Self-discharge detection method for nickel-cobalt-manganese lithium battery

Abstract

The invention discloses a self-discharge detection method for a nickel-cobalt-manganese lithium battery. The method comprises the steps that charge-discharge preprocessing is carried out on the nickel-cobalt-manganese lithium battery after capacity grading; standing in environments at different temperatures for a certain period of time is carried out; open circuit voltages V1 and V2 are tested; the value of W=V1-V2 is calculated; and a battery with large self-discharge is selected through the W value. According to the method, electrode polarization is eliminated through preprocessing; the effect of polarization and system instability on the voltage pair is minimized; batteries with large self-discharge can be quickly filtered out before grouping in a short period of time; the test is accurate and effective; the product quality is greatly improved; the consistency of the whole group of batteries is not affected by batteries with large self-discharge; and the service life of a battery group is extended.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and the invention relates to a self-discharge detection method of a nickel-cobalt lithium manganese oxide battery (i.e. a ternary lithium-ion battery). Background technique [0002] With the development of the electric vehicle industry, the application of ternary lithium batteries and electric vehicles has become a trend because nickel-cobalt lithium manganese oxide batteries have the advantages of higher energy density and longer life than other lithium-ion batteries. [0003] When the battery is not connected to the external circuit, the battery capacity loss caused by the internal polarization reaction is generally called self-discharge. Expressed by the percentage of capacity lost per year or per month, for example, the self-discharge of various lithium-ion batteries is very small, about 1-2% per month, and that of metal hydride batteries is as high as more than 10% per month. ...

AI Technical Summary

Problems solved by technology

[0004] In the production process of ternary lithium batteries, each manufacturer has its own discharge selection process. At present, there are mainly the following types: 1. Charge the battery to a half-electric state, store it for a period of time, and then select it, that is, select between voltage flat areas, but In this interval, the voltage and capacity of the battery do not change significantly, the required storage time is longer, and it is difficult to select; 2. Charge the battery to a fully charged state, store it for a period of time, and select it. In this interval, the voltage and The change in capacity is not obvious, it is difficult to pick out accurately, and the storage capacity of the battery is greatly lost when it is fully charged; 3. After the battery is divided and discharged (discharged to 2.0V or 2.5V), after a period of storage, pass The way to detect the rebound voltage is selected. This method has a short storage time and can shorten the process time. However, this method has high requirements for the consistency of product processing. Due to the inconsistent polarization state during the battery discharge process, some batteries cannot be judged by the rebound voltage. discharge

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