CN109581232B

CN109581232B - Method for judging whether battery cell can be retested or not

Info

Publication number: CN109581232B
Application number: CN201811517814.7A
Authority: CN
Inventors: 柳嘉伟; 包晓峰; 张盛武
Original assignee: Jiangsu Contemporary Amperex Technology Ltd
Current assignee: Jiangsu Contemporary Amperex Technology Ltd
Priority date: 2018-12-12
Filing date: 2018-12-12
Publication date: 2020-12-22
Anticipated expiration: 2038-12-12
Also published as: CN109581232A

Abstract

The invention discloses a method for judging whether a battery cell can be retested, which comprises the following steps: s1: according to the determined battery cell, determining a voltage drop value delta V by combining an SOC-OCV characteristic curve of the battery cell and an SOC drop value within an allowable time t and according to the SOC drop value and the SOC-OCV characteristic curve; s2: when the cell formation is abnormally stopped, recording the cell voltage V1 at the moment; s3: acquiring a cell voltage V2 of the 1 st minute when the cell formation is abnormally stopped, calculating a first pressure difference V12= V1-V2, and when the first pressure difference V12 exceeds a first pressure difference specification delta V1, indicating that the retesting cannot be carried out; Δ V1= (Δ V/t) × t1, t1=1 min; s4: when the first differential pressure V12 is within the first differential pressure specification Δ V1, acquiring a cell voltage V3 of the 4 th minute when the cell formation is abnormally stopped, calculating a second differential pressure V23= V2-V3, and when the second differential pressure V23 exceeds the second differential pressure specification Δ V2, indicating that the retesting cannot be performed; Δ V2= (Δ V/t) × t2, t2=3 min. The invention can carry out preliminary judgment on the safety performance of the battery cell, reduce the misjudgment of the battery cell and reduce the risk of formation retest.

Description

Method for judging whether battery cell can be retested or not

Technical Field

The invention relates to a method for judging whether a battery cell can be retested or not.

Background

At present, formation is an important step in the production process of lithium ion batteries, and mainly comprises the processes of activating the batteries, forming a stable SEI film, removing gas generated, and ensuring subsequent stable electrochemical performance, formation retest is a means for reforming bad products generated in the formation process, and disc binding is a process for binding each battery cell and a tray one by one. In the bad article of present formation process, only appear "voltage sudden change", "overtemperature", "the electrical core of unusual point number super standard" problem can retest after judging, the electrical core that appears other problems all does not judge and just directly retest, do not judge or artifical the judgement has certain erroneous judgement, can lead to retesting to have certain potential safety hazard, and the pull wire is higher to personnel's degree of dependence, bad article need artifical the discharge, and need artifical manual wiring harness to retest, equipment discharge need artifical wiring harness's electrical core quantity a lot each day.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for judging whether a battery cell can be retested, which can preliminarily judge the safety performance of the battery cell, reduce the misjudgment of the battery cell and reduce the risk of formation retesting.

In order to solve the technical problems, the technical scheme of the invention is as follows: a method for judging whether a battery cell can be retested or not comprises the following steps:

s1: according to the determined battery cell, determining a voltage drop value delta V by combining an SOC-OCV characteristic curve of the battery cell and an SOC drop value within an allowable time t and according to the SOC drop value and the SOC-OCV characteristic curve;

s2: in the process of forming the battery cell, when the battery cell formation is abnormally stopped, recording the battery cell voltage V1 at the moment;

s3: then, acquiring a cell voltage V2 of the 1 st minute when the cell formation is abnormally stopped, calculating a first pressure difference V12= V1-V2, and when the first pressure difference V12 exceeds a first pressure difference specification delta V1, indicating that the retesting cannot be carried out; wherein Δ V1= (Δ V/t) × t1, t1=1 min;

s4: when the first differential pressure V12 is within the first differential pressure specification Δ V1, then acquiring a cell voltage V3 of the cell formation abnormal stop for the 4 th minute, calculating a second differential pressure V23= V2-V3, and when the second differential pressure V23 exceeds the second differential pressure specification Δ V2, indicating that the retesting cannot be performed; where Δ V2= (Δ V/t) × t2, and t2=3 min.

Further, in step S3 and/or step S4, after the battery cell is determined to be unreleasable, it is manually determined whether the battery cell can be retested, and if the battery cell can be retested, the battery cell is bound to the tray again for retesting.

By adopting the technical scheme, the equipment can judge whether the safety risk exists in the battery cell by adopting the method, the battery cell without the safety risk can be automatically retested, the battery cell with the safety risk cannot be retested, and after the battery cell is discharged, an engineer can judge again, so that the misjudgment of the battery cell is reduced, and the retesting risk is reduced. And because the battery cell can be retested automatically, the number of the battery cells needing manual disc binding of staff is reduced from 300 EA/stay wire/day to 20 EA/stay wire/day, the automation degree is improved, and the manpower cost and the battery cell scrap caused by manual misoperation are reduced.

Drawings

Fig. 1 is a voltage curve diagram of a normal cell of the present invention after the formation of the cell is stopped;

FIG. 2 is a graph of voltage curves after the shutdown of the hazardous cell of the present invention;

fig. 3 is a SOC-OCV characteristic curve diagram of the battery cell.

Detailed Description

In order that the present invention may be more readily and clearly understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings.

After the formation is stopped, the voltage drop value between the normal cell and the risk cell has a large difference, and after the formation of the normal cell is stopped, the voltage drops to a certain extent due to depolarization effect, but the dropping speed is slow, as shown in fig. 1; after the formation of the risk cell is stopped, the voltage will continuously decrease, and the decreasing speed is obviously faster than that of the normal cell, as shown in fig. 2, according to this logic, a method for determining whether the cell can be retested is provided, and the steps of the method include:

s1: according to the determination cell, combining an SOC-OCV characteristic curve (shown in FIG. 3) of the cell and an SOC drop value in an allowable time t, and according to the SOC drop value and combining the SOC-OCV characteristic curve, confirming a voltage drop value delta V; the SOC-OCV characteristic curve of the battery cell and the SOC drop value in the allowed time t are performance data of the battery cell provided for a customer;

s3: then, acquiring a cell voltage V2 of the cell formation abnormal stop for the 1 st minute, calculating a first pressure difference V12= V1-V2, and when the first pressure difference V12 exceeds a first pressure difference specification delta V1, indicating that the cell cannot be retested, wherein the cell is a risk cell; wherein Δ V1= (Δ V/t) × t1, t1=1 min;

s4: when the first pressure difference V12 is within the first pressure difference specification Δ V1, then acquiring a cell voltage V3 of the cell formation abnormal stop for the 4 th minute, calculating a second pressure difference V23= V2-V3, and when the second pressure difference V23 exceeds the second pressure difference specification Δ V2, indicating that the cell is a risk cell and is not reteasurable; wherein Δ V2= (Δ V/t) × t2, t2=3 min; if the second pressure difference V23 is within the second pressure difference specification Δ V2, the cell may be retested automatically, so as to automatically determine whether the cell has a safety risk, and the cell without the safety risk may be retested automatically, and the cell with the safety risk may not be retested.

In step S3 and/or step S4, after the battery cell is determined to be unreleasable, it is manually determined whether the battery cell can be retested, and if the battery cell can be retested, the battery cell is bound again, so that the labor cost and the battery cell scrap caused by manual misoperation are reduced.

In this embodiment, the equipment may upload the cell voltage V1 at the time of abnormal stop, the cell voltage V2 at the 1 st minute of abnormal stop, and the cell voltage V3 at the 4 th minute of abnormal stop to the MES, and the MES determines whether the cell has a safety risk according to the method in this embodiment.

In this embodiment, formation, retesting, and disk binding are terms used in the production process of lithium ion batteries, and the formation mainly includes activating the battery to form a stable SEI film (solid electrolyte interface film), eliminating gas generation, and ensuring subsequent stable electrochemical performance.

The working principle of the invention is as follows:

by acquiring the cell voltage V1 when the abnormal stop is formed, the cell voltage V2 when the abnormal stop is formed for the 1 st minute and the cell voltage V3 when the abnormal stop is formed for the 4 th minute, a first differential pressure V12 and a second differential pressure V23 are calculated, and the first differential pressure V12, the first differential pressure specification delta V1, the second differential pressure V23 and the second differential pressure specification delta V2 are compared, when the first differential pressure V12 is in the first differential pressure specification delta V1 and the second differential pressure V23 is in the second differential pressure specification delta V2, the automatic retest can be performed, otherwise, whether the retest can be performed or not is manually judged, and the retest can be performed by binding again if the retest can be performed manually.

The above embodiments are described in further detail to solve the technical problems, technical solutions and advantages of the present invention, and it should be understood that the above embodiments are only examples of the present invention and are not intended to limit the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for judging whether a battery cell can be retested is characterized in that: the method comprises the following steps:

s3: then, acquiring a cell voltage V2 of the 1 st minute when the cell formation is abnormally stopped, calculating a first pressure difference V12 as V1-V2, and when the first pressure difference V12 exceeds a first pressure difference specification delta V1, indicating that the retest cannot be carried out; wherein Δ V1 ═ t1, (Δ V/t) t1 ═ 1 min;

s4: when the first differential pressure V12 is within the first differential pressure specification Δ V1, then acquiring a cell voltage V3 of which the cell formation is abnormally stopped for the 4 th minute, calculating a second differential pressure V23 as V2-V3, and when the second differential pressure V23 exceeds the second differential pressure specification Δ V2, indicating that the retesting cannot be performed; wherein Δ V2 ═ t2, (Δ V/t) t2 ═ 3 min.

2. The method of claim 1, wherein: in step S3 and/or step S4, after the retest is determined to be impossible, it is manually determined whether retest is possible, and if the retest is manually determined to be possible, the retest is performed again by binding.