Double-sided communicated functional current collector and preparation method and application thereof

Abstract

The invention provides a double-sided communicated functional current collector and a preparation method and application thereof.The double-sided communicated functional current collector comprises a macromolecule base film layer and metal layers arranged on the surfaces of the two sides of the macromolecule base film layer, and through holes are distributed in the surface of the double-sided communicated functional current collector; and the metal layers cover the inner walls of the through holes, so that the metal layers on the surfaces of the two sides of the macromolecular base film layer are directly conducted. The preparation method comprises the following steps: (1) punching a macromolecular base film to obtain a macromolecular base film layer of which the surface is provided with through holes; (2) depositing metal layers on the two side surfaces of the macromolecular base film layer and the inner walls of the through holes in a chemical plating manner; and (3) thickening the metal layer to a target thickness by adopting a water electroplating mode to obtain the double-sided communicated functional current collector. According to the functional current collector provided by the invention, the problems of difficult conduction, limited flow conductivity and low electrolyte infiltration efficiency of the existing composite copper foil double-sided metal layer are effectively solved, and the battery performance is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of battery manufacturing technology, and relates to a functional current collector, particularly a double-sided connected functional current collector and its preparation method and application. Background Technology

[0002] Against the backdrop of the rapid development of the new energy industry, lithium batteries, as core energy storage devices, have seen their energy density, safety, lightweight design, and production efficiency become key areas for technological breakthroughs. Current collectors, as crucial components within lithium batteries that carry active materials and conduct current, directly impact the overall performance of the battery. Currently, lithium batteries primarily use traditional aluminum and copper foil as current collectors, but these suffer from high density and weight, hindering further improvements in battery lightweighting and energy density.

[0003] To address the aforementioned issues, composite copper foil utilizes a sandwich structure of a "middle polymer base film + double-sided metal layers," achieving advantages in weight reduction and thinning. Furthermore, the insulating properties of the polymer base film significantly improve battery puncture safety, making it a crucial development direction for current collector technology. However, the structural characteristics of composite copper foil also introduce new technical challenges: the middle polymer base film itself is insulating, preventing direct conductivity between the upper and lower double-sided metal layers. Since current conduction is a prerequisite for the current collector to function, this issue directly limits the industrial application of composite copper foil.

[0004] To address the conductivity issue of the AB side metal layers, the industry primarily employs an adapter soldering process: two independent copper foils are soldered to the AB sides of the composite current collector to draw out the current. However, this solution requires an additional adapter soldering step, which not only extends the cell production process and increases processing costs, but also occupies effective space at the tab location due to the soldering width. More importantly, the current can only be conducted through the width of the solder wire, and the current-conducting area is limited by the solder wire size, resulting in insufficient current-conducting capacity and consequently increasing the cell's internal resistance.

[0005] In addition, existing composite copper foils also suffer from low electrolyte wetting efficiency. Due to the dense structure of the polymer base film and the metal layer, the electrolyte has difficulty penetrating into the electrode quickly, resulting in prolonged electrolyte injection time and affecting cell production efficiency. At the same time, uneven electrolyte distribution can easily lead to localized low lithium-ion concentrations, causing lithium plating and reducing battery cycle life and safety.

[0006] Therefore, how to provide a current collector that overcomes the shortcomings of existing composite copper foil double-sided metal layer, such as difficulty in conducting current, limited current carrying capacity, and low electrolyte wetting efficiency, and improves battery performance, has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a double-sided connected functional current collector, its preparation method, and its application, overcoming the defects of existing composite copper foil double-sided metal layer poor conductivity, limited current carrying capacity, and low electrolyte wetting efficiency, thereby improving battery performance.

[0008] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a double-sided interconnected functional current collector, comprising a polymer base film layer and a metal layer disposed on both sides of the polymer base film layer. The surface of the double-sided interconnected functional current collector is provided with through holes, and the metal layer covers the inner wall of the through holes, so that the metal layers on both sides of the polymer base film layer are directly connected.

[0009] This invention features through-holes on the surface of the functional current collector and a metal layer covering the inner wall of the through-holes. This enables direct conduction of the metal layers on both sides of the polymer base film without the need for transfer welding, thereby improving the production efficiency of the battery cell, reducing the internal resistance and conductive loss of the battery cell, and simultaneously leveraging the weight reduction advantage, which helps to improve the energy density of the battery.

[0010] In addition, the capillary permeation effect of the through holes shortens the electrolyte injection and immersion time, and the through holes can fill more electrolyte and active materials, improve the lithium-ion transport environment, effectively prevent lithium plating in the cell, and improve battery safety and cycle life. The perforated design increases the contact surface area between the current collector and the electrolyte and active materials, and the through holes keep the solution concentration on both sides of the electrode balanced, significantly optimizing the battery's rate discharge performance.

[0011] Preferably, the through hole satisfies at least one of the following conditions: The average diameter of the through hole is 5-500 μm; The spacing between adjacent through holes is 0.1-10 mm; The through hole has an annular protrusion structure on at least one side; The metal layer has a 100% coverage rate on the inner wall of the through hole; The strength ratio of (111) / (200) of the metal layer on the inner wall of the through hole is (1-5):1; The carbon content of the inner wall of the through hole is 0.1%-20% by mass, more preferably 0.1%-5%; The thickness of the metal layer on the inner wall of the through hole is thinner than the thickness of the metal layer on both sides of the polymer base film layer.

[0012] Preferably, the thickness of the metal layer on the inner wall of the through hole is 1 / 5 to 4 / 5 of the thickness of the metal layer on both sides of the polymer base film layer.

[0013] Preferably, the through holes exhibit a non-uniform hole diameter distribution along the length direction of the functional current collector, and the hole diameter in the electrode welding area is larger than the hole diameter in the non-electrode welding area.

[0014] Preferably, the diameter of the through hole in the electrode welding area is 50-100 μm.

[0015] Preferably, the diameter of the through hole in the non-tab welding area is 5-50 μm.

[0016] Preferably, the through holes exhibit a non-uniform hole spacing distribution along the length direction of the functional current collector, with the hole spacing in the tab welding area being smaller than the hole spacing in the non-tab welding area.

[0017] Preferably, the hole spacing in the electrode welding area is 0.1-5mm.

[0018] Preferably, the hole spacing in the non-tab welding area is 5-10 mm.

[0019] Preferably, an underlayer is provided between the polymer base film layer and the metal layer.

[0020] Preferably, the material of the underlayer includes palladium.

[0021] Preferably, the thickness of the underlayer is 20-100 nm.

[0022] Preferably, the polymer base film layer is made of at least one of polyethylene terephthalate (PET), polypropylene (PP), or polyimide (PI).

[0023] Preferably, the thickness of the polymer base film layer is 2-8 μm.

[0024] Preferably, the metal layer is made of at least one of copper, aluminum, zinc, iron, nickel, titanium, gold, silver, or chromium.

[0025] Preferably, the thickness of the metal layer is 0.8-1.2 μm.

[0026] Preferably, the metal layers on both sides of the polymer base film layer are made of the same or different materials.

[0027] In a second aspect, the present invention provides a method for preparing a two-sided interconnected functional current collector as described in the first aspect, comprising the following steps: (1) The polymer base film is perforated to obtain a polymer base film layer with through holes distributed on the surface; (2) A metal layer is deposited on both sides of the polymer base film and on the inner wall of the through hole by chemical plating; (3) The metal layer is thickened to the target thickness by electroplating to obtain a double-sided connected functional current collector.

[0028] This invention produces a double-sided interconnected functional current collector by sequentially performing drilling, chemical plating, and electroplating, eliminating additional processing steps such as transfer welding, simplifying the battery production process, significantly improving cell production efficiency, and reducing production costs.

[0029] Preferably, the drilling process in step (1) includes laser drilling.

[0030] Preferably, the laser type used for laser drilling includes nanosecond lasers.

[0031] Preferably, before the chemical plating in step (2), the polymer base film layer is subjected to cleaning treatment and ion beam treatment in sequence.

[0032] Preferably, the activation solution used in step (2) of the electroless plating contains palladium salt and reducing agent.

[0033] Preferably, the current intensity used in the electroplating process in step (3) is 4-25A.

[0034] Preferably, after electroplating in step (3), the functional current collector is sequentially washed with water, subjected to anti-oxidation, dried and wound up.

[0035] Thirdly, the present invention provides a bipolar battery comprising a bipolar interconnected functional current collector as described in the first aspect, wherein the metal layers on the two sides of the polymer base film layer of the bipolar interconnected functional current collector are made of different materials, one side is used to conduct positive electrode current and the other side is used to conduct negative electrode current, the surface of the current collector that conducts positive electrode current is provided with a positive electrode active material layer, and the surface of the current collector that conducts negative electrode current is provided with a negative electrode active material layer.

[0036] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides through holes on the surface of the functional current collector and covers the inner wall of the through holes with a metal layer, thereby realizing direct conduction of the metal layers on both sides of the polymer base film layer without the need for transfer welding, which improves the production efficiency of the battery cell, reduces the internal resistance and conductive loss of the battery cell, and at the same time plays the advantage of weight reduction, which helps to improve the energy density of the battery.

[0037] (2) The capillary permeation effect of the through hole shortens the electrolyte injection and immersion time, and the through hole can fill more electrolyte and active materials, improve the lithium-ion transport environment, effectively prevent lithium plating in the cell, and improve battery safety and cycle life; the perforation design increases the contact surface area between the current collector and the electrolyte and active materials, and the through hole keeps the solution concentration on both sides of the electrode balanced, significantly optimizing the battery rate discharge performance.

[0038] (3) The present invention obtains a double-sided connected functional current collector by sequentially performing drilling, chemical plating and electroplating, eliminating additional processing steps such as transfer welding, simplifying the battery production process, greatly improving the cell production efficiency and reducing production costs. Attached Figure Description

[0039] Figure 1 These are schematic diagrams of partial cross-sectional structures of the double-sided connected functional current collector provided in Examples 1-15.

[0040] Figure 2 This is a micrograph of the double-sided interconnected functional current collector through-hole provided in Example 1.

[0041] Figure 3 This is a schematic diagram of the distribution of the double-sided connected functional current collector through holes provided in Example 15.

[0042] Wherein: 1-polymer base film layer; 2-metal layer; 3-through pore. Detailed Implementation

[0043] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0044] One embodiment of the present invention provides a double-sided interconnected functional current collector, including a polymer base film layer and metal layers disposed on both sides of the polymer base film layer. The surface of the double-sided interconnected functional current collector is distributed with through holes, and the metal layers cover the inner walls of the through holes, so that the metal layers on both sides of the polymer base film layer are directly connected.

[0045] This invention features through-holes on the surface of the functional current collector and a metal layer covering the inner wall of the through-holes. This enables direct conduction of the metal layers on both sides of the polymer base film without the need for transfer welding, thereby improving the production efficiency of the battery cell, reducing the internal resistance and conductive loss of the battery cell, and simultaneously leveraging the weight reduction advantage, which helps to improve the energy density of the battery.

[0046] In addition, the capillary permeation effect of the through holes shortens the electrolyte injection and immersion time, and the through holes can fill more electrolyte and active materials, improve the lithium-ion transport environment, effectively prevent lithium plating in the cell, and improve battery safety and cycle life. The perforated design increases the contact surface area between the current collector and the electrolyte and active materials, and the through holes keep the solution concentration on both sides of the electrode balanced, significantly optimizing the battery's rate discharge performance.

[0047] In some embodiments, the through hole satisfies at least one of the following conditions: The average aperture of the through hole is 5-500μm, for example, it can be 5μm, 10μm, 50μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm or 500μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] The hole spacing between adjacent through holes is 0.1-10mm, for example, it can be 0.1mm, 0.5mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm or 10mm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0049] The through-hole has an annular protrusion structure on at least one side. This structure can be achieved by adjusting the laser drilling parameters, thereby significantly improving the bonding force between the current collector and the active material layer.

[0050] The metal layer has a 100% coverage rate on the inner wall of the through hole, which is achieved through a combination of electroless plating and electroplating.

[0051] The strength ratio of (111) / (200) of the metal layer on the inner wall of the through hole is (1-5):1, for example, it can be 1:1, 2:1, 3:1, 4:1 or 5:1, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] Since the existing through-hole inner wall metal layer has insufficient ductility and fatigue resistance, when the ratio of the diffraction peak heights of the (111) crystal plane and the (200) crystal plane is controlled within the above range, the plastic deformation ability of the metal layer can be strengthened, which can better adapt to the volume expansion during the charging and discharging of silicon-carbon negative electrode and reduce the risk of cracking of the metal layer on the inner wall of the through hole.

[0053] For example, in some embodiments of the present invention, the (111) / (200) strength ratio of the metal layer on the inner wall of the through hole can be adjusted by reducing the plating temperature or current density, increasing the inhibitor concentration, or reducing the accelerator concentration.

[0054] The carbon content of the inner wall of the through hole is 0.1%-20% by mass, for example, it can be 0.1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18% or 20%, and is more preferably 0.1%-5%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0055] The present invention limits the carbon content of the inner wall of the through hole to 0.1%-20% by mass, which can significantly improve the contact between the electrode and the electrolyte and enhance the wettability of the electrolyte. In particular, when focusing on improving the wear resistance of the inner wall of the through hole, in order to avoid the problem of inner wall damage during subsequent preparation, the carbon content of the inner wall of the through hole can be limited to 0.1%-5% by mass.

[0056] The thickness of the metal layer on the inner wall of the through hole is thinner than the thickness of the metal layer on both sides of the polymer base film layer.

[0057] In some embodiments, the thickness of the metal layer on the inner wall of the through hole is 1 / 5 to 4 / 5 of the thickness of the metal layer on both sides of the polymer base film layer. For example, it can be 1 / 5, 1.5 / 5, 2 / 5, 2.5 / 5, 3 / 5, 3.5 / 5 or 4 / 5, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0058] In some embodiments, the through holes exhibit a non-uniform aperture distribution along the length direction of the functional current collector, with the aperture diameter in the tab welding area being larger than that in the non-tab welding area.

[0059] In some embodiments, the aperture of the through hole in the tab welding area is 50-100μm, for example, it can be 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm or 100μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0060] In some embodiments, the aperture of the through hole in the non-tab welding area is 5-50 μm, for example, it can be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0061] In some embodiments, the through holes exhibit a non-uniform hole spacing distribution along the length direction of the functional current collector, with the hole spacing in the tab welding area being smaller than the hole spacing in the non-tab welding area.

[0062] The above structure can effectively solve the problem of edge warping in the tab area after rolling the active material area, thereby improving the flatness of the electrode sheet after rolling to a certain extent.

[0063] In some embodiments, the hole spacing of the electrode welding area is 0.1-5mm, for example, it can be 0.1mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm or 5mm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0064] In some embodiments, the hole spacing in the non-tab welding area is 5-10 mm, for example, it can be 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm or 10 mm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0065] This invention defines that the through holes have a non-uniform hole diameter distribution and / or a non-uniform hole spacing distribution along the length direction of the functional current collector, that is, to ensure large-diameter through holes and / or narrow-spacing through holes in the tab region, thereby significantly increasing the current conduction area and effectively solving the problem of current concentration near the tab in a uniform hole diameter structure.

[0066] In some embodiments, an underlayer is also provided between the polymer base film layer and the metal layer.

[0067] In some embodiments, the material of the underlay includes palladium.

[0068] In some embodiments, the thickness of the underlay layer is 20-100nm, for example, it can be 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0069] In some embodiments, the polymer base film layer is made of at least one of polyethylene terephthalate, polypropylene, or polyimide.

[0070] In some embodiments, the thickness of the polymer base film layer is 2-8 μm, for example, it can be 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 or 8 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0071] In some embodiments, the metal layer is made of at least one of copper, aluminum, zinc, iron, nickel, titanium, gold, silver, or chromium.

[0072] In some embodiments, the thickness of the metal layer is 0.8-1.2 μm, for example, it can be 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1 μm, 1.05 μm, 1.1 μm, 1.15 μm or 1.2 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0073] In some embodiments, the metal layers on both sides of the polymer base film layer are made of the same or different materials.

[0074] One embodiment of the present invention also provides a method for preparing the double-sided connected functional current collector as described in any of the above embodiments, comprising the following steps: (1) The polymer base film is perforated to obtain a polymer base film layer with through holes distributed on the surface; (2) A metal layer is deposited on both sides of the polymer base film and on the inner wall of the through hole by chemical plating; (3) The metal layer is thickened to the target thickness by electroplating to obtain a double-sided connected functional current collector.

[0075] This invention produces a double-sided interconnected functional current collector by sequentially performing drilling, chemical plating, and electroplating, eliminating additional processing steps such as transfer welding, simplifying the battery production process, significantly improving cell production efficiency, and reducing production costs.

[0076] In some embodiments, the drilling process in step (1) includes laser drilling.

[0077] In some embodiments, the laser type used for laser drilling includes nanosecond lasers, which not only ensures the accuracy of drilling but also improves drilling efficiency.

[0078] In some embodiments, the polymer base film layer is subjected to cleaning and ion beam treatment sequentially before the chemical plating in step (2).

[0079] Before electroless plating, the polymer base film layer is first cleaned. This is because some dust remains on the surface of the base film layer after the drilling process. The surface is cleaned by gas blowing and brush dust removal. Then, the polymer base film layer is treated with ion beam to roughen its surface, thereby increasing the dyne value, which is conducive to the smooth progress of subsequent electroless plating.

[0080] In some embodiments, the activation solution used in step (2) of the electroless plating contains palladium salt and reducing agent.

[0081] This invention involves immersing a perforated polymer base film in an activation solution containing palladium ions, causing a layer of palladium ions to adsorb onto its surface. These palladium ions act as a catalyst, initiating the subsequent chemical plating reaction. The activation solution used in this invention contains palladium salts (such as PdCl2) and reducing agents (such as sodium hypophosphite), and the reaction principle is as follows: The activated polymer base film is immersed in a chemical plating solution. Palladium ions in the solution are reduced to metallic palladium under the action of a catalyst and deposited on the surface of the polymer base film. During the surface chemical plating process, the activation solution is liquid and can penetrate into the pores of the polymer base film, thereby achieving palladium metal deposition on the inner walls of the pores.

[0082] Since the thickness of the palladium metal activation base layer is at the nanometer level, if chemical plating is used to thicken it to the target thickness, the processing cost is too high. Therefore, this invention performs rapid electroplating to thicken the palladium metal after the nanometer-level base layer. Specifically, a composite copper foil is used as the cathode, with anode plates on the top and bottom. Using a clip plating process, the composite copper is passed through a copper sulfate solution and an electric current is applied, so that the metallic copper is deposited on the palladium metal surface to thicken it.

[0083] In some embodiments, the current intensity used in the electroplating of water in step (3) is 4-25A, for example, it can be 4A, 6A, 8A, 10A, 12A, 14A, 16A, 18A, 20A, 22A, 24A or 25A, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0084] In some embodiments, the concentration of the copper sulfate solution during electroplating is 70-130 g / L, for example, it can be 70 g / L, 75 g / L, 80 g / L, 85 g / L, 90 g / L, 95 g / L, 100 g / L, 105 g / L, 110 g / L, 115 g / L, 120 g / L, 125 g / L or 130 g / L, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0085] In some embodiments, after electroplating in step (3), the functional current collector is sequentially washed with water, subjected to anti-oxidation, dried and wound up.

[0086] In this invention, the antioxidant is hexavalent chromium, and the drying temperature is 70-100℃, for example, it can be 70℃, 75℃, 80℃, 85℃, 90℃, 95℃ or 100℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0087] One embodiment of the present invention also provides a bipolar battery comprising the double-sided interconnected functional current collector described in any of the above embodiments. The metal layers on the two sides of the polymer base film layer of the double-sided interconnected functional current collector are made of different materials. One side is used to conduct positive electrode current, and the other side is used to conduct negative electrode current. The surface of the current collector that conducts positive electrode current is provided with a positive electrode active material layer, and the surface of the current collector that conducts negative electrode current is provided with a negative electrode active material layer.

[0088] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0089] Example 1 This embodiment provides a two-sided interconnected functional current collector and its preparation method, such as... Figure 1 As shown, the double-sided interconnected functional current collector includes a polymer base film layer and metal layers disposed on both sides of the polymer base film layer. The surface of the double-sided interconnected functional current collector is distributed with through holes, and the metal layers cover the inner walls of the through holes, so that the metal layers on both sides of the polymer base film layer are directly connected.

[0090] Specifically, the diameter of the through holes in both the tab region and the non-tab region is 10 μm, and the spacing between the through holes is 3 mm; at least one side of each through hole has an annular protrusion structure (see...). Figure 2 The metal layer has a coverage rate of 100% on the inner wall of the through hole (no damage to the metal layer was found after magnification by scanning electron microscope at 100 times); the strength ratio of (111) / (200) of the metal layer on the inner wall of the through hole is 3:1, and the carbon mass ratio is 0%; the thickness of the metal layer on the inner wall of the through hole is 1 / 5 of the thickness of the metal layer on both sides of the polymer base film layer.

[0091] In addition, a 60nm thick palladium layer (not shown in the figure) is disposed between the polymer base film layer and the metal layer as an underlayer; the polymer base film layer is made of PET and has a thickness of 4μm; the metal layer is made of copper and has a thickness of 1μm.

[0092] The preparation method of the above-mentioned two-sided connected functional current collector includes the following steps: (1) A polymer base film is perforated by using nanosecond laser perforation to obtain a polymer base film layer with through holes distributed on the surface; (2) The polymer base film is cleaned by gas purging and brush dust removal, and then ion beam treatment is performed to roughen its surface. Then the polymer base film is immersed in an activation solution containing PdCl2 and sodium hypophosphite to adsorb a layer of palladium ions on its surface. After reduction reaction, palladium metal is deposited on both sides of the polymer base film and the inner wall of the through hole. (3) The palladium metal was thickened to the target thickness using electroplating. Specifically, a composite copper foil was used as the cathode, with anode plates on both the top and bottom. Using a clip plating process, the composite copper was passed through a 100 g / L copper sulfate solution and an electric current was applied, causing the copper metal to deposit on the palladium metal surface to thicken. The chloride ion concentration in the electroplating solution was 60 ppm, and the current intensity was set to 15 A. Afterward, the functional current collector was sequentially washed with water, subjected to anti-oxidation, dried, and wound up. Hexavalent chromium was used for anti-oxidation, and the drying temperature was 90 °C. Finally, a double-sided connected functional current collector was obtained.

[0093] Example 2 This embodiment provides a double-sided interconnected functional current collector and its preparation method. Except for changing the pore diameter of the through holes in the tab region and the non-tab region to 30 μm, the other structures and conditions are the same as in Example 1, and will not be described in detail here.

[0094] Example 3 This embodiment provides a double-sided interconnected functional current collector and its preparation method. Except for changing the pore diameter of the through holes in the tab region and the non-tab region to 80 μm, the rest of the structure and conditions are the same as in Example 1, and will not be described in detail here.

[0095] Example 4 This embodiment provides a double-sided interconnected functional current collector and its preparation method. Except for changing the hole spacing between the through holes in the tab region and the non-tab region to 1 mm, the rest of the structure and conditions are the same as in embodiment 2, and will not be described in detail here.

[0096] Example 5 This embodiment provides a double-sided connected functional current collector and its preparation method. Except for changing the hole spacing between the through holes in the tab region and the non-tab region to 5mm, the rest of the structure and conditions are the same as in embodiment 2, and will not be described in detail here.

[0097] Example 6 This embodiment provides a double-sided connected functional current collector and its preparation method. Except for changing the hole spacing between the through holes in the tab region and the non-tab region to 10 mm, the other structures and conditions are the same as in embodiment 2, and will not be described in detail here.

[0098] Example 7 This embodiment provides a double-sided connected functional current collector and its preparation method. Except for adjusting the strength ratio of (111) / (200) of the metal layer on the inner wall of the through hole to 1:1, the other structures and conditions are the same as in embodiment 4, and will not be repeated here.

[0099] Example 8 This embodiment provides a double-sided connected functional current collector and its preparation method. Except for adjusting the strength ratio of (111) / (200) of the metal layer on the inner wall of the through hole to 5:1, the other structures and conditions are the same as in embodiment 4, and will not be repeated here.

[0100] Example 9 This embodiment provides a double-sided connected functional current collector and its preparation method. Except for adjusting the strength ratio of (111) / (200) of the metal layer on the inner wall of the through hole to 6:1, the other structures and conditions are the same as in embodiment 4, and will not be repeated here.

[0101] Example 10 This embodiment provides a double-sided connected functional current collector and its preparation method. Except for adjusting the carbon mass ratio of the inner wall of the through hole to 1%, the other structures and conditions are the same as in Example 4, and will not be described in detail here.

[0102] Example 11 This embodiment provides a double-sided interconnected functional current collector and its preparation method. Except for adjusting the carbon mass ratio of the inner wall of the through hole to 3%, the other structures and conditions are the same as in Example 4, and will not be described in detail here.

[0103] Example 12 This embodiment provides a double-sided connected functional current collector and its preparation method. Except for adjusting the carbon mass ratio of the inner wall of the through hole to 5%, the other structures and conditions are the same as in Example 4, and will not be described in detail here.

[0104] Example 13 This embodiment provides a double-sided connected functional current collector and its preparation method. Except for adjusting the carbon mass ratio of the inner wall of the through hole to 15%, the other structures and conditions are the same as in Example 4, and will not be described in detail here.

[0105] Example 14 This embodiment provides a double-sided interconnected functional current collector and its preparation method. The difference between this embodiment and Embodiment 4 is that the through-holes exhibit a non-uniform pore size distribution along the length of the functional current collector (see...). Figure 3 The through-hole diameter in the tab welding area is larger than that in the non-tab welding area. Specifically, the average through-hole diameter in the tab welding area is 50 μm, and the average through-hole diameter in the non-tab welding area is 5 μm. The through-holes exhibit a non-uniform hole spacing distribution along the length direction of the functional current collector, with the hole spacing in the tab welding area being smaller than that in the non-tab welding area. Specifically, the average hole spacing in the tab welding area is 0.1 mm, and the average hole spacing in the non-tab welding area is 5 mm.

[0106] Example 15 The difference between this embodiment and embodiment 14 is that, except for adjusting the carbon content of the inner wall of the through hole to 3%, the rest of the structure and conditions are the same as those in embodiment 14, and will not be repeated here.

[0107] Comparative Example 1 This comparative example provides a double-sided connected functional current collector and its preparation method. Except that the chemical plating in step (2) is replaced by magnetron sputtering, resulting in the metal layer covering the inner wall of the through hole with a coverage of about 95%, the other structures and conditions are the same as in Example 1, and will not be described in detail here.

[0108] Comparative Example 2 This comparative example provides a functional current collector and its preparation method. Except for not performing the perforation treatment in step (1), i.e., the surface of the obtained functional current collector does not have through holes, the rest of the structure and conditions are the same as in Example 1, and will not be described in detail here.

[0109] Comparative Example 3 This comparative example uses conventional copper foil (8μm thick) as the current collector.

[0110] Performance testing (1) Lithium-ion batteries were prepared using the current collectors obtained in Examples 1-15 and Comparative Examples 1-3. The specific preparation method is as follows: (1.1) Preparation of negative electrode sheet: The current collector obtained in the examples and comparative examples is used as the negative electrode current collector; the negative electrode slurry is prepared according to the mass ratio of silicon-carbon composite material (containing 15wt% silicon): conductive agent (SWCNT + Super P): polyacrylic acid (PAA) binder = 90: 3.5: 5.5; the slurry is uniformly coated on the active material coating area of ​​the current collector, and the negative electrode sheet is obtained after drying.

[0111] (1.2) Preparation of positive electrode sheet: Composite aluminum foil is used as positive electrode current collector; positive electrode slurry is prepared according to the mass ratio of NCM622: Super P: carbon nanotube (CNT): polyvinylidene fluoride (PVDF) = 96: 1.8: 0.5: 1.7; the slurry is coated on the active material area of ​​the current collector and then dried to obtain positive electrode sheet.

[0112] (1.3) Lithium-ion battery assembly: The positive electrode, polypropylene (PP) separator and negative electrode prepared above are stacked in sequence to form a bare cell; the bare cell is put into an aluminum-plastic film soft pack shell, electrolyte is injected in a dry environment, and then standard processes such as vacuum sealing, standing, formation and shaping are carried out to finally obtain a soft pack lithium-ion battery.

[0113] (2) The obtained lithium-ion battery was subjected to the following cycle test under a constant temperature environment of 25°C: (2.1) First discharge: Discharge at a constant current of 0.5C to 2.8V (this capacity is not included in the cycle data and is only used for activation); (2.2) Subsequent cycles: First, charge at a constant current and constant voltage of 0.5C to 4.2V (cutoff current is 0.05C), and let stand for 30 minutes; Then discharge at a constant current of 0.5C to 2.8V and let stand for 30 minutes. The above charge-discharge process is defined as one complete cycle. Repeat this process until the battery's discharge capacity decays to 80% of the initial reversible discharge capacity. The cumulative number of cycles completed at this point is the battery's cycle life (unit: cycles).

[0114] In addition, the present invention also tested the penetration resistance of the current collectors obtained in Examples 1-15 and Comparative Examples 1-3 and the corresponding liquid injection time of the cylindrical battery. The relevant test results are shown in Table 1 below.

[0115] Table 1 As can be seen, the present invention sets through holes on the surface of the functional current collector and covers the inner wall of the through holes with a metal layer, realizing direct conduction of the metal layers on both sides of the polymer base film layer without the need for transfer welding, which improves the production efficiency of the cell, reduces the internal resistance and conductive loss of the cell, and at the same time plays the advantage of weight reduction, which helps to improve the energy density of the battery.

[0116] In addition, the capillary permeation effect of the through holes shortens the electrolyte injection and immersion time, and the through holes can fill more electrolyte and active materials, improve the lithium-ion transport environment, effectively prevent lithium plating in the cell, and improve battery safety and cycle life. The perforated design increases the contact surface area between the current collector and the electrolyte and active materials, and the through holes keep the solution concentration on both sides of the electrode balanced, significantly optimizing the battery's rate discharge performance.

[0117] Furthermore, the present invention produces a double-sided interconnected functional current collector by sequentially performing drilling, chemical plating, and electroplating, eliminating additional processing steps such as transfer welding, simplifying the battery production process, significantly improving cell production efficiency, and reducing production costs.

[0118] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A double-sided interconnected functional current collector, comprising a polymer base film layer and metal layers disposed on both surfaces of the polymer base film layer, characterized in that, The surface of the double-sided interconnected functional current collector is distributed with through holes, and the metal layer covers the inner wall of the through holes, so that the metal layers on both sides of the polymer base film layer are directly connected.

2. The double-sided interconnected functional current collector according to claim 1, characterized in that, The through hole satisfies at least one of the following conditions: The average diameter of the through hole is 5-500 μm; The spacing between adjacent through holes is 0.1-10 mm; The through hole has an annular protrusion structure on at least one side; The metal layer has a 100% coverage rate on the inner wall of the through hole; The strength ratio of (111) / (200) of the metal layer on the inner wall of the through hole is (1-5):1; The carbon content of the inner wall of the through hole is 0.1%-20% by mass, more preferably 0.1%-5%; The thickness of the metal layer on the inner wall of the through hole is thinner than the thickness of the metal layer on both sides of the polymer base film layer.

3. The double-sided interconnected functional current collector according to claim 2, characterized in that, The thickness of the metal layer on the inner wall of the through hole is 1 / 5 to 4 / 5 of the thickness of the metal layer on both sides of the polymer base film.

4. The double-sided interconnected functional current collector according to claim 2 or 3, characterized in that, The through holes exhibit a non-uniform hole diameter distribution along the length direction of the functional current collector, with the hole diameter in the electrode welding area being larger than that in the non-electrode welding area. The diameter of the through hole in the electrode welding area is 50-100μm; And / or, the diameter of the through hole in the non-tab welding area is 5-50 μm.

5. The double-sided interconnected functional current collector according to claim 2 or 3, characterized in that, The through holes exhibit a non-uniform hole spacing distribution along the length direction of the functional current collector, with the hole spacing in the electrode welding area being smaller than the hole spacing in the non-electrode welding area. The hole spacing in the electrode welding area is 0.1-5mm; And / or, the hole spacing in the non-tab welding area is 5-10 mm.

6. The double-sided interconnected functional current collector according to claim 2 or 3, characterized in that, An underlayer is also provided between the polymer base film layer and the metal layer; The material of the underlayer includes palladium. And / or, the thickness of the substrate is 20-100nm.

7. The double-sided interconnected functional current collector according to claim 2 or 3, characterized in that, The polymer base film layer is made of at least one of polyethylene terephthalate, polypropylene, or polyimide. And / or, the thickness of the polymer base film is 2-8 μm; And / or, the material of the metal layer includes at least one of copper, aluminum, zinc, iron, nickel, titanium, gold, silver or chromium; And / or, the thickness of the metal layer is 0.8-1.2 μm; And / or, the metal layers on both sides of the polymer base film layer may be made of the same or different materials.

8. A method for preparing a double-sided interconnected functional current collector as described in any one of claims 1-7, characterized in that, The preparation method includes the following steps: (1) The polymer base film is perforated to obtain a polymer base film layer with through holes distributed on the surface; (2) A metal layer is deposited on both sides of the polymer base film and on the inner wall of the through hole by chemical plating; (3) The metal layer is thickened to the target thickness by electroplating to obtain a double-sided connected functional current collector.

9. The method for preparing the double-sided connected functional current collector according to claim 8, characterized in that, The drilling process described in step (1) includes laser drilling; The laser type used in the laser drilling includes nanosecond lasers; And / or, before the chemical plating in step (2), the polymer base film layer is sequentially cleaned and treated with an ion beam; And / or, the activation solution used in step (2) of the electroless plating contains palladium salt and reducing agent; And / or, the current intensity used in the electroplating of water in step (3) is 4-25A; And / or, after the electroplating in step (3), the functional current collector is sequentially washed with water, subjected to anti-oxidation, dried and wound up.

10. A bipolar battery comprising a bifacially connected functional current collector as described in any one of claims 1-7, characterized in that, The polymer base film layer of the double-sided connected functional current collector has different metal layer materials on both sides. One side is used to conduct positive current and the other side is used to conduct negative current. The current collector surface that conducts positive current is provided with a positive active material layer, and the current collector surface that conducts negative current is provided with a negative active material layer.

Images