A packaging process for lithium-ion batteries

Abstract

This invention discloses a lithium-ion battery packaging process. By processing chamfered edges on the electrodes, the electrode edges are free of stepped structures, allowing the aluminum-plastic film to completely wrap the electrodes and preventing cracks from forming between the outer casing and the electrodes. Furthermore, the battery cell is wrapped with a PET plastic film, providing protection with a rigid outer shell. The shape of the soft-pack battery is also reshaped to make its external shape more regular. Additionally, the gas inside the battery is evacuated through multiple heat-sealing processes on the sides, increasing the battery's energy density.

Description

Technical Field

[0001] This invention relates to a packaging process for lithium-ion batteries. Background Technology

[0002] The safety performance of lithium-ion batteries is a crucial factor in evaluating their performance as power batteries. Factors limiting lithium-ion battery safety include positive and negative electrode materials, electrode compaction, separators, and manufacturing process protection. Keeping other material conditions constant, improving the protection of stacked cells can effectively enhance cell safety. Pouch lithium-ion batteries offer advantages over prismatic and cylindrical batteries, such as higher energy density, lighter weight, better safety performance, and more flexible design, leading to their widespread application in mobile communications, energy storage, and power applications. The casing material for pouch lithium-ion batteries is typically an easily moldable aluminum-plastic film composite material. The battery cell is placed within the aluminum-plastic film, and the edges are sealed. Since the battery electrodes need to extend beyond the aluminum-plastic film, leakage is common at the electrode edges where they contact the film. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a packaging process for lithium-ion batteries.

[0004] The present invention is achieved through the following technical solutions.

[0005] The present invention provides a lithium-ion battery packaging process, the steps of which are as follows:

[0006] S1. Negative and positive electrode plates are neatly stacked, with the tabs of negative and positive electrode plates staggered and aligned respectively. Each layer of negative and positive electrode plates is then wrapped with a diaphragm to obtain a battery cell.

[0007] S2. Weld the negative electrode tab and the positive electrode tab to the positive electrode and the negative electrode, respectively;

[0008] S3. Use PET molding film to wrap the battery cell;

[0009] S4. Place the battery cell into the aluminum-plastic film packaging material and heat-seal the edges of the aluminum-plastic film to form the battery area and the gas generation area.

[0010] S5. Inject liquid into the battery area, and after multiple formation, degassing, and reshaping processes, cut off the gas-producing area.

[0011] The width of the diaphragm is 1.02-1.05 times that of the electrode.

[0012] The welding process in S2 is as follows:

[0013] S21. Place the electrode in the middle of the tab, and then pre-solder the tabs to the electrode from near to far.

[0014] S22. Use ultrasonic welding to reinforce the tabs onto the electrodes.

[0015] In S4, the heat-sealing position of the aluminum-plastic film on the electrode is 1.5m higher than the welding position between the electrode and the tab.

[0016] The electrode and the heat-sealed contact area are chamfered.

[0017] The steps of formation, degassing, and shaping in S5 are as follows:

[0018] S51, Inject liquid from the top of the gas-producing zone;

[0019] S52. After pre-filling and evacuating the gas from the aluminum-plastic film, add a side seal in the middle of the gas-generating area.

[0020] S53. After aging and evacuating the gas from the aluminum-plastic film, add a side seal at the edge of the battery area.

[0021] The diaphragm is made of PE material and has a thickness of 12-20μm.

[0022] The shaping film is made of PET material with a thickness of 50-100μm.

[0023] The shaping film includes two side films connected by a side edge. One side film is connected to the side edge and then to the adhesive edge, while the side edge of the other side film is directly connected to the adhesive edge. Both side films have a top edge connected to their top ends, and one side film has a bottom edge connected to its bottom end.

[0024] The molding film also has several through holes uniformly machined on it.

[0025] The beneficial effects of this invention are as follows: by processing chamfered edges on the electrodes, the electrode edges are free of stepped structures, and the aluminum-plastic film can completely wrap the electrodes, avoiding the formation of cracks between the outer casing and the electrodes; furthermore, by wrapping the battery cell with a plastic film made of PET material, the battery cell can be protected by a hard outer shell, and the shape of the soft-pack battery is shaped, making its external shape more regular; and by repeatedly evacuating and heat-sealing the sides, the gas inside the battery is evacuated, increasing the energy density of the battery. Attached Figure Description

[0026] Figure 1 This is a diagram of the battery packaging structure of the present invention;

[0027] Figure 2 This is a diagram showing the unfolded structure of the plastic film of the present invention;

[0028] 1-Battery cell, 2-Taper, 3-Plastic film, 31-Side film, 32-Top edge, 33-Bottom edge, 34-Side edge, 35-Bonding edge, 36-Through hole, 4-Taper protective tape. Detailed Implementation

[0029] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0030] Example 1: A lithium-ion battery packaging process, the steps of which are as follows:

[0031] S1. Negative and positive electrode plates are neatly stacked, with the tabs of the negative and positive electrode plates staggered and aligned respectively. Each layer of negative and positive electrode plates is wrapped with a diaphragm to obtain a battery cell. The positive and negative electrode plates are staggered and aligned respectively, which makes it easy to weld the positive and negative electrode plates to the positive and negative tabs respectively.

[0032] S2. Weld the negative electrode tab and the positive electrode tab to the positive electrode and the negative electrode, respectively;

[0033] S3. Use a PET molding film to wrap the battery cell. Use rigid PET to wrap the battery cell as a protective shell and fix the shape of the battery cell, so that the soft package becomes a square hard package structure.

[0034] S4. Place the battery cell into the aluminum-plastic film packaging material, heat seal the edges of the aluminum-plastic film to form the battery area and the gas generation area. The aluminum-plastic film serves as the encapsulation film for the electrolyte, wrapping the plastic film inside.

[0035] S5. Inject liquid into the battery area, and after multiple formation, degassing, and reshaping processes, remove the gas-producing area.

[0036] The width of the diaphragm is 1.02-1.05 times that of the electrode.

[0037] The welding process in S2 is as follows:

[0038] S21. Place the electrode in the middle of the tab, and then pre-solder the tabs to the electrode from near to far.

[0039] S22. Use ultrasonic welding to reinforce the tabs onto the electrodes.

[0040] In S4, the heat-sealing position of the aluminum-plastic film on the electrode is 1.5m higher than the welding position between the electrode and the tab.

[0041] The electrode and the heat seal contact area are chamfered, and no step is formed between the heat seal and the chamfered surface, so that there is no gap between the heat seal and the electrode, thus avoiding electrolyte leakage.

[0042] The steps of formation, degassing, and shaping in S5 are as follows:

[0043] S51. Inject liquid through the extraction hole in the gas production area;

[0044] S52. After pre-filling and evacuating the gas from the aluminum-plastic film, add a side seal in the middle of the extraction area.

[0045] S53. After aging and evacuating the gas from the aluminum-plastic film, add a side seal at the edge of the battery area.

[0046] The diaphragm is made of PE material and has a thickness of 12-20μm.

[0047] The shaping film is made of PET material with a thickness of 50-100μm.

[0048] like Figure 2 As shown, the shaping film 3 includes a side film 31, which consists of two pieces. The two side films 31 are connected by a side edge 34. The side edge of one side film 31 is connected to the side edge 34, and then the side edge 34 is connected to the adhesive edge 35. The side edge of the other side film 31 is directly connected to the adhesive edge 35. The top of both side films 31 is connected to a top edge 32, and the bottom of one side film 31 is connected to a bottom edge 33.

[0049] like Figure 1 As shown, the molding film 3 is also uniformly machined with several through holes 36. The top of the molding mold is open and its height cannot be higher than 1mm above the battery cell. This is to prevent the aluminum-plastic film from forming a step when it is being encapsulated because the top of the molding mold is too close to the tab sealing point, which would increase the difficulty of encapsulation.

[0050] The transformation steps are as follows:

[0051] 1) Place the battery to be formed and activated in the pressure formation device, ensuring good contact. First, charge the battery with a constant current of 0.05C for 120 minutes until the voltage is 3.2V, and then charge the battery with a constant current of 0.2C for 150 minutes until the voltage is 3.6V.

[0052] 2) Take out the battery after charging in step 1, insert a vacuum tube with a needle into the battery air bag, then connect the vacuum tube to the long tube of the return tank, and then connect the short tube of the return tank to the vacuum pumping device. After completing the vacuum pumping operation, maintain the pressure with a vacuum degree ≤ -60MPa and a pressure holding time of 1-2s.

[0053] 3) Seal the insertion point of the battery airbag bag with a heat sealing temperature of 180-230℃, a pressure of 0.2-0.4MPa, and a time of 2-4s;

[0054] 4) Place the battery obtained in step 3 in a pressure formation device to ensure good contact. Discharge the battery with a constant current of 0.08C for 130 minutes until the voltage is 2.75V, and then charge the battery with a constant current of 0.2C for 130 minutes until the voltage is 3.65V.

Claims

1. A packaging process of a lithium ion battery, comprising the following steps: S1. stacking negative and positive electrode sheets in order, staggering the negative and positive electrode tabs and aligning them respectively, and wrapping each layer of negative and positive electrode sheets with a separator to obtain a battery cell; S2. welding the negative and positive electrode tabs to the positive and negative electrodes respectively; S3. wrapping the battery cell with a plastic film made of PET material, and performing insulation and flattening treatment; S4. placing the battery cell into an aluminum plastic film packaging material, heat-sealing the edges of the aluminum plastic film to form a battery area and a gas production area; S5. injecting liquid into the battery area, and cutting off the gas production area after multiple formation, degassing and shaping; In S4, the heat-sealing position of the aluminum plastic film on the electrode is 5.5-7.5 mm higher than the welding position of the electrode and the tab; A chamfer is processed at the contact between the electrode and the heat-sealing position.

2. The packaging process of a lithium-ion battery as claimed in claim 1, wherein: The width of the separator is 1.02-1.05 times the width of the electrode sheet.

3. The packaging process of a lithium-ion battery as claimed in claim 1, wherein: The welding process in S2 comprises the following steps: S21. placing the electrode in the middle of the tab, and then pre-welding the tab to the electrode from near to far in order; S22. using ultrasonic welding to reinforce and weld the tab to the electrode.

4. The packaging process of a lithium-ion battery of claim 1, wherein: The steps of formation, degassing and shaping in S5 comprise the following steps: S51. injecting liquid from the top of the gas production area; S52. after pre-charging, evacuating the gas in the aluminum plastic film, and adding side sealing in the middle of the gas production area; S53. after aging, evacuating the gas in the aluminum plastic film, and adding side sealing at the edge of the battery area.

5. The packaging process of a lithium-ion battery as claimed in claim 1, wherein: The separator is made of PE material and has a thickness of 15-20 μm.

6. The packaging process of a lithium-ion battery as claimed in claim 1, wherein: The plastic film is made of PET material and has a thickness of 50-100 μm.

7. The packaging process of a lithium-ion battery as claimed in claim 1, wherein: The plastic film comprises two side films connected by a side edge, one of the side films is connected to the side edge and then connected to a bonding edge, the other side film is directly connected to the bonding edge by a side edge, and the top end of each side film is connected to a top edge, and the bottom end of one side film is connected to a bottom edge.

8. The packaging process of a lithium-ion battery as claimed in claim 7, wherein: A plurality of through holes are uniformly processed on the plastic film.

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