Aluminum-plastic film for long-life lithium battery and production process of aluminum-plastic film

Abstract

The aluminum-plastic film comprises a heat sealing layer with an anti-blocking agent embedded in the surface, the anti-blocking agent comprises composite microspheres, the composite microspheres are mesoporous inorganic microspheres internally loaded with water-absorbing expansion particles, the thickness of the heat sealing layer is T heat sealing, the average particle size of the water-absorbing expansion particles is D particles, and the average particle size of the water-absorbing expansion particles is T particles. The average particle size of the mesoporous inorganic microspheres is D microspheres, and the average mesoporous aperture of the mesoporous inorganic microspheres is D mesoporous. The long-service-life aluminum plastic film for the lithium battery is reasonable in formula and excellent in opening performance and heat sealing performance; mesoporous inorganic microspheres loaded with water-swelling microspheres are used as an anti-blocking agent of the heat-sealing layer, so that the anti-blocking agent is endowed with water absorption performance, and the service life of the battery is prolonged; according to the invention, the composite microspheres are used as the opening agent, so that the battery capacity attenuation amplitude in an extreme environment is relatively small. The invention further discloses a production process of the long-service-life aluminum plastic film for the lithium battery.

Description

Technical Field

[0001] This invention relates to the field of aluminum-plastic film technology, specifically to an aluminum-plastic film for long-life lithium batteries and its production process. Background Technology

[0002] Aluminum-plastic film is a key packaging material for pouch lithium batteries, and its water-resistant performance is one of its core indicators. Common aluminum-plastic films generally consist of a heat-sealing layer, a first adhesive layer, an aluminum foil layer, a second adhesive layer, and a surface layer, stacked in sequence.

[0003] To improve the opening performance of aluminum-plastic film, an opening agent is generally added to the heat-sealing layer. Opening agents used in aluminum-plastic film are divided into two categories: penetrating and dissociating type and particulate type, also known as organic and inorganic opening agents. Currently, aluminum-plastic film manufacturers generally improve opening agents by enhancing their opening performance or reducing their cost. Chinese invention patent application CN119029430A introduces modified silica into CPP film used as a heat-sealing layer. This modified silica imparts excellent anti-blocking properties, slip properties, and mechanical strength to the CPP film, and significantly reduces the release and volatilization of slip agents during heat sealing and curing processes. This solves the problem of increased friction coefficient in CPP film after lamination, reducing not only adhesion and uneven stress during aluminum-plastic film curing, but also damage and deformation of the film during mold stamping.

[0004] However, simply optimizing the opening performance of the opening agent or reducing its cost will have limited effect on improving the overall performance of aluminum-plastic film. Developing opening agents with new functions (such as extending the lifespan of aluminum-plastic film) is an inevitable choice for aluminum-plastic film manufacturers to break through current performance bottlenecks and meet the demands of the high-end market. Summary of the Invention

[0005] One of the objectives of this invention is to overcome the deficiencies in the prior art and provide an aluminum-plastic film for long-life lithium batteries, wherein lithium batteries using this aluminum-plastic film can still retain a high battery capacity after extreme environmental testing.

[0006] To address the aforementioned technical problems, this invention provides an aluminum-plastic film for long-life lithium batteries, comprising a heat-sealing layer with an opening agent embedded on its surface. The opening agent comprises composite microspheres, which are mesoporous inorganic microspheres internally loaded with water-absorbing and swelling microparticles. The thickness of the heat-sealing layer is T. 热封 The average particle size of the water-absorbing and swelling microparticles is D. 微粒 The average particle size of the mesoporous inorganic microspheres is D. 微球 The average mesoporous pore size of the mesoporous inorganic microspheres is D. 介孔 .

[0007] A preferred technical solution is that the water-absorbing and swelling microparticles are at least one of polyacrylamide microspheres, polyacrylic acid microspheres, and polyvinyl alcohol microspheres; And / or the mesoporous inorganic microspheres are at least one of mesoporous silica microspheres, mesoporous carbon microspheres, and mesoporous titanium oxide microspheres.

[0008] A preferred technical solution is that the heat-sealing layer comprises ternary copolymer polypropylene and POE elastomer, and the mass ratio of the ternary copolymer polypropylene to POE elastomer is 7:(2.8~3.1).

[0009] Furthermore, the mass ratio of the ternary copolymer polypropylene and POE elastomer can be selected as a point value of 7:2.8, 7:2.9, 7:3, or 7:3.1, or a range of the above two point values ​​as the maximum and minimum values.

[0010] A preferred technical solution is that the mass ratio of the water-absorbing and swelling microparticles to the mesoporous inorganic microspheres is 1:(9~15).

[0011] Furthermore, the mass ratio of the water-absorbing and swelling microparticles to the mesoporous inorganic microspheres can be selected as a point value of 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, or 1:15, or as an interval value of the above two point values ​​as the maximum and minimum values.

[0012] The preferred technical solution is D. 微球 :T 热封 1: (12~20).

[0013] Furthermore, D 微球 :T 热封 The range of values ​​can be selected as 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20, or two of the above values ​​as the range of maximum and minimum values.

[0014] The preferred technical solution is D. 微球 :D 介孔 The range is 100 to 210.

[0015] Furthermore, D 微球 :D 介孔 The range of values ​​can be selected as 100, 120, 140, 150, 170, 200, 210 points or two of the above points as the range of maximum and minimum values.

[0016] The preferred technical solution is D. 微粒 :D 介孔 It ranges from 0.5 to 0.7.

[0017] Furthermore, D 微粒 :D 介孔The range of values ​​for the maximum and minimum values ​​can be selected as 0.5, 0.6, 0.7, or two of the above values.

[0018] The second objective of this invention is to provide a manufacturing process for aluminum-plastic film for long-life lithium batteries, comprising the following steps: S1: The adsorbent mesoporous inorganic microspheres and the adsorbate water-absorbing and swelling microspheres are dispersed in the dispersant; S2: The dispersion system obtained after purifying S1; S3: The purified product obtained in S2 is dried to obtain composite microspheres.

[0019] The preferred technical solution is that S3 is dried under vacuum.

[0020] The preferred technical solution further includes the following steps: The heat-sealing resin is cast by spreading composite microspheres on the surface of the incompletely cured heat-sealing resin, heating the heat-sealing resin to its melting point, and then cooling the heat-sealing resin to obtain a heat-sealing film.

[0021] The advantages and beneficial effects of this invention are as follows: The aluminum-plastic film for long-life lithium batteries of this invention has a reasonable formulation and excellent opening and heat-sealing performance. This invention uses mesoporous inorganic microspheres loaded with water-absorbing and swelling microspheres as an opening agent for the heat-sealing layer, giving the opening agent water-absorbing properties, which helps to extend battery life. This invention uses composite microspheres as an opening agent, resulting in a smaller capacity decay of the battery under extreme conditions. Detailed Implementation

[0022] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0023] Preparation of polyacrylamide microspheres: Synthesis of hexadecyl dimethyl allyl ammonium chloride hydrophobic monomer: Hexadecyl dimethyl tertiary amine, allyl chloride and anhydrous ethanol were added to a three-necked flask and mixed thoroughly. After heating and refluxing at 50℃~60℃ for 24h, the resulting reaction solution was subjected to vacuum distillation, washed and filtered. The filter residue was dried at 40℃ to obtain hexadecyl dimethyl allyl ammonium chloride hydrophobic monomer. Synthesis of polyacrylamide nanospheres: The synthesized hexadecyl dimethyl allyl ammonium chloride hydrophobic monomer, acrylamide, deionized water, N,N-methylenebisacrylamide and ammonium persulfate were fully dissolved in a beaker to form the aqueous phase of the polymerization system; Weigh out kerosene and Span 20 / T heat seal ween 80 compound emulsifier and mix them evenly on a magnetic stirrer to form the oil phase of the polymerization system; Then the aqueous phase is slowly poured into the oil phase while continuously stirring to prepare a transparent microemulsion; The prepared transparent microemulsion was poured into a four-necked flask. Nitrogen gas was introduced while stirring at 350 r / min for 0.5 h. After the nitrogen gas was introduced, the water bath temperature was controlled at 35℃~40℃. Sodium bisulfite was added to initiate the reverse microemulsion polymerization reaction. After 6 h of reaction, a polyacrylamide nanosphere dispersion was obtained. The polyacrylamide nanosphere dispersion was washed with anhydrous ethanol, and after centrifugation, the polymer precipitate was redispersed. Polyacrylamide nanospheres with average particle sizes of 4 nm, 6 nm, and 8 nm were obtained by differential centrifugation.

[0024] raw material: Silica microspheres: average particle size 2μm, mesopores with an average pore size of 10nm; Outer adhesive: VN830 / CA-N6 (aluminum-plastic film outer adhesive), Shanghai Weikai Optoelectronic New Materials Co., Ltd.; Inner layer adhesive: VP118 / CA-P2 (inner layer adhesive for aluminum-plastic film), Shanghai Weikai Optoelectronic New Materials Co., Ltd.; PA film: PHA lithium battery film (functional biaxially oriented nylon film), Xiamen Changsu Industrial Co., Ltd.; Ternary copolymer polypropylene: PP FL7632, Singapore polyolefin; POE elastomer: XM-7070S, Mitsui Chemicals, Japan; Aluminum foil: 8021 O state, Henan Mingtai; Adhesive polyolefin: QF551, Mitsui Chemicals, Japan; Polyolefin elastomer: XM7070S, Mitsui Chemicals, Japan Polyolefin: FL7632, Singapore polyolefin.

[0025] 1. Examples and Comparative Examples Example 1

[0026] Preparation process of composite microspheres in Example 1: S01: 1g of water-absorbing and swelling microspheres (polyacrylamide nanospheres) with an average particle size of 6nm were ultrasonically dispersed in 100mL of anhydrous ethanol, and 12g of mesoporous inorganic microspheres (silica microspheres) were ultrasonically dispersed in 1L of anhydrous ethanol. S02: Mix the water-absorbing and swelling microsphere dispersion obtained in S01 with the mesoporous inorganic microsphere dispersion and stir for 12 hours at a speed of 80 rpm. S03: First, centrifuge the mixed dispersion obtained from S02 to obtain a solid product. Then, disperse the solid product again with anhydrous ethanol, centrifuge, and vacuum dry to obtain composite microspheres.

[0027] By measuring the mass of the mesoporous inorganic microspheres before and after loading, the mass ratio of the water-absorbing and swelling microparticles to the mesoporous inorganic microspheres in the composite microspheres was found to be 1:11.8.

[0028] Preparation process of heat-sealing film in Example 1: First, the molten heat-sealing resin is cast (casting temperature is 251℃). After the heat-sealing resin cools to 120℃, it is kept at this temperature (at which point the substrate resin is not fully cured). Then, composite microspheres are sprayed onto the surface of the heat-sealing resin using an electronic powder spraying device (spraying amount is 40mg / m²). 2 Then, heat the heat-sealing resin to 135°C, cool the substrate resin, and cure to obtain a 30μm heat-sealing film.

[0029] The heat-sealing resin in Example 1 was prepared by mixing and granulating a ternary copolymer polypropylene of grade PP FL7632 and a POE elastomer of grade XM-7070S in a mass ratio of 7:3.

[0030] The manufacturing process of the long-life lithium battery aluminum-plastic film in Example 1 includes: S1: A passivating solution containing chromate is applied to both surfaces of a 45μm aluminum foil using a coating machine to obtain a passivated aluminum foil; S2: After coating a 3μm outer layer of adhesive onto a 25μm PA film, it is laminated with the A side of a passivated aluminum foil; S3: After coating the heat-sealing film with a 3μm inner layer adhesive, it is laminated with the B side of the passivated aluminum foil to obtain an aluminum-plastic film for long-life lithium batteries.

[0031] Example 2

[0032] The production process of the long-life lithium battery aluminum-plastic film in Example 2 is based on Example 1, except that the composite microspheres used in Example 2 are polyacrylamide nanospheres with an average particle size of 4 nm.

[0033] Example 3

[0034] The production process of the long-life lithium battery aluminum-plastic film in Example 3 is based on Example 1, except that the composite microspheres used in Example 3 are polyacrylamide nanospheres with an average particle size of 8 nm.

[0035] Example 4

[0036] Example 4: The production process of aluminum-plastic film for long-life lithium batteries is based on Example 1, except that the drying process of S03 is atmospheric pressure drying.

[0037] Example 5

[0038] Example 5: The production process of aluminum-plastic film for long-life lithium batteries is based on Example 1, except that in the preparation process of composite microspheres, S01: 1 g of water-absorbing and swelling microspheres (polyacrylamide nanospheres) with an average particle size of 6 nm were ultrasonically dispersed in 100 mL of anhydrous ethanol, and 8 g of mesoporous inorganic microspheres (silica microspheres) were ultrasonically dispersed in 1 L of anhydrous ethanol.

[0039] By measuring the mass of the mesoporous inorganic microspheres before and after loading, the mass ratio of the water-absorbing and swelling microparticles to the mesoporous inorganic microspheres in the composite microspheres was found to be 1:7.9.

[0040] Example 6

[0041] Example 6: The production process of aluminum-plastic film for long-life lithium batteries is based on Example 1, except that in the preparation process of composite microspheres, S01: 1 g of water-absorbing and swelling microspheres (polyacrylamide nanospheres) with an average particle size of 6 nm were ultrasonically dispersed in 100 mL of anhydrous ethanol, and 20 g of mesoporous inorganic microspheres (silica microspheres) were ultrasonically dispersed in 1 L of anhydrous ethanol.

[0042] By measuring the mass of the mesoporous inorganic microspheres before and after loading, the mass ratio of the water-absorbing and swelling microparticles to the mesoporous inorganic microspheres in the composite microspheres was found to be 1:15.3.

[0043] Example 7

[0044] Example 7: The production process of aluminum-plastic film for long-life lithium batteries is based on Example 1, except for the preparation process of the heat-sealing film: First, the molten heat-sealing resin is cast (casting temperature is 251℃). After the heat-sealing resin cools to 120℃, it is kept at this temperature (at which point the substrate resin is not fully cured). Then, composite microspheres are sprayed onto the surface of the heat-sealing resin using an electronic powder spraying device (spraying amount is 40mg / m²). 2 Then, the substrate resin is cooled and cured to obtain a 30μm heat-sealing film.

[0045] Example 8

[0046] The production process of the long-life lithium battery aluminum-plastic film in Example 8 is based on Example 1, with the difference being: The structure of the long-life lithium battery aluminum-plastic film in Example 8 is composed of a PA layer, an outer adhesive layer, an aluminum layer, a PPA layer, and a PPB layer stacked sequentially. The thickness of the PA layer is 25 μm, the thickness of the outer adhesive layer is 3 μm, the thickness of the aluminum layer is 45 μm, and the thicknesses of the PPA and PPB layers are both 15 μm.

[0047] The masterbatch used in the PPA layer is obtained by granulation of adhesive polyolefin of type QF551 and polyolefin elastomer of type XM7070S at a mass ratio of 9:1.

[0048] The masterbatch used in the PPB layer was obtained by mixing polyolefin of type FL7632 and polyolefin elastomer of type XM7070S in a mass ratio of 7:3 (with the addition of 2000PPM of composite microspheres, which are the same as those used in Example 1) and then granulating.

[0049] The manufacturing process of the long-life lithium battery aluminum-plastic film in Example 8 includes: S1: 45μm aluminum foil is prepared and introduced into the plasma treatment machine. Both the bright and matte surfaces of the aluminum foil are subjected to plasma corona treatment. The plasma carrier air is oxygen-enriched air discharged from the nitrogen generator, with an oxygen content of 35%. The plasma power is 10KW and the vehicle speed is 100m / min. S2: The aluminum foil obtained in S1 is fed into the coating mechanism via the unwinding mechanism. The PPA layer material is fed into extruder A, and the PPB layer material is fed into extruder B. The extrusion temperature range for the PPA and PPB layers consists of five sections, with temperatures of 150℃, 200℃, 250℃, 280℃, and 300℃ respectively. The die temperature of the extruder is 300℃. A confluence section (500mm in length) connects extruder A and extruder B to the die. The molten resin of the PPA and PPB layers first enters the confluence section, and the two resin layers are fed together. Finally, the mixture is extruded through the die lip and coated onto the glossy surface of the aluminum foil. The discharged material passes through a cooling roller and is cooled to room temperature. Then, it is heated to 160℃, with a roller pressure of 0.3MPa, and subjected to a second pressing. The pressed aluminum foil / heat-sealing layer composite structure is then wound up for later use. The extrusion speed of the molten resin in the PPA and PPB layers is controlled during the extrusion process. The thickness of both the PPA and PPB layers is 15μm. S3: After coating a 3μm outer layer of adhesive onto a 25μm PA film, heat the film in a three-stage oven at 60℃, 70℃, and 80℃, with a material feeding speed of 100m / min and a heating time of 8 seconds. After drying, the film is laminated with the aluminum foil matte finish prepared in S1 at a lamination pressure of 0.4MPa to obtain an aluminum-plastic film for long-life lithium batteries.

[0050] Comparative Example The comparative production process of the aluminum-plastic film for long-life lithium batteries is based on Example 1, except for the preparation process of the heat-sealing film: First, the molten heat-sealing resin is cast (casting temperature is 251℃). After the heat-sealing resin cools to 120℃, it is held at this temperature (at which point the substrate resin is not fully cured). Then, silica microspheres (40 mg / m³) are sprayed onto the surface of the heat-sealing resin using an electronic powder spraying device. 2 Then, heat the heat-sealing resin to 135°C, cool the substrate resin, and cure to obtain a 30μm heat-sealing film.

[0051] 2. Detection methods for the examples and comparative samples 2.1. Heat sealing strength The heat-sealing strength of aluminum-plastic film was determined according to the testing standard QB / T Heat Sealing 2358-1998; 2.2. Methods for determining the coefficient of friction of plastic films and sheets The coefficient of friction of aluminum-plastic film was tested according to the national standard GB 10006-1988.

[0052] 2.3. Battery capacity degradation under extreme environments After heat sealing with aluminum-plastic film, a soft-pack lithium battery is obtained. The battery capacity is measured as C1. The battery is first placed in a sealed box with constant temperature and humidity at 90%RH for 30 days. Then it is placed in a constant temperature room at -18℃ for 12 hours. After being taken out, it is placed in a sealed box with constant temperature and humidity at 60%RH for 14 days. The battery capacity at this time is measured as C2. The battery capacity decay ratio is (C1-C2) / C1*100%.

[0053] 3. Performance test results of the examples and comparative samples

[0054] The heat-sealing strength of the aluminum-plastic films in both the examples and comparative examples is 70~80 N / 15 mm, which meets the standard of ≥50 N / 15 mm for heat-sealing strength of aluminum-plastic films. The coefficient of friction of the aluminum-plastic films in both the examples and comparative examples is 0.3~0.31, indicating good opening performance.

[0055] Based on Example 1, the reason for the increase in the comparative capacity decay ratio may be that: under the low temperature test environment, microcracks were generated in the heat seal layer, and the water-absorbing and expanding microspheres loaded in the mesoporous inorganic microspheres absorbed the water that seeped into the microcracks and expanded, but were stuck in the mesopores due to the restriction of the mesopores. The expansion and deformation of the spheres extended out of the mesopores and blocked part of the microcracks, reducing the channels for water to enter the battery and resulting in a smaller decrease in battery capacity.

[0056] Examples 1, 2, and 3 show that the preferred D 微粒 and D 介孔 The ratio of [value] is beneficial for reducing the capacity decay ratio of the battery.

[0057] Based on Example 1, the reason for the increase in capacity decay ratio in Example 4 may be that vacuum drying facilitates the aggregation of water-absorbing and swelling microspheres loaded in mesoporous inorganic microspheres, reducing the possibility of water-absorbing and swelling microspheres detaching from the mesoporous inorganic microspheres before expansion.

[0058] Examples 1, 5, and 6 show that the preferred mass ratio of water-absorbing and swelling microspheres to mesoporous inorganic microspheres is beneficial for reducing the capacity decay ratio of the battery.

[0059] Based on Example 1, the reason for the increase in capacity decay ratio in Example 7 may be that: after spreading the composite microspheres, heating the heat-sealing resin to its melting point and then cooling it helps to enhance the bonding force between the composite microspheres and the heat-sealing film. Under extreme conditions, the composite microspheres are not easy to detach from the heat-sealing layer.

[0060] Examples 1 and 8 show that using a dry process is beneficial for reducing the capacity decay ratio of the battery.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An aluminum-plastic film for long-life lithium batteries, comprising a heat-sealing layer with an opening agent embedded on its surface, characterized in that, The opening agent comprises composite microspheres, which are mesoporous inorganic microspheres internally loaded with water-absorbing and swelling microparticles. The thickness of the heat-sealing layer is T. 热封 The average particle size of the water-absorbing and swelling microparticles is D. 微粒 The average particle size of the mesoporous inorganic microspheres is D. 微球 The average mesoporous pore size of the mesoporous inorganic microspheres is D. 介孔 .

2. The aluminum-plastic film for long-life lithium batteries according to claim 1, characterized in that, The water-absorbing and swelling microparticles are at least one of polyacrylamide microspheres, polyacrylic acid microspheres, and polyvinyl alcohol microspheres; And / or the mesoporous inorganic microspheres are at least one of mesoporous silica microspheres, mesoporous carbon microspheres, and mesoporous titanium oxide microspheres.

3. The aluminum-plastic film for long-life lithium batteries according to claim 1, characterized in that, The heat-sealing layer comprises ternary copolymer polypropylene and POE elastomer, wherein the mass ratio of the ternary copolymer polypropylene to the POE elastomer is 7:(2.8~3.1).

4. The aluminum-plastic film for long-life lithium batteries according to claim 1, characterized in that, The mass ratio of the water-absorbing and swelling microparticles to the mesoporous inorganic microspheres is 1:(9~15).

5. The aluminum-plastic film for long-life lithium batteries according to claim 1, characterized in that, D 微球 :T 热封 1: (12~20).

6. The aluminum-plastic film for long-life lithium batteries according to claim 5, characterized in that, D 微球 :D 介孔 The range is 100 to 210.

7. The aluminum-plastic film for long-life lithium batteries according to claim 1, characterized in that, D 微粒 :D 介孔 It ranges from 0.5 to 0.

7.

8. A manufacturing process for a long-life aluminum-plastic film for lithium batteries, based on the long-life aluminum-plastic film for lithium batteries according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1: The adsorbent mesoporous inorganic microspheres and the adsorbate water-absorbing and swelling microspheres are dispersed in the dispersant; S2: The dispersion system obtained after purifying S1; S3: The purified product obtained in S2 is dried to obtain composite microspheres.

9. The production process of the long-life lithium battery aluminum-plastic film according to claim 8, characterized in that, S3 is dried under vacuum.

10. The production process of the long-life lithium battery aluminum-plastic film according to claim 8, characterized in that, It also includes the following steps: The heat-sealing resin is cast by spreading composite microspheres on the surface of the incompletely cured heat-sealing resin, heating the heat-sealing resin to its melting point, and then cooling the heat-sealing resin to obtain a heat-sealing film.

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