CN114178695A

CN114178695A - Laser welding method for metal foil of full-tab battery

Info

Publication number: CN114178695A
Application number: CN202210147641.4A
Authority: CN
Inventors: 冉昌林; 米仁兵; 雷波; 孟昌
Original assignee: Wuhan Yifi Laser Corp Ltd
Current assignee: Wuhan Yifi Laser Corp Ltd
Priority date: 2022-02-17
Filing date: 2022-02-17
Publication date: 2022-03-15

Abstract

The utility model provides a laser welding method of full utmost point ear battery foil, through bulldozing to utmost point ear simultaneously in the laser welding process, guarantee that there is the bonding rate of utmost point ear at 85%, improved the welding strength of utmost point ear. And the welding track is reasonably set according to the welding shape, so that the phenomenon that heat accumulation in a heat action area in the welding process causes damage to a cell structure in the full-tab battery is avoided. Furthermore, the output of power in the welding process is more reasonable through controlling the welding angle, the welding power and the welding speed. Through the mode, the effective bonding rate and the welding strength of the lugs of the full-lug battery are better, the structure of the battery cell inside the battery cannot be influenced, and the use and the safety performance of the full-lug battery are improved.

Description

Laser welding method for metal foil of full-tab battery

Technical Field

The disclosure relates to the technical field of welding, in particular to a laser welding method for a metal foil of a full-tab battery.

Background

At present, with the rapid development of electric automobiles, the occupation ratio of the electric automobiles in the automobile market is gradually increased. The problem of the endurance mileage of the electric automobile is attracting more and more attention. In order to meet the mileage requirement of the full-tab battery of the electric automobile, the research and development of the full-tab battery are gradually promoted, and the process problem in the production process of the full-tab battery is urgently needed to be solved.

The publication number is: CN112542641A patent application discloses a cylindrical full tab battery and a manufacturing method thereof. Through the cooperation of the laser cutting method and the subsequent electrode lug welding and flattening process, a section of a roll core formed by winding the positive and negative electrode plates can form a positive electrode lug area, a negative electrode lug area and a non-electrode lug area, the non-welding area between the electrode lugs is omitted, the contact compactness between the positive and negative electrode lugs after winding is reduced, the rate of infiltrating the positive and negative electrode plates with electrolyte can be accelerated when the electrolyte is subsequently injected, the production efficiency of the cylindrical full-electrode-lug battery is effectively improved, and the positive and negative electrode lugs are sequentially subjected to ultrasonic welding and mechanical flattening.

The publication number is: CN215451499U patent application discloses a full tab cylindrical full tab battery assembly structure. Through set up the screw thread and combine with the screw thread that the apron periphery set up in the side of casing internal peripheral side, the full utmost point ear cylinder battery of full utmost point ear need not the welding, and the problem of worrying utmost point ear desoldering does not promote efficiency.

In the prior art, one of the technologies provides a mode of combining laser cutting and kneading and flattening to process the full tab of the full tab battery, and then welds the tab of the full tab battery in an ultrasonic welding mode. Ultrasonic welding is performed by transmitting a high-frequency vibration wave to the surfaces of two objects to be welded, and the surfaces of the two objects are rubbed against each other under pressure to form a fusion between the molecular layers. In the process of using ultrasonic welding, metal materials rub against each other, so that metal scraps are easy to generate and enter an internal battery cell of the full-tab battery, and potential safety hazards of the full-tab battery exist; the other technology adopts a threaded connection mode, current conduction is carried out, certain processing difficulty exists, good contact between the lug and the pole column cannot be completely guaranteed due to combination between threads, and current channels between different lugs and cover plates do not have consistency. The situation that local resistance is large exists in the use process of the full-lug battery, and the safety problem of the full-lug battery is finally caused by the accumulation of local heat. In fact, in the process of welding the full tab by adopting the laser technology, due to uncertain factors of the full tab metal foil in the kneading and flattening stage, the kneading plane is rugged, so that the situations of hole explosion, insufficient welding and the like exist in the subsequent welding, and the safety performance of the full tab battery is influenced; and under the condition that welding power is increased to cover all the lugs, a heat affected zone is further enlarged, the safety of a battery cell in the full-lug battery is affected, and potential safety hazards exist.

Disclosure of Invention

The laser welding method of the metal foil of the full-tab battery is used for solving the potential safety hazard existing in the process of welding the full-tab battery by adopting the laser welding technology and improving the safety performance of the full-tab battery.

One of the ideas of the present disclosure is to ensure the flatness of the tab kneading plane in the welding process, ensure the smooth proceeding of welding, and improve the strength of the welding structure by means of welding and pressing.

Specifically, in the laser welding process, a welding and pressing tool is adopted to push and press the lug and the battery cell of the full-lug battery. The phenomenon that a gap exists in the attachment of the tab in the welding process, so that the situations of hole explosion, insufficient welding and the like in the welding process are avoided. Because the welding pressing mode eliminates the gap of the pole lug in the welding process, the flatness of the pole lug is ensured, and the adhesion rate and the welding strength of the metal foil are improved. Because the adhesion rate of the metal foil is improved, the current channel is widened, the internal resistance of the battery is further reduced, and the safety performance of the battery is ensured.

The welding mode can ensure that the adhesion rate of the metal foil is more than 85 percent.

Another idea of the present disclosure is to further ensure the adhesion rate and welding strength of the metal foil during the welding process by adjusting the pushing force.

Specifically, the welding tool adopts the cylinder to adjust the thrust. The gaps and the fitting degree of different lugs are inconsistent in the welding process. The welding pressure frock needs to adjust the thrust in the welding process according to particular case, eliminates the influence of different utmost point ear clearances in the welding process to the welding effect, further improves the adhesion rate and the welding strength of metal foil.

Another idea of the present disclosure is to solve the temperature rise problem in the thermal action region through the welding track, and avoid the influence on the cell structure inside the full tab battery due to the too high local temperature rise in the laser welding process of the full tab battery.

Specifically, the shape of the welding area of the full-tab battery is confirmed before welding, a proper welding starting point is selected, and then a welding track is planned. The phenomenon that the temperature of the intensive welding point region in a period of time is continuously increased due to the fact that the welding point and the welding point are too intensive in the period of time in the welding process is avoided, and then the internal cell structure of the battery is damaged. In the actual production process, the thickness of the metal foil is 2mm at present, so that the temperature change of the metal foil within the thickness of 2mm is within 80 ℃ through a welding track, and the purpose of ensuring the safety of the internal cell structure of the battery is further achieved. With the continuous development of the technology in the future, when the thickness of the metal foil or the internal structure of the battery core is changed, the temperature rise area and the temperature rise range which need to be controlled are also changed, and according to the change, the welding track needs to be correspondingly changed.

Another idea of the present disclosure is to control the welding trajectory by the welding segment.

Specifically, the welding track is composed of welding sections, and accumulation of heat in a heat action area is avoided through control of the distance between the welding sections.

Another concept of the present disclosure is that the welding trajectory may be X-shaped or butterfly-shaped, avoiding heat build-up in the heat affected zone caused by the build-up of weld spots over time during the welding process.

Another concept of the present disclosure is to control the welding depth through the welding angle, so as to protect the cell structure inside the full tab battery and the laser lens.

Specifically, the welding depth is along with the reduction of off-set angle and reduces, according to required welding depth, like the thickness of above-mentioned metal foil be 2mm, and the actual welding depth is because of being less than 2mm among the welding process, avoids on the one hand to weld through metal foil, and on the other hand avoids 2mm within range temperature rise too high to cause the influence to the inside inner core structure of full utmost point ear battery. Meanwhile, because the reflectivity of most metal foils to light is high, the selection of the welding angle can also avoid the damage caused by the fact that laser reflection enters the laser, and the effect of protecting the lens is achieved. Generally, the angle of the laser is selected to be between 30-50.

Furthermore, another concept of the present disclosure is that the laser outputs power of the laser in a combined power manner, and controls the temperature rise of the thermal action area by controlling the output power, so as to achieve the purpose of protecting the internal cell structure of the full-tab battery.

Specifically, the laser transfers the appropriate combined power to weld the metal foil through the welding depth and the welding angle. Compared with the prior art that the laser uses rated power to weld the metal foil, the laser adopts a combined power mode to control the power output of the laser in unit time and the total output power, and further realizes the control of the laser output energy in unit time and the total output energy in the welding process. Avoid the laser welding in-process, too big or too much to the regional output heat of heat action, make the regional interior energy of heat action produce and pile up, and then the too high electric core structure of destroying the battery of temperature rise.

Further, another concept of the present disclosure is to determine the power characteristics of the combined power to meet the laser welding requirements without causing heat build-up.

Specifically, the combined power includes a power for breaking the limit of the melting value of the metal foil and a power for stabilizing the welding of the metal foil. Wherein the power for stabilizing the welding of the metal foil is less than the power for breaking through the limit of the melting value of the metal foil. Through the combination of the two sections of power, on one hand, the requirement of the metal foil on the power in the welding process is met, and the welding strength is ensured; on the other hand, the output power is prevented from being too high, so that heat in a heat action area is accumulated.

Still further, another concept of the present disclosure is to define the power output time in the combined power, so as to control the total power and heat output.

Specifically, the power output time for breaking through the limit of the melting value of the metal foil is not easy to overlong, and the accumulation of heat in a heat action area in the high-power output process is avoided; the output time for the metal foil welding process is moderate, so that the welding strength of the metal foil can be ensured, and the excessive accumulation of energy of the metal foil in the welding process can be avoided.

Further, another concept of the present disclosure is to determine a welding speed, and control a power output of a laser per unit time during welding to avoid energy accumulation in a heat affected zone.

Specifically, the welding speed is confirmed based on the welding locus. On one hand, the phenomenon that the metal foil is not welded through due to the fact that the welding speed is too high is avoided. On the other hand, the welding speed ensures that the welding track fully welds the metal foil in the operation process, and the welding strength is improved.

The present disclosure provides a laser welding method for a metal foil of an all-tab battery, the method comprising:

compacting the lug, wherein the step of compacting the lug is to flatten a gap between the lug and the battery cell;

determining a welding track, wherein the welding track is used for ensuring that a welding action point does not generate aggregation in a heat action area within a period of time;

and laser welding, wherein the laser welding refers to welding the lugs of the full-lug battery by using the welding track in the state of compacting the lugs.

Based on the technical scheme, the pole lug is compacted in the laser welding process, so that the effective bonding rate of the metal foil in the welding process is ensured; meanwhile, the welding track is adopted to ensure that heat is not accumulated in a heat action area in the welding process, and the safety of an electric core in the battery is ensured.

Further, the mode of compacting the tab is limited as follows:

the compression of the pole lug is performed through the adjustment of the pushing force.

Based on above-mentioned technical scheme, through the regulation to thrust in the welding process, guarantee that the clearance between the different utmost point ears all is in the state of flattening, it is that welded bonding rate and welding strength are better.

Further, the welding track is limited by welding modeling:

the welding track is determined according to the shape of the welding position of the full-lug battery.

Based on the technical scheme, the welding track is suitable for batteries with different shapes. The generation of a gap in the welding process caused by the modeling problem is avoided.

Further, the welding track is composed of welding segments:

the welding track includes at least a first welding section and a second welding section.

Based on the technical scheme, the welding track is composed of at least two or more welding sections, and the control on the energy accumulation of the heat action area in the welding process can be better ensured through the arrangement of the welding sections.

Further, the combination mode of the welding sections is defined as follows:

based on the technical scheme, the welding sections in the welding track are combined in a crossed mode. The mode of adopting the cross arrangement can effectively avoid welding point gathering in the welding process.

Further, the combined shape of the welding segments is defined:

the welding track is X-shaped or butterfly-shaped.

Based on the technical scheme, the X-shaped or butterfly-shaped welding track is more beneficial to heat dissipation of a heat action area in the welding process.

Further, the angle of the weld is defined:

the welding angle is 30-50 degrees.

Based on the technical scheme, the proper welding angle can protect the lens of the laser on one hand, and the other hand can control the welding depth, so that the situation that the metal foil is not welded through or is welded through is avoided.

Further, the metal foil is welded in a combined power output mode:

the combined power includes at least a first power and a second power;

the first power is used for breaking through the melting value limit of the metal foil;

the second power is used for stable welding between the metal foil and the object to be welded.

Based on the technical scheme, the welding power is controlled in a combined power mode, and accumulation of heat in a heat action area caused by overlarge output power or overlarge output power in the welding process is avoided.

Further, the output time of the combined power is controlled:

the first power output time corresponds to first power;

the second power output time corresponds to second power;

wherein the first power output time is determined according to the time for the metal foil to start melting;

the second power output time is determined according to the time for finishing melting the metal foil;

the second power output time is greater than the first power output time.

Based on the technical scheme, the output time of the power is limited according to the function of the power section in the welding process. The reasonability of power output in unit time is ensured, the welding strength effect can be ensured, and meanwhile, the phenomenon that heat in a heat action area is accumulated due to overlong output can be avoided.

Further, the output of power is controlled by the running speed during the laser welding:

wherein the running speed is determined from the welding trajectory.

Based on the technical scheme, the running speed of the laser is reasonably configured in the welding process according to the welding track, the output power of the laser in unit time is ensured, and meanwhile, the phenomenon that heat in a heat action area is accumulated due to the fact that the power output time of the same welding point in unit time is too long is avoided.

This is openly through above-mentioned technical scheme, the utmost point ear welding adhesion rate is not enough among the laser welding process, welding strength is low and cause the technical problem of influence to battery inside electric core structure easily, has improved the effective adhesion rate and the welding strength of metal foil, has eliminated the potential safety hazard that full utmost point ear battery adopted the laser welding technique to exist simultaneously, has improved the use and the security performance of full utmost point ear battery.

Drawings

The present disclosure will be described in further detail below with reference to the drawings and preferred embodiments, but those skilled in the art will appreciate that the drawings are only drawn for the purpose of illustrating the preferred embodiments and therefore should not be taken as limiting the scope of the present disclosure. Furthermore, unless specifically stated otherwise, the drawings are merely schematic representations based on conceptual representations of elements or structures depicted and may contain exaggerated displays and are not necessarily drawn to scale.

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

FIG. 2 is a schematic view of the process of the present invention.

1. A battery tab; 2. and (7) welding points.

Detailed Description

The present disclosure will be described in detail below with reference to fig. 1 to 2.

In order to make the objects, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the disclosure and are not intended to limit the disclosure.

The utility model provides a laser welding method of full utmost point ear battery foil, solved utmost point ear welding bonding rate not enough, welding strength low and easily cause the technical problem of influence to battery internal electricity core structure among the laser welding process, improved the use and the security performance of full utmost point ear battery.

Fig. 1 is a specific embodiment 1 of the present disclosure.

In the laser welding process, thrust is applied to the welded pole lug through the pushing and pressing tool, so that the pole lug and the battery cell are combined more tightly, and the condition that the kneading plane is rugged and uneven in the kneading and flattening process of the pole lug is eliminated. Under the condition, the laser welding can ensure that the process defects of hole explosion and insufficient welding are not generated in the welding process, and the effective bonding rate and the welding strength of the tab are improved. Meanwhile, all tabs need to be welded, energy in a heat action area is easy to generate and gather in the laser welding process, and therefore the structure of a battery cell inside the battery is damaged. At the moment, through reasonable welding track setting, regional gathering of welding points and welding points in a period of time is avoided in the welding process, so that heat in a heat action area is accumulated, and the structure of an electric core inside a battery is damaged. Specifically, as shown in fig. 1, the tab of the full tab battery is welded by laser welding in a state of compacting the tab, and as shown in fig. 2, the welding track ensures that the welding between the welding points 2 is prevented from being too concentrated within a period of time, which causes too fast temperature rise in the heat action region.

On the basis of the embodiment 1, the pressure for compacting the tab is adjusted to form a specific embodiment 2.

Specifically, the welding tool provides thrust in a pneumatic mode in the laser welding process, and gaps between different lugs and battery cores of the full-lug battery are different. Therefore, the thrust in the welding process needs to be adjusted and compensated, so that the gaps between all the lugs and the battery cell are guaranteed to be flattened, and the effective bonding rate and the welding strength of the lugs are further guaranteed.

On the basis of the embodiment 1, the welding track is determined according to the shape of the welding, and a specific embodiment 3 is formed.

Specifically, the shape of the welded part of the full-tab battery may be different, and when there is a difference, the same welding track may reduce the effective bonding rate and strength of tab welding. Therefore, the welding track needs to be determined according to the welding shape of the full-tab battery.

On the basis of example 3, the welding track is subdivided into welding segments to form specific example 4.

Specifically, the welding section of the full tab battery may be circular as shown in fig. 1, or may be approximately circular or other shapes. If the tracks are connected into a whole during the welding process, heat in a heat action area in the welding process can be accumulated, and therefore the cell structure in the battery is damaged. Therefore, the welding track is formed by the welding section combination, and the energy output in the welding process can be effectively controlled.

On the basis of example 4, the combination mode of the welding segments is determined, and a specific example 5 is formed.

Specifically, the welding section and the next welding section are combined in a crossed mode, so that the phenomenon that the distance between the welding section and the welding section is too short, and energy in a heat action area is gathered is avoided.

On the basis of example 5, a preferred trajectory of the welding trajectory is determined, and a specific example 6 is formed.

In particular, the welding trajectory is of the X-type or butterfly type. The welding tracks are combined together in a one-section and one-section combination mode to form an X-shaped or butterfly-shaped track, so that the welding between welding points of the full-tab battery is more sufficient.

On the basis of the above embodiment, a specific embodiment 7 is formed by controlling the welding angle.

Specifically, in the actual production process, the metal foil is mostly copper foil or aluminum foil, and the reflectivity of copper is 90%, and the reflectivity of aluminum is 92%. Therefore, the closer the welding angle is to 90 degrees, the greater the welding depth is, and the more difficult the heat action area in the process is to be controlled; the laser enters the lens of the laser to cause damage due to the reflection of the metal foil to the light; the closer the welding angle is to 0 °, the smaller the welding depth is, and the more dispersed the reflection of light is. Generally, when the welding angle is close to 30 °, its effective penetration is close to 0. Therefore, the welding angle is 30-50 degrees, the lens cannot be burnt due to light reflection in the use process of the laser, meanwhile, the welding depth can be effectively controlled, and the requirements of completely welding through the metal foil and not penetrating the metal foil to damage the internal cell structure of the full-lug battery are met.

On the basis of the above embodiment, a specific embodiment 8 is formed by setting the welding power.

On the basis of the above embodiment, the output time of the welding power segment is set, forming a specific embodiment 9.

On the basis of the above embodiment, the operation speed of the laser during the welding process is designed to form a specific embodiment 10.

Specifically, the operation speed of the laser has a control effect on the power output in unit time, and the melting points and the absorption rates of different metal foils are different. Thus, a reasonable laser operating speed facilitates a reasonable output of power to the butt joint 2 during welding without excessive build-up of heat in the heat affected zone.

The present disclosure has been described in detail above, and the principles and embodiments of the present disclosure have been explained herein using specific examples, which are provided only to assist understanding of the present disclosure and the core concepts. It should be noted that, for those skilled in the art, it is possible to make several improvements and modifications to the present disclosure without departing from the principle of the present disclosure, and such improvements and modifications also fall within the scope of the claims of the present disclosure.

Claims

1. A laser welding method for metal foil of a full-tab battery is characterized by comprising the following steps:

2. The laser welding method for the metal foil of the full-tab battery as claimed in claim 1, wherein the step of compacting the tabs is to push and press the tabs and the battery cell of the full-tab battery by using a welding and pressing tool.

3. The laser welding method for metal foils of full-tab batteries according to claim 1, wherein the welding track is composed of welding segments, and the accumulation of heat in the heat action area is prevented by controlling the distance between the welding segments.

4. The laser welding method for full tab battery foil as claimed in claim 3, wherein the welding trajectory comprises at least a first welding segment and a second welding segment.

5. The laser welding method for full tab battery foil as claimed in claim 4, wherein the first welding segment and the second welding segment are crossed.

6. The laser welding method for metal foils of full-tab batteries according to claim 5, wherein the welding track is X-shaped or butterfly-shaped.

7. The laser welding method for full tab battery foil as claimed in any one of claims 1 to 6, wherein the laser welding further comprises a welding angle;

wherein the welding angle is 30-50 degrees.

8. The laser welding method of full tab battery foil as claimed in any one of claims 1 to 6, wherein the laser welding further comprises combining power;

wherein the combined power comprises at least a first power and a second power;

9. The laser welding method of full tab battery foil as claimed in claim 8, wherein said laser welding further comprises power output time;

the first power output time corresponds to first power;

the second power output time corresponds to second power;

the second power output time is greater than the first power output time.