Electrode assembly and lithium ion battery

Abstract

The invention provides an electrode assembly and a lithium ion battery. The electrode assembly comprises a positive pole piece, an isolating membrane and a negative pole piece, wherein the negative pole piece comprises a negative current collector and a negative active material layer, and further comprises a metal lithium layer, the metal lithium layer is formed by a plurality of regular or irregular strip-shaped lithium-rich areas, and the plurality of lithium-rich areas are distributed at intervals in the length direction of the negative pole piece in a non-continuous form. The electrode assembly also satisfies the following conditions: the ratio of the negative electrode capacity per unit area to the positive electrode capacity per unit area is 1.2-2.1, and the ratio of the negative electrode capacity per unit area to the sum of the positive electrode capacity per unit area and 80% of the capacity of the metal lithium layer on the surface of the negative electrode active material layer per unit area is greater than or equal to 1.10. The lithium ion battery disclosed by the invention has relatively high lithium supplementing efficiency and relatively low direct-current impedance,and meanwhile, the lithium ion battery also has long cycle life and storage life.

Description

technical field [0001] The invention relates to the battery field, and more specifically relates to an electrode assembly and a lithium ion battery. Background technique [0002] Among secondary batteries, compared with other types of secondary batteries, lithium-ion batteries occupy a mainstream position in the market due to their higher energy density advantages. Among them, lithium-ion batteries with lithium iron phosphate as the positive electrode active material are widely used in electric bus power systems due to their high safety, low cost, and long life, and have broad application prospects in the field of large-scale energy storage. [0003] In recent years, based on the cost of electricity, the requirements for the life of lithium-ion batteries have become higher and higher. Due to the dissolution-repair equilibrium of the solid-electrolyte interface film (SEI film) on the surface of the graphite anode, the active lithium available for shuttle between the anode an...

AI Technical Summary

Problems solved by technology

Usually, an appropriate amount of lithium is directly covered on the surface of the negative electrode sheet to form a lithium metal layer, but after lithium is covered on the surface of the negative electrode sheet, part of the lithium will react with the air, resulting in a low utilization rate of lithium in the lithium metal layer. The battery life improvement effect is not as good as expected; at the same time, the products of lithium and air reaction, such as lithium oxide and lithium carbonate, accumulate on the surface of the negative electrode sheet, which will cause the impedance of the negative electrode to increase after pre-intercalation of lithium, and affect the DC impedance of the lithium-ion battery.

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