A lithium-ion battery

Abstract

The application relates to the technical field of lithium ion batteries, in particular to a lithium ion battery with excellent high-temperature storage performance and room-temperature cycle life. The lithium ion battery comprises a positive electrode sheet, a negative electrode sheet and a non-aqueous electrolyte; the negative electrode sheet comprises a negative electrode material layer and a sodium-containing solid electrolyte interface film formed on the surface of the negative electrode material layer; the non-aqueous electrolyte comprises a lithium salt and a sodium salt; the lithium ion battery satisfies the conditions of 0.1 <= m / (n*x*s) <= 50, 0.01 <= m <= 3, 0.01 <= n <= 5 and 0.2 <= s <= 5. In the lithium ion battery, the sodium salt preferentially forms the sodium-containing solid electrolyte interface film on the negative electrode during the first charging of the battery due to the lower desolvation energy, and the sodium salt has higher thermal stability; by controlling the specific surface area of the negative electrode material layer and the content of sodium in the solid electrolyte interface film on the surface of the negative electrode material layer, the transmission path of lithium ions through the interface film is increased, the diffusion distance of lithium ions in the negative electrode active material particles is reduced, the diffusion and transmission dynamics of lithium ions are improved, impedance and polarization are reduced, and good room-temperature cycle life is ensured.

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