Polymer-based membrane, current collector, pole piece and electrochemical device

Abstract

The utility model discloses a polymer base membrane, a current collector, a pole piece and an electrochemical device and belongs to the technical field of secondary batteries. The current collector comprises a polymer base film and two conductive metal layers, the polymer base film is arranged between the two conductive metal layers, the polymer base film comprises a first region and a second region, the second region is arranged on at least part of the edge of the first region, the component of the first region is a polar polymer, and the component of the second region is a non-polar polymer; the characteristic that the polar polymer can have good binding force with the conductive metal layer is utilized, so that good adhesion is achieved between the polymer base film and the conductive metal layer. Meanwhile, the non-polar polymer is arranged on the edge of the first region formed by the polar polymer, so that the possibility that the polar polymer is in contact with electrolyte when being used as a battery can be reduced, and the possibility that the polar polymer is subjected to depolymerization reaction is further reduced; and the possibility of reaction between the whole polymer base membrane and the electrolyte is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of secondary batteries, in particular, to a polymer-based film, a current collector, a pole piece and an electrochemical device. BACKGROUND

[0002] As an important component in a battery, the performance improvement of the current collector can bring great benefits to the battery. The current composite current collector has a polymer base material in the middle layer and conductive metal layers on both sides. This structure can greatly save the cost of the current collector, reduce the weight of the current collector, and make the battery safer.

[0003] The polymer-based film of the composite current collector is usually formed by stretching a polymer film. When a polar polymer is used as the polymer in the middle layer of the composite current collector, the base material has good adhesion to the metal layer and strong structural stability, but it is generally inert in the battery environment and is prone to depolymerization. When a non-polar polymer is used as the polymer in the middle layer of the composite current collector, it has good chemical inertness and strong stability in the battery environment, but its adhesion to the metal layer is generally poor, which can cause the metal layer to fall off during the processing process and subsequent long-term cycling of the battery. SUMMARY

[0004] The present application provides a polymer-based film, a current collector, a pole piece and an electrochemical device. The polymer-based film has good adhesion to the metal layer, and also has good chemical inertness, reducing the possibility of reaction with the electrolyte.

[0005] In a first aspect, the embodiments of the present application provide a current collector, which includes a polymer-based film and two conductive metal layers. The polymer-based film is arranged between the two conductive metal layers. The polymer-based film includes a first region and a second region. The second region is arranged at least part of the edge of the first region along the film surface direction. The composition of the first region includes a polar polymer, and the composition of the second region includes a non-polar polymer.

[0006] In the above implementation process, the polar polymer and the non-polar polymer are arranged between the two conductive metal layers as the material of the polymer-based film. The polar polymer has good adhesion to the conductive metal layer, which makes the polymer-based film and the conductive metal layer have good adhesion. The non-polar polymer is arranged at the edge of the first region formed by the polar polymer, which can reduce the possibility of the polar polymer contacting the electrolyte when used as a battery, thereby reducing the possibility of depolymerization of the polar polymer. The chemical inertness of the non-polar polymer makes the whole polymer-based film less likely to react with the electrolyte.

[0007] As an optional implementation, the width W1 of the first region and the width W2 of the second region satisfy: W1:W2=(5-10):1.

[0008] In the above implementation process, by controlling the width W1 of the first region and the width W2 of the second region to satisfy W1:W2=(5-10):1, the first region and the second region have appropriate widths, which can make the entire polymer base film less likely to react with the electrolyte, while the polymer base film and the conductive metal layer have good bonding force.

[0009] As an optional implementation, the width of the first region is 5-100 cm.

[0010] In the above implementation process, the width of the first region is usually not less than the width of the active material layer coated on the current collector, which can help reduce the probability of separation between the polymer base film and the conductive metal layer during the cold pressing process of the pole piece preparation. By controlling the width of the first region to be 5-100 cm, it can be applied to most pole piece preparations at present.

[0011] As an optional implementation, the polar polymer includes at least one of polyethylene terephthalate, polyimide, polyvinyl chloride, and polyacrylonitrile; and / or

[0012] The non-polar polymer includes at least one of polypropylene, polytetrafluoroethylene, polyethylene, and polystyrene; and / or

[0013] The components of the two conductive metal layers independently include copper or aluminum.

[0014] As an optional implementation, the components of the second region further include a compatibilizer.

[0015] In the above implementation process, by adding the compatibilizer in the second region, the adhesion of the second region and the first region can be improved, and the bonding force of the second region and the conductive metal layer can also be improved.

[0016] As an optional implementation, the compatibilizer includes at least one of PP-g-MAH, PE-g-MAH, and PS-g-MAH; and / or

[0017] The mass fraction of the compatibilizer in the second region is not more than 10%.

[0018] As an optional implementation, the components of the second region further include a conductive medium.

[0019] In the above implementation process, by adding the conductive medium in the second region, the two conductive metal layers can conduct electrons, so that the welding of the tab does not need to use a switching foil, effectively reducing the difficulty of the pole piece preparation.

[0020] As an optional implementation, the conductive medium comprises at least one of graphite, graphene and carbon nanotube; and / or

[0021] The mass percentage of the conductive medium in the second region is not more than 10%.

[0022] As an optional implementation, the second region is arranged at two edges of the first region.

[0023] As an optional implementation, the second region is arranged at two opposite edges of the first region.

[0024] In the above implementation, by arranging the second region at two opposite edges of the first region, the product can be manufactured in an electrostatic manner, and the product can be applied to the preparation of electrodes of various sizes.

[0025] As an optional implementation, the second region is arranged at all edges of the first region.

[0026] In the above implementation, by arranging the second region at all edges of the first region, the contact probability of the material of the first region and the electrolyte is further reduced, and the depolymerization reaction of the polar polymer is further reduced.

[0027] As an optional implementation, the mass percentage of the polar polymer in the first region is 90% to 100%; and / or

[0028] The mass percentage of the non-polar polymer in the second region is 90% to 100%.

[0029] As an optional implementation, the first region is composed of a polar polymer, and the second region is composed of a non-polar polymer.

[0030] As an optional implementation, the thickness of the polymer-based film is 2 to 10 microns; and / or

[0031] The thickness of the conductive metal layer is 0.5 to 10 microns.

[0032] In a second aspect, the embodiments of the present application provide an electrode sheet, which comprises an active material layer and the current collector provided by the first aspect, and the active material layer is arranged on at least part of the surface of the current collector.

[0033] In the above implementation process, by setting the polar polymer and the non-polar polymer as the material of the polymer-based film between the two conductive metal layers, the polar polymer has the characteristic of having good bonding force with the conductive metal layer, so that the polymer-based film and the conductive metal layer have good adhesion, which can reduce the probability of separation between the conductive metal layer and the polymer-based film during cold pressing of the active material layer. At the same time, the non-polar polymer is arranged at the edge of the first area formed by the polar polymer, which can reduce the possibility of the polar polymer contacting the electrolyte when used as a battery, thereby reducing the possibility of depolymerization of the polar polymer, and the chemical inertness of the non-polar polymer makes the possibility of reaction between the entire polymer-based film and the electrolyte lower.

[0034] As an optional implementation, the active material layer corresponds to at least part of the first area.

[0035] As an optional implementation, the position of the active material layer corresponds to the first area, and the relationship between the width W3 of the active material layer and the width W1 of the first area satisfies W3≤W1.

[0036] In the above implementation process, by setting the width of the first area to be not less than the width of the active material layer coated on the current collector, the probability of separation between the polymer-based film and the conductive metal layer during the cold pressing process of the pole piece can be reduced.

[0037] In a third aspect, the embodiments of the present application provide an electrochemical device, which comprises the pole piece provided in the second aspect.

[0038] In a fourth aspect, the embodiments of the present application provide a polymer-based film, which comprises a first area and a second area, the second area is arranged at least at part of the edge of the first area along the film surface direction, the composition of the first area comprises a polar polymer, and the composition of the second area comprises a non-polar polymer.

[0039] In the above implementation process, by using the polar polymer and the non-polar polymer as the material of the polymer-based film, when the polymer-based film is used as a pole piece, the polymer-based film is arranged between the two conductive metal layers, and the polar polymer has the characteristic of having good bonding force with the conductive metal layer, so that the polymer-based film and the conductive metal layer have good adhesion. At the same time, the non-polar polymer is arranged at the edge of the first area formed by the polar polymer, which can reduce the possibility of the polar polymer contacting the electrolyte when used as a battery, thereby reducing the possibility of depolymerization of the polar polymer, and the chemical inertness of the non-polar polymer makes the possibility of reaction between the entire polymer-based film and the electrolyte lower.

[0040] As an optional implementation, the polymer-based film satisfies one or more of the following characteristics:

[0041] A) the width W1 of the first region and the width W2 of the second region satisfy: W1:W2=(5-10):1;

[0042] B) the width of the first region is 5-100 cm;

[0043] C) the thickness of the polymer-based film is 2-10 μm;

[0044] D) the polar polymer comprises at least one of polyethylene terephthalate, polyimide, polyvinyl chloride and polyacrylonitrile;

[0045] E) the non-polar polymer comprises at least one of polypropylene, polytetrafluoroethylene, polyethylene and polystyrene;

[0046] F) the composition of the second region further comprises a compatibilizer;

[0047] G) the composition of the second region further comprises a conductive medium.

[0048] In a fifth aspect, the embodiments of the present application provide a preparation method of a polymer-based film, the polymer-based film being the polymer-based film provided in the fourth aspect; the method comprises:

[0049] preparing a polar polymer into a first slurry;

[0050] preparing a non-polar polymer into a second slurry;

[0051] electrospinning the first slurry and the second slurry to obtain the polymer-based film.

[0052] In the above implementation process, the polar polymer and the non-polar polymer are prepared into a whole polymer-based film by electrospinning, and when the polymer-based film is used as a pole piece, it is clamped between two conductive metal layers. The polar polymer has the characteristics of good bonding force with the conductive metal layer, so that the polymer-based film and the conductive metal layer have good adhesion. At the same time, the non-polar polymer is arranged at the edge of the first region formed by the polar polymer, which can reduce the possibility of the polar polymer contacting the electrolyte when used as a battery, thereby reducing the possibility of depolymerization reaction of the polar polymer, and using the chemical inertness of the non-polar polymer, the possibility of reaction between the whole polymer-based film and the electrolyte is low.

[0053] As an optional implementation, the electrospinning of the first slurry and the second slurry to obtain the polymer-based film comprises:

[0054] simultaneously electrospinning the first slurry and the second slurry on a substrate to obtain the polymer-based film.

[0055] As an optional implementation, the material of the substrate comprises conductive carbon; and / or

[0056] The substrate is a conductive metal layer. BRIEF DESCRIPTION OF DRAWINGS

[0057] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the application and, together with the description, serve to explain the principles of the application.

[0058] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings required by the embodiments or prior art description will be briefly introduced as follows. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0059] Figure 1 A structural schematic diagram of the pole piece provided by the embodiments of the present application;

[0060] Figure 2 A flowchart of the method provided by the embodiments of the present application;

[0061] Figure 3 A spinning process schematic diagram of the polymer base film provided by the embodiments of the present application;

[0062] Figure 4 A hot-pressing melting process schematic diagram of the current collector provided by the embodiments of the present application.

[0063] Figure legend: 1000-pole piece; 100-current collector; 10-polymer base film; 11-first region; 12-second region; 20-conductive metal layer; 200-active material layer. DETAILED DESCRIPTION

[0064] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort fall within the scope of protection of the present application.

[0065] Unless otherwise specified, various raw materials, reagents, instruments and equipment, etc. used in the present application can be purchased from the market or can be prepared by existing methods.

[0066] The polymer base film 10 of the composite current collector 100 is usually formed by stretching a polymer into a film. When the intermediate layer polymer of the composite current collector 100 is a polar polymer, the substrate and the metal layer have good adhesion and strong structural stability, but its inertness in the battery environment is generally low and it is prone to depolymerization reaction. When the intermediate layer polymer of the composite current collector 100 is a non-polar polymer, its chemical inertness is good and its stability in the battery environment is strong, but its adhesion to the metal layer is generally low, which leads to the metal layer falling off during the processing and subsequent long-term battery cycling.

[0067] To ensure good adhesion between the polymer base film 10 and the metal layer, while also maintaining good chemical inertness to reduce the possibility of reaction with the electrolyte, this application aims to provide a polymer base film 10 that uses both polar and non-polar polymers as materials. The polar polymer's ability to bond well with the conductive metal layer 20 results in good adhesion between the polymer base film 10 and the conductive metal layer 20. Simultaneously, placing the non-polar polymer at the edge of the first region 11 formed by the polar polymer reduces the possibility of the polar polymer contacting the electrolyte when used as a battery, thereby reducing the possibility of depolymerization. Furthermore, the chemical inertness of the non-polar polymer further minimizes the likelihood of the entire polymer base film 10 reacting with the electrolyte.

[0068] Figure 1 This is a schematic diagram of the structure of the electrode 1000 provided in the embodiments of this application, as shown below. Figure 1 As shown, this application provides a current collector 100, which includes a polymer base film 10 and two conductive metal layers 20. The polymer base film 10 is disposed between the two conductive metal layers 20. The polymer base film 10 includes a first region 11 and a second region 12. Along the film surface direction, the second region 12 is disposed at least at a portion of the edge of the first region 11. The composition of the first region 11 includes a polar polymer, and the composition of the second region 12 includes a non-polar polymer.

[0069] The second region 12 being located at least part of the edge of the first region 11 means that at least a section of the edge of the first region 11 is provided with the second region 12. The second region 12 can be continuously arranged, intermittently arranged, or all edges of the first region 11 can be provided with the second region 12, that is, the second region 12 surrounds the edge of the first region 11. Typically, the current collector 100 is in the shape of a rectangular sheet, and the corresponding polymer base film 10 is also in the shape of a rectangular sheet. In this case, the second region 12 can be distributed on one side of the first region 11, or on the adjacent or opposite sides of the first region 11, or on the three adjacent sides of the first region 11, or the second region 12 can be provided around the first region 11.

[0070] The polar polymer contains polar bonds or polar groups in its molecule, such as hydroxyl (-OH), carboxyl (-COOH), amine (-NH2), etc. These polar groups can form hydrogen bonds or other polar interactions with other molecules, thus showing special properties in solubility, surface tension, etc. Generally, when it is used as the base film material of the current collector 100, it can have good adhesion with the conductive metal layer 20.

[0071] The non-polar polymer generally does not contain polar bonds or polar groups in its molecular structure, and its molecules are uniformly distributed. This makes the non-polar polymer show uniform characteristics in solubility and interaction with other substances. Generally, when it is used as the base film material of the current collector 100, it has good chemical inertness and can reduce the reaction with the electrolyte.

[0072] By setting the polar polymer and the non-polar polymer as the material of the polymer base film 10 between the two conductive metal layers 20, the polar polymer can have good adhesion with the conductive metal layer 20 by using the characteristic that the polar polymer can have good adhesion with the conductive metal layer 20. At the same time, the non-polar polymer is arranged at the edge of the first area 11 formed by the polar polymer, which can reduce the possibility of the polar polymer contacting the electrolyte when used as a battery, thereby reducing the possibility of depolymerization reaction of the polar polymer, and using the chemical inertness of the non-polar polymer, the possibility of the whole polymer base film 10 reacting with the electrolyte is low.

[0073] In some embodiments, the width W1 of the first area 11 and the width W2 of the second area 12 satisfy: W1: W2 = (5-10): 1. By controlling the width W1 of the first area 11 and the width W2 of the second area 12 to satisfy: W1: W2 = (5-10): 1, the first area 11 and the second area 12 both have a suitable width, which can reduce the possibility of the whole polymer base film 10 reacting with the electrolyte, while taking into account the good adhesion between the polymer base film 10 and the conductive metal layer 20.

[0074] For example, the ratio of the width W1 of the first area 11 to the width W2 of the second area 12 can be 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc., and it can also be any value within the range of (5-10): 1.

[0075] In some embodiments, the width of the first area 11 is 5-100 cm. Generally, the width of the first area 11 is not less than the width of the active material layer 200 coated on the current collector 100, which can help to reduce the probability of separation between the polymer base film 10 and the conductive metal layer 20 during the cold pressing process of the pole piece 1000. By controlling the width of the first area 11 to be 5-100 cm, it can be suitable for the preparation of most pole pieces 1000 at present.

[0076] For example, the width of the first region 11 can be 5 cm, 10 cm, 15 cm, 20 cm, 25 cm, 30 cm, 35 cm, 40 cm, 45 cm, 50 cm, 55 cm, 60 cm, 65 cm, 70 cm, 75 cm, 80 cm, 85 cm, 90 cm, 95 cm, or 100 cm, etc., which can also be any value within the range of 5-100 cm.

[0077] In some embodiments, the thickness of the polymer base film 10 is 2-10 μm; the thickness of the conductive metal layer 20 is 0.5-10 μm.

[0078] For example, the thickness of the polymer base film 10 can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, etc., which can also be any value within the range of 2-10 μm. The thickness of the conductive metal layer 20 can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, or 10 μm, etc., which can also be any value within the range of 0.5-10 μm.

[0079] In some embodiments, the polar polymer includes at least one of polyethylene terephthalate (PET), polyimide (PI), polyvinyl chloride (PVC), and polyacrylonitrile (PAN); the non-polar polymer includes at least one of polypropylene (PP), polytetrafluoroethylene (PTFE), polyethylene (PE), and polystyrene (PS); and the two conductive metal layers 20 independently include copper or aluminum.

[0080] In some embodiments, the composition of the second region 12 further includes a compatibilizer.

[0081] The compatibilizer refers to an auxiliary agent that promotes the combination of two incompatible polymers into one body by means of intermolecular bonding force, thereby obtaining a stable blend.

[0082] By adding the compatibilizer in the second region 12, the adhesion of the second region 12 and the first region 11 can be facilitated, and the bonding force of the second region 12 and the conductive metal layer 20 can also be facilitated.

[0083] The compatibilizer can be selected from at least one of PP-g-MAH, PE-g-MAH, and PS-g-MAH; and the mass ratio of the compatibilizer in the second region 12 is not more than 10%.

[0084] In some embodiments, the composition of the second region 12 further includes a conductive medium.

[0085] The conductive medium refers to material particles with conductive ability.

[0086] By adding the conductive medium in the second area 12, the two conductive metal layers 20 are allowed to conduct electrons, thereby making the welding of the tab not need to use a switching foil, effectively reducing the difficulty of preparing the tab 1000.

[0087] The conductive medium can be selected from at least one of graphite, graphene and carbon nanotubes; and the mass percentage of the conductive medium in the second area 12 is not more than 10%.

[0088] In some embodiments, the mass percentage of the polar polymer in the first area is 90% to 100%, and the mass percentage of the non-polar polymer in the second area is 90% to 100%. When the mass percentage of the polar polymer in the first area is 90% to 100%, the corresponding mass percentage of the non-polar polymer is in a smaller range, which has a smaller influence on the adhesion between the entire base film and the conductive metal layer. Similarly, when the mass percentage of the non-polar polymer in the second area is 90% to 100%, the corresponding mass percentage of the polar polymer is in a smaller range, and the second area can still better block the electrolyte and reduce the contact between the first area and the electrolyte. Further, the first area is composed of a polar polymer, and the second area is composed of a non-polar polymer.

[0089] The embodiment of the present application provides a tab 1000, which comprises an active material layer 200 and a current collector 100 as provided above, and the active material layer 200 is arranged on at least part of the surface of the current collector 100.

[0090] The tab 1000 is realized based on the above-mentioned current collector 100, and the specific content of the current collector 100 can be referred to the above-mentioned embodiments. Since the tab 1000 adopts part or all of the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0091] By setting the polar polymer and the non-polar polymer as the material of the polymer base film 10 between the two conductive metal layers 20, the polar polymer can have a better bonding force with the conductive metal layer 20, so that the polymer base film 10 and the conductive metal layer 20 have a better adhesion, which can reduce the probability of separation of the conductive metal layer 20 and the polymer base film 10 when the active material layer 200 is cold-pressed. Meanwhile, the non-polar polymer is arranged at the edge of the first area 11 formed by the polar polymer, which can reduce the possibility of the polar polymer contacting with the electrolyte when the battery is in use, thereby reducing the possibility of depolymerization of the polar polymer, and the chemical inertness of the non-polar polymer makes the possibility of reaction between the entire polymer base film 10 and the electrolyte lower.

[0092] In some embodiments, the active material layer 200 corresponds to the first area 11 in position, and the relationship between the width W3 of the active material layer 200 and the width W1 of the first area 11 satisfies: W3≤W1.

[0093] The active material layer 200 corresponds to the first area 11 in position means that, in the thickness direction, the projection of the active material layer 200 is within the projection of the first area 11.

[0094] By making the width of the first area 11 not less than the width of the active material layer 200 coated on the current collector 100, it is possible to reduce the probability of separation between the polymer-based film 10 and the conductive metal layer 20 occurring during the cold pressing process for preparing the current sheet 1000.

[0095] For example, the current sheet can be a positive electrode sheet, and the material of the electrode active material layer of the positive electrode sheet is selected from a positive electrode active material. For example, the positive electrode active material can be selected from lithium cobaltate, lithium manganate, lithium iron phosphate, or a nickel-cobalt-manganese ternary positive electrode material.

[0096] For example, the current sheet can be a negative electrode sheet, and the material of the electrode active material layer of the negative electrode sheet is selected from a negative electrode active material. For example, the negative electrode active material can be selected from one or more of a silicon-based negative electrode material and a graphite negative electrode material.

[0097] The embodiments of the present application provide an electrochemical device, which comprises the current sheet 1000 provided above.

[0098] The electrochemical device is realized based on the current sheet 1000 described above, and the specific content of the current sheet 1000 can be referred to the above embodiments. Since the electrochemical device adopts part or all of the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0099] For example, the electrochemical device further comprises a separator, and the separator is arranged between the positive electrode sheet and the negative electrode sheet.

[0100] For example, the electrochemical device further comprises an electrolyte, and the electrolyte can be an electrolyte solution or a solid-state electrolyte.

[0101] Figure 2 The flowchart of the method provided by the embodiments of the present application is shown in Figure 2 The embodiments of the present application provide a preparation method of a polymer-based film 10, and the polymer-based film 10 is the polymer-based film 10 provided in the fourth aspect. The method comprises the following steps:

[0102] S1. Preparing a first slurry by using a polar polymer;

[0103] S2. Preparing a second slurry by using a non-polar polymer;

[0104] S3. Electrospin the first slurry and the second slurry to obtain a polymer base film 10.

[0105] The specific implementation process is as follows: Figure 3 This is a schematic diagram of the spinning process of the polymer-based film 10 provided in the embodiments of this application, as shown below. Figure 3 As shown, a first slurry is added to an electrospinning emitter, and a second slurry is added to another electrospinning emitter. The distance between the emitter nozzle and the receiving roller is 10-30 cm. The receiving roller is a conductive carbon roller or a conductive metal layer 20. The voltage is adjusted, and a polymer base film 10 including a first region 11 and a second region 12 is prepared. The thickness of the polymer base film 10 is controlled by adjusting the polymer concentration and the spinning time.

[0106] When the receiving roller is a conductive carbon roller, after the preparation is completed, the polymer base film 10 is peeled off, and metal is deposited on both sides by vacuum sputtering or vacuum evaporation to obtain a conductive metal layer 20. The thickness of the conductive metal layer 20 is controlled by the deposition time. After the process is completed, the foil is hot-pressed to obtain the current collector 100.

[0107] When the receiving roller is the conductive metal layer 20, the conductive metal layer 20 is peeled off entirely, revealing a polymer base film 10 on one side and the conductive metal layer 20 on the other. Figure 4 This is a schematic diagram of the hot-pressing and melting process of the current collector 100 provided in an embodiment of this application, as shown below. Figure 4 As shown, two identical materials with corresponding polymer interfaces are directly melted under hot pressing to obtain a composite current collector 100 with upper and lower metal layers and a middle polymer layer. The thickness of the polymer substrate is controlled by spinning.

[0108] This method uses electrospinning to fabricate a monolithic polymer base film 10 from polar and non-polar polymers. When used as an electrode 1000, the polymer base film 10 is sandwiched between two conductive metal layers 20. Utilizing the strong adhesion between the polar polymer and the conductive metal layers 20, good adhesion is achieved between the polymer base film 10 and the conductive metal layers 20. Simultaneously, placing the non-polar polymer at the edge of the first region 11 formed by the polar polymer reduces the possibility of the polar polymer coming into contact with the electrolyte when used as a battery, thereby reducing the possibility of depolymerization. Furthermore, the chemical inertness of the non-polar polymer further minimizes the likelihood of the entire polymer base film 10 reacting with the electrolyte.

[0109] The present application is further described in conjunction with the following specific examples. It should be understood that these examples are intended to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods in the following examples, if not otherwise specified, are generally determined according to the national standards. If there is no corresponding national standard, it is determined according to the general international standards, conventional conditions, or according to the conditions recommended by the manufacturer.

[0110] Example 1

[0111] A current collector is prepared as follows:

[0112] Step one: electrospinning to prepare a polymer-based film

[0113] First, polyethylene terephthalate (PET) is dissolved in an organic solvent to prepare a PET glue solution, and poured into a polar polymer emitter. A polypropylene (PP) glue solution is prepared, and 5% of PP-g-MAH and 5% of conductive graphite are added to form a non-polar polymer glue solution, which is poured into a non-polar polymer emitter. The distance between the receiving roller and the emitter is adjusted to 10 cm, the potential difference between the emitter and the receiving roller is controlled to 10 kV, the receiving roller is selected to be a conductive copper foil with a thickness of 3 um and a width of 30 cm. The effective jet length of the polar polymer emitter and the non-polar polymer emitter is adjusted so that the width of the polar polymer area is 24 cm, and the width of the non-polar polymer area on both sides is 3 cm. Electrospinning is performed to obtain a polymer-based film.

[0114] Step two: obtaining a current collector from the polymer-based film

[0115] The material prepared in step one has a metal copper foil on one side and a polymer-based film on the other side. The polymer interfaces of the two foil materials are opposite to each other, and the surfaces are fused by heating and pressing to bond them together to obtain a current collector.

[0116] Example 2

[0117] A current collector is prepared as follows:

[0118] Step one: electrospinning to prepare a polymer-based film

[0119] First, polyimide (PI) is dissolved in an organic solvent to prepare PI glue solution, and poured into the polar polymer emitter. Then, polyethylene (PE) glue solution is prepared, and 5% of PE-g-MAH and 5% of graphene are added to form a non-polar polymer glue solution, which is poured into the non-polar polymer emitter. The distance between the receiving roller and the emitter is adjusted to 10 cm, and the potential difference between the emitter and the receiving roller is controlled to 10 kV. The receiving roller is selected to be a conductive copper foil with a thickness of 3 um and a width of 30 cm. The effective jet length of the polar polymer emitter and the non-polar polymer emitter is adjusted to make the width of the polar polymer region 24 cm, and the width of the non-polar polymer region on both sides 3 cm. Electrospinning is performed to obtain a polymer-based film.

[0120] Step two: obtaining a current collector from the polymer-based film

[0121] The material prepared in step one is obtained, one side is a metal copper foil, the other side is a polymer-based film, the polymer interfaces of the two foil materials are opposite, the surfaces are melted by heating and pressing to bond them together to obtain a current collector.

[0122] Example 3

[0123] A current collector is prepared as follows:

[0124] Step one: electrospinning to prepare a polymer-based film

[0125] First, polyvinyl chloride (PVC) is dissolved in an organic solvent to prepare PVC glue solution, and poured into the polar polymer emitter. Then, polystyrene (PS) glue solution is prepared, and 5% of PS-g-MAH and 5% of carbon nanotubes are added to form a non-polar polymer glue solution, which is poured into the non-polar polymer emitter. The distance between the receiving roller and the emitter is adjusted to 10 cm, and the potential difference between the emitter and the receiving roller is controlled to 10 kV. The receiving roller is selected to be a conductive copper foil with a thickness of 3 um and a width of 30 cm. The effective jet length of the polar polymer emitter and the non-polar polymer emitter is adjusted to make the width of the polar polymer region 24 cm, and the width of the non-polar polymer region on both sides 3 cm. Electrospinning is performed to obtain a polymer-based film.

[0126] Step two: obtaining a current collector from the polymer-based film

[0127] The material prepared in step one is obtained, one side is a metal copper foil, the other side is a polymer-based film, the polymer interfaces of the two foil materials are opposite, the surfaces are melted by heating and pressing to bond them together to obtain a current collector.

[0128] Example 4

[0129] A current collector is prepared as follows:

[0130] Step one: preparing polymer base film by electrospinning

[0131] Firstly, polyethylene terephthalate (PET) is dissolved in an organic solvent to prepare a PET glue solution, which is poured into a polar polymer emitter. Then, a polypropylene (PP) glue solution is prepared, and 5% of PP-g-MAH and 5% of conductive graphite are added to form a non-polar polymer glue solution, which is poured into a non-polar polymer emitter. The distance between the emitter and the receiving roller is adjusted to 10 cm, and the potential difference between the emitter and the receiving roller is controlled to be 10 kV. The receiving roller is selected to be a conductive carbon roller with a width of 30 cm. The effective jet length of the polar polymer emitter and the non-polar polymer emitter is adjusted so that the width of the polar polymer region is 24 cm, and the width of the non-polar polymer region on both sides is 3 cm. Finally, a polymer base film is prepared.

[0132] Step two: obtaining a current collector from the polymer base film

[0133] The polymer base film prepared in step one is removed from the conductive carbon roller. In a vacuum state, metal nano-copper with a thickness of 1 um is deposited on both sides of the surface by magnetron sputtering to obtain a current collector.

[0134] Comparative example 1

[0135] A current collector is prepared by the following process:

[0136] Step one: preparing a polymer base film by stretching

[0137] Firstly, polyethylene terephthalate (PET) is stretched to obtain a polymer base film.

[0138] Step two: obtaining a current collector from the polymer base film

[0139] The polymer base film prepared in step one is removed from the conductive carbon roller. In a vacuum state, metal nano-copper with a thickness of 1 um is deposited on both sides of the surface by magnetron sputtering to obtain a current collector.

[0140] Comparative example 2

[0141] A current collector is prepared by the following process:

[0142] Step one: preparing a polymer base film by stretching

[0143] Firstly, polypropylene (PP) is stretched to obtain a polymer base film.

[0144] Step two: obtaining a current collector from the polymer base film

[0145] The polymer base film prepared in step one is removed from the conductive carbon roller. In a vacuum state, metal nano-copper with a thickness of 1 um is deposited on both sides of the surface by magnetron sputtering to obtain a current collector.

[0146] The current collectors provided in Examples 1-4 and Comparative Examples 1-2 were subjected to interlayer adhesion tests and chemical inertness tests, and the test procedures were as follows:

[0147] Interlayer adhesion test: the sample was cut into a 10 cm*2 cm strip, and a 2 cm wide 3M681 tape was used to perform a peeling test on it using a tensile testing machine.

[0148] Chemical inertness test: after the foil was coated with a negative electrode material, it was cut into a 10 cm*10 cm size, and immersed in a lithium ion battery electrolyte at 85°C for 20 days, and the metal plating layer was observed for whether it fell off.

[0149] The results are shown in the following table:

[0150] interlayer adhesion chemical inertness Example 1 > 5 N / cm coating did not peel off Example 2 2 N / cm coating did not peel off Example 3 1 N / cm coating did not peel off Example 4 > 5 N / cm coating did not peel off Comparative Example 1 > 5 N / cm coating peeled off Comparative Example 2 0.4 N / cm coating did not peel off

[0151] As shown in the above table, the current collector provided in the present application has good interlayer adhesion, and also has good chemical inertness.

[0152] Example 5

[0153] An active material layer was prepared on the current collector provided in Example 1 to obtain a pole piece. The width of the active material layer was 20 cm.

[0154] Example 6

[0155] An active material layer was prepared on the current collector provided in Example 1 to obtain a pole piece. The width of the active material layer was 25 cm.

[0156] The pole pieces provided in Examples 5-6 were subjected to interlayer adhesion tests, and the test procedures were as follows: Interlayer adhesion test: the sample was cut into a 10 cm*2 cm strip, and a 2 cm wide 3M681 tape was used to perform a peeling test on it using a tensile testing machine.

[0157] The results are shown in the following table:

[0158] interlayer adhesion Example 5 0.1 N / cm Example 6 0.06 N / cm

[0159] As shown in the above table, the width of the first region is not less than the width of the active material layer coated on the current collector, and the interlayer adhesion of the pole piece prepared therefrom is greater. The applicant speculates that the reason is that such a setting reduces the probability of separation between the polymer base film and the conductive metal layer during the cold pressing process of pole piece preparation, so that the active material layer is tightly attached to the foil.

[0160] The foregoing detailed description of the application has been presented for purposes of illustration and description. Various modifications and changes can be made to these embodiments without departing from the spirit and scope of the application. It is intended that the scope of the application should not be limited by the particular representative embodiments described above.

Claims

1. A current collector characterized by comprising: The current collector comprises a polymer base film and two conductive metal layers, the polymer base film is arranged between the two conductive metal layers, the polymer base film comprises a first region and a second region, along the film surface direction, the second region is arranged at least part of the edge of the first region, the composition of the first region is a polar polymer, and the composition of the second region is a non-polar polymer.

2. The current collector of claim 1, wherein The width W1 of the first region and the width W2 of the second region satisfy: W1: W2 = (5-10):

1.

3. The current collector of claim 2, wherein The width of the first region is 5-100 cm.

4. The current collector of claim 1, wherein The polar polymer is polyethylene terephthalate, polyimide, polyvinyl chloride or polyacrylonitrile; and / or The non-polar polymer is polypropylene, polytetrafluoroethylene, polyethylene or polystyrene; and / or The composition of the two conductive metal layers is independently copper or aluminum.

5. The current collector of claim 1, wherein The second region is arranged at two edges of the first region.

6. The current collector of claim 1 or 5, wherein The second region is arranged at two opposite edges of the first region.

7. The current collector of claim 1, wherein The second region is arranged at all edges of the first region.

8. The current collector of claim 1, wherein The thickness of the polymer base film is 2-10 μm; and / or The thickness of the conductive metal layer is 0.5-10 μm.

9. A pole piece characterized by, The pole piece comprises an active material layer and the current collector of any one of claims 1-8, and the active material layer is arranged on at least part of the surface of the current collector.

10. The pole piece of claim 9, wherein, The active material layer corresponds to at least part of the first region.

11. The pole piece of claim 9, wherein The position of the active material layer corresponds to the first region, and the relationship between the width W3 of the active material layer and the width W1 of the first region satisfies: W3≤W1.

12. An electrochemical device, characterized by, The electrochemical device comprises the pole piece of any one of claims 9-11.

13. A polymer-based film, characterized by, The polymer base film comprises a first region and a second region, along the film surface direction, the second region is arranged at least part of the edge of the first region, the composition of the first region is a polar polymer, and the composition of the second region is a non-polar polymer.

14. The polymer-based film according to claim 13, characterized in that, The polymer base film satisfies one or more of the following characteristics: A) The width W1 of the first region and the width W2 of the second region satisfy: W1: W2 = (5-10): 1; B) The width of the first region is 5-100 cm; C) The thickness of the polymer base film is 2-10 μm; D) The polar polymer is polyethylene terephthalate, polyimide, polyvinyl chloride or polyacrylonitrile; E) The non-polar polymer is polypropylene, polytetrafluoroethylene, polyethylene or polystyrene.

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