CN116296133A

CN116296133A - Method for testing reliability of battery welding seam

Info

Publication number: CN116296133A
Application number: CN202310128631.0A
Authority: CN
Inventors: 邱世涛
Original assignee: Eve Energy Co Ltd
Current assignee: Eve Energy Co Ltd
Priority date: 2023-02-15
Filing date: 2023-02-15
Publication date: 2023-06-23

Abstract

The invention discloses a method for testing the reliability of a battery welding seam, which comprises the following steps of S1: introducing pressure gas into the test cell, wherein the total pressure value of the pressure gas is P1; s3, pumping at least part of the pressure gas from the test cell, wherein the pumped pressure gas has a pressure value P3; monitoring and analyzing the pressure change curve in the test cell; the test cell is filled with pressure gas and is pumped out of the pressure gas, the process of charge expansion and discharge contraction of the cell is simulated in sequence, and the reliability of the weld joint of the test cell under each state change is judged by monitoring and analyzing the pressure change curve of the test cell caused by the pressure gas change.

Description

Method for testing reliability of battery welding seam

Technical Field

The invention relates to the field of batteries, in particular to a method for testing the reliability of a battery welding seam.

Background

Batteries are widely used as electric energy storage products, and the shells of the electric cores of the existing batteries comprise a shell and a cover plate which are spliced in a welding mode; in order to ensure the use safety of the battery, the tightness detection is carried out after the welding is finished; the existing detection method comprises the following steps: and measuring design parameters such as the penetration width of the welding line and the like to judge the reliability of the welding.

However, in the actual use process, as the charge and discharge cycle is carried out, the battery cell gradually expands, the thickness of the battery cell increases, the large surface of the battery cell shows a bulge state, a certain acting force exists on the welding seam between the cover plate and the shell, so that the strength of the welding seam is weakened, and whether the strength of the weakened welding seam meets the safety of the battery cell or not cannot be verified.

Disclosure of Invention

In order to overcome at least one defect in the prior art, the invention provides a method for testing the reliability of a battery welding seam, which is characterized in that the pressure gas is introduced into a test cell and the pressure gas is extracted from the test cell to sequentially correspond to the charge expansion and discharge contraction processes of an analog cell, and the reliability of the test cell welding seam under each state change is judged by monitoring and analyzing the pressure change curve of the test cell caused by the pressure gas change.

A method for testing the reliability of a battery weld joint comprises the following steps:

s1: introducing pressure gas into the test cell, wherein the total pressure value of the pressure gas is P1;

s3, pumping at least part of the pressure gas from the test cell, wherein the pumped pressure gas has a pressure value P3;

and monitoring and analyzing the pressure change curve in the test cell.

Further, the step S3 further includes:

s5: introducing the pressure gas with the pressure value of P5 into the test cell;

s7: at least part of the pressure gas is extracted from the test cell, and the pressure value P7 of the extracted pressure gas is obtained.

Further, S6 is included between S5 and S7;

s6, the pressure gas is kept in the test cell for a period of time T3;

and/or S8 is further included after S7;

s8: the pressure gas is held in the test cell for a period of time T4.

Further, at least S5, S6, S7 and S8 include S5 and S7 as one operation cycle, and the number of operation cycles is a plurality of.

Further, S2 is further included between S1 and S3;

s2, the pressure gas is kept in the test cell for a period of time T1;

and/or S4 is further included between S3 and S5;

s4: the pressure gas is held in the test cell for a period of time T2.

Further, said P3, said P5 and said P7 are equal, and/or said T1 is equal to said T3, and/or said T2 is equal to said T4.

Further, the P1 is 0.45MPa;

and/or the P3, the P5 and the P7 are all 0.3MPa, the T1 and the T3 are all 1min, and the T2 and the T4 are all 0.5min.

Further, the speed of introducing the pressure gas into the S1 and the S5 is 0.01MPa/S;

and/or the rate at which the pressure gas is extracted by both the S3 and the S7 is 0.01MPa/S.

Further, before the step S1, a pressure release valve of the test cell is blocked.

Further, before S1, a pre-tightening force is applied to the test cell.

In summary, the method for testing the reliability of the battery weld joint provided by the invention has the following technical effects:

1) The test cell is filled with pressure gas and is pumped out of the pressure gas to sequentially correspond to the process of simulating charge expansion and discharge contraction of the cell, and the reliability of the weld joint of the test cell under each state change is judged by monitoring and analyzing the pressure change curve of the test cell caused by the pressure gas change; the stability of the pressure change curve of the same trend indicates that the welding line of the battery cell is reliable, otherwise, the welding line of the battery cell is unreliable, so that the method can simulate the dynamic processes of different working states of the test battery cell, and monitor the reliability of the welding line of the test battery cell in real time in the simulation process, so that the reliability of all the dynamic processes of the test battery cell is tested to form comprehensive dynamic detection advantages;

2) After S1, the test cell expands (namely, charging expansion (S1)), and then the continuously introduced pressure gas and the continuously extracted pressure gas S3 (namely, discharging contraction) are both reliable tests on the expanded test cell welding seam, so that the first cycle process step of the cell is completed; the number of operation cycles is multiple, and S5 and S7 are used as one operation cycle, so that it can be known that S1 and S3 complete the simulation of the initial charge expansion and discharge contraction states of the test battery cell, and then the simulation of the charge expansion (S5) and the discharge contraction (S7) is carried out by taking S5 and S7 as operation cycles, so that the operation of the cycle test is more standard due to the fixed arrangement of the operation cycles, the error of the test operation is prevented, and the accuracy and the reliability of the test result are ensured.

3) S2 (expansion rest), S4 (contraction rest), S6 (expansion rest), and S8 (contraction rest) all belong to rest holding, and the rest holding can be used for testing the continuous reliability of the battery cell in a certain state, so that the diversity of the testing method is improved, and the reliability of the testing method is enhanced.

4) The ventilation rate of S1 and S5 and the extraction rate of S3 and S7 are both 0.01MPa/S, and the specific rate is used for simulating normal charge and discharge, so that the authenticity of the test is guaranteed;

5) And when the pretightening force is applied, the pretightening force applied to the actual product of the test cell is simulated, so that the effect of simulation is achieved.

Drawings

FIG. 1 is a graph showing the pressure change of the first and second embodiments of the present invention;

FIG. 2 is a perspective view of a third embodiment of the present invention;

fig. 3 is a side view of a third embodiment of the present invention.

Wherein the reference numerals have the following meanings:

1. testing the battery cell; 2. an air duct; 3. an end plate; 4. a buffer strip; 5. a clamping plate; 6. and (5) fixing bolts.

Detailed Description

For a better understanding and implementation, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.

In the description of the present invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, only for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements to be referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Example 1

Referring to fig. 1, the invention discloses a method for testing the reliability of a battery weld joint, which comprises the following steps:

the test cell 1 is specifically a false cell with a core package but no liquid injection, the outer shell of the false cell comprises a shell and a cover plate, the shell and the cover plate are directly connected in a welded mode, and a pressure relief valve is arranged on the cover plate.

In this embodiment, the test cell 1 has a rectangular parallelepiped shape, so the long side of the housing is a large surface of the test cell 1.

In the test method, the pressure release valve is plugged before the test starts.

The pre-tightening force is applied to the two large surfaces of the test battery cell relatively, and the pre-tightening force is applied according to the standards corresponding to the test battery cells with different sizes, which are not exemplified one by one.

The test method of the test cell 1 comprises the following steps:

s1: and introducing pressure gas into the test cell 1 to enable the total value of the gas pressure value in the test cell 1 to reach P1.

S3: at least part of the gas in the test cell 1 is extracted, and the pressure value of the extracted gas is P3.

The weld joints of the test cells in different states are analyzed to be cracked by monitoring the change of the pressure value of the pressure gas in the test cell 1 in the S1 and the S3.

Specifically, the analysis process is as follows:

firstly, a step S1 of introducing gas into the test cell 1, wherein when the gas is introduced into the test cell 1, the test cell 1 expands (simulates the charging expansion process), a pressure change curve in the test cell 1 rises at a stable rate, and if the pressure change curve suddenly drops, the rising rate is reduced or the rising is stopped before the pressure value of the pressure gas reaches P1 in the process of continuously introducing the gas into the test telecommunication 1, the weld joint of the test cell 1 is indicated to crack; the reason is that the cracking of the welding seam is the leakage of the pressure gas, and the pressure value of the test cell 1 is reduced, so that the originally rising pressure change curve suddenly drops, the rising rate is reduced or the rising is stopped; if the pressure value of the pressure change curve steadily rises all the time and finally reaches P1, the condition that the welding seam is not cracked and the like although the test cell 1 is continuously expanded in the process of introducing pressure gas is indicated, and the welding seam is reliable.

Step S3 of extracting gas from the test cell 1, wherein in the process of extracting the pressure gas with the preset pressure value of P3 (the process of simulating discharge shrinkage, which is the shrinkage after the relative charge expansion), the pressure value of the pressure gas in the test cell 1 gradually decreases, the pressure change curve decreases from P1 at a stable rate, and in the process, if the decrease of the pressure change curve suddenly increases, the weld joint of the test cell 1 is cracked to cause the leakage of the pressure gas; when the total pressure value of the pumped pressure gas reaches P3, but the falling rate of the pressure gas does not suddenly change in the whole process, the welding line is proved to be reliable without cracking.

From the above, it can be known that when judging whether the weld joint cracks and leaks, the stability of the rising rate and the falling rate of the pressure change curve is analyzed to determine that the rising rate and the falling rate of the pressure change curve are influenced by the rising rate and the falling rate of the pressure change curve to eliminate the influence of the speed of the pressure gas inlet and the speed of the pressure gas outlet on the rising rate and the falling rate of the pressure change curve, that is, the rising rate and the falling rate of the pressure change curve are influenced by the sudden increase or the decrease of the pressure gas inlet and the pressure gas outlet, and at the moment, the reliability of the weld joint may be misjudged, so that the inlet rate and the outlet rate of the pressure gas should be constant in the process of testing the inlet and the outlet rate of the pressure gas from the cell 1.

Specifically, in the embodiment, the rate of introducing the pressure gas into the S1 is 0.01MPa/S; s3, the pressure gas extraction rate is 0.01MPa/S.

In the S1, the total value P1 of the pressure gas introduced into the test cell 1 is 0.45MPa, and in order to ensure the authenticity of the simulation, the pressure value 00.45MPa of the extracted pressure gas is less than P3 and less than P1, and in the embodiment, P3 is 0.3MPa.

Further, in order to increase the test of the continuous reliability of the weld at a specific value, the present embodiment performs the static simulation on the test cell 1 at the maximum pressure value and the minimum pressure value, respectively, and has:

s2: after step S1 is completed, the pressure value in the test cell 1 reaches the maximum value P1, so that the pressure gas with the gas pressure value P1 is kept in the test cell 1 for a certain period of time, where the period of time is T1, and preferably, T1 is 1min.

A process S2 of maintaining the gas in the test cell 1, wherein after the pressure gas is introduced into the S1, the pressure value of the pressure gas in the test cell 1 is P1, the duration of the test cell 1 is T1 (a process of simulating expansion and standing) under the pressure value, and the test cell 1 is in an expansion maintaining state; in the time T1, if the pressure value in the test cell 1 is consistent and kept unchanged at P1 (namely, the pressure change curve is kept horizontal), the welding line is proved to have no cracking, and the welding line is reliable; if the pressure value of the test cell 1 suddenly decreases (i.e., the pressure change curve decreases), i.e., the pressure value is less than P1, during time T1, a pressure gas leak caused by the weld cracking is indicated.

Similarly, referring to S2 (expansion standing), after S3 is completed, the test cell 1 also performs shrinkage standing simulation, that is, after the total value P1 of the pressure gas of 0.45MPa is extracted by the amount of P3, the pressure gas of 0.15MPa remains, and the test cell is kept under the pressure gas of 0.15 for a time period of T2, preferably, T2 is 0.5min.

In summary, S1, S2, S3, and S4 may be used as a first cycle step, which may complete the simulation of the four states of the test cell 1.

In particular, the amount and rate of the pressure gas introduced during the test may vary according to the size of the test sample, for example, the greater the thickness of the housing, the greater the rate of introduction and extraction of the pressure gas, and the greater the total value P1 of the pressure gas introduced.

Example two

Referring to fig. 1, in the first embodiment, a plurality of cycle tests, called operation cycles, are performed on the test cells after the first cycle step.

Specifically, the operation cycle includes S5 and S7.

S5: and introducing the pressure gas with the pressure value of P5 into the test cell 1.

S7: at least part of the pressure gas is extracted from the test cell 1, the pressure value P7 of the extracted pressure gas.

The above-mentioned steps S5 and S1 correspond to each other, S7 and S3 correspond to each other, and between the two corresponding steps, when S5 and S7 are performed, the change of the test cell 1 is the same as S1 and S3, that is, S5 simulates expansion and standing, and S7 simulates contraction and standing, which will not be described here.

As can be seen from the first embodiment, the first cycle process step further includes expansion rest simulation S2 and contraction rest simulation S4.

The operating cycle in this embodiment includes S6 and S8 as well; specifically, there is a step S6 of expansion standing simulation between S5 and S7, in which the pressure gas is kept in the test cell 1 for a period of time T3; s7 is followed by a step S8 of shrink-stand simulation (i.e. the operating cycle also includes S6 and S8), in which the pressure gas is maintained in the test cell 1 for a period T4.

In particular, p5=p7=0.3 MPa, and the rate of introducing the compressed gas into the reactor is 0.01MPa/s for s 5; s7, pumping out the pressure gas at the rate of 0.01MPa/S; from this, it can be seen that P5, P5 and P7 are equal, and the rate of introducing the pressure gas into S1 and S5 is 0.01MPa/S; the rate of pumping out the pressure gas is 0.01MPa/S in both S3 and S7; t1=t3=1 min; t2=t4=0.5 min; the uniformity of data among the steps with the same purpose is beneficial to simplifying the operation difficulty of the steps and reducing the probability of operation errors.

It will be appreciated that the operating cycle may be determined based on the various parameters of the test cell being tested, i.e., the number of operating cycles may be a plurality of times, and preferably the number of operating cycles of the present embodiment is three.

In this embodiment, before step S5, the pressure value of the pressure gas of the test cell 1 is 0.15MPa, after step S5 is completed, the pressure value of the pressure gas of the test cell 1 reaches the maximum value P1 again, and after step S7, the test cell is supported to return to 0.15MPa, and the cycle is thus repeated.

Example III

Referring to fig. 2 and 3, for the test methods of the first embodiment and the second embodiment, specific test equipment includes: test cell 1, airway 2, and end plate 3 and buffer strip 4.

The two large surfaces of the test cell 1 are respectively provided with an end plate 3, preferably, the end plates 3 are consistent with the shape and the area of the large surfaces (the end plates 3 are used for actually using the battery products), a plurality of buffer strips 4 are arranged between one large surface and one end plate 3 which are adjacently arranged, in the embodiment, the number of the buffer strips 4 is two, the two buffer strips 4 are respectively arranged at two ends of the large surface and are arranged along the edge directions of the two ends of the large surface, and preferably, the buffer strips 4 have viscosity, so that the two surfaces of the buffer strips 4 are respectively bonded with the large surface and the end plate 3; in particular, the buffer strip 4 does not fill the entire large surface, so that there is a gap between the large surface and the end plate 3, which is used to test the expansion gap of the cell 1.

Before the test of the test cell 1, corresponding pretightening force is applied to the end plate according to the specifications of different test cells 1.

It can be appreciated from the above that, to protect the end plate 3, the test equipment further comprises a clamping plate 5 and at least four fixing bolts 6, the embodiment being exemplified by four fixing bolts 6; the outer side of each clamping plate 5 is provided with a clamping plate 5, the shape of the clamping plate 5 is consistent with that of the end plate 3, but the area of the clamping plate is larger than that of the end plate 3, and in particular, the length and the width of the clamping plate 5 are respectively larger than that of the end plate 3; one fixing bolt 6 penetrates through two corresponding angles of the two clamping plates 5 in the thickness direction of the test cell 1, the four fixing bolts 6 connect the corresponding angles of the two clamping plates 5, and the pretightening force applied to the clamping plates 5 is adjusted by screwing nuts.

In addition, be provided with two through-holes on the apron of test cell 1, every through-hole is provided with the breather valve respectively, sets up air duct 2 on the breather valve respectively, and air duct 2 extends outside test cell 1, and one air duct 2 is as the air inlet of pressure gas, and another then is as the air outlet of pressure gas, and the breather valve then controls the switching of corresponding air duct 2.

In addition, in the aspects of pressure detection and data acquisition of the pressure gas, the implementation sets a pressure sensor in the test cell, the pressure sensor is connected with an external pressure display, and the pressure display is used for displaying a pressure change curve so as to reflect a real-time pressure value inside the test cell 1.

The technical means disclosed by the scheme of the invention is not limited to the technical means disclosed by the embodiment, and also comprises the technical scheme formed by any combination of the technical features. It should be noted that modifications and adaptations to the invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be within the scope of the present invention.

Claims

1. The method for testing the reliability of the battery weld joint is characterized by comprising the following steps of:

s1: introducing pressure gas into the test cell (1), wherein the total pressure value of the pressure gas is P1;

s3, extracting at least part of the pressure gas from the test cell (1), wherein the extracted pressure value P3 of the pressure gas;

and monitoring and analyzing the pressure change curve of the test cell (1).

2. The method for testing the reliability of a battery weld according to claim 1, wherein the step S3 further comprises:

s5: introducing the pressure gas with the pressure value of P5 into the test cell (1);

s7: -extracting at least part of said pressure gas from said test cell (1), the pressure value P7 of said extracted pressure gas.

3. The method for testing the reliability of a battery weld according to claim 2, wherein S6 is further included between S5 and S7;

s6, the pressure gas is kept in the test cell (1) for a period of time T3;

and/or S8 is further included after S7;

s8: the pressure gas is held in the test cell (1) for a period of time T4.

4. A method of testing the reliability of a battery weld according to claim 3, wherein at least one of S5, S6, S7 and S8 includes S5 and S7 as one operation cycle, and the number of operation cycles is a plurality.

5. A method of testing the reliability of a battery weld according to claim 3, further comprising S2 between S1 and S3;

s2, the pressure gas is kept in the test cell (1) for a period of time T1;

and/or S4 is further included between S3 and S5;

s4: the pressure gas is held in the test cell (1) for a period of time T2.

6. The method of claim 5, wherein P3, P5 and P7 are equal, and/or T1 is equal to T3, and/or T2 is equal to T4.

7. The method for testing the reliability of a battery weld according to claim 6, wherein P1 is 0.45MPa;

8. The method for testing the reliability of a battery weld according to claim 2, wherein the rate of introducing the pressure gas into the battery is 0.01MPa/S for both the S1 and the S5;

9. The method for testing the reliability of the battery weld according to claim 1, wherein the pressure release valve of the test cell (1) is plugged before the step S1.

10. The method according to claim 1, wherein a pre-tightening force is applied to the test cell (1) before S1.