WO2021190101A1 - 导电膜及其制备工艺、极片和电池 - Google Patents

导电膜及其制备工艺、极片和电池 Download PDF

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Publication number
WO2021190101A1
WO2021190101A1 PCT/CN2021/071676 CN2021071676W WO2021190101A1 WO 2021190101 A1 WO2021190101 A1 WO 2021190101A1 CN 2021071676 W CN2021071676 W CN 2021071676W WO 2021190101 A1 WO2021190101 A1 WO 2021190101A1
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Prior art keywords
base film
conductive film
film
layer
film according
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PCT/CN2021/071676
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English (en)
French (fr)
Inventor
吴婷婷
冯俊敏
张万财
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深圳市海瀚新能源技术有限公司
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Priority claimed from CN202020415366.6U external-priority patent/CN211719714U/zh
Priority claimed from CN202010233536.3A external-priority patent/CN114023971A/zh
Application filed by 深圳市海瀚新能源技术有限公司 filed Critical 深圳市海瀚新能源技术有限公司
Priority to EP21775486.0A priority Critical patent/EP4131512A1/en
Publication of WO2021190101A1 publication Critical patent/WO2021190101A1/zh
Priority to US17/949,161 priority patent/US20230035561A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/668—Composites of electroconductive material and synthetic resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/82—Multi-step processes for manufacturing carriers for lead-acid accumulators
    • H01M4/84—Multi-step processes for manufacturing carriers for lead-acid accumulators involving casting
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application relates to the technical field of conductive films, specifically, to conductive films and their preparation process, pole pieces and batteries.
  • the multi-layer structure of the composite conductive film to replace the traditional copper and aluminum foil as the current collector is gradually mature.
  • conventional materials are used as the base film of the multilayer structure film due to various reasons such as many processing procedures, and the corresponding product physical properties are not ideal, which affects the development of the multilayer structure composite conductive film as a current collector.
  • Biaxially oriented polypropylene film is a polymer flexible material, but the multi-layer structured composite conductive film made directly from this material has poor performance and cannot be used as a current collector.
  • the purpose of this application includes providing a conductive film and its preparation process, pole piece and battery, using a base film with better tensile mechanical properties to improve the technical problem of poor tensile properties of the existing conductive film.
  • embodiments of the present application include providing a conductive film having a multilayer structure, including a base film and a functional layer and a protective layer sequentially disposed on the base film, the base film being a modified biaxially oriented polypropylene film.
  • the tensile strength of the base film in the machine direction is not less than 200 MPa, and the elongation at break in the machine direction of the base film is not less than 75%.
  • the conductive film uses modified biaxially oriented polypropylene film as the base film, which has higher tensile strength and suitable elongation at break than conventional biaxially oriented polypropylene film (BOPP), making the conductive film have a higher Tensile strength and elongation at break, improve the performance, reduce the interruption of the belt in the processing process, and improve the excellent rate.
  • BOPP biaxially oriented polypropylene film
  • the mechanical direction tensile strength of the base film is 220-260 MPa.
  • the base film with tensile strength in the MD direction can enable the conductive film to have higher tensile strength and elongation at break.
  • the preparation method of the base film includes: adopting a two-way simultaneous stretching process, under the condition that the stretching ratio in the width direction is 8-10 times and the stretching ratio in the mechanical direction is not less than 6.2 times. , The polypropylene film is stretched simultaneously in both directions.
  • the stretch magnification in the width direction of the base film is 8-8.5 times
  • the stretch magnification in the mechanical direction is 6.5-6.8 times.
  • the preparation process improves the tensile strength of the base film by increasing the stretching ratio of the bidirectional simultaneous stretching.
  • the thickness of the base film is 2.0-8.0 ⁇ m.
  • the elongation at break in the mechanical direction of the base film is not less than 75%.
  • the thickness of the base film is 3.4-3.8 ⁇ m, the elongation at break in the mechanical direction of the base film is not less than 80%.
  • the thickness of the base film is 4-5 ⁇ m, the elongation at break in the machine direction of the base film is not less than 90%.
  • the base film While increasing the stretching ratio of the two-way simultaneous stretching and increasing the tensile strength of the base film, it is necessary to ensure that the base film has a certain elongation at break. When the elongation at break of the base film is in the above range, the base film can have better tensile mechanical properties to meet the tensile properties of the conductive film.
  • the conductive film further includes an adhesive layer and a transition layer disposed between the base film and the functional layer, and the adhesive layer and the transition layer are sequentially disposed on the base film.
  • the embodiments of the present application include providing a pole piece including the above-mentioned conductive film and an active material coated on the conductive film.
  • the pole piece has higher tensile strength and elongation at break, and has a higher rate of superiority during processing, which reduces the loss of superiority caused by material breakage.
  • the embodiments of the present application include providing a battery, including a casing, a battery core, an insulating member, and a top cover assembly.
  • the cover assembly is arranged on the shell and connected with the electric core through the tabs.
  • the cell includes the pole piece described above.
  • the current collector tears and breaks are reduced when subjected to changes such as movement, cold and heat contraction, expansion, squeeze, and deformation, and the occurrence of battery failures is reduced.
  • the embodiments of the present application include providing a process for preparing a conductive film, including: bi-directional simultaneous stretching of the cast sheet to obtain a film, the stretching ratio in the width direction is 8-10 times, and the stretching in the machine direction The magnification is not less than 6.2 times, and then the stretched film is rewinded and left standing for aging to obtain the base film.
  • a functional layer and a protective layer are sequentially formed on the surface of the base film.
  • the preparation process increases the stretching ratio of the bidirectional simultaneous stretching, increases the stretching strength of the base film, and obtains a conductive film with better stretching performance.
  • FIG. 1 is a schematic diagram of the structure of a conductive film provided by an embodiment of the application
  • FIG. 2 is a schematic diagram of another structure of a conductive film provided by an embodiment of the application.
  • Icon 100-conductive film; 110-base film; 120-functional layer; 130-protective layer; 140-adhesive layer; 150-transition layer.
  • the materials used in the base film of the multilayer structure composite conductive film mainly include polypropylene (PP), polyethylene terephthalate (PET), polyimide (PI), PPS, polyethylene (PE), etc.
  • PP polypropylene
  • PET polyethylene terephthalate
  • PI polyimide
  • PPS polyethylene
  • BOPP is a thin film with the smallest density among several flexible materials, and it is one of the best materials as a multilayer composite conductive copper film.
  • the BOPP material for making capacitor films is directly used to make multilayer composite conductive copper films, the final product often exhibits low tensile strength (MD tensile strength ⁇ 130MPa), low elongation at break (MD elongation at break ⁇ 2.8%).
  • the conductive film proposed in this application uses modified BOPP as the base film.
  • the modified BOPP has better tensile strength and elongation at break, so that the tensile performance of the base film is improved, and thus Improve the tensile properties of the conductive film and reduce the occurrence of tearing and breakage of the negative current collector during the application process of battery materials.
  • FIG. 1 and FIG. 2 are schematic diagrams of the conductive film 100 with two different layer structures provided by this embodiment.
  • the conductive film includes a base film 110 and a functional layer 120 and a protective layer 130 sequentially disposed on the base film.
  • the functional layer 120 and the protective layer 130 are sequentially provided on the two opposite sides of the base film 110.
  • the conductive film may also include an adhesive layer 140 and a transition layer 150 disposed between the base film and the functional layer.
  • the adhesive layer 140 and the transition layer 150 are sequentially disposed on the base film.
  • the two opposite sides of the base film 110 are provided with an adhesive layer 140 and a transition layer 150.
  • the tensile properties have a greater impact on the performance of the conductive film.
  • a modified BOPP with excellent tensile properties is obtained.
  • modified BOPP preparation process of modified BOPP includes:
  • the masterbatch is placed in a feeding device, the temperature of the melt extrusion section is controlled to 210-260°C, the temperature is maintained at this temperature, and then the casting is performed, and the temperature of the cast piece is controlled at 60-100°C.
  • the temperature of the extrusion section may be 210°C, 230°C, 250°C, or 260°C.
  • the cast piece temperature can be controlled to 60°C, 70°C, 90°C or 100°C.
  • the cast piece is simultaneously stretched in both directions to obtain a film with a certain thickness.
  • the production line speed of two-way simultaneous stretching is 230m/min-260m/min
  • the stretching ratio in the TD direction is 8-10 times
  • the stretching ratio in the MD direction is not less than 6.2 times.
  • the production line speed of the bidirectional simultaneous stretching is 230m/min, 240m/min, 250m/min or 260m/min.
  • the PP macromolecular chains and crystal structure in the film are highly oriented, which significantly improves the tensile strength and modulus of the film, increases the elongation at break in the MD direction, and makes it haze Lower, better transparency, higher gloss.
  • the stretching ratio of the two-way simultaneous stretching is an important process parameter, which not only has a great influence on the stress-strain behavior of the film stretching, but also restricts the film performance and whether the film stretching can proceed smoothly.
  • the stretching parameters in the MD direction and the TD direction have an effect on the tensile mechanical properties of the base film, but the stretching process in the MD direction and the TD direction are different, and the effect on the tensile properties of the base film is also different.
  • the stretch magnification in the MD direction has an effect on the MD stretch modulus and tensile strength of the base film as well as the TD stretch modulus and tensile strength.
  • the stretch magnification in the TD direction mainly affects the tensile strength in the TD direction. Influence.
  • the tensile properties in the MD direction change, the tensile properties in the TD direction also change accordingly. Therefore, when adjusting the stretching process of bidirectional simultaneous stretching, it is necessary to consider the influence of each parameter on the tensile mechanical properties of the base film in many aspects.
  • the preparation process of the present application has increased the stretching ratio, the stretching ratio in the TD direction is 8-10 times, and the MD
  • the stretching ratio in the direction is not less than 6.2 times.
  • the stretch magnification in the TD direction of the base film is 8-8.5 times
  • the stretch magnification in the MD direction is 6.5-6.8 times.
  • the stretching magnification in the TD direction is 8 times, 8.3 times, 8.5 times, 9 times, 9.3 times, 9.5 times, 90.7 times, or 10 times.
  • the stretch magnification in the MD direction is 6.2 times, 6.5 times, 6.6 times, 6.7 times, 6.8 times, or 7 times.
  • the rewinding and standing aging of the film material is performed in an environment with a cleanliness level of 100,000, 25°C ⁇ 5°C, and 40%-70% humidity, and the film material is allowed to stand for 34h-38h, After standing and aging, it can be cut into a base film with the required width.
  • the humidity of the standing environment is 40%, 50%, 60%, or 70%.
  • the standing time may be 34h, 36h or 38h.
  • the base film obtained by the above preparation process that is, the tensile strength of the modified BOPP in the MD direction is not less than 200 MPa, and the elongation at break in the MD direction of the base film is not less than 75%.
  • the tensile mechanical properties of the modified BOPP prepared in this application can meet the mechanical performance requirements of the pole piece for the conductive film.
  • the MD direction tensile strength of the base film is 220-260 MPa.
  • the MD direction tensile strength of the base film is 220 MPa, 230 MPa, 240 MPa, 250 MPa or 260 MPa.
  • the thickness of the base film in the embodiment of the present application is 2.0-8.0 ⁇ m. With different stretching processes and different thicknesses, the tensile mechanical properties of the obtained base film are also different.
  • the elongation at break in the MD direction of the base film is not less than 75%;
  • the thickness of the film is 3.4-3.8 ⁇ m, the elongation at break in the MD direction of the base film is not less than 80%;
  • the thickness of the base film is 4-5 ⁇ m, the elongation at break in the MD direction of the base film is not less than 90%.
  • the present application also provides a preparation process of the above-mentioned conductive film including:
  • the modified BOPP is prepared as the base film according to the above-mentioned preparation process of the modified BOPP.
  • the base film roll material is placed in a double-sided magnetron sputtering coating machine, NiCr can be selected as the material of the bonding layer, the vacuum chamber is sealed, and the vacuum is gradually evacuated until the vacuum degree reaches ⁇ 8 ⁇ 10 -3 Pa, then turn on Ar gas as the bombardment gas, and deposit a layer of bonding layer on both sides of the base film at a film speed of 10-70m/min under the condition of working vacuum of 0.1-0.8Pa , The thickness is generally 2-20nm. Further, the film running speed can be 10m/min, 30m/min, 50m/min or 70m/min. A transition layer is formed on the surface of the bonding layer.
  • the thin film coil plated with the adhesive layer is placed in a double-sided magnetron sputtering coating machine, Cu can be used as the target material, and the purity is ⁇ 99.999%.
  • the vacuum chamber is sealed, and the vacuum chamber is sealed step by step. Evacuate until the vacuum degree reaches ⁇ 8 ⁇ 10 -3 Pa, then turn on Ar gas as the bombardment gas.
  • the film speed of 20-40m/min is applied to the two bonding layers.
  • a layer of transition layer is deposited on the surface of, the thickness is generally 10-50nm.
  • the film running speed can be 20m/min, 30m/min or 40m/min.
  • a functional layer is formed on the surface of the transition layer.
  • the film roll plated with a conductive adhesive layer and a transition layer is placed in a roll-to-roll water electroplating equipment, and the sheet resistance of the conductive film is 0.5-1 ⁇ . Proper winding and unwinding speed, current, copper ion concentration, brightener concentration, auxiliary agent concentration, pH value and electrolyte temperature.
  • a functional layer is formed on the surfaces of the two transition layers, and the thickness is generally 800-1200 nm.
  • a protective layer is formed on the surface of the functional layer.
  • the coil material with the functional layer is placed in the roll-to-roll surface coating equipment or device, and the material is passed through the coating device by winding the film.
  • the coating device can adjust the appropriate concentration
  • the organic matter with anti-oxidation properties is uniformly coated on the surface of the functional layer, and an appropriate winding and unwinding speed is adjusted to form a coating layer on the surface of the functional layer, that is, a protective layer.
  • the conductive film provided in this application uses a modified BOPP material, which has higher tensile strength and higher elongation at break.
  • the tensile strength in the MD direction is greater than or equal to 130 MPa, and further, it can reach 135-160 MPa; the elongation at break in the MD direction is greater than or equal to 3%, and further, it can reach 3.2-9%.
  • the embodiments of the present application also provide a pole piece (not shown in the figure) and a battery (not shown in the figure).
  • the battery includes a casing, a battery cell, an insulator, and a top cover assembly, and the battery core is housed in the casing. Inside, the insulator is arranged between the battery core and the shell, and the top cover assembly is arranged on the shell and connected with the battery core through the tabs.
  • the electric core includes the above pole piece, and the pole piece includes the above conductive film and an active material coated on the conductive film.
  • the conductive film provided by the application has higher tensile strength and elongation at break, so that the pole piece has higher tensile strength and elongation at break, and has a higher rate of excellence in the processing process, and reduces the material breakage.
  • the resulting loss of superiority rate increases the superiority rate by more than 30%.
  • This embodiment provides a modified BOPP, which is mainly prepared through the following steps:
  • the production line speed is controlled at 230m/min, the stretching ratio is 8.3 times in the TD direction and 6.8 times in the MD direction to obtain a film with a thickness of 3.2 ⁇ m;
  • the film is rewinded and left to stand for aging. After standing for 36 hours in an environment with a cleanliness level of 100,000, 25°C ⁇ 5°C, and 50% humidity, the film can be cut into rolls of the required width.
  • This embodiment provides a modified BOPP, which is mainly prepared through the following steps:
  • the production line speed is controlled at 240m/min, the stretching ratio is 8.3 times in the TD direction and 6.7 times in the MD direction to obtain a film with a thickness of 3.6 ⁇ m;
  • the film is rewinded and left to stand for aging. After standing for 36 hours in an environment with a cleanliness level of 100,000, 25°C ⁇ 5°C, and 50% humidity, the film can be cut into rolls of the required width.
  • This embodiment provides a modified BOPP, which is mainly prepared through the following steps:
  • the production line speed is controlled at 250m/min, and the stretching ratio is 8.3 times in the TD direction and 6.6 times in the MD direction to obtain a film with a thickness of 4.5 ⁇ m;
  • This embodiment provides a conductive film, which is mainly produced through the following steps:
  • an adhesive layer is formed on both surfaces of the base film.
  • Select Ni as the material of the bonding layer place the base film roll in the double-sided magnetron sputtering coating machine, seal the vacuum chamber, evacuate step by step until the vacuum degree reaches 5 ⁇ 10 -3 Pa, and then turn on the Ar gas
  • a bombardment gas under the condition of working vacuum of 0.4 Pa, at a film speed of 20m/min, a bonding layer can be deposited on both sides of the base film, the thickness is generally 2-15nm.
  • a transition layer is formed on the surface of the bonding layer.
  • the Ar gas is turned on as the bombardment gas, and under the condition of working vacuum of 0.3 Pa, at a film speed of 30 m/min, a bonding layer can be deposited on both sides of the base film, the thickness is generally 20-50nm.
  • This embodiment provides a conductive film, which is mainly produced through the following steps:
  • an adhesive layer is formed on both surfaces of the base film.
  • Select NiCr as the material of the bonding layer place the base film roll in the double-sided magnetron sputtering coating machine, seal the vacuum chamber, evacuate step by step until the vacuum degree reaches 7 ⁇ 10 -3 Pa, and then turn on the Ar gas
  • a bombardment gas under the condition of working vacuum of 0.2Pa, at a film speed of 60m/min, a bonding layer can be deposited on both sides of the base film, the thickness is generally 2-20nm.
  • a transition layer is formed on the surface of the bonding layer. Place the film coil plated with a conductive adhesive layer in a roll-to-roll water electroplating equipment, the conductive film surface square resistance is 15 ⁇ , adjust the appropriate winding speed, current, copper ion concentration, and brightness Agent concentration, auxiliary agent concentration, pH value and electrolyte temperature. A transition layer can be formed on the surface of the transition layer, and the thickness is generally 60-180nm.
  • a functional layer on the surface of the transition layer. Place the film coil plated with conductive adhesive layer and transition layer in a roll-to-roll water electroplating equipment, the conductive film surface square resistance is 0.3 ⁇ , adjust the appropriate winding speed, current, and copper Ion concentration, brightener concentration, auxiliary agent concentration, pH value and electrolyte temperature. A functional layer is formed on the surfaces of the two transition layers, and the thickness is generally 800-1200 nm.
  • This embodiment provides a conductive film, which is mainly produced through the following steps:
  • an adhesive layer is formed on both surfaces of the base film.
  • Select NiCr as the material of the bonding layer place the base film roll in the double-sided magnetron sputtering coating machine, seal the vacuum chamber, evacuate step by step until the vacuum degree reaches 5 ⁇ 10 -3 Pa, and then turn on the Ar gas
  • a bombardment gas under the condition of working vacuum of 0.5Pa, at a film speed of 60m/min, a bonding layer can be deposited on both sides of the base film, the thickness is generally 2-20nm.
  • a transition layer is formed on the surface of the bonding layer. Place the film roll coated with a conductive adhesive layer in a double-sided magnetron sputtering coating machine. Cu can be used as a target with a purity of ⁇ 99.999%.
  • the vacuum chamber is sealed, and the vacuum is evacuated step by step until the vacuum degree is reached. 5 ⁇ 10 -3 Pa, and then turn on Ar gas as the bombardment gas. Under the condition of working vacuum of 0.1Pa, at a film speed of 30m/min, a transition layer is deposited on the surfaces of the two bonding layers with thickness Generally 10-50nm.
  • a functional layer on the surface of the transition layer. Place the film coil plated with conductive adhesive layer and transition layer in a roll-to-roll water electroplating equipment, the conductive film surface square resistance is 0.6 ⁇ , adjust the appropriate winding speed, current, and copper Ion concentration, brightener concentration, auxiliary agent concentration, pH value and electrolyte temperature. A functional layer is formed on the surfaces of the two transition layers, and the thickness is generally 800-1200 nm.
  • This comparative example provides a BOPP material with a thickness of 3.2 ⁇ m.
  • the difference from Example 1 is only that the stretching ratio in the bidirectional simultaneous stretching process is 8.3 times in the TD direction and 5.6 times in the MD direction.
  • This comparative example provides a BOPP material with a thickness of 3.6 ⁇ m, which is different from Example 2 only in that the stretching ratio in the bidirectional simultaneous stretching process is 8.3 times in the TD direction and 5.6 times in the MD direction.
  • This comparative example provides a BOPP material with a thickness of 4.5 ⁇ m.
  • the difference from Example 3 is only that the stretching ratio in the bidirectional simultaneous stretching process is 8.3 times in the TD direction and 5.6 times in the MD direction.
  • This comparative example provides a conductive film, which is different from Example 6 in that this comparative example selects the BOPP material provided in Comparative Example 3 as the base film.
  • the thickness is detected by the laminated micrometer method.
  • the tensile properties are tested by the tensile machine method.
  • the tensile performance testing method is: put the original film to be tested on the sampler, use the sampler to cut out a 15mm wide sample, set the parameters of the product to be tested and the running speed of the tensile machine at 50MM/min, original gauge length, etc. For related parameters, place the sample to be tested in the upper and lower chucks, tighten it, and click Start on the control end to obtain the corresponding tensile strength and elongation at break data on the computer end.
  • the MD and TD tensile strengths of the modified BOPP materials provided in Examples 1-3 are respectively higher than those of Comparative Examples 1-3, and the MD tensile strength is improved more.
  • the modified BOPP material provided in Examples 1-3 has a slight decrease in the elongation at break in the MD direction and a slight increase in the elongation at break in the TD direction. Significantly improve the tensile strength corresponding to the MD direction. In this way, when the conductive film is made, the elongation of the product can be guaranteed to meet the standard, while the tensile strength of the conductive film in the MD direction is improved, and its superiority in the manufacturing section and the load-bearing strength at the product end are improved.
  • the conductive films provided in Examples 4-6 and Comparative Example 4 were selected, and the tensile properties were tested by a tensile machine.
  • the tensile performance testing method is: put the original film to be tested on the sampler, use the sampler to cut out a 15mm wide sample, set the parameters of the product to be tested and the running speed of the tensile machine at 50MM/min, original gauge length, etc. For related parameters, place the sample to be tested in the upper and lower chucks, tighten it, and click Start on the control end to obtain the corresponding tensile strength and elongation at break data on the computer end. The results are as follows:
  • the modified BOPP is used as the base film in Examples 4-6, and the MD elongation and MD tensile strength of the prepared conductive film are higher than those of the traditional conductive film provided in Comparative Example 4.
  • the tensile strength and The elongation can reduce the loss caused by the breakage of the conductive film during the processing, and improve the excellent rate.
  • the conductive film provided in this application uses a polypropylene film with a mechanical direction tensile strength of not less than 200 MPa and a mechanical direction elongation at break of not less than 75% as the base film after biaxial stretching modification.
  • This base film is compared with ordinary BOPP has better tensile strength and elongation at break, which improves the tensile performance of the base film, thereby improving the tensile performance of the conductive film, and reducing the tearing and damage of the negative electrode current collector during the application process of the battery material happened. Therefore, the conductive film provided in the present application can be widely used as a current collector in pole pieces and batteries.

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Abstract

一种导电膜（100）及其制备工艺、极片和电池，涉及导电膜（100）技术领域。一种导电膜（100），包括基膜（110）和依次设置于基膜（110）的功能层（120）和保护层（130），基膜（110）为改性双向拉伸聚丙烯薄膜。基膜（110）的机械方向的拉伸强度不小于200MPa，基膜（110）的机械方向的断裂延伸率不小于75％。该导电膜（100）采用改性双向拉伸聚丙烯薄膜作为基膜（110），相比常规的双向拉伸聚丙烯薄膜（BOPP）具有更高的拉伸强度和适宜的断裂延伸率，使得导电膜（100）具有更高的拉伸强度和断裂延伸率，提高使用性能，减少在加工过程中断带的情况，提高优率。

Description

导电膜及其制备工艺、极片和电池
相关申请的交叉引用
本申请要求于2020年03月27日提交中国专利局的申请号为202010233536.3、名称为“导电膜及其制备工艺、极片和电池”和申请号为202020415366.6、名称为“导电膜、极片和电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及导电膜技术领域，具体而言，涉及导电膜及其制备工艺、极片和电池。
背景技术
随着动力电池技术不断的发展，对电芯的轻量化、高能量密度的要求逐渐提高，同时消费市场对电芯的降本也极具挑战。因此，多层结构的复合导电薄膜替代传统铜铝箔作为集流体的应用逐渐成熟。目前常规的材料作为多层结构薄膜的基膜由于其加工工序多等多种原因，对应的产品物性不够理想，影响了多层结构的复合导电薄膜作为集流体的发展。
双向拉伸聚丙烯薄膜(BOPP)是一种高分子柔性材料，但是直接由该材料制得的多层结构的复合导电薄膜的性能差，无法作为集流体使用。
发明内容
本申请的目的包括提供导电膜及其制备工艺、极片和电池，采用拉伸力学性能较好的基膜，以改善现有导电膜拉伸性能差的技术问题。
为实现本申请的上述目的中的至少一个目的，本申请可采用以下技术方法：
第一方面，本申请实施例包括提供一种导电膜，具有多层结构，包括基膜和依次设置于基膜的功能层和保护层，基膜为改性双向拉伸聚丙烯薄膜。基膜的机械方向的拉伸强度不小于200MPa，基膜的机械方向的断裂延伸率不小于75％。
该导电膜采用改性双向拉伸聚丙烯薄膜作为基膜，相比常规的双向拉伸聚丙烯薄膜(BOPP)具有更高的拉伸强度和适宜的断裂延伸率，使得导电膜具有更高的拉伸强度和断裂延伸率，提高使用性能，减少在加工过程中断带的情况，提高优率。
在一种可能的实现方式中，基膜的机械方向的拉伸强度为220-260MPa。该MD方向拉伸强度的基膜能够使得导电膜具有较高的拉伸强度和断裂延伸率。
在一种可能的实现方式中，基膜的制备方法包括：采用双向同步拉伸工艺，在幅宽方 向的拉伸倍率为8-10倍、机械方向的拉伸倍率不小于6.2倍的条件下，对聚丙烯薄膜进行双向同步拉伸。
在一种可能的实现方式中，基膜的幅宽方向的拉伸倍率为8-8.5倍，机械方向的拉伸倍率为6.5-6.8倍。
该制备工艺通过提升双向同步拉伸的拉伸倍率，提高基膜的拉伸强度。
在一种可能的实现方式中，基膜的厚度为2.0-8.0μm。在一种可能的实现方式中，基膜的厚度为3-3.3μm时，基膜的机械方向的断裂延伸率不小于75％。或基膜的厚度为3.4-3.8μm时，基膜的机械方向的断裂延伸率不小于80％。或基膜的厚度为4-5μm时，基膜的机械方向的断裂延伸率不小于90％。
在提升双向同步拉伸的拉伸倍率、提高基膜的拉伸强度的同时，需要保证基膜具有一定的断裂延长率。当基膜的断裂延伸率在上述范围时，能够使得基膜具有较好的拉伸力学性能以满足导电膜的拉伸性能。
在一种可能的实现方式中，导电膜还包括设置于基膜和功能层之间的粘结层和过渡层，粘结层和过渡层依次设置于基膜。
第二方面，本申请实施例包括提供一种极片，包括上述导电膜和涂覆于导电膜上的活性材料。该极片具有较高的拉伸强度和断裂延伸率，在加工过程中的优率更高，减少了因物料断带而造成的优率损失。
第三方面，本申请实施例包括提供一种电池，包括壳体、电芯、绝缘件以及顶盖组件，电芯收容于壳体的内部，绝缘件设置于电芯与壳体之间，顶盖组件盖设于壳体，且通过极耳与电芯连接。电芯包括上述极片。
该电池在使用过程中，降低了受运动、冷热收缩膨胀、挤压、变形等变化时容易产生集流体撕裂、破损等情况，减少了电池失效情况的发生。
第四方面，本申请实施例包括提供一种导电膜的制备工艺，包括：对铸片进行双向同步拉伸得到膜材，幅宽方向的拉伸倍率为8-10倍，机械方向的拉伸倍率不小于6.2倍，再对拉伸后的膜材进行收卷静置老化得到基膜。在基膜的表面依次形成功能层和保护层。该制备工艺通过提升双向同步拉伸的拉伸倍率，提高基膜的拉伸强度，得到拉伸性能较优的导电膜。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对实施例中所需要使用的附图作简单地介绍，应当理解，以下附图仅示出了本申请的某些实施例，因此不应被看作是对范围的限定，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这 些附图获得其他相关的附图。
图1为本申请实施例提供的导电膜的结构示意图；
图2为本申请实施例提供的导电膜的另一种结构示意图。
图标：100-导电膜；110-基膜；120-功能层；130-保护层；140-粘结层；150-过渡层。
具体实施方式
为使本申请实施例的目的、技术方案和优点更加清楚，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。通常在此处附图中描述和示出的本申请实施例的组件可以以各种不同的配置来布置和设计。因此，以下对在附图中提供的本申请的实施例的详细描述并非旨在限制要求保护的本申请的范围，而是仅仅表示本申请的选定实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
目前应用于多层结构复合导电薄膜基膜的材料主要有聚丙烯(PP)、聚对苯二甲酸乙二酯(PET)、聚酰亚胺(PI)、PPS、聚乙烯(PE)等高分子柔性材料。BOPP是几种柔性材料中密度最小的一种薄膜，是作为多层复合导电铜薄膜最佳的材料之一。虽然BOPP在制作电容薄膜领域已经得到了极为广泛的应用，但是如果直接以制作电容薄膜的BOPP材料直接制作多层复合导电铜薄膜，其最终产品往往表现为拉伸强度低(MD拉伸强度≤130MPa)，断裂延伸率(MD断裂延伸率≤2.8％)低等特征，这样的多层复合导电铜薄膜产品作为集流体使用时，往往会造成电芯加工过程制程困难，优率低。特别是在负极涂布经过烘箱时容易断带，极片材料经过冷压时容易脆裂，同时材料在完成电芯制作后受冷热膨胀作用时容易断裂而无法支撑电芯的基础结构。
本申请提出的导电膜采用改性后的BOPP作为基膜，该改性后的BOPP相比普通的BOPP具有更好的拉伸强度和断裂延伸率，使得基膜的拉伸性能得到提升，进而提高导电膜的拉伸性能，降低电池材料在施用过程中，负极集流体撕裂、破损等情况的发生。下面结合附图，对本申请的一些实施方式作详细说明。
请参照图1和图2，图1和图2为本实施例提供的两种不同层结构的导电膜100的结构示意图。
本实施例提供一种导电膜100，具有多层结构。在本申请的部分实施例中，导电膜包括基膜110和依次设置于基膜的功能层120和保护层130。作为优选地，基膜110的相对两面均依次设置有功能层120和保护层130。
在本申请的其他实施例中，如图2，导电膜还可以包括设置于基膜和功能层之间的粘结 层140和过渡层150，粘结层140和过渡层150依次设置于基膜。作为优选地，基膜110的相对两面均设置有粘结层140和过渡层150。
对于多层结构复合导电薄膜而言，拉伸性能对导电膜的使用性能具有较大的影响。本申请通过对BOPP的制备工艺进行创新，得到拉伸性能优异的改性BOPP。
进一步地，改性BOPP的制备工艺包括：
将母粒置于投料装置中，控制熔融挤出段的温度为210-260℃，保持该温度挤出后进行流延铸片，控制铸片温度在60-100℃。
可选地，挤出段的温度可以是210℃、230℃、250℃或者260℃。
可选地，铸片温度可以控制为60℃、70℃、90℃或者100℃。
得到铸片后，对铸片进行双向同步拉伸得到一定厚度的膜材。其中，双向同步拉伸的产线速度为230m/min-260m/min，TD方向(幅宽方向)的拉伸倍率为8-10倍，MD方向(机械方向)的拉伸倍率不小于6.2倍。可选地，双向同步拉伸的产线速度为230m/min、240m/min、250m/min或260m/min。
BOPP薄膜经拉伸处理后，薄膜中的PP大分子链和结晶结构发生高度取向，从而显著提高了薄膜的拉伸强度和模量，提高了MD方向的断裂伸长率，并使其雾度更低，透明性更好，光泽度更高。在制备工艺中，双向同步拉伸的拉伸倍率为重要的工艺参数，不仅对薄膜拉伸的应力-应变行为有较大影响，还制约了薄膜的性能以及薄膜拉伸是否能顺利进行。经过实验研究可知，MD方向和TD方向的拉伸参数均对基膜的拉伸力学性能有影响，但MD方向和TD方向的拉伸工艺有区别，对基膜的拉伸性能影响也不同。MD方向的拉伸倍率对基膜的MD方向拉伸模量和拉伸强度以及TD方向拉伸模量和拉伸强度均有影响，TD方向的拉伸倍率主要对TD方向的拉伸强度有影响。根据大量实验研究可知，当MD方向的拉伸性能改变时，TD方向的拉伸性能也进行相应的改变。因此，调整双向同步拉伸的拉伸工艺时，需要多方面考虑每一个参数对基膜拉伸力学性能的影响。
在经过大量的实验研究后，本申请发明人得出，相比常规的BOPP采用的拉伸倍率，本申请的制备工艺提升了拉伸倍率，TD方向的拉伸倍率为8-10倍，MD方向的拉伸倍率不小于6.2倍。在本申请的部分实施例中，基膜的TD方向的拉伸倍率为8-8.5倍，MD方向的拉伸倍率为6.5-6.8倍。可选地，TD方向的拉伸倍率为8倍、8.3倍、8.5倍、9倍、9.3倍、9.5倍、90.7倍或10倍。MD方向的拉伸倍率为6.2倍、6.5倍、6.6倍、6.7倍、6.8倍或7倍。
对膜材进行收卷静置老化。本申请实施例中，优选地，对膜材进行收卷静置老化是在十万级别洁净度、25℃±5℃、40％-70％湿度的环境中，膜材静置34h-38h，静置老化后即可分切成所需幅宽的基膜。可选地，静置环境的湿度为40％、50％、60％或70％。可选地， 静置时间可以是34h、36h或38h。
通过上述制备工艺得到的基膜，即改性BOPP的MD方向的拉伸强度不小于200MPa，基膜的MD方向的断裂延伸率不小于75％。相比现有的BOPP材料，本申请制得的改性BOPP的拉伸力学性能能够满足极片对导电膜的力学性能要求。在本申请的部分实施例中，基膜的MD方向的拉伸强度为220-260MPa。可选地，基膜的MD方向的拉伸强度为220MPa、230MPa、240MPa、250MPa或260MPa。
本申请实施例中的基膜的厚度为2.0-8.0μm。采用的拉伸工艺不同、厚度不同，得到的基膜的拉伸力学性能也有区别。为了满足导电膜作为集流体的应用，在本申请的部分实施例中，优选地，当基膜的厚度为3-3.3μm时，基膜的MD方向的断裂延伸率不小于75％；当基膜的厚度为3.4-3.8μm时，基膜的MD方向的断裂延伸率不小于80％；当基膜的厚度为4-5μm时，基膜的MD方向的断裂延伸率不小于90％。
进一步地，本申请还提供了上述导电膜的制备工艺包括：
按上述改性BOPP的制备工艺制得改性BOPP作为基膜。
在基膜的两个表面形成粘结层。在一种可实现的实例中，将基膜卷料置于双面磁控溅射镀膜机内，可选用NiCr作为粘结层的材料，将真空室密封，逐级抽真空至真空度达到＜8×10 -3Pa，然后打开Ar气作为轰击气体，在工作真空0.1-0.8Pa的条件下，以10-70m/min的走膜速度，在基膜的两面均沉积上一层粘结层，厚度一般为2-20nm。进一步地，走膜速度可以是10m/min、30m/min、50m/min或70m/min。在粘结层的表面形成过渡层。在一种可实现的实例中，将镀有粘结层的薄膜卷料置于双面磁控溅射镀膜机内，可使用Cu作为靶材，纯度≥99.999％，将真空室密封，逐级抽真空至真空度达到＜8×10 -3Pa，然后打开Ar气作为轰击气体，在工作真空0.1-0.8Pa的条件下，以20-40m/min的走膜速度，在两个粘结层的表面均沉积上一层过渡层，厚度一般为10-50nm。进一步地，走膜速度可以是20m/min、30m/min或40m/min。
在过渡层的表面形成功能层。在一种可实现的实例中，将镀有可导电的粘结层和过渡层的薄膜卷料置于卷对卷的水电镀设备中，可导电的膜面方块电阻为0.5-1Ω，调好适当的收放卷速度、电流、铜离子浓度、光亮剂浓度、辅助剂浓度、pH值和电解液温度。在两个过渡层的表面均形成一层功能层，厚度一般为800-1200nm。
在功能层的表面形成保护层。在一种可实现的实例中，将具有功能层的卷料置入卷对卷表面涂覆设备或装置中，采用卷绕走膜的方式使物料通过涂覆装置，涂覆装置可将适当浓度的具备抗氧化性能的有机质均匀地涂覆在功能层表面，调好适当的收放卷速度，即可在功能层表面上形成一层涂覆层，即保护层。
本申请提供的导电膜采用了改性BOPP材料，具有更高的拉伸强度和更高的断裂延伸 率。MD方向的拉伸强度≥130MPa，进一步地，可达到135-160MPa；MD方向的断裂延伸率≥3％，进一步地，可达到3.2-9％。
进一步地，本申请实施例还提供了一种极片(图未示)和一种电池(图未示)，电池包括壳体、电芯、绝缘件以及顶盖组件，电芯收容于壳体的内部，绝缘件设置于电芯与壳体之间，顶盖组件盖设于壳体，且通过极耳与电芯连接。电芯包括上述极片，该极片包括上述导电膜和涂覆于导电膜上的活性材料。
本申请提供的导电膜具有较高的拉伸强度和断裂延伸率，使得该极片具有较高的拉伸强度和断裂延伸率，在加工过程中的优率更高，减少了因物料断带而造成的优率损失，提高优率30％以上。制得的电池在使用过程中，降低了受运动、冷热收缩膨胀、挤压、变形等变化时容易产生集流体撕裂、破损等情况，减少了电池失效情况的发生。
以下结合实施例对本申请的特征和性能作进一步地详细描述。
实施例1
本实施例提供了一种改性BOPP，主要通过以下步骤制得：
将母粒置于投料装置中，控制熔融挤出段的温度为230℃，保持该温度挤出后进行流延铸片，控制铸片温度在90℃；
然后在双向同步拉伸设备中进行双向同步拉伸，产线速度控制在230m/min，拉伸倍率为TD方向8.3倍，MD方向6.8倍，得到厚度为3.2μm的薄膜；
然后对薄膜进行收卷静置老化，在十万级别洁净度、25℃±5℃、50％湿度的环境中静置36小时，即可分切成所需幅宽的卷料。
实施例2
本实施例提供了一种改性BOPP，主要通过以下步骤制得：
将母粒置于投料装置中，控制熔融挤出段的温度为240℃，保持该温度挤出后进行流延铸片，控制铸片温度在80℃；
然后在双向同步拉伸设备中进行双向同步拉伸，产线速度控制在240m/min，拉伸倍率为TD方向8.3倍，MD方向6.7倍，得到厚度为3.6μm的薄膜；
然后对薄膜进行收卷静置老化，在十万级别洁净度、25℃±5℃、50％湿度的环境中静置36小时，即可分切成所需幅宽的卷料。
实施例3
本实施例提供了一种改性BOPP，主要通过以下步骤制得：
将母粒置于投料装置中，控制熔融挤出段的温度为230℃，保持该温度挤出后进行流延铸片，控制铸片温度在80℃；
然后在双向同步拉伸设备中进行双向同步拉伸，产线速度控制在250m/min，拉伸倍率 为TD方向8.3倍，MD方向6.6倍，得到厚度为4.5μm的薄膜；
然后对薄膜进行收卷静置老化，在十万级别洁净度、25℃±5℃、60％湿度的环境中静置36小时，即可分切成所需幅宽的卷料。
实施例4
本实施例提供了一种导电膜，主要通过以下步骤制得：
1.以实施例1提供的厚度为3.2μm的改性BOPP作为基膜，在基膜的两个表面形成粘结层。选用Ni作为粘结层的材料，将基膜卷料置于双面磁控溅射镀膜机内，将真空室密封，逐级抽真空至真空度达到5×10 -3Pa，然后打开Ar气作为轰击气体，在工作真空0.4Pa的条件下，以20m/min的走膜速度，就得以在基膜的两面沉积上一层粘结层，厚度一般为2-15nm。
2.在粘结层的表面形成过渡层。将镀有粘结层的薄膜卷料置于卷对卷的磁控溅射设备中，选用Cu作为过渡层的材料，将真空室密封，逐级抽真空至真空度达到7×10-3Pa，然后打开Ar气作为轰击气体，在工作真空0.3Pa的条件下，以30m/min的走膜速度，就得以在基膜的两面沉积上一层粘结层，厚度一般为20-50nm。
3.在过渡层的表面形成功能层。将镀有可导电的粘结层和过渡层的薄膜卷料置于卷对卷的水电镀设备中，可导电的膜面方块电阻为2Ω，调好适当的收放卷速度、电流、铜离子浓度、光亮剂浓度、辅助剂浓度、pH值和电解液温度。在两个过渡层的表面均形成一层功能层，厚度一般为800-1200nm。
4.在功能层的表面形成保护层。将具有功能层的卷料置入卷对卷水电镀设备或装置中，使用重铬酸钾作为抗氧化剂，调好适当的收放卷速度、电流和电解液温度，即可在功能层表面上形成一层涂覆层，即保护层。
实施例5
本实施例提供了一种导电膜，主要通过以下步骤制得：
1.以实施例2提供的厚度为3.6μm的改性BOPP作为基膜，在基膜的两个表面形成粘结层。选用NiCr作为粘结层的材料，将基膜卷料置于双面磁控溅射镀膜机内，将真空室密封，逐级抽真空至真空度达到7×10 -3Pa，然后打开Ar气作为轰击气体，在工作真空0.2Pa的条件下，以60m/min的走膜速度，就得以在基膜的两面沉积上一层粘结层，厚度一般为2-20nm。
2.在粘结层的表面形成过渡层。将镀有可导电的粘结层的薄膜卷料置于卷对卷的水电镀设备中，可导电的膜面方块电阻为15Ω，调好适当的收放卷速度、电流、铜离子浓度、光亮剂浓度、辅助剂浓度、pH值和电解液温度。可在过渡层的表面形成一层过渡层，厚度一般为60-180nm。
3.在过渡层的表面形成功能层。将镀有可导电的粘结层和过渡层的薄膜卷料置于卷对 卷的水电镀设备中，可导电的膜面方块电阻为0.3Ω，调好适当的收放卷速度、电流、铜离子浓度、光亮剂浓度、辅助剂浓度、pH值和电解液温度。在两个过渡层的表面均形成一层功能层，厚度一般为800-1200nm。
4.在功能层的表面形成保护层。将具有功能层的卷料置入卷对卷表面涂覆设备或装置中，采用卷绕走膜的方式使物料通过涂覆装置，涂覆装置可将适当浓度的具备抗氧化性能的有机质均匀地涂覆在功能层表面，调好适当的收放卷速度，即可在功能层表面上形成一层涂覆层，即保护层。
实施例6
本实施例提供了一种导电膜，主要通过以下步骤制得：
1.以实施例3提供的厚度为4.5μm的改性BOPP作为基膜，在基膜的两个表面形成粘结层。选用NiCr作为粘结层的材料，将基膜卷料置于双面磁控溅射镀膜机内，将真空室密封，逐级抽真空至真空度达到5×10 -3Pa，然后打开Ar气作为轰击气体，在工作真空0.5Pa的条件下，以60m/min的走膜速度，就得以在基膜的两面沉积上一层粘结层，厚度一般为2-20nm。
2.在粘结层的表面形成过渡层。将镀有可导电的粘结层的薄膜卷料置于双面磁控溅射镀膜机内，可使用Cu作为靶材，纯度≥99.999％，将真空室密封，逐级抽真空至真空度达到5×10 -3Pa，然后打开Ar气作为轰击气体，在工作真空0.1Pa的条件下，以30m/min的走膜速度，在两个粘结层的表面均沉积上一层过渡层，厚度一般为10-50nm。
3.在过渡层的表面形成功能层。将镀有可导电的粘结层和过渡层的薄膜卷料置于卷对卷的水电镀设备中，可导电的膜面方块电阻为0.6Ω，调好适当的收放卷速度、电流、铜离子浓度、光亮剂浓度、辅助剂浓度、pH值和电解液温度。在两个过渡层的表面均形成一层功能层，厚度一般为800-1200nm。
4.在功能层的表面形成保护层。将具有功能层的卷料置入卷对卷表面涂覆设备或装置中，采用卷绕走膜的方式使物料通过涂覆装置，涂覆装置可将适当浓度的具备抗氧化性能的有机质均匀地涂覆在功能层表面，调好适当的收放卷速度，即可在功能层表面上形成一层涂覆层，即保护层。
对比例1
本对比例提供一种厚度为3.2μm的BOPP材料，与实施例1的不同之处仅在于：其双向同步拉伸工艺中的拉伸倍率为TD方向8.3倍，MD方向5.6倍。
对比例2
本对比例提供一种厚度为3.6μm的BOPP材料，与实施例2的不同之处仅在于：其双向同步拉伸工艺中的拉伸倍率为TD方向8.3倍，MD方向5.6倍。
对比例3
本对比例提供一种厚度为4.5μm的BOPP材料，与实施例3的不同之处仅在于：其双向同步拉伸工艺中的拉伸倍率为TD方向8.3倍，MD方向5.6倍。
对比例4
本对比例提供了一种导电膜，与实施例6的不同之处在于：本对比例选择对比例3提供的BOPP材料作为基膜。
试验例
选取实施例1-3提供的改性BOPP材料和对比例1-3提供的常规的BOPP材料，对其进行性能检测。
厚度通过叠层万分尺方法检测。厚度检测使用万分尺，通过叠层法测试，一般取10层同样的材料叠放在一起，使用硬质的工装排出其中空气，使用万分尺测试10层的厚度D，单层薄膜的厚度即为d＝D/10。
拉伸性能通过拉力机方法检测。拉伸性能检测方法为：将待测的原膜至于取样器上，使用取样器切出15mm宽的样品，在电脑端设置待测产品参数和拉力机的运行速度50MM/min、原始标距等相关参数，将待测样品置于上下夹头中，扭紧，控制端点击开始，即可在电脑端获得对应的拉伸强度和断裂延伸率的数据。
结果如下表：
表1材料物性数据
Figure PCTCN2021071676-appb-000001
Figure PCTCN2021071676-appb-000002
由表1可知，实施例1-3提供的改性BOPP材料的MD和TD拉伸强度分别高于对比例1-3，其中，MD拉伸强度提高较多。实施例1-3提供的改性BOPP材料的MD方向的断裂伸长率略有下降，TD方向的断裂伸长率稍有提高，正是利用了略微降低的MD方向断裂伸长率的方法，显著提高了对应MD方向的拉伸强度。这样在制作导电膜时，既可以保障产品延伸率达标，同时又提高了导电膜MD方向的拉伸强度，提高了其在制造段的优率和在产品端的承载强度。
选择实施例4-6和对比例4提供的导电膜，采用拉力机检测拉伸性能。拉伸性能检测方法为：将待测的原膜至于取样器上，使用取样器切出15mm宽的样品，在电脑端设置待测产品参数和拉力机的运行速度50MM/min、原始标距等相关参数，将待测样品置于上下夹头中，扭紧，控制端点击开始，即可在电脑端获得对应的拉伸强度和断裂延伸率的数据。结果如下表：
表2测试结果
  MD延伸率 MD拉伸强度
实施例4 3.0-5.5％ 142-165MPa
实施例5 3.2-6％ 140-160MPa
实施例6 4.5-9％ 135-150MPa
对比例4 1-2.5％ 110-125MPa
由表2可知，实施例4-6采用改性BOPP作为基膜，制得的导电膜的MD延伸率和MD拉伸强度均高于对比例4提供的传统的导电膜，该拉伸强度和延伸率可以减少导电膜在加工过程断带造成的损失，提高优率。
以上所述仅为本申请的优选实施例而已，并不用于限制本申请，对于本领域的技术人员来说，本申请可以有各种更改和变化。凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。
工业实用性
本申请提供的导电膜，以双向拉伸改性后机械方向的拉伸强度不小于200MPa，机械方向的断裂延伸率不小于75％的聚丙烯薄膜作为基膜，这种基膜相较于普通的BOPP具有更好的拉伸强度和断裂延伸率，使得基膜的拉伸性能得到提升，进而提高导电膜的拉伸性能，降低电池材料在施用过程中，负极集流体撕裂、破损等情况的发生。因此，本申请提供的导电膜可作为集流体广泛应用于极片和电池中。

Claims (20)

  1. 一种导电膜，具有多层结构，其特征在于，包括基膜和依次设置于所述基膜的功能层和保护层，所述基膜为改性双向拉伸聚丙烯薄膜；
    所述基膜的机械方向的拉伸强度不小于200MPa，所述基膜的机械方向的断裂延伸率不小于75％。
  2. 根据权利要求1所述的导电膜，其特征在于，所述基膜的机械方向的拉伸强度为220-260MPa。
  3. 根据权利要求1或2所述的导电膜，其特征在于，所述基膜的制备方法包括：采用双向同步拉伸工艺，在幅宽方向的拉伸倍率为8-10倍、机械方向的拉伸倍率不小于6.2倍的条件下，对聚丙烯薄膜进行双向同步拉伸。
  4. 根据权利要求3所述的导电膜，其特征在于，所述基膜的幅宽方向的拉伸倍率为8-8.5倍，机械方向的拉伸倍率为6.5-6.8倍。
  5. 根据权利要求1-4任一项所述的导电膜，其特征在于，所述基膜的厚度为2.0-8.0μm。
  6. 根据权利要求5所述的导电膜，其特征在于，所述基膜的厚度为3-3.3μm时，所述基膜的机械方向的断裂延伸率不小于75％；
    或所述基膜的厚度为3.4-3.8μm时，所述基膜的机械方向的断裂延伸率不小于80％；
    或所述基膜的厚度为4-5μm时，所述基膜的机械方向的断裂延伸率不小于90％。
  7. 根据权利要求1-6任一项所述的导电膜，其特征在于，所述导电膜还包括设置于所述基膜和所述功能层之间的粘结层和过渡层，所述粘结层和所述过渡层依次设置于所述基膜。
  8. 根据权利要求1-6任一项所述的导电膜，其特征在于，所述基膜的相对两面均依次设置有所述功能层和所述保护层。
  9. 根据权利要求8所述的导电膜，其特征在于，所述导电膜还包括依次设置于所述基膜的相对两面，位于所述基膜和所述功能层之间的粘结层和过渡层。
  10. 根据权利要求7所述的导电膜，其特征在于，所述粘接层的材料为NiCr。
  11. 根据权利要求7所述的导电膜，其特征在于，所述过渡层的材料为Cu。
  12. 根据权利要求1-11任一项所述的导电膜，其特征在于，所述保护层为具备抗氧化性能的有机质形成的涂覆层。
  13. 一种极片，其特征在于，包括如权利要求1-12任一项所述的导电膜和涂覆于所述导电膜上的活性材料。
  14. 一种电池，其特征在于，包括壳体、电芯、绝缘件以及顶盖组件，所述电芯收容于 所述壳体的内部，所述绝缘件设置于所述电芯与所述壳体之间，所述顶盖组件盖设于所述壳体，且通过极耳与所述电芯连接；
    所述电芯包括如权利要求13所述的极片。
  15. 一种如权利要求1-13任一项所述的导电膜的制备工艺，其特征在于，包括：
    对铸片进行双向同步拉伸得到膜材，幅宽方向的拉伸倍率为8-10倍，机械方向的拉伸倍率不小于6.2倍，再对拉伸后的膜材进行收卷静置老化得到所述基膜；
    在所述基膜的表面依次形成所述功能层和所述保护层。
  16. 根据权利要求15所述的导电膜的制备工艺，其特征在于，双向同步拉伸的产线速度为230m/min-260m/min。
  17. 根据权利要求15或16所述的导电膜的制备工艺，其特征在于，幅宽方向的拉伸倍率为8-8.5倍，机械方向的拉伸倍率为6.5-6.8倍。
  18. 根据权利要求15-17任一项所述的导电膜的制备工艺，其特征在于，静置老化是：将拉伸所得膜材置于十万级别洁净度、25℃±5℃、40％-70％湿度的环境中，静置34h-38h。
  19. 根据权利要求15-18任一项所述的导电膜的制备工艺，其特征在于，
    在形成所述功能层和所述保护层之前还包括在所述基膜表面形成粘接层和过渡层；所述功能层和所述保护层依次设置于所述过渡层表面。
  20. 根据权利要求15-19任一项所述的导电膜的制备工艺，其特征在于，对铸片进行双向同步拉伸之前还包括：
    将母粒熔融，控制熔融挤出段的温度为210-260℃，保持该温度挤出后进行流延铸片，控制铸片温度为60-100℃。
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