Lithium ion battery with NP ratio smaller than 1 and preparation method thereof

Abstract

The invention discloses a lithium ion battery with the NP ratio smaller than 1 and a preparation method of the lithium ion battery. The preparation method comprises the following steps: S1, preparing a positive pole piece and a negative pole piece; s2, rolling the positive pole piece and the negative pole piece, and then carrying out die cutting or striping treatment; s3, assembling the positive pole piece, the negative pole piece and the battery diaphragm to form a battery cell; and S4, injecting an electrolyte into the battery cell, and packaging to obtain the lithium ion battery. Wherein the positive pole piece and the negative pole piece meet the following relational expression: positive pole coating surface density * positive pole active material ratio * positive pole first charging gram volume = negative pole coating surface density * negative pole active material ratio * negative pole first lithium embedding gram volume, and the negative pole first effect is smaller than the positive pole first effect. Under the condition that the manufacturing cost of the lithium ion battery is not increased, the design relational expression is provided, the lithium ion battery designed according to the relational expression does not have the lithium precipitation condition when the N / P ratio is smaller than 1, and the safety performance of the battery cell is guaranteed.

Description

technical field [0001] The invention relates to the technical field of lithium ion battery preparation, in particular to a lithium ion battery with an NP ratio less than 1 and a preparation method thereof. Background technique [0002] Energy is a major pillar of scientific and technological progress in modern society. With the increasing demand for energy in society, the total amount of traditional fossil energy is limited and non-renewable. Therefore, it is urgent to develop new renewable energy. Among them, lithium-ion batteries have become one of the important parts of new renewable energy due to their low manufacturing cost, large specific energy and long working life. The core of the lithium-ion battery is the cell. For the design of the cell, the N / P ratio design is one of the key parameters. N / P (Negative / Positive) (hereinafter referred to as NP) refers to the unit at the same stage and under the same conditions. The ratio of the actual capacity of the positive and ...

AI Technical Summary

Problems solved by technology

However, NP>1 is not conducive to improving the high-temperature performance of the battery (high-temperature gas mainly comes from the negative electrode), and when NP>1, too much negative electrode material will consume more lithium ions embedded in the positive electrode during the first charge and discharge. Causes the overall capacity of the battery to decrease in subsequent charge and discharge cycles