Functional current collector with low residual stress and preparation method thereof

Abstract

The invention discloses a functional current collector with low residual stress and a preparation method thereof, and the functional current collector comprises a base film which is made of a polymer material; the transition layer is arranged on the surface of the base film; the transition layer contains cadmium and copper; the mass fraction of cadmium in the transition layer is 10-90%, and the mass fraction of copper in the transition layer is 10-90%; and the copper layer is arranged on the surface, far away from the base film, of the transition layer. According to the invention, metal cadmium which has a thermal expansion coefficient closest to that of plastic and is cheaper than that of copper is sputtered on the surface of the polymer high-molecular base material, and the gradient change of cadmium-containing components is controlled to form a copper-cadmium alloy metal layer as a transition layer, so that residual stress caused by different expansion or contraction degrees of plastic and metal due to higher sputtering temperature is reduced, and the service life of the copper-cadmium alloy metal layer is prolonged. The condition of thermal runaway of the battery caused by stress concentration deformation is reduced, and the stability of the battery is improved while the production cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a functional current collector with low residual stress and its preparation method. Background Technology

[0002] The rapid development of new energy vehicles and energy storage has spurred a surge in demand for lithium-ion batteries. However, the limitations of traditional metal current collectors have hindered further development of lithium-ion batteries, leading companies to demand higher performance from current collectors. Currently, lithium-ion batteries relying on metal foil as current collectors suffer from low energy density and poor safety. Therefore, current collectors are evolving towards thinner, lighter, and safer designs. Functional current collectors, as the most promising alternative material, revolutionize traditional current collectors with their "metal-polymer-metal" sandwich structure, improving safety while simultaneously increasing energy density and reducing raw material costs.

[0003] Currently, the most mainstream polymeric material base films for functional current collectors are typically polypropylene (PP) (thermal expansion coefficient between 80 and 160 E-6 / ℃) and polyethylene terephthalate (PET) (thermal expansion coefficient between 60 and 70 E-6 / ℃). However, during magnetron sputtering, due to the high sputtering temperature, the plastic and metal expand and contract at different rates, resulting in residual stress at the plastic-metal interface. This stress can easily induce debonding of the copper layer from the substrate, severely affecting the stability of composite copper current collectors in lithium batteries.

[0004] Therefore, in order to address the above problems, it is necessary to invent a functional current collector and its preparation method, so as to prepare a functional current collector that meets the requirements of power batteries. Summary of the Invention

[0005] To reduce the residual stress and improve the performance of functional current collectors, this invention proposes a low-residual-stress functional current collector and its preparation method. The above objective can be achieved through the following technical solutions:

[0006] A functional current collector with low residual stress, comprising:

[0007] The base film is made of a polymer material;

[0008] A transition layer is disposed on the surface of a base film; the transition layer contains cadmium and copper; the mass fraction of cadmium in the transition layer is 10-90%, and the mass fraction of copper in the transition layer is 10-90%.

[0009] A copper layer is disposed on the surface of the transition layer away from the base film.

[0010] Optionally, the low residual stress functional current collector includes at least two transition layers stacked together; the mass fraction of cadmium in each transition layer decreases as the distance between it and the base film increases;

[0011] Preferably, the low residual stress functional current collector comprises 4 to 8 layers stacked together as a transition layer;

[0012] Preferably, the thickness of each transition layer is 25-35 nm.

[0013] Optionally, the thickness of the copper layer is 20-275 nm.

[0014] Optionally, the combined thickness of the transition layer and the copper layer is 280–320 nm.

[0015] Optionally, the difference in cadmium mass fraction between two adjacent transition layers is 10–20%.

[0016] Optionally, the base film is made of at least one of polyethylene terephthalate (PET), polypropylene (PP), polyvinyl chloride (PVC), polyamide (PA), polystyrene (PS), polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVDF).

[0017] Preferably, the base film is made of polypropylene or polyethylene terephthalate.

[0018] Optionally, the low residual stress functional current collector includes five layers stacked together as a transition layer;

[0019] In the first transition layer set on the base film layer, the mass fraction of cadmium is 90% and the mass fraction of copper is 10%.

[0020] In the second transition layer disposed on the first transition layer, the mass fraction of cadmium is 80%, and the mass fraction of copper in the transition layer is 20%.

[0021] In the third transition layer disposed on the second transition layer, the mass fraction of cadmium is 70%, and the mass fraction of copper in the transition layer is 30%.

[0022] In the fourth transition layer disposed on the third transition layer, the mass fraction of cadmium is 60%, and the mass fraction of copper in the transition layer is 40%.

[0023] In the fifth transition layer disposed on the fourth transition layer, the mass fraction of cadmium is 40%, and the mass fraction of copper in the transition layer is 60%.

[0024] Optional steps include the following:

[0025] Step 1) Deposit a transition layer containing cadmium and copper on the base film;

[0026] Step 2) Deposit a copper layer on the transition layer so that the sum of the thicknesses of the transition layer and the copper layer reaches a preset thickness.

[0027] Optionally, in step one), the surface of the base film is subjected to plasma treatment before depositing the transition layer on the base film.

[0028] This invention also proposes the application of the aforementioned low residual stress functional current collector in the fabrication of batteries.

[0029] This invention achieves its goal by sputtering a coating onto a polymer substrate with a thermal expansion coefficient (41 × 10⁻⁶) that is closest to that of plastic. -6 ( / ℃) and cadmium, a metal cheaper than copper, is used to form a copper-cadmium alloy metal layer as a transition layer by controlling the gradient change of cadmium content. This reduces residual stress caused by the different expansion or contraction of plastic and metal due to the high sputtering temperature, reduces stress concentration deformation leading to battery thermal runaway, and reduces production costs while improving battery stability.

[0030] Furthermore, cadmium exhibits better wettability on polymer surfaces than copper, allowing for more effective physical and chemical bonding with the polymer substrate, thus providing a stronger adhesion foundation than direct copper sputtering. Simultaneously, copper and cadmium have good compatibility, enabling copper atoms to nucleate and grow relatively easily on the cadmium layer, forming a copper layer with strong adhesion. The cadmium-copper alloy, as the underlayer, provides an ideal surface for subsequent copper deposition, enhancing the adhesion between the polymer film and the copper layer. Detailed Implementation

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0032] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0033] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0034] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0035] Example 1

[0036] A functional current collector, using a 4μm commercially available polypropylene film as the polymer film, is prepared by a method comprising:

[0037] S1: Plasma treatment of polymer film surface: Roll-to-roll plasma treatment equipment is used, the working gas is a mixture of 80% Ar + 20% O2, the radio frequency power is 100W, the modification time is 15min, the gas flow rate is 100mL / min, and the winding tension is controlled to not exceed 80N.

[0038] S2: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer containing 10% copper is sputtered onto the film surface after step S1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0039] S3: Magnetron deposition of a pure copper conductive layer: A 270 nm thick pure copper metal layer is sputtered onto the surface of the film prepared after step S2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0040] Example 2

[0041] S1: The process is the same as the first step of Example 1, and the remaining processes are as follows:

[0042] S2: Magnetron-deposited alloy transition layer:

[0043] S2-1: A 30 nm thick cadmium-copper alloy layer containing 10% copper is sputtered onto the film surface after step 1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0044] S2-2: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 20% is sputtered onto the surface of the film prepared in step S2-1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0045] S3: Magnetron Deposition of Pure Copper Conductive Layer: A 240 nm thick pure copper metal layer is sputtered onto the film surface after step 2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0046] Example 3

[0047] S1: The process is the same as the first step of Example 1, and the remaining processes are as follows:

[0048] S2: Magnetron-deposited alloy transition layer:

[0049] S2-1: A 30 nm thick cadmium-copper alloy layer containing 10% copper is sputtered onto the film surface after step 1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0050] S2-2: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 20% is sputtered onto the film surface after step S2-1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0051] S2-3: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 30% is sputtered onto the film surface after step S2-2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0052] S3: Magnetron deposition of a pure copper conductive layer: A 210 nm thick pure copper metal layer is sputtered onto the film surface after step 2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0053] Example 4

[0054] S1: The process is the same as the first step of Example 1, and the remaining processes are as follows:

[0055] S2: Magnetron-deposited alloy transition layer:

[0056] S2-1: A 30 nm thick cadmium-copper alloy layer containing 10% copper is sputtered onto the film surface after step 1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0057] S2-2: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 20% is sputtered onto the film surface after step S2-1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0058] S2-3: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 30% is sputtered onto the film surface after step S2-2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0059] S2-4: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 40% is sputtered onto the film surface after step S2-3 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0060] S3: Magnetron Deposition of Pure Copper Conductive Layer: A 180nm thick pure copper metal layer is sputtered onto the film surface after step 2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15kW, and the equipment conveyor speed is 8m / min.

[0061] Example 5

[0062] S1: The process is the same as the first step of Example 1, and the remaining processes are as follows:

[0063] S2: Magnetron-deposited alloy transition layer:

[0064] S2-1: A 30 nm thick cadmium-copper alloy layer containing 10% copper is sputtered onto the film surface after step 1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0065] S2-2: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 20% is sputtered onto the film surface after step S2-1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0066] S2-3: Magnetron Deposition Alloy Transition Layer: A 30nm thick cadmium-copper alloy layer with a copper content of 30% is sputtered onto the surface of the film after S2-2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15kW, and the equipment conveyor speed is 8m / min.

[0067] S2-4: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 40% is sputtered onto the film surface after step S2-3 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0068] S2-5: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 60% is sputtered onto the film surface after step S2-4 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0069] S3: Magnetron deposition of a pure copper conductive layer: A 150 nm thick pure copper metal layer is sputtered onto the film surface after step 2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0070] Example 6

[0071] S1: The process is the same as the first step of Example 1, and the remaining processes are as follows:

[0072] S2: Magnetron-deposited alloy transition layer:

[0073] S2-1: A 30 nm thick cadmium-copper alloy layer containing 10% copper is sputtered onto the film surface after step 1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0074] S2-2: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 20% is sputtered onto the film surface after step S2-1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0075] S2-3: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 30% is sputtered onto the film surface after step S2-2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0076] S2-4: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 40% is sputtered onto the film surface after step S2-3 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0077] S2-5: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 60% is sputtered onto the film surface after step S2-4 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0078] S2-6: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with 80% copper content is sputtered onto the film surface after step S2-5 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0079] S3: Magnetron Deposition of Pure Copper Conductive Layer: A 120nm thick pure copper metal layer is sputtered onto the film surface after step 2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15kW, and the equipment conveyor speed is 8m / min.

[0080] Example 7

[0081] S1: The process is the same as the first step of Example 1, and the remaining processes are as follows:

[0082] S2: Magnetron-deposited alloy transition layer:

[0083] S2-1: A 30 nm thick cadmium-copper alloy layer containing 10% copper is sputtered onto the film surface after step 1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0084] S2-2: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 20% is sputtered onto the film surface after step S2-1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0085] S2-3: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 30% is sputtered onto the film surface after step S2-2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0086] S2-4: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 40% is sputtered onto the film surface after step S2-3 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0087] S2-5: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 50% is sputtered onto the film surface after step S2-4 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0088] S2-6: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 60% is sputtered onto the film surface after step S2-5 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0089] S2-7: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with 80% copper content is sputtered onto the film surface after step S2-6 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0090] S2-8: Magnetron Deposition of Alloy Transition Layer: A 30nm thick cadmium-copper alloy layer with a copper content of 90% is sputtered onto the film surface after step S2-7 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15kW, and the equipment conveyor speed is 8m / min.

[0091] S3: Magnetron Deposition of Pure Copper Conductive Layer: A 60nm thick pure copper metal layer is sputtered onto the film surface after step 2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15kW, and the equipment conveyor speed is 8m / min.

[0092] Example 8

[0093] S1: The process is the same as the first step of Example 1, and the remaining processes are as follows:

[0094] S2: Magnetron-deposited alloy transition layer:

[0095] S2-1: A 30 nm thick cadmium-copper alloy layer with a copper content of 25% is sputtered onto the thin film surface after step 1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0096] S2-2: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 20% is sputtered onto the film surface after step S2-1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0097] S2-3: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 30% is sputtered onto the film surface after step S2-2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0098] S2-4: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 40% is sputtered onto the film surface after step S2-3 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0099] S2-5: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 60% is sputtered onto the film surface after step S2-4 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0100] S3: Magnetron deposition of a pure copper conductive layer: A 150 nm thick pure copper metal layer is sputtered onto the film surface after step 2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0101] Example 9

[0102] S1: The process is the same as the first step of Example 1, and the remaining processes are as follows:

[0103] S2: Magnetron-deposited alloy transition layer:

[0104] S2-1: A 30 nm thick cadmium-copper alloy layer containing 10% copper is sputtered onto the film surface after step 1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0105] S2-2: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 30% is sputtered onto the film surface after step S2-1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0106] S2-3: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 50% is sputtered onto the film surface after step S2-2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0107] S2-4: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 70% is sputtered onto the film surface after step S2-3 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0108] S2-5: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 90% is sputtered onto the film surface after step S2-4 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0109] S3: Magnetron deposition of a pure copper conductive layer: A 150 nm thick pure copper metal layer is sputtered onto the film surface after step 2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0110] Example 10

[0111] S1: The process is the same as the first step of Example 1, and the remaining processes are as follows:

[0112] S2: Magnetron-deposited alloy transition layer:

[0113] S2-1: A 30 nm thick cadmium-copper alloy layer with a copper content of 20% is sputtered onto the thin film surface after step 1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0114] S2-2: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 40% is sputtered onto the film surface after step S2-1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0115] S2-3: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 60% is sputtered onto the film surface after step S2-2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0116] S2-4: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with 80% copper content is sputtered onto the film surface after step S2-3 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0117] S2-5 Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 90% is sputtered onto the film surface after step S2-4 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0118] S3: Magnetron deposition of a pure copper conductive layer: A 150 nm thick pure copper metal layer is sputtered onto the film surface after step 2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0119] Example 11

[0120] S1: The process is the same as the first step of Example 1, and the remaining processes are as follows:

[0121] S2: Magnetron-deposited alloy transition layer:

[0122] S2-1: A 30 nm thick cadmium-copper alloy layer with a copper content of 20% is sputtered onto the thin film surface after step 1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0123] S2-2: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 60% is sputtered onto the film surface after step S2-1 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0124] S2-3: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 70% is sputtered onto the film surface after step S2-2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0125] S2-4: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with 80% copper content is sputtered onto the film surface after step S2-3 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0126] S2-5: Magnetron Deposition of Alloy Transition Layer: A 30 nm thick cadmium-copper alloy layer with a copper content of 90% is sputtered onto the film surface after step S2-4 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0127] S3: Magnetron deposition of a pure copper conductive layer: A 150 nm thick pure copper metal layer is sputtered onto the film surface after step 2 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0128] Comparative Example 1

[0129] A functional current collector, the preparation method of which includes:

[0130] S1: Plasma treatment of polymer film surface: Roll-to-roll plasma treatment equipment is used, the working gas is a mixture of 80% Ar + 20% O2, the radio frequency power is 100W, the modification time is 15min, the gas flow rate is 100mL / min, and the winding tension is controlled to not exceed 80N.

[0131] S2: Magnetron deposition of a pure copper conductive layer: A 300 nm thick pure copper metal layer is sputtered onto the film surface after step 3 using a roll-to-roll magnetron sputtering system. The preferred working gas is argon, with a flow rate of 90 sccm. The sputtering power is 15 kW, and the equipment conveyor speed is 8 m / min.

[0132] Comparative Example 2

[0133] A functional current collector uses a 4μm commercial polyimide film as the polymer film, and the remaining steps are the same as those in Example 5.

[0134] Comparative Example 3

[0135] A functional current collector, in S2: magnetron deposition alloy transition layer: sputtered nickel-copper alloy layer replaces cadmium-copper alloy layer, the remaining step parameters are the same as in Example 5.

[0136] Performance testing:

[0137] The testing method is as follows:

[0138] Residual stress test: The finished product prepared according to this invention was used as a sample, and the residual stress was determined by Bruker D8 X-ray diffraction. XRD test conditions: 40kV, 40mA, scan rate 0.08s / step, step size 0.01°, grazing incidence angle 3°.

[0139] The test standard for the bonding force of the current collector is based on the "Test Method for Bonding Force of Functional Current Collectors" issued by the China Association of Automobile Manufacturers.

[0140] Tensile strength test: Tensile strength, the test standard refers to the national standard GB / T 1040.3-2006.

[0141] Table 1

[0142]

[0143]

[0144] Results analysis:

[0145] As shown in Table 1, compared with Comparative Example 1, it is evident that sputtering a buffer layer onto the plastic surface significantly improves the adhesion between the base film and the copper layer. Simultaneously, it effectively reduces residual stress and significantly improves tensile strength. This is because a transition layer with a coefficient of thermal expansion similar to that of the substrate is sputtered onto the substrate surface. When the coefficient of thermal expansion of the transition layer is close to that of the substrate, the expansion or contraction caused by temperature changes is more consistent, reducing interface cracks or failures caused by thermal stress. The transition layer design enhances the bonding strength between different materials, thereby forming a more stable composite structure that resists external loads and environmental changes. Furthermore, the structure of setting multiple transition layers with progressively increasing copper content combines the advantages of material composition gradients, forming a composite material that improves the overall strength and toughness of the functional current collector.

[0146] A comparison of Example 5 and Comparative Example 2 shows that the selection of the base film material has a certain impact on the product stress. To obtain a product with low residual stress, a suitable polymer needs to be used as the base film. A comparison of Example 5 and Comparative Example 3 shows that when nickel is used instead of cadmium, a good effect on reducing residual stress cannot be achieved.

[0147] However, analysis of Examples 5, 6, and 7 shows that when the transition layer is thicker, the adhesion decreases. This is because an excessively thick underlayer can generate defects or inhomogeneities within itself, which can affect the contact and bonding between the copper layer and the substrate. Furthermore, an excessively thick transition layer can cause significant internal stress to accumulate within the film.

[0148] As shown in Table 1, comparing Example 5 and Example 8, the copper concentration of the initial layer of the transition layer is higher, which is significantly different from the subsequent transition layers. This results in greater internal stress or defects, which in turn affects the adhesion and mechanical properties of the copper layer.

[0149] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A functional current collector with low residual stress, characterized in that, include: The base film is made of a polymer material; A transition layer is disposed on the surface of a base film; the transition layer contains cadmium and copper; the mass fraction of cadmium in the transition layer is 10-90%, and the mass fraction of copper in the transition layer is 10-90%. A copper layer is disposed on the surface of the transition layer away from the base film.

2. The low residual stress functional current collector according to claim 1, characterized in that, The low residual stress functional current collector includes at least two stacked transition layers; the mass fraction of cadmium in each transition layer decreases as the distance between it and the base film increases; Preferably, the low residual stress functional current collector comprises 4 to 8 layers stacked together as a transition layer; Preferably, the thickness of each transition layer is 25-35 nm.

3. The low residual stress functional current collector according to claim 1, characterized in that, The thickness of the copper layer is 20-275 nm.

4. The low residual stress functional current collector according to claim 1, characterized in that, The combined thickness of the transition layer and the copper layer is 280–320 nm.

5. The low residual stress functional current collector according to claim 2, characterized in that, The difference in cadmium mass fraction between two adjacent transition layers is 10–20%.

6. The low residual stress functional current collector according to claim 1, characterized in that, The base film is made of at least one of polyethylene terephthalate, polypropylene, polyvinyl chloride, polyamide, polystyrene, polytetrafluoroethylene, and polyvinylidene fluoride. Preferably, the base film is made of polypropylene or polyethylene terephthalate.

7. The low residual stress functional current collector according to claim 2, characterized in that, The low residual stress functional current collector comprises five layers stacked together as a transition layer; In the first transition layer disposed on the base film layer, the mass fraction of cadmium is 90% and the mass fraction of copper is 10%; in the second transition layer disposed on the first transition layer, the mass fraction of cadmium is 80% and the mass fraction of copper in the transition layer is 20%. In the third transition layer disposed on the second transition layer, the mass fraction of cadmium is 70%, and the mass fraction of copper in the transition layer is 30%. In the fourth transition layer disposed on the third transition layer, the mass fraction of cadmium is 60%, and the mass fraction of copper in the transition layer is 40%. In the fifth transition layer disposed on the fourth transition layer, the mass fraction of cadmium is 40%, and the mass fraction of copper in the transition layer is 60%.

8. A method for preparing a low residual stress functional current collector according to any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1) Deposit a transition layer containing cadmium and copper on the base film; Step 2) Deposit a copper layer on the transition layer so that the sum of the thicknesses of the transition layer and the copper layer reaches a preset thickness.

9. The preparation method according to claim 8, characterized in that, In step one), the surface of the base film is subjected to plasma treatment before depositing the transition layer on the base film.

10. The use of the low residual stress functional current collector according to any one of claims 1 to 7 in the preparation of batteries.

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