Sealing method

Abstract

The invention discloses a sealing method which is suitable for sealing a liquid injection port of a battery cell, the battery cell comprises a cover plate and a sealing nail, a groove is formed in the cover plate, the liquid injection port is formed in the bottom wall of the groove, the sealing nail covers the liquid injection port, and an annular groove is formed between the outer circumference of the sealing nail and the inner circumference of the groove; the sealing method comprises the following steps: preparing an annular solder piece; an annular welding piece is placed in the annular groove; heating welding is conducted through induction welding equipment, the welding flux piece is melted so that the sealing nail and the groove can be welded and fixed, and the liquid injection opening is sealed; and the welding position between the sealing nail and the groove is cooled. According to the invention, the equipment cost and the maintenance cost can be reduced, the sealing performance of the liquid injection port can be improved, and the product yield can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of battery core sealing, and in particular to a sealing method. Background Art

[0002] New energy vehicles powered by batteries are now rapidly developing and being used because of their advantages such as no greenhouse gas emissions, no pollution to the environment, high efficiency and low noise.

[0003] The power battery is composed of several battery cells. The production and manufacturing process of the battery cells involves various welding processes. Among them, the welding of the liquid filling port seal has high requirements and is also relatively difficult. The welding quality and yield rate are directly related to the quality and yield rate of the entire battery cell and power battery.

[0004] The welding of the battery cell liquid filling port seal is to weld the aluminum sealing pin to the aluminum cover plate to prevent the internal electrolyte from escaping and causing safety hazards or accidents. The current existing liquid filling port sealing method is to use laser fusion welding, but laser fusion welding has some obvious disadvantages and shortcomings, such as large equipment investment and high maintenance cost, and it is easy to produce spatter, holes, thermal cracks and other phenomena during welding, resulting in low welding yield. In addition, when the sealing pin area is welded by a laser, it is easy to form heat concentration in the welding area, causing the sealing pin to burn and deform, affecting the later sealing. Summary of the invention

[0005] The object of the present invention is to provide a sealing method, which is beneficial to reducing equipment cost and maintenance cost and can improve sealing performance.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0007] A sealing method is applicable to sealing a liquid injection port of a battery cell, wherein the battery cell comprises a cover plate and a sealing pin, wherein a groove is formed on the cover plate, a liquid injection port is formed on the bottom wall of the groove, the sealing pin is covered on the liquid injection port, and an annular groove is formed between the outer periphery of the sealing pin and the inner periphery of the groove;

[0008] The sealing method comprises the following steps:

[0009] preparing a ring-shaped solder piece;

[0010] Place the annular solder piece into the annular groove;

[0011] Using induction welding equipment to heat up the welding, so that the solder piece melts to allow the sealing pin to be welded and fixed to the groove, and the liquid injection port is sealed;

[0012] The welding point between the sealing pin and the groove is cooled.

[0013] Preferably, preparing the annular solder piece specifically includes:

[0014] A flux is coated on the outside of the annular solder to form an annular solder piece.

[0015] Preferably, preparing the annular solder piece specifically includes:

[0016] A coating machine is used to coat the brazing flux on the outside of the annular brazing material to form an annular brazing material piece.

[0017] Preferably, the brazing material is aluminum silicon brazing material, and the brazing flux is cesium fluoroaluminate brazing flux.

[0018] Preferably, the weight percentage of the flux is 2wt%-40wt%.

[0019] Preferably, cooling the welding point between the sealing pin and the groove specifically includes:

[0020] Liquid nitrogen is used to cool the welding point between the sealing pin and the groove.

[0021] Preferably, the induction current of the induction welding equipment during the welding process is 20-200A.

[0022] Preferably, the operating frequency of the induction welding equipment during the welding process is 10-200 KHz.

[0023] Preferably, the induction welding equipment comprises an induction coil, and the number of turns of the induction coil is 1-5 turns.

[0024] Preferably, the induction coil is in the shape of a notched circle, the induction coil is provided with at least two turns, and two adjacent turns of the induction coil are connected by a copper wire.

[0025] Compared with the prior art, the sealing method according to the embodiment of the present invention has the following beneficial effects:

[0026] In the present invention, the sealing pin is placed in the groove and covers the liquid injection port, so that an annular groove is formed between the outer periphery of the sealing pin and the inner periphery of the groove. Then, an annular solder piece is prepared and fitted into the annular groove so that the solder piece is wrapped around the outer periphery of the sealing pin. Then, the solder piece is heated by an induction welding device so that the solder piece melts between the sealing pin and the groove to seal the liquid injection port. Specifically, after the solder piece melts, the melted solder piece can penetrate between the bottom surface of the sealing top and the bottom wall of the groove, and the melted solder piece can also cover between the outer peripheral wall of the sealing pin and the groove to ensure that the gap is filled, so as to increase the area covered by the solder piece, thereby increasing the sealing area and ensuring the sealing performance. Finally, the welding point between the sealing pin and the groove is cooled to complete the sealing of the liquid injection port. Compared with the related art, the present invention adopts induction welding equipment for welding, which can greatly reduce the equipment cost and the subsequent maintenance cost compared with laser welding equipment. Moreover, the induction welding process is to introduce external solder parts for filling welding, which is easy to improve the sealing of the liquid filling port of the battery cell and effectively improve the product yield. The laser fusion welding process is to seal by melting the base material itself, which is easy to cause poor sealing due to inaccurate assembly or careless operation, and the product yield is difficult to improve. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of a battery cell according to an embodiment of the present invention;

[0028] Figure 2 is an exploded view of a cover plate according to an embodiment of the present invention;

[0029] Figure 3 is a schematic diagram of a cover plate according to an embodiment of the present invention;

[0030] Figure 4 Detailed description of the invention The figure is a flow chart of a sealing method according to an embodiment of the present invention.

[0031] In the figure, 1. battery cell; 2. cover plate; 3. sealing pin; 4. groove; 5. liquid filling port; 6. solder part. DETAILED DESCRIPTION

[0032] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0033] In the description of the present invention, it should be understood that the wording "comprising" used in the present specification refers to the presence of the features, integers, steps, operations, parts / components and / or assemblies, but does not exclude the presence or addition of one or more other features, integers, steps, operations, parts / components, assemblies and / or their groups. It should be understood that when we say a part / component is "connected" to another part / component, it can be directly connected to the other part / component, or there can be intermediate parts / components. The wording "and / or" used here includes all or any unit and all combinations of one or more associated listed items.

[0034] like Figures 1 to 4 As shown, the present invention relates to a sealing method, which is suitable for sealing a liquid injection port 5 of a battery cell 1. The battery cell 1 comprises a cover plate 2 and a sealing nail 3. A circular groove 4 is formed on the cover plate 2. A liquid injection port 5 is formed on the bottom wall of the groove 4 and in the central area. The sealing nail 3 is arranged in the groove 4 and covers the liquid injection port 5. An annular groove is formed between the outer periphery of the sealing nail 3 and the inner periphery of the groove 4.

[0035] The sealing method comprises the following steps:

[0036] Preparing a ring-shaped solder piece 6;

[0037] Place the annular solder piece 6 into the annular groove;

[0038] Using induction welding equipment to heat up the welding, so that the solder piece 6 melts to allow the sealing pin 3 to be welded and fixed to the groove 4, and the liquid injection port 5 is sealed;

[0039] The welding point between the sealing pin 3 and the groove 4 is cooled.

[0040] In the present invention, the sealing pin 3 is placed in the groove 4 and covers the liquid injection port 5, so that an annular groove is formed between the outer periphery of the sealing pin 3 and the inner periphery of the groove 4. Then, an annular solder piece 6 is prepared and fitted into the annular groove so that the solder piece 6 is wrapped around the outer periphery of the sealing pin 3. Then, the solder piece 6 is heated by an induction welding device so that the solder piece 6 melts between the sealing pin 3 and the groove 4 to seal the liquid injection port 5. Specifically, after the solder piece 6 melts, the melted solder piece 6 can penetrate between the bottom surface of the sealing top and the bottom wall of the groove 4, and the melted solder piece 6 can also cover between the outer peripheral wall of the sealing pin 3 and the groove 4 to ensure that the gap is filled, so as to increase the area covered by the solder piece 6, thereby increasing the sealing area and ensuring the sealing performance. Finally, the welding point between the sealing pin 3 and the groove 4 is cooled to complete the sealing of the liquid injection port 5. Compared with the related art, the present invention adopts induction welding equipment for welding, which can greatly reduce the equipment cost and the subsequent maintenance cost compared with laser welding equipment. Moreover, the induction welding process is to introduce external solder parts 6 for caulking welding, which is easy to improve the sealing of the liquid filling port 5 of the battery cell 1 and effectively improve the product yield. The laser fusion welding process is to seal by melting the parent material itself, which is easy to cause poor sealing due to inaccurate assembly or careless operation, and the product yield is difficult to improve.

[0041] In this embodiment, the preparation of the annular solder member 6 specifically includes:

[0042] The annular solder part 6 is produced by applying a flux to the outside of the annular solder.

[0043] Specifically, the annular solder is pre-formed according to the shape of the annular groove between the sealing pin 3 and the groove 4, and then a brazing agent is coated on the outside of the solder to play a role of flux.

[0044] Preferably, the preparation of the annular solder piece 6 specifically includes:

[0045] A coating machine is used to coat the soldering material with flux to form a ring-shaped solder member 6 .

[0046] That is, using a coating machine to coat the flux can improve the efficiency of coating, and can also accurately control the speed, thickness and uniformity of spraying, so that the quality of the coating is stable, which is conducive to ensuring the smoothness of subsequent welding and ensuring the product yield.

[0047] In this embodiment, the brazing material is aluminum silicon brazing material, the brazing agent is cesium fluoroaluminate brazing agent, and the weight percentage of the brazing agent is 2wt%-40wt% to ensure the sealing of the injection port 5 after welding.

[0048] In this embodiment, cooling the welding point between the sealing pin 3 and the groove 4 specifically includes:

[0049] Liquid nitrogen is used to cool the welding point between the sealing pin 3 and the groove 4 .

[0050] Specifically, the welding point between the sealing pin 3 and the groove 4 is cooled by a cooling device, the cooling device includes a nitrogen storage tank, a control valve, a connecting air pipe and a nozzle, the cooling nitrogen in the nitrogen storage tank is gasified from liquid nitrogen to ensure that the cooling nitrogen is at a relatively low temperature, to ensure the cooling speed and effect, and the cooling nitrogen is sprayed to the welding point between the sealing pin 3 and the groove 4 through a nozzle to perform cooling work. By using nitrogen at a relatively low temperature for rapid cooling, the temperature can be quickly reduced to a safe range to protect the plastic parts in the battery cell 1 from being damaged.

[0051] In this embodiment, the induction welding device includes an induction coil, the number of turns of the induction coil is between 1-5 turns, the induced current of the induction welding device during the welding process is 20-200A, and the operating frequency of the induction welding device during the welding process is 10-200KHz to ensure smooth welding work.

[0052] In this embodiment, the induction coil is in the shape of a notched circle, the induction coil is provided with at least two turns, and two adjacent turns of the induction coil are connected by a copper wire to achieve conduction.

[0053] In this embodiment, the sealing method can be controlled as a whole by an automated control system to achieve fully automated operations such as automatic feeding, automatic heating, automatic identification of welds, and automatic cooling. In particular, during the welding stage, infrared rays can be used to irradiate the solder to obtain comparison information, and whether the solder is melted and completely melted can be used as identification features to control the entire welding process.

[0054] In order to ensure the effect of the sealing method of the present invention, an experiment is performed below to illustrate the effect.

[0055] Comparative Example 1: 8 wt% cesium fluoroaluminate brazing flux was manually coated on an annular aluminum silicon brazing filler metal, wherein the brazing filler metal composition was Al Si 12 and the size was φ8.8×φ7.95×1.0 mm. The sealing pin and the brazing filler metal coated with the brazing flux were assembled on the power battery cell liquid injection port structure, placed in the induction coil of the induction welding equipment, and heated using a manually controlled one-stage constant induction current with the induction current set to 90 A. The induction welding equipment was started, and after the brazing filler metal was melted, the power battery cell liquid injection port structure was cooled using vaporized liquid nitrogen.

[0056] Embodiment 1: A coating machine is used to coat 8 wt% of cesium fluoroaluminate brazing flux on an annular aluminum silicon brazing filler metal, wherein the brazing filler metal composition is Al Si 12 and the size is φ8.8×φ7.95×1.0 mm. A sealing pin and the brazing filler metal coated with the brazing flux are assembled on the power battery cell injection port structure, placed in the induction coil of the induction welding equipment, and heated by a manually controlled one-stage constant induction current, the induction current is set to 90 A, the induction welding equipment is started, and after the brazing filler metal is melted, the power battery cell injection port structure is cooled by gasified liquid nitrogen.

[0057] Example 2: A coating machine is used to coat 8wt% of cesium fluoroaluminate brazing flux on an annular aluminum silicon brazing filler metal, wherein the brazing filler metal composition is Al Si 12 and the size is φ8.8×φ7.95×1.0mm. A sealing pin and the coated brazing filler metal are assembled on the power battery cell injection port structure, placed in the induction coil of the induction welding equipment, and heated using a manually controlled one-stage constant induction current with the induction current set to 20A. The induction welding equipment is started, and after the brazing filler metal is melted, the power battery cell injection port structure is cooled using vaporized liquid nitrogen.

[0058] Example 3: A coating machine is used to coat 8wt% of cesium fluoroaluminate brazing flux on an annular aluminum silicon brazing filler metal, wherein the brazing filler metal composition is Al Si 12 and the size is φ8.8×φ7.95×1.0mm. The sealing pin and the brazing filler metal coated with the brazing flux are assembled on the power battery cell injection port structure, placed in the induction coil of the induction welding equipment, and heated by a manually controlled one-stage constant induction current, the induction current is set to 200A, the induction welding equipment is started, and after the brazing filler metal is melted, the power battery cell injection port structure is cooled by gasified liquid nitrogen.

[0059] Example 4: A coating machine is used to coat 8 wt% of cesium fluoroaluminate brazing flux on an annular aluminum silicon brazing filler metal, wherein the brazing filler metal composition is Al Si 12 and the size is φ8.8×φ7.95×1.0 mm. The sealing pin and the brazing filler metal coated with the brazing flux are assembled on the power battery cell injection port structure, placed in the induction coil of the induction welding equipment, and heated using an automatically controlled gradient induction current, with the first gradient being 105 A for 6 s and the second gradient being 90 A for 1.5 s. The induction welding equipment is started, and after the brazing filler metal is melted, the power battery cell injection port structure is cooled using vaporized liquid nitrogen.

[0060] Example 5: A coating machine is used to coat 2 wt% of cesium fluoroaluminate brazing flux on an annular aluminum silicon brazing filler metal, wherein the brazing filler metal composition is Al Si 12 and the size is φ8.8×φ7.95×1.0 mm. The sealing pin and the brazing filler metal coated with the brazing filler metal are assembled on the power battery cell injection port structure, placed in the induction coil of the induction welding equipment, and heated using an automatically controlled gradient induction current, with the first gradient being 105 A for 6 s and the second gradient being 90 A for 1.5 s. The induction welding equipment is started, and after the brazing filler metal is melted, the power battery cell injection port structure is cooled using vaporized liquid nitrogen.

[0061] Example 6: A coating machine is used to coat 40 wt% of cesium fluoroaluminate brazing flux on an annular aluminum silicon brazing filler metal, wherein the brazing filler metal composition is Al Si 12 and the size is φ8.8×φ7.95×1.0 mm. The sealing pin and the brazing filler metal coated with the brazing flux are assembled on the power battery cell injection port structure, placed in the induction coil of the induction welding equipment, and heated using an automatically controlled gradient induction current, with the first gradient being 105 A for 6 s and the second gradient being 90 A for 1.5 s. The induction welding equipment is started, and after the brazing filler metal is melted, the power battery cell injection port structure is cooled using vaporized liquid nitrogen.

[0062] The surface quality of the comparative examples and embodiments was observed after welding, and 3kPa compressed gas was introduced to detect the air tightness of the power battery cell injection port. The final results are shown in Table 1.

[0063] Table 1 Example welding results

[0064]

[0065]

[0066] Comparative Example 1, Example 1 and Example 4 were used for small batch experiments. The device was defined as having no obvious burnout, complete wetting of the solder, and no airtightness as a qualified part. The yield rate was tested, and the results are shown in Table 2. As can be seen from Table 2, the yield rate of the device with the solder manually coated with solder is relatively low, and the yield rate of the device using the coating machine and the gradient induced current process is the highest, that is, Example 4 is the best process, and the automated process can be used for stable production.

[0067] Table 2 Device yield under different process conditions

[0068] Yield Comparative Example 1 91％ Example 1 95％ Example 4 99％

[0069] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A sealing method, suitable for sealing the liquid injection port of a battery cell, characterized in that: The battery cell comprises a cover plate and a sealing pin, the cover plate is provided with a groove, the bottom wall of the groove is provided with a liquid injection port, the sealing pin is covered on the liquid injection port, and an annular groove is formed between the outer periphery of the sealing pin and the inner periphery of the groove; The sealing method comprises the following steps: preparing a ring-shaped solder piece; Place the annular solder piece into the annular groove; Using induction welding equipment to heat up the welding, so that the solder piece melts to allow the sealing pin to be welded and fixed to the groove, and the liquid injection port is sealed; The welding point between the sealing pin and the groove is cooled.

2. The sealing method according to claim 1, characterized in that: The method comprises preparing a ring-shaped solder part, specifically comprising: A flux is coated on the outside of the annular solder to form an annular solder piece.

3. The sealing method according to claim 2, characterized in that: The method comprises preparing a ring-shaped solder part, specifically comprising: A coating machine is used to coat the brazing flux on the outside of the annular brazing material to form an annular brazing material piece.

4. The sealing method according to claim 2, characterized in that: The brazing material is aluminum silicon brazing material, and the brazing flux is cesium fluoroaluminate brazing flux.

5. The sealing method according to claim 2, characterized in that: The weight percentage of the flux is 2wt%-40wt%.

6. The sealing method according to claim 1, characterized in that: Cooling the welding point between the sealing pin and the groove specifically includes: Liquid nitrogen is used to cool the welding point between the sealing pin and the groove.

7. The sealing method according to claim 1, characterized in that: The induction current of the induction welding equipment during welding is 20-200A.

8. The sealing method according to claim 1, characterized in that: The operating frequency of the induction welding equipment during the welding process is 10-200KHz.

9. The sealing method according to claim 1, characterized in that: The induction welding equipment comprises an induction coil, and the number of turns of the induction coil is 1-5 turns.

10. The sealing method according to claim 9, characterized in that: The induction coil is in the shape of a notched circle, and is provided with at least two turns, and two adjacent turns of the induction coil are connected by a copper wire.

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