CN111751738A - Process for detecting fragment cracking or tab cold welding of lithium ion battery pole - Google Patents

Abstract

A process for detecting the fragment cracking or tab cold welding of a lithium ion battery pole comprises a voltage internal resistance tester and a resistor; firstly, testing the initial voltage value V0 of the battery core, and grading the battery according to the voltage values, wherein the voltage is changed from high to low by L1, L2 and L3- -. Secondly, loading a resistor on a clamp of the voltage and internal resistance tester, testing a voltage value V1 step by step according to the level, judging the level of the battery according to the voltage value, and referring to the level grades L1, L2 and L3- - -of the voltage standard V0; if the same cell voltage V1 grade is the same as V0 grade or the V1 grade is lower than V0 grade, the product is qualified. Conversely, the pressure drop is not acceptable, i.e. the load capacity is not acceptable. The method can effectively screen out the battery cell with the broken pole piece and the tab rosin joint, and has the advantages of low investment of process equipment, simple and effective operation and easy popularization.

Description

Process for detecting fragment cracking or tab cold welding of lithium ion battery pole

Technical Field

The invention relates to the technical field of lithium ion batteries, in particular to a process for detecting the fragment cracking or tab cold welding of a lithium ion battery core.

Background

The lithium ion battery is the most widely used energy at present, and is continuously expanded and popularized in the fields of portable mobile power supplies, smart phones, notebook computers, tablet computers, cameras and other portable electronic products. In the manufacturing and production process of the lithium ion battery, the winding process is adopted by most manufacturers due to high efficiency and low cost. Lithium ion batteries have many working procedures and long manufacturing process, and partial key working procedures can only monitor the overall quality state through sampling inspection, but can not find the abnormal problems of individual electric cores, such as: the winding core electrode plate has cracks or fractures when being folded, and the electrode has poor welding and the like when being spot welded.

At present, the resistance and voltage in the lithium ion battery cell are tested to determine the resistance and voltage in a common mode. However, the internal resistance of the lithium ion battery cell is in the milliohm level, and experiments prove that cracks or fractures are formed in the rolled pole piece, insufficient welding and other adverse phenomena occur in the pole piece during spot welding, and the internal resistance is only slightly biased. Therefore, the method for measuring the internal resistance of the battery core is difficult to completely pick out the lithium ion battery with poor lithium ion battery such as insufficient solder during spot welding of the tab due to cracks or fractures in the rolled core electrode sheet, and the risk of missing judgment exists.

Disclosure of Invention

How to completely pick out the bad lithium ion battery cell such as the crack or fracture in the winding core electrode plate and the cold joint when the electrode plate is spot welded is one of the key points of the work and quality control of the development department.

The invention utilizes the loading resistor to observe the voltage drop through rapid overload to identify cracks or fractures in the winding core pole piece, and potential defects of cold welding exist in the pole piece during spot welding.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:

a process for detecting the fragment cracking or tab cold welding of a lithium ion battery pole comprises the following steps:

s1: measuring an initial voltage value V0 of the battery cell;

s2: grading the lithium ion battery cells according to a voltage value V0, taking 20mV as a grade, and carrying out L1, L2 and L3- -;

s3: loading a resistor on a clamp of the voltage internal resistance tester, wherein the resistance value of the loading resistor is 300 times of the battery core internal resistance of 280 plus materials;

s4: gradually testing the instantaneous voltage value V1 of the lithium ion cell according to the voltage grade in the step S2, judging the grade of the battery according to the voltage value, and referring to the grade grades L1, L2 and L3 < - > of the voltage standard V0;

s5: and (3) judging: if the voltage V1 grade of the same cell is the same as the V0 grade or the V1 grade is lower than the V0 grade, the battery is qualified; on the contrary, the method can be used for carrying out the following steps,

the pressure drop is not acceptable, i.e. the load capacity is not acceptable.

The interval between the voltage values V0 and V1 is less than 24 hours.

Compared with the prior art, the invention has the beneficial effects that:

(1) the invention can pick out the lithium ion battery cell with potential defects of pole piece fracture or tab cold welding;

(2) the process has low equipment investment, simple operation and easy popularization.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention.

FIG. 1 is a flow chart of the present invention.

Detailed Description

The present invention will be further described with reference to the following specific examples.

A process for detecting the fragment cracking or tab cold welding of a lithium ion battery pole comprises the following steps:

s1: measuring an initial voltage value V0 of the battery cell;

s2: grading the lithium ion battery cells according to a voltage value V0, taking 20mV as a grade, and carrying out L1, L2 and L3- -;

s3: loading a resistor on a clamp of the voltage internal resistance tester, wherein the resistance value of the loading resistor is 300 times of the battery core internal resistance of 280 plus materials;

s4: gradually testing the instantaneous voltage value V1 of the lithium ion cell according to the voltage grade in the step S2, judging the grade of the battery according to the voltage value, and referring to the grade grades L1, L2 and L3 < - > of the voltage standard V0;

and S5, judgment: if the voltage V1 grade of the same cell is the same as the V0 grade or the V1 grade is lower than the V0 grade, the battery is qualified; on the contrary, the method can be used for carrying out the following steps,

the pressure drop is not acceptable, i.e. the load capacity is not acceptable.

The interval between the voltage values V0 and V1 is less than 24 hours.

The method detects and detects 1000 lithium ion cells according to the traditional detection method and the detection method of the invention, and the process and the test data are as follows:

example (b):

according to the detection method, 626196-5.0Ah 1000 battery cells are detected through the following steps:

s1: measuring an initial voltage value V0 of the battery cell;

s2: grading the battery according to a cell voltage value V0, taking 20mV as a grade, and grading from high to low by L1, L2 and L3, wherein the L1 grade: the voltage is 3.901V-3.920V 262; l2 grade: the voltage is between 3.881V and 3.900V 358; l3 grade: the voltage is 3.861V-3.880V 202; l4 grade: the voltage is 3.841V-3.860V 155; l5 grade: the voltage is between 3.821V and 3.840V 23; l6 grade: the voltage is between 3.801V and 3.820V 0; the voltage is less than 3.800V 0;

s3: loading a resistor with the resistance value of 6 omega on a clamp of a voltage internal resistance tester;

s4: and step-by-step testing the voltage value V1 of the battery core according to the grade, and judging the grade of the battery according to the voltage value V1:

(1) measuring the current voltage of the original L1 battery cell to be 3.901V-3.920V 102; the voltage is between 3.881V and 3.900V 160, namely, all the cell voltage ranges fall into the grades L1 and L2;

(2) measuring the voltage of the original L2 battery cell at the current voltage of 3.881V-3.900V 125; the voltage is 3.861V-3.880V 233, and all the cell voltage ranges belong to the grades of L2 and L3;

(3) measuring the current voltage of the original L3 battery cell to be 3.861V-3.880V 49; the voltage is 3.841V-3.860V 151; the pressure is 3.821V-3.840V 2; the cell voltage ranges belong to the L3 and L4 grades of 49 and 151 respectively, and the voltage of 2 cells is two levels lower than the original voltage;

(4) measuring the voltage of the original L4-grade battery cell at the present time, wherein the voltage is 3.841V-3.860V 52; the voltage is between 3.821V and 3.840V 103, and all the cell voltage ranges belong to the grades L4 and L5;

(5) measuring the voltage of the original L5-grade battery cell at present to be 3.821V-3.840V 10; the voltage is 3.801V-3.820V 11; the voltage is less than 3.800V 1; the cell voltage ranges belong to 10 and 11L 5 and L6 grades respectively, and the voltage of 1 cell is two grades lower than the original voltage.

The experimental results show that the detection of 626196-5.0Ah 1000 cells exceeds the standard: 2 cells of the original attribution L3 grade and 1 cell of the original attribution L5 grade, and 3 cells in total are marked as defective products.

All the cells in the above embodiment are subjected to 0.5C cycle for 10 weeks, and as a result, the capacity of the cells without marked defects is not significantly attenuated, and 3 cells marked with defects have large capacity fluctuation and a tendency of attenuation, and the performances of pole piece fracture and tab cold joint are found after disassembly.

Comparative example:

the traditional detection method comprises the following steps: and detecting another 1000 battery cells of 626196-5.0 Ah:

and measuring the initial voltage value V0 and the internal resistance of the voltage according to 3.821-3.920V, and the internal resistance value according to 15-30 m omega, and measuring that all the battery cores are in the range.

All the cells of the comparative examples were subjected to 0.5C cycle for 10 weeks, and as a result, 4 cells had large capacity fluctuation and tended to decay, and the appearance of pole piece fracture and tab cold joint was found after disassembly. Therefore, the traditional detection method is difficult to crack or break the winding core electrode plate, poor lithium ion batteries such as cold solder are completely picked out when the electrode plate is subjected to spot welding, and the risk of missing judgment exists.

Compared with the traditional detection method, the detection method can quickly and accurately pick out the lithium ion battery cell with the potential defects of pole piece fracture and tab cold welding, and has the advantages of less equipment investment, simple operation and easy popularization.

The technical solutions provided by the embodiments of the present invention are described in detail above, and the specific examples are applied herein to explain the principles and embodiments of the present invention, and the descriptions of the embodiments are only used to help understanding the principles of the embodiments of the present invention; while the invention has been described with reference to specific embodiments and applications, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims (2)

1. A process for detecting the fragment cracking or tab cold welding of a lithium ion battery pole is characterized by comprising the following steps:

s1: measuring an initial voltage value V0 of the battery cell;

s2: grading the lithium ion battery cells according to a voltage value V0, taking 20mV as a grade, and carrying out L1, L2 and L3- -;

s3: loading a resistor on a clamp of the voltage internal resistance tester, wherein the resistance value of the loading resistor is 300 times of the battery core internal resistance of 280 plus materials;

s4: gradually testing the instantaneous voltage value V1 of the lithium ion cell according to the voltage grade in the step S2, judging the grade of the battery according to the voltage value, and referring to the grade grades L1, L2 and L3 < - > of the voltage standard V0;

s5: and (3) judging: if the voltage V1 grade of the same cell is the same as the V0 grade or the V1 grade is lower than the V0 grade, the battery is qualified; on the contrary, the method can be used for carrying out the following steps,

the pressure drop is not acceptable, i.e. the load capacity is not acceptable.

2. The process of claim 1, wherein the time interval between the voltage values V0 and V1 is less than 24 hours.

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