lithium-rich metal oxide, and the lithium-rich metal oxide contains one or more elements among Ni, Co, Fe, Mn, and Cu. The electrolyte solution comprises an electrolyte lithium salt and a solvent, and the ratio ε of the total mass of fluorine in the anion of the electrolyte lithium salt relative to the total mass of the electrolyte solution is less than 14%.