A negative pole piece and a secondary battery

Abstract

The present invention provides a negative electrode sheet, comprising a negative electrode current collector and a multi-layer active material layer formed on the negative electrode current collector; the multi-layer active material layer includes at least a first active material layer and a second active material layer; the first The active material layer contains the first negative electrode active material, and the second active material layer contains the second negative electrode active material; the ratio of the gram capacity of the negative electrode active material to the thickness of the first active material layer is 3.5-10.0. The ratio of the gram capacity of the negative active material of the second active material layer to its thickness is 6.5-23.0. The battery using the negative electrode sheet of the present invention can simultaneously have high energy density and good cycle life.

Description

technical field [0001] The present application relates to the technical field of secondary batteries, in particular to a negative pole piece and a secondary battery using the negative pole piece. Background technique [0002] Due to the advantages of high energy density, high operating voltage, long service life and low self-discharge, secondary batteries have been widely used in recent years. In addition, with the increasing popularity of electric vehicles, the demand for secondary batteries has also exploded. But at the same time, there are several problems that still plague consumers: safety, cost and cruising range. [0003] Among them, the improvement of the cruising range mainly depends on the improvement of the energy density of the battery cell. Usually, there are two ways to solve this problem: 1) thicken the pole piece to increase the capacity of the active material per unit area, thereby increasing the energy density. 2) The active material with high gram capaci...

AI Technical Summary

Problems solved by technology

For example, after the coating thickness increases, the battery polarization is serious, which affects the cycle life of the battery cell

After the gram capacity (negative electrode graphite material) increases, the lithium deintercalation ability of the negative electrode graphite material will become worse. If the charging rate is large, the lithium ions released from the positive electrode will not have time to be embedded in the negative electrode material, which will lead to the precipitation of metal lithium on the surface of the electrode sheet, causing Side reactions and the production of a large number of by-products, which can lead to cycle diving and even safety issues

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