Composite current collector and preparation system thereof, secondary battery and electronic device

Abstract

The utility model discloses a composite current collector and a preparation system thereof, a secondary battery and an electronic device. The composite current collector comprises a composite region and a tab connecting region arranged at at least one end of the composite region, the first metal layer and the second metal layer are arranged on the two sides of the polymer layer respectively, the longitudinal tensile strength of the composite area is larger than or equal to 160 MPa, and the transverse tensile strength of the composite area is larger than or equal to 120 MPa; the tab connecting area comprises a first metal layer and a second metal layer which extend from the end part of the polymer layer and are attached to each other, and the tensile strength of the tab connecting area is greater than or equal to 150MPa. The composite current collector has relatively low resistance, still has relatively high tensile strength and bending resistance, and can be widely applied to secondary batteries and electronic devices; the preparation system can continuously prepare the composite current collector on a large scale.

Description

Technical Field

[0001] The utility model relates to, in particular to, a composite current collector and a preparation system thereof, a secondary battery and an electronic device. Background Art

[0002] As the concept of sustainable development gradually deepens and environmental awareness strengthens, new energy sources that can replace traditional petroleum are developing rapidly. As the core of new energy sources, batteries often bear high-power power input and output during operation. Traditional composite current collectors have the risk of brittle fracture and cracks leading to internal short circuits in the battery due to their low toughness; composite current collectors with high molecular polymers as core materials with excellent tensile strength and toughness have excellent anti-bending ability and have received widespread attention.

[0003] Although polymers have strong tensile strength and bending resistance, polymers that can be processed over large areas, such as polypropylene and polyester films, have huge insulation resistance, so metal layers need to be attached to both sides of the polymer. For production efficiency, the mass production process often produces composite current collectors that are not conductive on both sides, so the tabs need to be processed to make them conductive on both sides. Utility Model Content

[0004] The technical problem to be solved by the utility model is to overcome the defects of the existing composite current collector, which has huge insulation resistance and no conduction on both sides, and provide a composite current collector and its preparation system, secondary battery, and electronic device. The composite current collector has low resistance and still has large tensile strength and bending resistance, and can be widely used in secondary batteries and electronic devices; the preparation system of the present application can continuously prepare the composite current collector in large quantities.

[0005] The utility model solves the above technical problems through the following technical solutions:

[0006] In a first aspect, the utility model provides a composite current collector, which comprises: a composite region and a tab connection region provided at at least one end of the composite region;

[0007] The composite region comprises a polymer layer, and a first metal layer and a second metal layer respectively arranged on both sides of the polymer layer, and the longitudinal tensile strength of the composite region is ≥160MPa, and the transverse tensile strength is ≥120MPa;

[0008] The tab connection area includes the first metal layer and the second metal layer extending from the end of the polymer layer and attached to each other, and the tensile strength of the tab connection area is ≥150 MPa.

[0009] In a second aspect, the utility model provides a secondary battery, which includes the composite current collector as described above, and a tab connected to a tab connection region in the composite current collector.

[0010] In a third aspect, the utility model provides an electronic device, which includes the secondary battery as described above.

[0011] In a fourth aspect, the utility model provides a system for preparing the composite current collector as described above, comprising at least one heating unit and at least one group of roller elements; the heating unit is arranged upstream of the roller element along the processing and transmission direction of the composite material; the composite material comprises a first metal foil, a polymer film, and a second metal foil arranged in a stacked manner;

[0012] The heating unit is used to heat the portion of the composite material where the tab connection area is preformed;

[0013] The pressing roller element is used to press the composite material part into the composite region of the composite current collector, and to press the part of the composite material heated by the heating unit into the tab connection region of the composite current collector.

[0014] The positive and progressive effects of the utility model are:

[0015] (1) The composite current collector of the present application has a low resistance, thus avoiding the situation where the two sides of the current collector are not conductive;

[0016] (2) The composite current collector of the present application still has a large tensile strength and bending resistance, which can avoid the risk of brittle fracture and cracks in the current collector causing internal short circuit of the battery, and can thus be widely used in secondary batteries and electronic devices;

[0017] (3) The preparation system of the present application can continuously prepare the composite current collector in large quantities, and no additional device is required to add additional metal sheets on both sides of the composite current collector to solve the conduction problem. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic structural diagram of a system for preparing a composite current collector according to Example 1 of the utility model;

[0019] Figure 2 This is a planar development schematic diagram of the pressure roller element of Example 1 of the utility model;

[0020] Figure 3 This is a schematic diagram of the structure of the composite current collector of Example 2 of the utility model.

[0021] Description of reference numerals:

[0022] Composite current collector 1

[0023] First metal foil 101

[0024] Polymer film 102

[0025] Second metal foil 103

[0026] Tab connection area 104

[0027] Multiple District 105

[0028] Preparation system of composite current collector 2

[0029] First conveying roller 201

[0030] Second conveying roller 202

[0031] The third conveying roller 203

[0032] Heating unit 204

[0033] Cooling unit 205

[0034] First pressing roller 206

[0035] Second pressing roller 207

[0036] Roll gap 208. DETAILED DESCRIPTION

[0037] A preferred embodiment is given below, and the present invention is described more clearly and completely in conjunction with the accompanying drawings.

[0038] In the composite current collector of the first aspect of the utility model:

[0039] In some embodiments, the material of the polymer layer includes PP, PE or PET.

[0040] Among them, the PP is conventional polypropylene in the art; the PE is conventional polyethylene in the art; and the PET is conventional polyethylene terephthalate in the art.

[0041] In some embodiments, the thickness of the polymer layer is 2-10 μm, for example, 7 μm or 10 μm. By controlling the thickness of the polymer layer within the above range, possible cracking of the metal layer material during hot pressing can be prevented.

[0042] In a specific embodiment, when the material of the polymer layer is PP or PE, the longitudinal tensile strength of the polymer layer is ≥100 MPa, for example, 100 MPa.

[0043] In a specific embodiment, when the material of the polymer layer is PET, the longitudinal tensile strength of the polymer layer is ≥130 MPa, for example, 150 MPa.

[0044] In some embodiments, the transverse tensile strength of the polymer layer is ≥80 MPa, for example, 80 MPa or 130 MPa.

[0045] In the present invention, by controlling the transverse tensile strength and / or longitudinal tensile strength of the polymer layer within the above range, the possibility of rebound of the material after hot pressing can be effectively avoided.

[0046] In some embodiments, the material of the first metal layer includes aluminum foil or copper foil.

[0047] In some embodiments, the thickness of the first metal layer is 2-10 μm, for example, 7 μm.

[0048] In some embodiments, the peel strength of the first metal layer is ≥ 2 N / cm, for example, 2 N / cm.

[0049] In some embodiments, the surface density of the first metal layer is 30-40 g / 100 cm 2 , for example 33g / 100cm 2 .

[0050] In some embodiments, the tensile strength of the first metal layer is ≥190 MPa, for example, 200 MPa.

[0051] In the present invention, by controlling the tensile strength of the first metal layer within the above range, the possibility of rebound of the material after hot pressing can be effectively avoided.

[0052] In the utility model, the tensile strength of the first metal layer is greater than the tensile strength of the polymer layer; after the metal layer and the polymer layer are composited, the tensile strength of the composite layer is improved relative to the tensile strength of the original polymer layer.

[0053] In some embodiments, the elongation of the first metal layer is ≥3%, for example, 3.2%.

[0054] In some embodiments, the surface wetting tension of the first metal layer is ≥25 mN / m, for example ≥27 mN / m.

[0055] In a specific embodiment, the second metal layer is made of the same material as the first metal layer.

[0056] In a specific embodiment, the second metal layer has the same mechanical properties as the first metal layer.

[0057] In one embodiment of the present application, the longitudinal tensile strength of the composite zone is 160 MPa, and the transverse tensile strength is 130 MPa.

[0058] In one embodiment of the present application, the tensile strength of the tab connection area is 185 MPa.

[0059] In one embodiment of the present application, the longitudinal tensile strength of the composite zone is 170 MPa, and the transverse tensile strength is 160 MPa.

[0060] In one embodiment of the present application, the tensile strength of the tab connection area is 185 MPa.

[0061] In some embodiments, the length ratio of the tab connection region to the composite current collector is 1:(10-15), for example, 1:10.

[0062] In some embodiments, in the composite region, the first metal layer and the polymer layer, and the second metal layer and the polymer layer are bonded together by bonding.

[0063] In some embodiments, in the tab connection region, the first metal layer and the second metal layer are bonded together by bonding.

[0064] In some embodiments, the resistance of the tab connection area is less than 0.1Ω / m 2 .

[0065] In the preparation system of the fourth aspect of the utility model:

[0066] In the present invention, the processing and conveying direction of the composite material refers to the conveying direction from a device for stacking the material layers to a device for pressing the material layers.

[0067] In the utility model, when the stacked composite material is not heated, the pressing roller element can directly press the composite material into a composite area, or called a non-tab connection area; when the stacked composite material is heated, the pressing roller element can extrude the softened polymer layer from between the first metal layer and the second metal layer, so that the first metal layer and the second metal layer are directly connected, and the tab connection area is pressed.

[0068] In some embodiments, the preparation system of the composite current collector also includes a first conveying roller, a second conveying roller, and a third conveying roller, which are all arranged upstream of the heating unit along the processing and transmission direction of the composite material; the first conveying roller, the second conveying roller, and the third conveying roller are respectively used to convey the first metal foil, the polymer film, and the second metal foil, and are arranged in sequence along the stacking arrangement direction of the composite material.

[0069] In some embodiments, the system for preparing the composite current collector further comprises a cooling unit, which is disposed downstream of the pressing roller element along the processing and conveying direction of the composite material, and is used to reduce the temperature of the composite zone.

[0070] In some embodiments, the pressure roller elements may be collectively referred to as process rollers, which include a first pressure roller and a second pressure roller disposed one above the other, with a roller gap being provided between the first pressure roller and the second pressure roller.

[0071] Wherein, the tension of the first pressing roller and the second pressing roller may be 10-30N.

[0072] Preferably, the width of the roller gap is equal to the sum of the thickness of the first metal foil and the thickness of the polymer film, or the sum of the thickness of the second metal foil and the thickness of the polymer film, so as to provide pressure for the molding of the composite current collector during the pressing process.

[0073] In one embodiment of the present application, the width of the roller gap is 12 μm.

[0074] In some embodiments, the heating unit is disposed on one side of the first metal layer and / or on one side of the second metal layer.

[0075] In a specific embodiment, when the number of the pressing roller elements is 1 group, the heating unit is arranged inside the pressing roller element and located at the front end of the contact point between the pressing roller element and the composite material; the cooling unit is arranged inside the pressing roller element and located at the rear end of the contact point between the pressing roller element and the composite material;

[0076] In a specific implementation, when the number of the pressing roller elements is greater than one group, the heating unit is disposed inside the first pressing roller element; and the cooling unit is disposed inside the last pressing roller element.

[0077] In a specific embodiment, the number of the pressing roller elements is 5 groups; through the 5 groups of pressing roller elements, the polymer layer can be completely heated and extruded from between the first metal layer and the second metal layer when the production rate is fast.

[0078] In the utility model, in the process of producing the composite current collector using the preparation system, the linear speed difference between each of the conveying rollers and the pressure roller in the pressure roller element needs to be maintained at ≤5%, and the conveying rollers include a first conveying roller, a second conveying roller and a third conveying roller.

[0079] In the present invention, during the process of producing the composite current collector using the preparation system, the linear speed of the pressing roller in the pressing roller element may be 10 m / s.

[0080] In the present invention, during the process of producing the composite current collector using the preparation system, the set pressure of the pressing roller element may be 0.1-0.3 MPa.

[0081] In the present invention, during the process of producing the composite current collector using the preparation system, the set temperature of the heating unit may be 10° C. higher than the melting point of the polymer layer.

[0082] In the utility model, in the process of producing the composite current collector using the preparation system, after the pressing of the tab connection area is completed, the extruded polymer film located at the edge of the composite current collector can be cut off by a cutter.

[0083] A preferred embodiment is given below, and the present invention is described more clearly and completely in conjunction with the accompanying drawings.

[0084] Example 1

[0085] This embodiment discloses a preparation system 2 of a composite current collector. Figure 1 is a schematic structural diagram of a system for preparing a composite current collector of this embodiment; Figure 2 The planar unfolding schematic diagram of the pressure roller element of this embodiment. The preparation system 2 of the composite current collector includes a first conveying roller 201, a second conveying roller 202, a third conveying roller 203, a heating unit 204, a group of pressure roller elements, and a cooling unit 205; the first conveying roller 201, the second conveying roller 202, and the third conveying roller 203 are respectively used to convey the first metal foil 101, the polymer film 102, and the second metal foil 103, and are arranged in sequence along the stacking direction of the composite material; the heating unit 204 is arranged upstream of the pressure roller element along the processing and transmission direction of the composite material; the cooling unit 205 is arranged downstream of the pressure roller element along the processing and transmission direction of the composite material; the composite material includes a first metal foil 101, a polymer film 102, and a second metal foil 103 arranged in a stacked manner;

[0086] The heating unit 204 is used to heat the portion of the composite material where the tab connection area 104 is preformed;

[0087] The pressing roller element is used to press the composite material part into the composite area 105 of the composite current collector 1, and to press the part of the composite material that has been heated by the heating unit 204 into the tab connection area 104 of the composite current collector 1;

[0088] Cooling unit 205 is used to reduce the temperature of recombination zone 105 .

[0089] The roller element includes a first roller 206 and a second roller 207 arranged up and down, and a roller gap 208 is provided between the first roller 206 and the second roller 207; the tension of the first roller 206 and the second roller 207 is 30N; the width of the roller gap 208 is equal to the sum of the thickness of the first metal layer and the thickness of the polymer layer.

[0090] The number of the pressing roller elements is 1 group. The heating unit 204 is arranged inside the pressing roller element and at the front end of the contact point between the pressing roller element and the composite material. The cooling unit 205 is arranged inside the pressing roller element and at the rear end of the contact point between the pressing roller element and the composite material.

[0091] Example 2

[0092] This embodiment discloses a composite current collector, which is prepared using the preparation system of embodiment 1. Figure 3 The structure diagram of the composite current collector of this embodiment is shown in FIG. The polymer layer of the composite current collector is made of PP, the thickness of the polymer layer is 7 μm, the longitudinal tensile strength is 100 MPa, and the transverse tensile strength is 80 MPa. The first metal layer and the second metal layer are made of copper foil, the thickness is 7 μm, the peel strength is 2 N / cm, and the surface density is 33 g / 100 cm 2 , the tensile strength is 200MPa, the elongation is 3.2%, and the surface wetting tension meets ≥27mN / m.

[0093] In the process of using the preparation system to produce a composite current collector, the difference in linear speed between each of the conveying rollers and the rollers in the pressure roller element must be maintained at ≤5%; the linear speed of the rollers in the pressure roller element can be 10m / s; the set pressure of the pressure roller element can be 0.1MPa, and the pole ear connection area and the composite area are pressed separately by heating and non-heating; the heating temperature of the heating unit is set to 170°C.

[0094] After the above operation, the prepared composite current collector includes: a composite area and a tab connection area arranged at at least one end of the composite area; the length ratio of the tab connection area to the composite current collector is 1:10; the composite area includes a polymer layer, and a first metal layer and a second metal layer respectively arranged on both sides of the polymer layer, the longitudinal tensile strength of the composite area is 160MPa, and the transverse tensile strength is 130MPa; the tab connection area includes the first metal layer and the second metal layer extending from the end of the polymer layer and bonded to each other, and the tensile strength of the tab connection area is 185MPa.

[0095] Comparative Example 1

[0096] This comparative example is a composite current collector prepared by a conventional preparation system and method in the art.

[0097] The materials and mechanical properties of the first metal layer, the second metal layer, and the polymer layer are the same as those in Example 2.

[0098] The composite current collector of this comparative example comprises: a first metal layer, a polymer layer, and a second metal layer arranged in sequence from top to bottom. The first metal layer and the polymer layer, and the second metal layer and the polymer layer are bonded by bonding; the longitudinal tensile strength is 160 MPa, and the transverse tensile strength is 130 MPa.

[0099] Comparative Example 2

[0100] This comparative example is a composite current collector.

[0101] In the process of producing the composite current collector using the preparation system, the heating temperature of the heating unit is set to 130°C.

[0102] Other conditions and process parameters are the same as those in Example 2.

[0103] In this comparative example, the structure of the composite current collector prepared by the above process is as in comparative example 1, which includes a first metal layer, a polymer layer and a second metal layer arranged in sequence from top to bottom; the longitudinal tensile strength of the composite current collector is 160 MPa, and the transverse tensile strength is 130 MPa.

[0104] Example 3

[0105] This embodiment discloses a composite current collector, the polymer layer of which is made of PET, has a thickness of 10 μm, a longitudinal tensile strength of 150 MPa, and a transverse tensile strength of 130 MPa.

[0106] In the process of producing the composite current collector using the preparation system, the heating temperature of the heating unit is set to 270° C. Other conditions and process parameters are the same as those in Example 2.

[0107] After the above operation, the prepared composite current collector includes: a composite area and a tab connection area arranged at at least one end of the composite area; the length ratio of the tab connection area to the composite current collector is 1:10; the composite area includes a polymer layer, and a first metal layer and a second metal layer respectively arranged on both sides of the polymer layer, and the longitudinal tensile strength of the composite area is 170MPa, and the transverse tensile strength is 160MPa; the tab connection area includes the first metal layer and the second metal layer extending from the end of the polymer layer and bonded to each other, and the tensile strength of the tab connection area is 185MPa.

[0108] Comparative Example 3

[0109] This comparative example is a composite current collector prepared by a conventional preparation system and method in the art.

[0110] The materials and mechanical properties of the first metal layer, the second metal layer, and the polymer layer are the same as those in Example 3.

[0111] The composite current collector of this comparative example comprises: a first metal layer, a polymer layer, and a second metal layer arranged in order from top to bottom. The first metal layer and the polymer layer, and the second metal layer and the polymer layer are bonded by bonding; the longitudinal tensile strength is 170 MPa, and the transverse tensile strength is 160 MPa.

[0112] Comparative Example 4

[0113] This comparative example is a composite current collector.

[0114] In the process of producing the composite current collector using the preparation system, the heating temperature of the heating unit is set to 170°C.

[0115] Other conditions and process parameters are the same as those in Example 3.

[0116] In this comparative example, the structure of the composite current collector prepared by the above process is as in comparative example 3, which includes a first metal layer, a polymer layer and a second metal layer arranged in sequence from top to bottom; its longitudinal tensile strength is 170 MPa, and its transverse tensile strength is 160 MPa.

[0117] Effect Example 1

[0118] In this effect embodiment, the resistance of the composite current collector in Examples 2-3 and Comparative Examples 1-4 was tested by a multimeter; the specific test method is as follows: the test site is the positive and negative positions relative to the connection part of the tab area and the composite area, and the resistance of the composite current collector with a length of 10 cm is tested under the condition of single-end conduction. The results are shown in Table 1.

[0119] Table 1

[0120] Resistance (Ω) Example 2 0.06 Comparative Example 1 ＞1G Comparative Example 2 ＞1G Example 3 0.03 Comparative Example 3 ＞1G Comparative Example 4 ＞1G

[0121] As can be seen from the above table, by using this preparation system and controlling the relevant process conditions, the composite current collector prepared by Example 2 and Example 3 has a very small resistance, which effectively solves the problem of large current collector resistance caused by the introduction of the polymer layer. Comparative Examples 1 and 3 are composite current collectors of conventional structures in the field. Because the polymer layer exists between the first metal layer and the second metal layer, the two sides of the composite current collector are not conductive, so the resistance is very large. Although Comparative Examples 2 and 4 use this preparation system, because the temperature of the heating unit does not reach the melting point of the polymer layer, the polymer film cannot be squeezed out during the pressing process, and the structure of the obtained composite current collector is as in Comparative Examples 1 and 3. The two sides of the composite current collector are not conductive, so the resistance is very large.

Claims

1. A composite current collector, characterized in that: It includes: A composite region and a tab connection region disposed at at least one end of the composite region; The composite region comprises a polymer layer, and a first metal layer and a second metal layer respectively arranged on both sides of the polymer layer, and the longitudinal tensile strength of the composite region is ≥160MPa, and the transverse tensile strength is ≥120MPa; The tab connection area includes the first metal layer and the second metal layer extending from the end of the polymer layer and attached to each other, and the tensile strength of the tab connection area is ≥150 MPa.

2. The composite current collector according to claim 1, characterized in that: The polymer layer satisfies one or more of the following conditions: ① The material of the polymer layer is PP, PE or PET; ② The thickness of the polymer layer is 2-10 μm; ③ When the material of the polymer layer is PP or PE, the longitudinal tensile strength of the polymer layer is ≥100MPa; when the material of the polymer layer is PET, the longitudinal tensile strength of the polymer layer is ≥130MPa; ④ The transverse tensile strength of the polymer layer is ≥80MPa.

3. The composite current collector according to claim 1, characterized in that: The first metal layer satisfies one or more of the following conditions: ① The material of the first metal layer is aluminum foil or copper foil; ② The thickness of the first metal layer is 2-10 μm; ③ The peel strength of the first metal layer is ≥2N / cm; ④The surface density of the first metal layer is 30-40g / 100cm 2 ; ⑤The tensile strength of the first metal layer is ≥190MPa; ⑥ The tensile strength of the first metal layer is greater than the tensile strength of the polymer layer; ⑦The elongation of the first metal layer is ≥3%; ⑧The surface wetting tension of the first metal layer is ≥25mN / m.

4. The composite current collector according to claim 3, characterized in that: The second metal layer is made of the same material as the first metal layer; The second metal layer has the same mechanical properties as the first metal layer.

5. The composite current collector according to claim 1, characterized in that: The length ratio of the tab connection area to the composite current collector is 1:(10-15); In the composite area, the first metal layer and the polymer layer, and the second metal layer and the polymer layer are bonded together by bonding; In the tab connection area, the first metal layer and the second metal layer are bonded together by bonding; The resistance of the tab connection area is less than 0.1Ω / m 2 .

6. A secondary battery, characterized in that: The composite current collector comprises the composite current collector as claimed in any one of claims 1 to 5, and a tab connected to a tab connection region in the composite current collector.

7. An electronic device, characterized in that: It comprises the secondary battery as claimed in claim 6.

8. A system for preparing a composite current collector according to any one of claims 1 to 5, characterized in that: It comprises at least one heating unit and at least one group of pressing roller elements; the heating unit is arranged upstream of the pressing roller elements along the processing and transmission direction of the composite material; the composite material is a first metal foil, a polymer film and a second metal foil arranged in layers; The heating unit is used to heat the portion of the composite material where the tab connection area is preformed; The pressing roller element is used to press the composite material part into the composite region of the composite current collector, and to press the part of the composite material heated by the heating unit into the tab connection region of the composite current collector.

9. The system for preparing a composite current collector according to claim 8, characterized in that: The composite current collector preparation system further includes a first conveying roller, a second conveying roller, and a third conveying roller, which are all arranged upstream of the heating unit along the processing and conveying direction of the composite material; the first conveying roller, the second conveying roller, and the third conveying roller are respectively used to convey the first metal foil, the polymer film, and the second metal foil, and are arranged in sequence along the stacking arrangement direction of the composite material; The composite current collector preparation system further comprises a cooling unit, which is arranged downstream of the pressing roller element along the processing and conveying direction of the composite material, and is used to reduce the temperature of the composite zone; The pressing roller element includes a first pressing roller and a second pressing roller which are arranged up and down, and a roller gap is provided between the first pressing roller and the second pressing roller; the tension of the first pressing roller and the second pressing roller is 10-30N; the width of the roller gap is equal to the sum of the thickness of the first metal foil and the thickness of the polymer film, or the sum of the thickness of the second metal foil and the thickness of the polymer film.

10. The system for preparing a composite current collector according to claim 9, characterized in that: When the number of the pressing roller elements is 1 group, the heating unit is arranged inside the pressing roller element and located at the front end of the contact point between the pressing roller element and the composite material; the cooling unit is arranged inside the pressing roller element and located at the rear end of the contact point between the pressing roller element and the composite material; Alternatively, when the number of the pressing roller elements is greater than one group, the heating unit is disposed inside the first pressing roller element; and the cooling unit is disposed inside the last pressing roller element.

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