LITHIUM ION SECONDARY BATTERY

This application relates to a lithium ion secondary battery comprising a battery core and an electrolyte, wherein the battery core comprises a lithium-manganese-based positive electrode active material; the electrolyte comprises a solvent, a lithium salt and an additive comprising vinylene carbonate; and wherein the weight percentage q of the electrolyte based on the total weight of the positive electrode active material layer in the battery core, the weight percentage r of vinylene carbonate present in the electrolyte, the compaction density s of the negative electrode active material layer in the battery core and the weight percentage p of manganese element present in the positive electrode active material satisfies 0.05≤q·r·s/p≤6, wherein the units of q, r, and p are wt %, and the unit of s is g/cm. The lithium ion secondary battery in this application has relatively high safety performance, cycle performance and storage performance.