Composite current collector, preparation method thereof, electrode plate containing composite current collector, electrochemical device and electronic equipment

Abstract

The invention discloses a composite current collector, a preparation method thereof, an electrode plate containing the composite current collector, an electrochemical device and electronic equipment. The composite current collector comprises an insulating layer, a first conductive layer and a second conductive layer, wherein the insulating layer is arranged between the first conductive layer and the second conductive layer; the first conductive layer comprises a first active material supporting region and a first tab region, and the first active material supporting region is connected with the first surface of the insulating layer; the first tab region is not in contact with the first surface of the insulating layer and is in contact with the third surface; the third surface refers to at least one side surface vertical to the first surface; the second conductive layer comprises a second active material supporting region; the second active material supporting region is in contact connection with the second surface of the insulating layer; the first surface and the second surface are two opposite surfaces; and the first tab region is in contact connection with the second conductive layer. The composite current collector provided by the invention can effectively improve the binding force between metal and a high polymer material.

Description

TECHNICAL FIELD

[0001] The present application relates to a composite current collector, a preparation method thereof, an electrode sheet containing the same, an electrochemical device, and an electronic device. BACKGROUND

[0002] The ternary positive electrode material of the high-nickel system has been widely used in lithium ion batteries due to its high capacity. However, the combustion temperature of the ternary positive electrode material of the high-nickel system is relatively low, and it is easy to catch fire when colliding, which has a potential safety hazard. The composite aluminum foil (a composite material with a polymer-based film plated with aluminum on both sides) can cut off the short-circuit current when the internal short circuit of the lithium battery occurs, thereby improving the safety performance of the battery, and thus has important potential value in the high-nickel system lithium ion battery. In addition, the application of the composite aluminum foil can also effectively improve the lightweight level of the lithium battery.

[0003] Although the polymer material in the composite aluminum foil improves the safety and lightweight level of the lithium battery, the polymer material therein is not conductive, and as a current collector, an additional switching welding process is required to realize the export of electrons, which increases the use cost of the composite aluminum foil and reduces the production efficiency. At the same time, the traditional composite foil is prepared by directly plating metal on the surface of the polymer material, and there is a common problem of low bonding force between the metal and the polymer material. During the cycle process of the battery cell, the active material is easy to fall off, which directly affects the cycle performance of the battery and the performance of the battery cell. SUMMARY

[0004] The present application mainly aims to overcome the defects of the composite current collector in the prior art, such as the need for an additional switching welding process and the poor bonding force between the polymer material and the metal, which affects the performance of the battery cell, and provides a composite current collector, a preparation method thereof, an electrode sheet containing the same, an electrochemical device, and an electronic device. The composite current collector provided by the present application can effectively improve the bonding force between the metal and the polymer material.

[0005] In order to overcome the above technical problems, the present application provides the following technical solutions.

[0006] In a first aspect, the present application provides a composite current collector, comprising: an insulating layer, a first conductive layer and a second conductive layer, the insulating layer being arranged between the first conductive layer and the second conductive layer;

[0007] The first conductive layer comprises a first active material support area and a first tab area, the first active material support area being connected with a first surface of the insulating layer; the first tab area is not in contact with the first surface of the insulating layer and is in contact with a third surface; the third surface refers to at least one side surface perpendicular to the first surface;

[0008] The second conductive layer comprises a second active material support region, which is in contact with the second surface of the insulating layer.

[0009] The first surface and the second surface are two opposite surfaces.

[0010] The first tab region and the second conductive layer are in contact.

[0011] In a second aspect, the present application provides a method for preparing the composite current collector as described above, which comprises the following steps:

[0012] S1. bonding a metal foil to the first surface of the insulating layer to form a first conductive layer, which comprises a first active material support region and a first tab region;

[0013] S2. forming a second conductive layer on the second surface of the insulating layer or on the second surface of the insulating layer and the first tab region by plating; the second conductive layer comprises a second active material support region.

[0014] The first surface and the second surface are two opposite surfaces.

[0015] In a third aspect, the present application provides an electrode sheet, which comprises the composite current collector as described above and an electrode material layer arranged on at least one surface of the composite current collector.

[0016] In a fourth aspect, the present application provides an electrochemical device, which comprises the electrode sheet as described above.

[0017] In a fifth aspect, the present application provides an electronic device, which comprises the electrochemical device as described above.

[0018] On the basis of common knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred examples of the present application.

[0019] The reagents and raw materials used in the present application are commercially available.

[0020] The positive progress of the present application is that:

[0021] The composite current collector provided by the present application does not need to be connected to the tab by adapter welding when used, but directly uses a part of the region in the composite current collector as the tab, thereby improving the connection force between the tab and the current collector and not introducing additional resistance. The preparation method does not need the adapter welding process, thereby greatly simplifying the use of the composite current collector at the battery manufacturing end. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 Structure schematic diagram of the composite current collector prepared in Example 1.

[0023] Figure 2 A schematic view of the structure of the composite current collector prepared for Example 2.

[0024] Reference signs

[0025] 1 - first conductive layer; 2 - insulating layer; 3 - second conductive layer; 11 - first tab area; 12 - first active material support area; 31 - second tab area; 32 - second active material support area. DETAILED DESCRIPTION

[0026] Composite current collector

[0027] The first aspect of the present application provides a composite current collector, comprising an insulating layer, a first conductive layer and a second conductive layer, the insulating layer being disposed between the first conductive layer and the second conductive layer;

[0028] The first conductive layer comprises a first active material support area and a first tab area, the first active material support area being connected with a first surface of the insulating layer; the first tab area is not in contact with the first surface of the insulating layer and is in contact with a third surface; the third surface refers to at least one side surface perpendicular to the first surface;

[0029] The second conductive layer comprises a second active material support area, the second active material support area being in contact with a second surface of the insulating layer;

[0030] The first surface and the second surface are two opposite surfaces;

[0031] The first tab area and the second conductive layer are in contact.

[0032] In the present application, the first active material support area and the second active material support area refer to the area coated with active material when the pole piece is prepared, and the width thereof can be equal to or different from the width of the insulating layer.

[0033] In some specific embodiments, the second conductive layer only comprises a second active material support area, preferably, the width of the second active material support area is greater than the width of the insulating layer.

[0034] In some specific embodiments, the second conductive layer comprises a second active material support area and a second tab area, preferably, the width of the second active material support area is greater than the width of the insulating layer.

[0035] In the present application, the material of the first conductive layer is copper foil or aluminum foil.

[0036] In the present application, the width of the first conductive layer is greater than the width of the insulating layer.

[0037] In the present application, the material of the second conductive layer is copper foil or aluminum foil.

[0038] In the present application, the thickness of the second conductive layer can be 1 μm-2 μm, and the thickness of the second conductive layer refers to the thickness of the region where the second conductive layer contacts the insulating layer.

[0039] In the present application, the width of the second conductive layer is greater than or equal to the width of the insulating layer.

[0040] In the present application, the width of the composite current collector is equal to the width of the first conductive layer or the second conductive layer, and preferably, the width of the composite current collector, the width of the first conductive layer and the width of the second conductive layer are all equal.

[0041] In some embodiments, a part of the one surface of the first tab region is in contact with the insulating layer.

[0042] In some specific embodiments, the material of the first conductive layer is the same as or different from the material of the second conductive layer, and preferably, the same.

[0043] In some specific embodiments, the thickness of the first conductive layer is the same as the thickness of the second conductive layer.

[0044] In the present application, the material of the insulating layer is one or more of polypropylene, polyethylene terephthalate and polyimide.

[0045] In the present application, the thickness of the insulating layer is 4-8 μm, for example, 6 μm.

[0046] Method of making a composite current collector

[0047] The second aspect of the present application provides a method for preparing the composite current collector as described above, which comprises the following steps: S1. bonding a metal foil to the first surface of the insulating layer to form a first conductive layer, wherein the first conductive layer comprises a first active material support region and a first tab region;

[0048] S2. forming a second conductive layer on the second surface of the insulating layer or on the second surface of the insulating layer and the first tab region by plating;

[0049] In the present application, the first surface and the second surface are two opposite surfaces.

[0050] In the present application, the thickness of the metal foil can be 6 μm-10 μm.

[0051] In the present application, the width of the metal foil can be the width of the composite current collector plus 2 mm. This facilitates the cutting of the edge of the mother roll in the actual production process, while reducing the probability of edge tearing in the later thinning process.

[0052] In the present application, the metal foil has a groove, wherein the height of the groove is equal to the thickness of the insulating layer or the sum of the thicknesses of the insulating layer and the second conductive layer.

[0053] In some embodiments, the groove can be made by etching the metal foil using an oxidizing acid, which is preferably nitric acid or sulfuric acid.

[0054] In the present application, the bonding is achieved by forming a bonding layer of the bonding agent by hot pressing to connect the metal foil and the insulating layer, and the temperature of the hot pressing is 10-15°C higher than the glass transition temperature of the bonding agent.

[0055] In the present application, the bonding agent can be one or more of the substances commonly used in the art, such as ethylene vinyl acetate copolymer (EVA), polytetrafluoroethylene (PTFE), ethylene vinyl acetate derivative, ethylene vinyl acetate crosslinking material, ethylene vinyl acetate copolymer, polytetrafluoroethylene derivative, polytetrafluoroethylene crosslinking material, and polytetrafluoroethylene copolymer.

[0056] In the present application, the plating method is one or more of vacuum evaporation, electroless plating, magnetron sputtering, and chemical vapor deposition.

[0057] In some preferred embodiments, the plating process includes a first plating and a second plating. In this embodiment, the plating process is carried out in two steps, first plating to obtain a conductive layer of a certain thickness, and then second plating to obtain a second conductive layer of a target thickness.

[0058] In some preferred embodiments, the first plating method is any one of vacuum evaporation, magnetron sputtering, and chemical vapor deposition; and the second plating method is any one of electroless plating and vacuum plating.

[0059] In some specific embodiments, the first plating method is chemical vapor deposition; and the second plating method is vacuum evaporation.

[0060] Electrode sheet

[0061] The third aspect of the present application provides an electrode sheet comprising the composite current collector described above and an active material layer, wherein the active material layer is disposed on at least one surface of the composite current collector.

[0062] In the present application, the active material layer is disposed on the first active material support area and / or the second active material support area of the composite current collector.

[0063] In the present application, the electrode sheet can be a positive electrode sheet or a negative electrode sheet.

[0064] In the present application, the active material layer can include an active material, and a binder and a conductive agent can be further added as needed.

[0065] The active material can be a positive active material or a negative active material.

[0066] The positive active material can be a positive active material conventionally used for a lithium ion battery positive electrode in the art, and can include, but is not limited to, one or more of lithium iron phosphate, lithium iron manganese phosphate, a ternary positive electrode material, and a lithium-rich manganese-based material.

[0067] The negative active material can be a compound capable of reversibly intercalating and deintercalating lithium. Specific examples of the negative active material include, but are not limited to, carbon materials such as crystalline carbon (natural graphite and artificial graphite, etc.), amorphous carbon, carbon-coated graphite, and resin-coated graphite, or oxide materials such as indium oxide, silicon oxide, tin oxide, lithium titanate, zinc oxide, lithium oxide, and the like, and can also be lithium metal or a metal material that can form an alloy with lithium. The metal material that can form an alloy with lithium is, for example, Cu, Sn, Si, Co, Mn, Fe, Sb, and Ag. Alloys containing two or three of these metals and lithium can also be used as the negative active material. These negative active materials can be used alone or in combination of two or more. From the perspective of high energy density, a carbon material such as graphite can be used in combination with a Si-based material such as Si, Si alloy, Si oxide, and the like.

[0068] The binder can be a component that facilitates the binding between the active material and the conductive agent and facilitates the binding of the active material to the current collector. It can be typically selected from polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, and various copolymers.

[0069] The conductive agent can be an agent for ensuring that the electrode has good charge and discharge performance. It can be optionally selected from graphite-based materials such as natural graphite, artificial graphite, and the like, carbon black-based materials such as acetylene black, ketjen black, channel black, slot carbon black, furnace black, lamp black, thermal cracking carbon black, and the like, conductive fibers such as carbon fibers, metal fibers, and the like, metal powders such as fluorinated carbon powder, aluminum powder, nickel powder, and the like, conductive whiskers such as zinc oxide, potassium titanate, and the like, and conductive metal oxides such as titanium dioxide, or polyphenylene derivatives.

[0070] Electrochemical device

[0071] The fourth aspect of the present application provides an electrochemical device comprising the electrode sheet as described above.

[0072] In the present application, the electrochemical device is preferably a lithium ion battery, which comprises the electrode sheet as described above, a separator and an electrolyte, wherein the electrode sheet is a positive electrode sheet and a negative electrode sheet.

[0073] The separator

[0074] In some embodiments, the separator can be a polypropylene separator or a polyethylene separator.

[0075] In some embodiments, the thickness of the separator can be about 9 μm.

[0076] The electrolyte

[0077] In some embodiments, the electrolyte can be an electrolyte commonly used in the art for batteries, which generally comprises a non-aqueous solvent, a lithium salt and an additive.

[0078] In some embodiments, the non-aqueous solvent can be a non-aqueous solvent commonly used in the art, which is preferably an ester solvent, more preferably a carbonate solvent. The carbonate solvent can be one or more of ethylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC) and butylene carbonate (BC).

[0079] In some preferred embodiments, the non-aqueous solvent is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) and propylene carbonate (PC) in a volume ratio of 1:1:1:1.

[0080] In some embodiments, the additive can be one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl ethylene carbonate (VEC), vinyl sulfate (DTD), vinylene sulfate, 1,3-propane sulfonolactone (PS), propylene sulfonolactone and 1,4-butane sulfonolactone.

[0081] In the present application, the preparation method of the lithium ion battery can be a conventional preparation method in the art, which can be rolling the positive electrode sheet, the negative electrode sheet and the separator to obtain an electrode core, then packaging with a packaging shell and injecting the electrolyte; or stacking the negative electrode sheet, the separator, the positive electrode sheet and the separator in sequence to obtain an electrode core, then packaging with a packaging shell and injecting the electrolyte.

[0082] Electronic device

[0083] In a fifth aspect, the present application provides an electronic device comprising the electrochemical device as described above.

[0084] Exemplarily, the electronic device of the present application can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a notebook computer, a video recorder, a portable printer / copier, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, a backup power supply, etc. The above optional conditions can be combined in any manner to obtain preferred examples of the present application, based on common general knowledge in the art.

[0085] The present application will be further described in the following by way of examples without thereby limiting the present application to the described examples. The experimental methods in the following examples, for which no specific conditions are indicated, are selected according to conventional methods and conditions, or according to the instructions of the commercial products.

[0086] Example 1

[0087] S1. Preparation of the first conductive layer

[0088] (1) Etching an aluminum foil with a width of 182 mm and a thickness of 7 μm by 1.0 mol / L nitric acid at room temperature to form a groove with a width of 148 mm and a depth of 6 μm; then washing the etched aluminum foil with deionized water and drying to obtain the first conductive layer; wherein the region with a width of 150 mm in the middle of the first conductive layer is the first active material support area, and the remaining part on both sides is the first tab area.

[0089] (2) Bonding the PET insulating layer to the groove of the first conductive layer obtained in step (1) by EVA adhesive, hot-press bonding at a temperature of 110°C, and then trimming the edge; the size of the PET insulating layer is: width of 148 mm, thickness of 6 μm.

[0090] S2. Preparation of the second conductive layer

[0091] (3) Vacuum evaporation on the second surface of the PET insulating layer and the first tab area in S1, first depositing an aluminum oxide layer of 10 nm on the second surface of the PET insulating layer by chemical vapor deposition, and then thickening the aluminum oxide layer to a thickness of 1 μm of the second conductive layer by physical vapor deposition to obtain the second conductive layer, the region with a width of 150 mm in the middle is the second active material support area, and the remaining part on both sides is the second tab area; then trimming the edge and winding to obtain the composite current collector.

[0092] The structure of the composite current collector prepared in Example 1 is as follows: Figure 1As shown in FIG. 2, the width of the composite current collector is 180 mm, wherein the width of the first active material support area 12 and the second active material support area 32 is 150 mm, and the first tab area 11 and the second tab area 31 on both sides are connected to form a tab area, and the width of both sides is 15 mm.

[0093] Example 2

[0094] A tab with a size of an active material support area width of 150 mm and a total width of 180 mm is prepared, and a structural schematic diagram thereof is shown in FIG. 2. Figure 2 As shown in FIG. 2.

[0095] S1. Preparation of a first conductive layer

[0096] (1) Etching an aluminum foil with a width of 182 mm and a thickness of 8 μm by using nitric acid with a concentration of 1.0 mol / L at room temperature to form a groove with a width of 148 mm and a depth of 7 μm; then washing the etched aluminum foil with deionized water and drying to obtain a first conductive layer; wherein the area with a width of 150 mm in the middle of the first conductive layer is a first active material support area, and the remaining part on both sides is a first tab area.

[0097] (2) Bonding the PET insulating layer to the groove of the first conductive layer obtained in step (1) by using an EVA adhesive, hot-press bonding at a temperature of 110°C, and then trimming the edge; the size of the PET insulating layer is: width of 148 mm, thickness of 6 μm.

[0098] S2. Preparation of a second conductive layer

[0099] (3) Vacuum evaporation on the second surface opposite to the first surface of the PET insulating layer in S1, first depositing an aluminum oxide layer of 10 nm on the second surface of the PET insulating layer in a chemical vapor deposition manner, and then thickening the aluminum layer to a thickness of 1 μm of the second conductive layer in a physical vapor deposition manner to obtain a second conductive layer, wherein the second conductive layer only includes a second active material support area; then trimming the edge and winding to obtain a composite current collector.

[0100] The structure of the composite current collector prepared in Example 2 is shown in FIG. 2. Figure 2 As shown in FIG. 2, the width of the composite current collector is 180 mm, wherein the width of the first active material support area 12 and the second active material support area 32 is 150 mm, and the first tab area 11 and the second tab area 31 on both sides are connected to form a tab area, and the width of both sides is 15 mm.

[0101] Example 3

[0102] The width of the PET insulating layer and the groove width of the aluminum foil in Example 1 are replaced with 152 mm, and the remaining operation steps refer to Example 1.

[0103] Example 4

[0104] The width of the PET insulation layer and the width of the aluminum foil groove in Example 2 are replaced with 152 mm, and the remaining operation steps refer to Example 2.

[0105] Comparative Example 1

[0106] First, 10 nm of an aluminum oxide layer is deposited on the opposite surfaces of a PET insulation layer with a thickness of 4 μm in a chemical vapor deposition manner, then the aluminum oxide layer is thickened to 1 μm in a physical vapor deposition manner, and then tab welding is performed on both ends of the composite current collector prepared in the above steps to prepare a conventional composite aluminum foil current collector.

[0107] Effect Example 1: Tab Tensile Force

[0108] The composite current collectors of Examples 1-4 and Comparative Example 1 are tested for tab tensile force using a Vantage tensile tester, and sampling is performed according to the tab tensile force sampling requirements. The sample size is taken according to the actual situation, and the width is controlled to be 15 mm, and the test speed is 5 mm / min. The test results are shown in Table 1.

[0109] Effect Example 2: Tab Welding Resistance

[0110] The current collector prepared in Comparative Example 1 is tested for resistance using a low resistance measuring needle for a direct current resistance meter, the model number is Riken RM3545-02, the test range is 1200000 mΩ, and the resolution is 1 uΩ. The four contact points of the test wire are connected to the four contact points of the resistance to be measured, and then the measurement is started and the result is read. The test results are shown in Table 1.

[0111] Table 1

[0112]

[0113] The composite current collector designed in the present application does not introduce tab welding resistance because it does not need tab welding. In addition, the tab tensile force is also significantly improved compared to the conventional composite aluminum foil current collector. The tab tensile force of the composite current collector prepared in the examples is all above 132 N, which is improved by more than 15.7% compared to the prior art. The tab tensile force of the composite current collectors with different structures within the scope of the present application differs due to differences in contact surfaces, etc.

[0114] The above examples are only part of the embodiments of the present application, which can be understood and used by those skilled in the art. Obviously, any skilled person in the art can make slight modifications or changes without creative labor and apply them to other embodiments. Therefore, the present application is not limited to the above examples, and any equivalent changes, simple modifications and modifications within the scope of the present application still belong to the scope of the present application.

Claims

1. A composite current collector, characterized by, It comprises an insulating layer, a first conductive layer and a second conductive layer, the insulating layer is arranged between the first conductive layer and the second conductive layer; The first conductive layer comprises a first active material support area and a first tab area, the first active material support area is connected with a first surface of the insulating layer; the first tab area is not in contact with the first surface of the insulating layer and is in contact with a third surface; the third surface refers to at least one side surface perpendicular to the first surface; The second conductive layer comprises a second active material support area, the second active material support area is in contact with a second surface of the insulating layer; The first surface and the second surface are two opposite surfaces; The first tab area and the second conductive layer are in contact.

2. The composite current collector of claim 1, wherein The first conductive layer satisfies one or both of the following conditions a-b: a. The material of the first conductive layer is copper foil or aluminum foil; b. The width of the first conductive layer is greater than the width of the insulating layer.

3. The composite current collector of claim 2, wherein The second conductive layer satisfies one or more of the following conditions c-e: c. The material of the second conductive layer is copper foil or aluminum foil; d. The thickness of the second conductive layer is 1-2 μm, the thickness of the second conductive layer refers to the thickness of the area where the second conductive layer is in contact with the insulating layer; e. The width of the second conductive layer is greater than or equal to the width of the insulating layer.

4. The composite current collector of claim 1, wherein The insulating layer satisfies one or both of the following conditions f and g: f. The material of the insulating layer is one or more of polypropylene, polyethylene terephthalate and polyimide; g. The thickness of the insulating layer is 4-8 μm.

5. A method of making a composite current collector as claimed in any one of claims 1 to 4, characterised in that, It comprises the following steps: S1. Bonding a metal foil to a first surface of an insulating layer to form a first conductive layer, the first conductive layer comprising a first active material support area and a first tab area; S2. Forming a second conductive layer on the second surface of the insulating layer or the second surface of the insulating layer and the first tab area by plating; the second conductive layer comprises a second active material support area; Wherein, the first surface and the second surface are two opposite surfaces.

6. The method of making a composite current collector of claim 5, wherein, Step S1 satisfies one or more of the following conditions i-j: i. The metal foil has a groove, wherein the height of the groove is equal to the thickness of the insulating layer or the sum of the thickness of the insulating layer and the second conductive layer; j. The bonding is to form a bonding layer by hot pressing the adhesive to connect the metal foil and the insulating layer, the temperature of the hot pressing is 10-15℃ higher than the glass transition temperature of the adhesive.

7. The method of making a composite current collector of claim 5, wherein, The plating method in step S2 is one or more of vacuum evaporation, electroplating, magnetron sputtering and chemical vapor deposition.

8. An electrode sheet characterized by It comprises a composite current collector as claimed in any one of claims 1-5 and an electrode material layer arranged on at least one surface of the composite current collector.

9. An electrochemical device, characterized by, It comprises an electrode sheet as claimed in claim 8.

10. An electronic device, comprising: It comprises an electrochemical device as claimed in claim 9.

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