Multilayer distributed current collector with improved binding force and preparation method thereof, pole piece and battery

Abstract

The application discloses a multilayer distributed current collector with improved binding force and a preparation method thereof, a pole piece and a battery, and comprises a polymer film, a copper foil and an aluminum foil, the two sides of the polymer film are respectively provided with a first adhesive layer and a second adhesive layer, the polymer film is combined with the copper foil on one side through the first adhesive layer and is combined with the aluminum foil on the other side through the first adhesive layer, the side of the copper foil and the side of the aluminum foil facing the polymer film are respectively provided with a hole array, and the combination of the polymer film, the copper foil and the aluminum foil is provided with controllable corrugation. Through the synergistic scheme of nano-hole anchoring and controllable corrugation structure, the interface stability and safety of the pole piece are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a multilayer distributed current collector for improving bonding strength, its preparation method, electrode sheet, and battery. Background Technology

[0002] Traditional electrode plates use positive electrode material coated on the surface of pure aluminum foil and negative electrode material coated on the surface of pure copper foil. Individual cells are manufactured into uniform large cells through winding or stacking processes. However, in this type of battery, defects at any location on the positive and negative electrodes can seriously affect battery safety, limit the diversity of lithium battery structural design, and hinder the application of advanced materials such as solid electrolytes.

[0003] Currently, a novel functional current collector structure has been proposed. An adhesive layer is coated on each side of a polymer film with a certain strength. One side is composited with copper foil, and the other side with aluminum foil, forming a distributed copper-aluminum functional current collector. Subsequently, a positive electrode material is coated or hot-pressed onto the aluminum foil surface, and a negative electrode material is coated or hot-pressed onto the copper foil surface, forming a novel composite electrode. This novel electrode can solve the following problems: reduce the impact of internal stress, which helps to form a long-term stable interface for the solid electrolyte in solid-state lithium battery applications, thereby improving battery life; improve safety: by decomposing a large battery into numerous sub-cells, safety is significantly enhanced in safety tests such as nail penetration; and solve the problem of tab breakage, improving the difficulty of tab breakage in the stacking process. However, this novel electrode still faces certain interlayer bonding strength issues. Summary of the Invention

[0004] The purpose of this invention is to provide a multilayer distributed current collector with improved bonding strength, its preparation method, electrode, and battery. This invention significantly improves the interface stability and safety of the electrode through a synergistic scheme of nanopore anchoring and controllable corrugated structure.

[0005] To achieve the above objectives, the technical solution provided by this invention is as follows: The first aspect of this application provides a multilayer distributed current collector for improving bonding strength, comprising: The polymer film, copper foil, and aluminum foil are provided, wherein the polymer film has a first adhesive layer and a second adhesive layer on its two sides; the polymer film is laminated with the copper foil on one side through the first adhesive layer and with the aluminum foil on the other side through the first adhesive layer. The copper foil and aluminum foil each have an array of pores on the side facing the polymer film; the polymer film combined with the copper foil and aluminum foil has controllable wrinkles.

[0006] To optimize the above technical solution, the specific measures / limitations also include: The aperture array has a diameter of 80~200 nm, a depth of 30~50 nm, and a spacing of 200~400 nm.

[0007] Furthermore, the wavelength range of the controllable folds is 15~25μm, and the amplitude is 3~4μm.

[0008] Furthermore, when copper foil and aluminum foil are laminated, the array of holes in both is arranged in an alternating pattern.

[0009] The second aspect of this application provides a method for preparing a multilayer distributed current collector with improved bonding strength, comprising the following steps: S1: Nanoscale pore arrays are prepared on one side surface of copper foil and aluminum foil respectively; S2: Heating and stretching the aluminum foil with a hole array to deform it; S3: An adhesive layer is coated on one side of the polymer film, and the polymer film is hot-pressed together with a preheated and stretched aluminum foil with a porous array; after the composite is formed, as the deformation stress is released during the cooling process, controllable ripples are formed on the polymer film. S4: Coat the other side of the polymer film with an adhesive layer, and hot-press the other side of the polymer film with a copper foil having a pore array.

[0010] Step S1 involves preparing nanoscale pore arrays on one side of both copper and aluminum foils. The copper foil is processed using reactive ion beam etching, and the aluminum foil is processed using inductively coupled plasma etching.

[0011] Step S2 involves heating and stretching the aluminum foil with the array of holes to deform it by a deformation of 4-7%.

[0012] Furthermore, the heating temperature of the aluminum foil with the hole array is 110~130℃, and the stretching rate is 0.2~0.5mm / s.

[0013] A third aspect of this application provides an electrode sheet comprising the aforementioned multilayer distributed current collector, wherein a positive electrode material is disposed on the surface of the multilayer distributed current collector aluminum foil and a negative electrode material is disposed on the surface of the copper foil.

[0014] A fourth aspect of this application provides a battery comprising the aforementioned electrode.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention prepares nanoscale pore arrays on one side of copper foil and aluminum foil respectively. The aluminum foil with the pore array is heated and stretched to deform, forming controllable ripples on the composite polymer film. The synergistic effect of the nanoscale pore array and the controllable folds significantly improves the bonding force. The nanoscale pores on the surface of the copper foil and aluminum foil form a riveted mechanical anchoring structure with the polymer material. The directional ripples formed on the surface of the polymer film can absorb the thermal stress deformation during battery charging and discharging, and prevent the interface from delaminating due to repeated expansion and contraction. The pore anchoring provides basic bonding force, while the ripple structure converts the in-plane stress into the bending deformation of the ripples, preventing stress concentration from causing the anchoring point to fail in a chain reaction, thereby protecting the anchoring interface.

[0016] Furthermore, when copper foil and aluminum foil are combined, the pore arrays of the two are arranged in an alternating manner to optimize stress dispersion. The pore anchoring points are evenly distributed in three-dimensional space to avoid stress concentration. After the polymer penetrates into the pores, it forms a cross-anchoring network, resulting in mechanical interlocking reinforcement. Detailed Implementation

[0017] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0018] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the reagents, methods and equipment used are conventional reagents, methods and equipment in this technical field.

[0019] This invention provides a multilayer distributed current collector for improving bonding strength, comprising: The polymer film comprises a polymer film, a copper foil, and an aluminum foil, with a first adhesive layer and a second adhesive layer on each side of the polymer film; the polymer film is bonded to the copper foil on one side via the first adhesive layer, and to the aluminum foil on the other side via the first adhesive layer. The copper foil and aluminum foil each have an array of pores on the side facing the polymer film; the polymer film combined with the copper foil and aluminum foil has controllable wrinkles.

[0020] The present invention achieves a significant improvement in bonding strength through the synergistic effect of nanopore arrays and controllable wrinkles. During hot-pressing composite, some polymer materials penetrate into the nanopores on the surface of copper and aluminum foils, forming a riveted mechanical anchoring structure after cooling. After pre-stretching and composite, the aluminum foil forms directional ripples on the surface of the polymer film during cooling and shrinkage. This wrinkled structure can absorb thermal stress deformation during battery charging and discharging, preventing the interface from delaminating due to repeated expansion and contraction. Furthermore, the riveted mechanical anchoring and the wrinkled structure work synergistically: the pore anchoring provides basic bonding strength, while the rippled structure converts in-plane stress into wavy deformation, preventing stress concentration from causing a chain failure of the anchoring point, thereby protecting the anchoring interface and achieving a balance between strength and toughness.

[0021] In some implementations, the aperture array has a diameter of 80-200 nm, a depth of 30-50 nm, and a spacing of 200-400 nm.

[0022] In some implementations, the wavelength range of the controllable folds is 15~25μm, and the amplitude is 3~4μm.

[0023] In some embodiments, when copper foil and aluminum foil are composited, their pore arrays are arranged in an alternating pattern. This alternating arrangement of pore arrays optimizes stress dispersion, ensures uniform distribution of pore anchoring points in three-dimensional space, avoids stress concentration, and allows the polymer to penetrate the pores to form a cross-anchoring network, creating mechanical interlocking reinforcement. Furthermore, during battery charge-discharge cycles, the alternating pores can suppress crack propagation paths.

[0024] The adhesive of the present invention can be a water-soluble adhesive, a hot-melt adhesive, a solvent-based adhesive, an emulsion adhesive, a solvent-free liquid adhesive, or a pellet adhesive; generally preferred adhesives include epoxy-imide composite adhesives, waterborne polyurethane acrylic adhesives, silane-modified polyester adhesives, conductive polypyrrole / epoxy adhesives, and thermoplastic polyimide adhesives.

[0025] Generally, the thickness of the copper foil of the present invention can be 3~15μm; the thickness of the aluminum foil of the present invention can be 5~18μm; and the thickness of the polymer film of the present invention can be 5~15μm.

[0026] This invention also provides a method for preparing a multilayer distributed current collector with improved bonding strength, comprising the following steps: S1: Nanoscale pore arrays are prepared on one side surface of copper foil and aluminum foil respectively; S2: Heating and stretching the aluminum foil with a hole array to deform it; S3: An adhesive layer is coated on one side of the polymer film, and the polymer film is hot-pressed together with a preheated and stretched aluminum foil with a porous array; after the composite is formed, as the deformation stress is released during the cooling process, controllable ripples are formed on the polymer film. S4: Coat the other side of the polymer film with an adhesive layer, and hot-press the other side of the polymer film with a copper foil having a pore array.

[0027] In some embodiments, step S1 involves preparing nanoscale pore arrays on one side of the copper foil and the aluminum foil, respectively. The copper foil is processed by reactive ion beam etching, and the aluminum foil is processed by inductively coupled plasma etching.

[0028] In some embodiments, step S2 involves heating and stretching the aluminum foil with the perforated array to deform it by a deformation of 4-7%. The heating temperature of the aluminum foil with the perforated array is 110-130°C, and the stretching rate is 0.2-0.5 mm / s.

[0029] The present invention also provides an electrode sheet comprising the above-mentioned multilayer distributed current collector for improving bonding strength, wherein a positive electrode material is coated or hot-pressed onto the surface of the multilayer distributed current collector aluminum foil, and a negative electrode material is coated or hot-pressed onto the surface of the copper foil.

[0030] The present invention also provides a battery comprising electrode sheets, wherein the electrode sheets are die-cut; the cut electrode sheets are stacked using a stacking device; and the stacked electrode sheets are assembled, baked, injected with electrolyte, aged, formed, and capacity tested to form a battery cell.

[0031] The peel test involved in this invention is as follows: Cut the prepared electrode sheet into long strips, then attach 3M double-sided tape to the back of the strips. Attach the other side of the tape to the prepared glass slide, then attach the 3M double-sided tape to the surface of the electrode. After flipping the tape, attach one side of the tape to the upper clamp of the computer-controlled electronic universal testing machine, and attach the other end of the glass slide to the lower clamp of the testing machine. Select the tension-displacement mode and the tensile speed as 5 mm / min.

[0032] The technical solution of the present invention will be further described in detail below with reference to specific embodiments: Example 1 This embodiment uses a 5μm thick copper foil, a 7μm thick aluminum foil, and an 8μm thick PVDF film. The steps are as follows: 1. Nanoscale pore arrays were fabricated on one side surface of copper foil and aluminum foil, respectively: Copper foil treatment: Reactive ion beam etching (RIE), gas ratio CF4 / O2=4:1, power 200W, etching time 90s; Aluminum foil processing: Inductively coupled plasma etching (ICP) using Cl2 / BCl3 mixed gas, cavity pressure 5mTorr, and RF power 300W.

[0033] 2. Heating and stretching the aluminum foil with an array of holes to deform it: Aluminum foil heating conditions: Preheat in a 125℃ constant temperature chamber for 3 minutes; Tensile parameters of the micro-force testing machine: deformation 5%, tensile rate 0.3 mm / s.

[0034] 3. An adhesive layer is coated on one side of the polymer film, and the polymer film is then hot-pressed together with a preheated and stretched aluminum foil with a porous array. After lamination, as the deformation stress is released during the cooling process, controllable ripples are formed on the polymer film. One side of the PVDF membrane is coated with an adhesive: epoxy-imide composite adhesive, with a coating thickness of 3μm; It is hot-pressed with preheated and stretched aluminum foil with a porous array. The hot-pressing parameters are: 190℃, 10MPa pressure for 60 seconds, and then naturally cooled to room temperature to form regular wrinkles with a wavelength of 16~20μm and a wrinkle amplitude of 3~4μm.

[0035] 4. Apply an adhesive layer to the other side of the polymer film, and then hot-press the other side of the polymer film with a copper foil having a porous array: An adhesive is coated on the other side of the PVDF membrane: an epoxy-imide composite adhesive, with a coating thickness of 3μm. Hot-pressed composite with copper foil having a perforated array, hot-pressing parameters: 190℃, 10MPa pressure held for 60 seconds; Furthermore, during the composite process, the holes in the copper foil and the array of holes in the aluminum foil are arranged in a completely staggered manner.

[0036] The peel strength of the electrode prepared in Example 1 was tested and found to be 3.50 N / mm.

[0037] Example 2 The process of this embodiment is basically the same as that of embodiment 1, except that in the hot pressing composite step 4, the holes of the copper foil and the hole array of the aluminum foil are arranged in a semi-staggered manner.

[0038] The peel strength of the electrode prepared in Example 2 was tested and found to be 3.00 N / mm.

[0039] Example 2: Half-interlaced holes lead to decreased anchoring density: When the holes are only half-interlaced, the stress distribution is uneven and the local shear stress is high, so the effect is not as good as in Example 1.

[0040] In addition, the electrochemical performance of the batteries prepared from the electrodes of Examples 1 and 2 meets the application standards.

[0041] Comparative Example 1 The conventional process was used, which did not involve the step of preparing a hole array on the surface of the copper foil and aluminum foil, nor the step of heating and stretching the aluminum foil with the hole array. Other parameters were the same as in Example 1.

[0042] The peel strength of the electrode prepared in Comparative Example 1 was tested and found to be 1.6 N / mm.

[0043] Comparative Example 1 relies solely on intermolecular forces of the adhesive, primarily van der Waals forces, resulting in a significant decrease in peel strength compared to Example 1.

[0044] Comparative Example 2 This comparative example does not include the step of preparing a hole array on the surface of copper foil and aluminum foil, but it does include the step of heating and stretching the aluminum foil with the hole array, with the same parameters as in Example 1.

[0045] The peel strength of the electrode prepared in Comparative Example 2 was tested and found to be 2.0 N / mm.

[0046] Although the wrinkles in Comparative Example 2 can provide some buffer stress, they lack mechanical anchoring points and are prone to large-area interface separation during peeling tests.

[0047] Comparative Example 3 This comparative example does not include the step of heating and stretching the aluminum foil with the hole array, but it does include the step of preparing the hole array on the surface of the copper foil and aluminum foil, with the same parameters as in Example 1.

[0048] The peel strength of the electrode prepared in Comparative Example 3 was tested and found to be 2.4 N / mm.

[0049] Comparative Example 3: Hole anchoring provides basic strength, but the anchoring point is subjected to alternating shear forces during cycling. After 200 cycles, microcracks easily appear around the holes in the battery made from this electrode.

[0050] Comparative Example 4 The process of this comparative example is basically the same as that of Example 1, except that the deformation is 2% in the tensile deformation of step 2.

[0051] The peel strength of the electrode prepared in Comparative Example 4 was tested and found to be 2.2 N / mm.

[0052] The aluminum foil in Comparative Example 4 had too small a tensile deformation and insufficient wrinkle development, with a wrinkle amplitude of only 1.5~2.0μm, resulting in high stress at the anchoring point of the hole anchor.

[0053] Comparative Example 5 The process of this comparative example is basically the same as that of Example 1, except that the deformation is 10% in the tensile deformation of step 2.

[0054] The peel strength of the electrode prepared in Comparative Example 5 was tested and found to be 2.7 N / mm.

[0055] In Comparative Example 5, excessive stretching caused wrinkles with an amplitude of 5-6 μm, but the large-amplitude wrinkles caused local buckling of the polymer film, resulting in microvoids during hot-pressing composite.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A multilayer distributed current collector for improving bonding strength, characterized in that, include: The polymer film, copper foil, and aluminum foil are provided, wherein the polymer film has a first adhesive layer and a second adhesive layer on its two sides; the polymer film is laminated with the copper foil on one side through the first adhesive layer and with the aluminum foil on the other side through the first adhesive layer. The copper foil and aluminum foil each have an array of pores on the side facing the polymer film; the polymer film combined with the copper foil and aluminum foil has controllable wrinkles.

2. The multilayer distributed current collector for improving bonding strength according to claim 1, characterized in that: The aperture array has a diameter of 80~200 nm, a depth of 30~50 nm, and a spacing of 200~400 nm.

3. The multilayer distributed current collector for improving bonding strength according to claim 1, characterized in that: The wavelength range of the controllable folds is 15~25μm, and the amplitude is 3~4μm.

4. The multilayer distributed current collector for improving bonding strength according to claim 1, characterized in that: When copper foil and aluminum foil are laminated, the array of holes in both is arranged in an alternating pattern.

5. The method for preparing a multilayer distributed current collector with improved bonding force according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Nanoscale pore arrays are prepared on one side surface of copper foil and aluminum foil respectively; S2: Heating and stretching the aluminum foil with a hole array to deform it; S3: An adhesive layer is coated on one side of the polymer film, and the polymer film is hot-pressed together with a preheated and stretched aluminum foil with a porous array; after the composite is formed, as the deformation stress is released during the cooling process, controllable ripples are formed on the polymer film. S4: Coat the other side of the polymer film with an adhesive layer, and hot-press the other side of the polymer film with a copper foil having a pore array.

6. The method for preparing a multilayer distributed current collector with improved bonding strength according to claim 5, characterized in that: Step S1 involves preparing nanoscale pore arrays on one side of both copper and aluminum foils. The copper foil is processed using reactive ion beam etching, and the aluminum foil is processed using inductively coupled plasma etching.

7. The method for preparing a multilayer distributed current collector with improved bonding strength according to claim 5, characterized in that: Step S2 involves heating and stretching the aluminum foil with the array of holes to deform it by a deformation of 4-7%.

8. The method for preparing a multilayer distributed current collector with improved bonding strength according to claim 7, characterized in that: The heating temperature for the aluminum foil with a hole array is 110~130℃, and the stretching rate is 0.2~0.5mm / s.

9. An electrode sheet, characterized in that: The multilayer distributed current collector with improved bonding strength is prepared by the method described in any one of claims 1 to 4 or any one of claims 5 to 8, wherein a positive electrode material is disposed on the surface of the aluminum foil of the multilayer distributed current collector and a negative electrode material is disposed on the surface of the copper foil.

10. A battery, characterized in that: It includes the electrode sheet as described in claim 9.