Two-seal air exhaust method of soft package battery and application of two-seal air exhaust method

Abstract

The invention provides a secondary sealing air exhaust method of a soft package battery and application of the secondary sealing air exhaust method, and relates to the technical field of batteries. The invention provides a two-seal air exhaust method of a soft package battery. The two-seal air exhaust method comprises the following steps: circularly and sequentially carrying out low-voltage treatment, medium-voltage treatment and high-voltage treatment on a battery cell; the low-pressure treatment comprises the step of applying a pressure of 0.1-0.2 Mpa to the surface of the battery cell under the vacuum degree of 75-85 kPa; in the medium-pressure treatment, the pressure of 0.2-0.3 Mpa is applied to the surface of the battery cell under the vacuum degree of 80-90 kPa; the high-pressure treatment comprises the step of applying pressure of 0.3-0.5 Mpa to the surface of the battery cell under the vacuum degree of 85-95 kPa; the cycle number of the low-pressure treatment, the medium-pressure treatment and the high-pressure treatment is more than one. According to the method, through cooperative control of stepped pressure circulation and stepped vacuum pressure maintaining, the contradiction between gas residue and electrolyte extrusion in the secondary sealing process of the soft package lithium battery is fundamentally solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a two-sealing gas extraction method for soft package batteries and application thereof. BACKGROUND

[0002] Soft package lithium battery and two-sealing gas extraction process: Soft package lithium batteries are widely used in consumer electronics, new energy vehicles, energy storage and other fields due to their high energy density, light weight, flexible shape and other advantages. The packaging usually adopts aluminum plastic film and is completed by a heat sealing process. The two-sealing process is one of the key steps in battery manufacturing, and the main task is to effectively extract the residual gas (such as incompletely reacted electrolyte solvent vapor, gas generated during formation, etc.) in the battery (especially the cavity between the battery cell and the aluminum plastic film edge) after liquid injection and before the final sealing of the battery, and complete the final heat sealing. This process is crucial to the performance (such as cycle life, rate capability), safety (such as preventing swelling, reducing the risk of thermal runaway) and long-term reliability (such as preventing electrolyte leakage, slowing down the interface side reaction) of the battery.

[0003] At present, the two-sealing gas extraction method commonly used in the industry is to apply a constant pressure directly to the surface of the battery (usually through a pressure plate or a pressure block) under a vacuum environment, tightly pressing the aluminum plastic film on the battery cell, and at the same time, using a bayonet to pierce the gas bag to perform vacuum extraction operation. The principle is to rely on continuous and stable pressure to exhaust gas and maintain the adhesion of the aluminum plastic film during heat sealing. However, this method has the following defects: 1. Risk of gas residue: Constant pressure cannot completely adapt to the complex gas exhaust path and dynamic process of gas generation inside the battery. Initially, too high a pressure may instantaneously compress the aluminum plastic film, thereby blocking the channels for the diffusion of deep-layer gas outward, making it difficult to completely extract the internal gas (especially in dead corner areas such as the edges of the battery cell and the root of the tab). The residual gas forms bubbles on the battery cell interface, and expands upon heating during subsequent use, which is a major cause of battery swelling and even edge bulging and cracking, seriously threatening the safety and life of the battery.

[0004] 2. Risk of electrolyte extrusion: To avoid gas residue, if a higher constant pressure is selected, there is a risk of extruding the liquid electrolyte inside the battery from the pores of the electrode or the weak part of the edge. The loss of electrolyte will directly affect the capacity and performance of the battery, and the extruded electrolyte may also contaminate the equipment or affect the sealing of the edge.

[0005] 3. Pressure selection dilemma and unstable effect: The selection of constant pressure value faces a dilemma: if the pressure is too low, the gas extraction is not complete, and there is too much residual gas; if the pressure is too high, the electrolyte is easily squeezed out or the structure of the battery cell is damaged. At the same time, for different batches, different state of charge (SOC) or different designs (such as the compaction density of the pole piece), the internal gas volume and discharge resistance are different, and a single constant pressure cannot achieve stable and optimal gas extraction effect, resulting in poor product quality consistency.

[0006] 4. Rough process control: The constant pressure process lacks dynamic adjustment capability and cannot adapt to the gas extraction process (such as changes in gas discharge rate and aluminum plastic film deformation state), which is a relatively rough control method.

[0007] Therefore, it is urgent to develop a more advanced two-seal gas extraction pressure application method to achieve breakthrough optimization between the mutually contradictory goals of effectively and completely removing residual gas, strictly avoiding electrolyte extrusion, ensuring excellent sealing of the edge, and improving process stability and product consistency.

[0008] Therefore, the present application is proposed. SUMMARY

[0009] The first object of the present application is to provide a two-seal gas extraction method for soft package batteries to solve the above technical problems.

[0010] The second object of the present application is to provide the application of the above two-seal gas extraction method in battery preparation.

[0011] In order to achieve the above objects, the following technical solutions are adopted: In a first aspect, the present application provides a two-seal gas extraction method for soft package batteries, comprising: cyclically and sequentially performing low pressure treatment, medium pressure treatment and high pressure treatment on the battery cell; The low pressure treatment is to apply a pressure of 0.1-0.2 MPa to the surface of the battery cell under a vacuum degree of 75-85 kPa; The medium pressure treatment is to apply a pressure of 0.2-0.3 MPa to the surface of the battery cell under a vacuum degree of 80-90 kPa; The high pressure treatment is to apply a pressure of 0.3-0.5 MPa to the surface of the battery cell under a vacuum degree of 85-95 kPa; The cycle number of the low pressure treatment, medium pressure treatment and high pressure treatment is more than 1.

[0012] As a further technical solution, the low pressure treatment is to apply a pressure of 0.1-0.2 MPa to the surface of the battery cell under a vacuum degree of 75-85 kPa for 1-2 s.

[0013] As a further technical solution, if the viscosity of the electrolyte of the battery cell is > 5cP, the pressure of 0.2 Mpa is applied to the surface of the battery cell during the low-pressure treatment.

[0014] As a further technical solution, the medium-pressure treatment is to apply a pressure of 0.2-0.3 Mpa to the surface of the battery cell for 1-2s under a vacuum degree of 80-90 kPa.

[0015] As a further technical solution, the high-pressure treatment is to apply a pressure of 0.3-0.5 Mpa to the surface of the battery cell for 1-5s under a vacuum degree of 85-95 kPa.

[0016] As a further technical solution, the pressure applied to the surface of the battery cell during the high-pressure treatment is less than 80% of the critical exudation pressure of the electrolyte.

[0017] As a further technical solution, after the low-pressure treatment, the medium-pressure treatment and the high-pressure treatment, the battery cell is further subjected to a pre-sealing treatment. The pre-sealing treatment is to apply a pressure of 0.1-0.3 Mpa to the surface of the battery cell under a vacuum degree of 85-95 kPa.

[0018] As a further technical solution, the soft package battery includes a lithium ion battery and a sodium ion battery.

[0019] In a second aspect, the application provides an application of the above-mentioned double-sealing and air-extracting method in battery preparation.

[0020] Compared with the prior art, the application has the following beneficial effects: The double-sealing and air-extracting method of the soft package battery provided by the application fundamentally solves the contradiction between "gas residue" and "electrolyte extrusion" in the double-sealing process of the soft package lithium battery through the synergistic control of "ladder pressure cycle" and "ladder vacuum pressure preservation", and realizes a leap-forward improvement in air-extracting effect and packaging quality. It successfully breaks the paradox that "gas residue" and "electrolyte overflow" cannot be considered at the same time in the double-sealing process, and at the same time realizes more thorough gas removal, more perfect packaging and sealing, and more excellent electrolyte retention capacity, thereby providing key technical support for improving the overall performance, safety and production efficiency of the soft package lithium battery. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the specific embodiments or the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0022] Figure 1 The liquid loss amount detection results of Comparative Examples 1 to 3 and Example 1; Figure 2 The hardness detection results of Comparative Examples 1 to 3 and Example 1; Figure 3 The liquid loss amount detection results of Example 2; Figure 4 The hardness detection results of Example 2; Figure 5 The liquid loss amount detection results of Example 3; Figure 6 The hardness detection results of Example 3. DETAILED DESCRIPTION

[0023] The embodiments of the present application will be described in detail below with reference to the embodiments and examples, but those skilled in the art will understand that the following embodiments and examples are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without making creative efforts are within the scope of the present application. If the specific conditions are not specified, the conventional conditions or the conditions recommended by the manufacturer are used. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased on the market.

[0024] In a first aspect, the present application provides a two-seal gas extraction method for a soft package battery, comprising: cyclically sequentially performing low pressure treatment, medium pressure treatment and high pressure treatment on the battery cell; The low pressure treatment is to apply a pressure of 0.1-0.2 MPa (for example, but not limited to 0.1 MPa, 0.15 MPa or 0.2 MPa) to the surface of the battery cell under a vacuum degree of 75-85 kPa (for example, but not limited to 75 kPa, 78 kPa or 85 kPa); The medium pressure treatment is to apply a pressure of 0.2-0.3 MPa (for example, but not limited to 0.2 MPa, 0.25 MPa or 0.3 MPa) to the surface of the battery cell under a vacuum degree of 80-90 kPa (for example, but not limited to 80 kPa, 85 kPa or 90 kPa); The high pressure treatment is to apply a pressure of 0.3-0.5 MPa (for example, but not limited to 0.3 MPa, 0.4 MPa or 0.5 MPa) to the surface of the battery cell under a vacuum degree of 85-95 kPa (for example, but not limited to 80 kPa, 90 kPa or 95 kPa); The number of cycles of the low pressure treatment, the medium pressure treatment and the high pressure treatment is more than 1, for example, 1, 2, 3, etc.

[0025] In the present application, the time of high-pressure treatment is controlled according to the pressure of the high-pressure treatment, so as to avoid the outflow of the electrolyte.

[0026] The principle of the present application is as follows: Low-pressure treatment: open the gas channel, avoid the blockage of the gas channel by the high pressure, make the deep bubbles separate from the interface adsorption, and allow the deep gas to diffuse to the surface (reduce the residual gas); Medium-pressure treatment: drive the directional migration of the gas, so that the bubbles rise along the pores and gradually discharge the gas accumulated in the shallow layer; High-pressure treatment: eliminate the gap between the pole piece and the diaphragm, so that the bubbles break through the gas-liquid interface to discharge the deep internal gas, and ensure that the aluminum plastic film is tightly attached to the battery (improve the sealing performance); Cyclic treatment: break the gas-liquid balance through pressure rise and fall cycle, and completely remove the dead angle gas.

[0027] In the above treatment process, the vacuum degree is adjusted synchronously to strengthen the gas-liquid separation effect. Through the cooperation of pressure and vacuum degree, the gas breaks through the gas adsorption resistance step by step, and at the same time, the loss of electrolyte caused by single high vacuum is avoided.

[0028] In the present application, the vacuum value needs to be flexibly configured according to the battery liquid loss and the gas production during formation. When the battery liquid retention is large and the electrolyte retention needs to be increased, the vacuum degree is appropriately reduced, the medium-pressure treatment pressure, the high-pressure treatment pressure and the pre-sealing stage all adopt 85Kpa vacuum degree, and the liquid loss is reduced; when the battery gas production is large, the vacuum degree is appropriately increased, the medium-pressure treatment pressure, the high-pressure treatment pressure and the pre-sealing stage all adopt 90Kpa vacuum degree, and the gas extraction efficiency is improved.

[0029] In some optional embodiments, the low-pressure treatment is: applying a pressure of 0.1-0.2 Mpa to the surface of the battery cell for 1-2s (for example, but not limited to, 1s, 1.5s or 2s) under a vacuum degree of 75-85 kPa.

[0030] By reasonably controlling the time of low-pressure treatment, the gas extraction efficiency is improved.

[0031] In some optional embodiments, if the viscosity of the electrolyte of the battery cell is >5cP, a pressure of 0.2 Mpa is applied to the surface of the battery cell during the low-pressure treatment.

[0032] In some optional embodiments, the medium-pressure treatment is: applying a pressure of 0.2-0.3 Mpa to the surface of the battery cell for 1-2s (for example, but not limited to, 1s, 1.5s or 2s) under a vacuum degree of 80-90 kPa.

[0033] By reasonably controlling the time of medium-pressure treatment, the gas extraction efficiency is improved.

[0034] In some optional embodiments, the high-pressure treatment is: applying a pressure of 0.3-0.5 MPa to the surface of the battery cell for 1-5 s (for example, but not limited to, 1 s, 3 s or 5 s) under a vacuum degree of 85-95 kPa.

[0035] By reasonably controlling the time of the high-pressure treatment, the exhaust efficiency is improved.

[0036] In some optional embodiments, the pressure applied to the surface of the battery cell during the high-pressure treatment is less than 80% of the critical exudation pressure of the electrolyte, so as to avoid exudation of the electrolyte.

[0037] In some optional embodiments, after the low-pressure treatment, the medium-pressure treatment and the high-pressure treatment, the battery cell is further subjected to a pre-sealing treatment. The pre-sealing treatment is: applying a pressure of 0.1-0.3 MPa to the surface of the battery cell under a vacuum degree of 85-95 kPa.

[0038] The value of the pre-sealing pressure of the present application is based on the lower limit of the critical pressure at which the electrolyte does not flow, so as to avoid extrusion of the electrolyte.

[0039] The pre-sealing is performed under the critical pressure at which the electrolyte does not flow, so as to reduce / control the inflow of the electrolyte into the air bag, which is beneficial to the retention amount of the electrolyte and the long-term circulation; at the same time, the pre-sealing is beneficial to the effect of the second sealing and the precision sealing, and greatly reduces the risk of the un-dissolved gel caused by the inflation of the seal.

[0040] In some optional embodiments, the pressure is applied to the surface of the battery cell by a pressure plate or a pressure block.

[0041] In some optional embodiments, the soft package battery includes a lithium ion battery and a sodium ion battery.

[0042] The method provided by the present application is suitable for lithium ion batteries and sodium ion batteries.

[0043] In a second aspect, the present application provides an application of the above-mentioned second-sealing and air-exhausting method in the preparation of a battery.

[0044] The second-sealing and air-exhausting method of the soft package battery provided by the present application can effectively remove the gas in the battery cell, thereby improving the cycle performance and the service life of the battery.

[0045] The present application will be further described below through specific examples, but it should be understood that these examples are only for more detailed description and should not be understood as limiting the present application in any form.

[0046] Example 1 A second-sealing and air-exhausting method of a soft package battery, the battery parameters are as follows: Battery capacity: 37 Ah; Battery SOC: 70%; Battery thickness: 11.6mm; Electrolyte density: 1.203 g / cm³ 3 ; Electrolyte viscosity: 1.04 mPa·s; Critical efflux pressure of electrolyte: 0.3 MPa.

[0047] The specific process parameters are shown in Table 1, including: the battery cells are subjected to low-voltage treatment, medium-voltage treatment and high-voltage treatment in a cyclical manner, followed by pre-sealing treatment; The low-pressure treatment involves applying a pressure of 0.15 MPa to the surface of the battery cell for 1 second under a vacuum of 80 kPa. The medium-pressure treatment involves applying a pressure of 0.25 MPa to the surface of the battery cell for 1 second under a vacuum of 85 kPa. The high-voltage treatment involves applying a pressure of 0.4 MPa to the surface of the battery cell for 3 seconds under a vacuum of 90 kPa. The low-pressure treatment, medium-pressure treatment, and high-pressure treatment cycle is repeated three times. Pre-sealing treatment: Apply a pressure of 0.2 MPa to the surface of the cell under a vacuum of 85 kPa.

[0048] Table 1

[0049] Example 2 A method for double-sealing and evacuating a pouch cell, the battery having the following parameters: Battery capacity: 50Ah; Battery SOC: 70%; Battery thickness: 14.3mm; Electrolyte density: 1.203 g / cm³ 3 ; Electrolyte viscosity: 1.04 mPa·s; Critical efflux pressure of electrolyte: 0.3 MPa.

[0050] The difference from Example 1 lies in the specific procedures shown in Table 2.

[0051] Table 2

[0052] Example 3 A method for double-sealing and evacuating a pouch cell, the battery having the following parameters: Battery capacity: 25Ah; Battery SOC: 70%; Battery thickness: 7.9mm; Electrolyte density: 1.203 g / cm 3 ; Electrolyte viscosity: 1.04 mPa.s; Electrolyte critical exudation pressure: 0.3 Mpa.

[0053] The difference from Example 1 is that the specific process is shown in Table 3.

[0054] Table 3

[0055] Comparative Example 1 The difference from Example 1 is that the specific process is shown in Table 4.

[0056] Table 4

[0057] Comparative Example 2 The difference from Example 1 is that the specific process is shown in Table 5.

[0058] Table 5

[0059] Comparative Example 3 The difference from Example 1 is that the specific process is shown in Table 6.

[0060] Table 6

[0061] Test Example Example 1 and Comparative Examples 1-3 are used to package batteries, respectively, and 30 pcs of battery cells are taken from each group, and the test results are as follows: 1. The amount of electrolyte retained is evaluated by the amount of liquid loss, and the data of Comparative Examples 1-3 and Example 1 are compared as shown in Table 1. Figure 1 Appendix: Liquid loss calculation formula: liquid loss = weight before sealing - weight after sealing - gas bag weight; 2. To quantify the effect of air extraction, the hardness is evaluated, and the data of Comparative Examples 1-3 and Example 1 are compared as shown in Table 2 (Note: the hardness cannot completely evaluate the air extraction effect, and the greater the hardness, the more the electrode sheet is attached to the electrode sheet, and the actual air extraction effect of each group of batteries is qualified). Figure 2

[0062] Appendix: Hardness measurement method: use three-point bending, test direction compression, constant speed 35 mm / min, switching condition: deformation ≥ 3 mm; ​​According to the verification results, the liquid loss of Example 1 is lower than that of Comparative Examples 1-3, and the hardness of Example 1 is higher than that of Comparative Examples 1-3, thus indicating that the electrolyte retention and the air extraction effect of Example 1 are better than those of Comparative Examples 1-3. Meanwhile, the electrolyte retention and the air extraction effect of Example 2-3 are also relatively excellent, the average liquid loss of Example 2 is 0.22 g, and the average hardness is 130.9 N; the average liquid loss of Example 3 is 0.068 g, and the average hardness is 77.8 N. Figures 3-6 .

[0063] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions described in the foregoing examples can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of double sealing and pumping down a soft package battery, characterized by, The method comprises: sequentially performing low-pressure treatment, medium-pressure treatment and high-pressure treatment on the battery cell in cycles; the low-pressure treatment is to apply a pressure of 0.1-0.2 MPa to the surface of the battery cell under a vacuum degree of 75-85 kPa; the medium-pressure treatment is to apply a pressure of 0.2-0.3 MPa to the surface of the battery cell under a vacuum degree of 80-90 kPa; the high-pressure treatment is to apply a pressure of 0.3-0.5 MPa to the surface of the battery cell under a vacuum degree of 85-95 kPa; the cycle number of the low-pressure treatment, the medium-pressure treatment and the high-pressure treatment is more than 1.

2. The double pumped gas extraction method of claim 1, wherein the low-pressure treatment is to apply a pressure of 0.1-0.2 MPa to the surface of the battery cell under a vacuum degree of 75-85 kPa for 1-2 s.

3. The double pumped gas extraction method of claim 1, wherein if the viscosity of the electrolyte of the battery cell is >5 cP, a pressure of 0.2 MPa is applied to the surface of the battery cell during the low-pressure treatment.

4. The double pumped gas extraction method of claim 1, wherein the medium-pressure treatment is to apply a pressure of 0.2-0.3 MPa to the surface of the battery cell under a vacuum degree of 80-90 kPa for 1-2 s.

5. The double pumped gas extraction method of claim 1, wherein the high-pressure treatment is to apply a pressure of 0.3-0.5 MPa to the surface of the battery cell under a vacuum degree of 85-95 kPa for 1-5 s.

6. The double pumped gas removal method of claim 1, wherein, the pressure applied to the surface of the battery cell during the high-pressure treatment is less than 80% of the critical exudation pressure of the electrolyte.

7. The double pumped gas removal method of claim 1, wherein, after the low-pressure treatment, the medium-pressure treatment and the high-pressure treatment, the method further comprises pre-sealing treatment on the battery cell; the pre-sealing treatment is to apply a pressure of 0.1-0.3 MPa to the surface of the battery cell under a vacuum degree of 85-95 kPa.

8. The double pumped gas removal method of claim 1, wherein, the soft package battery comprises a lithium ion battery and a sodium ion battery.

9. Use of the double-seal air extraction method according to any one of claims 1-8 in battery preparation.

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