A copper-aluminum bipolar current collector and a preparation method thereof

Abstract

This invention discloses a copper-aluminum bipolar current collector and its preparation method, relating to the field of current collector technology. The preparation steps include: pre-cleaning copper and aluminum parts; preparing a nickel barrier layer by electroplating or electroless plating on one or both of the cleaned copper and aluminum parts; coating or evaporating a sacrificial layer on the surface of the nickel barrier layer; stacking the treated copper and aluminum parts and performing low-temperature diffusion bonding to obtain a copper-aluminum composite; and finally, post-processing the copper-aluminum composite to obtain the copper-aluminum bipolar current collector. This invention integrates four core processes—"deep surface cleaning and sulfur removal," "interfacial functional transition layer deposition," "sulfur sacrificial phase introduction," and "low-temperature solid-phase diffusion bonding"—to ensure the thorough removal of sulfur contaminants before interfacial bonding, enhancing the interfacial bonding strength of the copper-aluminum bipolar fluid, weakening the negative impact of sulfides, and improving the product's stability and service life.

Description

Technical Field

[0001] This invention relates to the field of current collector technology, specifically a copper-aluminum bipolar current collector and its preparation method. Background Technology

[0002] Copper and aluminum, due to their excellent electrical and thermal conductivity and significant cost advantages, have become indispensable structural connection materials in fields such as power electronics, new energy vehicles, and energy storage equipment. However, during the preparation and service process, the copper / aluminum interface is highly susceptible to contamination by trace amounts of sulfur (S) in the environment, leading to the formation of brittle metal sulfides (such as Cu2S and Al2S3). These sulfides not only severely weaken the interfacial bonding strength but also induce microcrack propagation, causing interfacial embrittlement or even delamination, directly threatening the mechanical reliability and long-term service life of the product. This problem has become a core technical bottleneck restricting the large-scale application of copper-aluminum composite components. Currently, although various surface treatments and joining processes exist for copper-aluminum connections, most focus on improving the interfacial bonding strength in a single dimension, failing to systematically address the sulfur contamination problem. While some improvement solutions attempt to introduce nickel barrier layers or zinc elements for optimization, they lack precise design for sulfur contamination control. They cannot completely remove surface and shallow sulfides at the source, nor can they effectively block the diffusion path of sulfur during the joining process. Furthermore, they lack subsequent protection mechanisms to resist secondary pollution from environmental sulfur. This results in the continued risk of sulfide formation, falling far short of meeting the stringent requirements for interfacial stability in high-reliability industrial applications.

[0003] In summary, solving the above problems and constructing a complete and systematic sulfur pollution prevention and control system, as well as preparing a copper-aluminum bipolar current collector, are of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide a copper-aluminum bipolar current collector and its preparation method to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing a copper-aluminum bipolar current collector includes the following preparation steps: S1: Take copper and aluminum parts for pre-surface cleaning; S2: Take any one or two of the cleaned copper and aluminum parts and prepare a nickel barrier layer by electroplating or chemical plating. S3: A sacrificial layer is coated or evaporated onto the surface of the nickel barrier layer, and then stacked for low-temperature diffusion bonding to obtain a copper-aluminum composite. S4: Post-process the copper-aluminum composite to obtain a copper-aluminum bipolar current collector; Preferably, the sacrificial layer comprises the following components by mass percentage: 75-100% Sn, 0-10% Zn, and 0-15% Bi. More preferably, the sacrificial layer comprises the following components by mass percentage: 75-95% Sn, 1-10% Zn, and the balance being Bi; Preferably, the pre-surface treatment includes solvent degreasing, chemical activation, and plasma cleaning; More preferably, the plasma cleaning includes the addition of a sulfur removal agent; the sulfur removal agent is atomized and sprayed, and the sulfur removal agent is a 0.5~1% trisodium citrate solution by volume concentration.

[0006] Preferably, the electroplating in step S2 uses a sulfate nickel plating system; the sulfate nickel plating system comprises the following raw material components: deionized water as solvent, 250-300 g / L nickel sulfate heptahydrate, 40-50 g / L nickel chloride hexahydrate, and 30-40 g / L boric acid; the electroplating process parameters are: current density 2-3 A / dm³. 2 Electroplating time: 15-25 minutes.

[0007] Preferably, the plating solution used for chemical plating in S2 includes the following raw material components: 20-25 g / L nickel sulfate heptahydrate, 25-30 g / L sodium hypophosphite monohydrate, and 15-20 g / L sodium acetate, with deionized water as the solvent; the process parameters for chemical plating are: pH of the plating solution is 4.5-5.0, temperature is 85-90℃, and plating time is 20-30 min.

[0008] Preferably, the thickness of the sacrificial layer is 3-20 μm; Preferably, the coating in S3 is applied by thermal spraying; the temperature of the thermal spraying is 280-320℃. Preferably, the process parameters for evaporation deposition in S3 are: evaporation temperature of 350-400℃ and vacuum degree of 5×10⁻⁶. -3 Pa; Preferably, the low-temperature diffusion bonding in S3 includes single-step low-temperature diffusion bonding and step-by-step low-temperature diffusion bonding; the process parameters for single-step low-temperature diffusion bonding are: under a controlled atmosphere, the temperature is 220-230℃, the holding time is 30-40min, and the applied pressure is 0.5-1MPa; the controlled atmosphere is 5%H2, and the balance is N2 or Ar; More preferably, the process parameters for stepwise cryogenic diffusion bonding are: S1 Preliminary wetting stage: Under a nitrogen atmosphere, heat to 180-200℃ and hold for 20-25 minutes; S2 interface diffusion stage: heat to 230-240℃ and hold for 35-45 minutes; S3 stress relief stage: Cool down to 200-210℃ and hold for 15-20 minutes.

[0009] Preferably, the structure of the copper-aluminum composite is any combination of copper-nickel barrier layer-sacrificial layer-aluminum, copper-sacrificial layer-nickel barrier layer-aluminum, and copper-nickel barrier layer-sacrificial layer-sacrificial layer-nickel barrier layer-aluminum. Preferably, the post-treatment in S4 includes annealing and passivation; the process parameters for annealing are: temperature 150-200℃, holding time 20-40min.

[0010] More preferably, the passivation treatment uses a phosphate passivation solution or a silane passivation solution; the phosphate passivation solution comprises the following raw material components: 80-100 g / L zinc dihydrogen phosphate and 20-30 g / L nickel nitrate, with deionized water as the solvent; the process parameters for passivation treatment using the phosphate passivation solution are: temperature 50-60℃ and passivation time 10-15 min; the volume concentration of the silane passivation solution is 2-3 wt%; the process parameters for passivation treatment using the silane passivation solution are: temperature 25-30℃ and passivation time 15-20 min.

[0011] A copper-aluminum bipolar current collector is prepared by the above-described preparation method.

[0012] Compared with the prior art, the beneficial effects achieved by the present invention are: This invention integrates four core processes—"deep surface cleaning and sulfur removal," "interfacial functional transition layer deposition," "introduction of sulfur sacrificial phase," and "low-temperature solid-phase diffusion bonding"—for synergistic effects. The deep surface cleaning and sulfur removal process sequentially employs solvent degreasing, acid / alkali activation, and plasma cleaning to remove oil, oxide layers, and trace amounts of sulfides from copper and aluminum surfaces. Simultaneously, a selective sulfur removal agent (trisodium citrate) is introduced to precisely remove residual sulfur from the surface and shallow layers. In the production of copper-aluminum current collectors, the sulfur removal agent is added during the surface treatment stage of both copper and aluminum parts to ensure complete removal of sulfur contaminants before interfacial bonding. In the deposition of functional transition layers at the interface, a nickel layer is prepared on one or both sides of aluminum or copper by deposition, electroplating or chemical plating. This nickel layer can block the diffusion of sulfur and react with other elements to form a harmless phase before the formation of stable sulfides, keeping sulfur away from the supporting interface. At the same time, it improves the interfacial wettability and composite metallurgical reaction, reduces the concentration of brittle intermetallic compounds, and enhances the interfacial plasticity and mechanical interlocking effect. In the low-temperature solid-state diffusion process, tin (Sn) is used as the main component to ensure the film-forming properties of the sacrificial layer and the foundation for interfacial bonding. A trace amount of zinc (Zn) is added as a "sacrificial phase" to preferentially form stable sulfides with sulfur, avoiding the formation of brittle phases at critical interfaces. Bismuth (Bi) is selectively added as an auxiliary modifying phase according to process requirements. Without bismuth, it is a binary system; with bismuth, it is a ternary system, optimizing the melting point of the sacrificial layer and the interfacial reaction rate. A controllable low-temperature solid-state diffusion process is adopted to reduce sulfur migration at high temperatures and the formation of harmful intermetallic compounds at the interface. The technical solution adopted in this invention not only realizes closed-loop control from substrate pretreatment to final passivation protection, but also weakens the negative impact of sulfides through the dual mechanism of nickel layer barrier and zinc element preferential sulfur fixation, enhances the interfacial bonding strength of copper-aluminum bipolar fluid, significantly improves the mechanical properties and environmental adaptability of copper-aluminum composite interface, and provides a scientific and engineering feasible overall solution for copper-aluminum dissimilar metal connection, improving the stability and service life of the final product. Detailed Implementation

[0013] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] It should be noted that the silane passivation solution is prepared by mixing γ-glycidoxypropyltrimethoxysilane, ethanol and deionized water in a volume ratio of 1:2:27, and the pH of the solution is adjusted to 4 with acetic acid. Finally, the solution is shaken thoroughly until it becomes clear and transparent. There are no special restrictions on the manufacturers from which the raw materials involved in this invention are purchased; they are all commercially available.

[0015] Example 1: This example provides a method for preparing a copper-aluminum bipolar current collector, including the following preparation steps: S1: Take copper and aluminum parts, place them in an alkaline solution at 45℃ for ultrasonic degreasing for 8 minutes, and then perform acid activation. The aluminum parts are activated by instantaneous activation with 10% dilute nitric acid for 60 seconds, and the copper parts are activated by 5% dilute nitric acid for 25 seconds. The activated copper and aluminum parts are rinsed with deionized water and dried, and then subjected to argon plasma cleaning at 200W for 3 minutes. The alkaline solution includes the following raw material components: deionized water as solvent, 60g / L sodium hydroxide, and 25g / L sodium carbonate. S2: Take the cleaned copper parts and prepare a nickel barrier layer with a thickness of 5μm by chemical plating; the plating solution used for chemical plating includes the following raw material components: deionized water as solvent, 25g / L nickel sulfate heptahydrate, 28g / L sodium hypophosphite monohydrate, and 20g / L sodium acetate; the process parameters for chemical plating are: pH of the plating solution is 4.5, and the temperature is 90℃; S3: A thin tin layer with a thickness of 15μm is coated on the surface of the nickel barrier layer as a sacrificial layer, and the layers are stacked and low-temperature diffusion bonding is performed. In nitrogen gas containing 5% H2, the temperature is raised to 220℃ to obtain a copper-aluminum composite. The structure of the copper-aluminum composite is copper-nickel barrier layer-sacrificial layer-aluminum. S4: Anneal the copper-aluminum composite part at 180℃ for 30 minutes, then passivate the surface using silane passivation solution at 25℃ for 18 minutes, and then air dry to obtain the copper-aluminum bipolar current collector.

[0016] Example 2: This example provides a method for preparing a copper-aluminum bipolar current collector, including the following preparation steps: S1: Take copper and aluminum parts, place them in ethanol at 25℃ for ultrasonic degreasing for 10 minutes, and then perform acid activation. The aluminum parts are activated with 10% hydrochloric acid solution for 75 seconds, and the copper parts are activated with 8% sulfuric acid solution for 60 seconds. The activated copper and aluminum parts are rinsed with deionized water 3 times for 3 minutes each time, and then placed in an 85℃ oven for drying for 15 minutes, and then subjected to plasma cleaning treatment for 3 minutes. S2: Take the cleaned aluminum parts and electroplate them using a sulfate nickel plating system at a current density of 3A / dm³. 2 A nickel barrier layer with a thickness of 6 μm was prepared. The sulfate nickel plating system includes the following raw material components: deionized water as solvent, 280 g / L nickel sulfate heptahydrate, 45 g / L nickel chloride hexahydrate, and 35 g / L boric acid. S3: A 10μm thick tin-zinc alloy fusible layer is obtained by thermal spraying on the surface of the nickel barrier layer at a spraying temperature of 300℃ as a sacrificial layer. The layers are then stacked and subjected to low-temperature diffusion bonding. In an argon atmosphere containing 5% H2, the temperature is raised to 220℃, held for 30 minutes, and a pressure of 0.8MPa is applied to obtain a copper-aluminum composite. The zinc content in the sacrificial layer is 8%, and the remainder is tin. The structure of the copper-aluminum composite is copper-sacrificial layer-nickel barrier layer-aluminum. S4: Anneal the copper-aluminum composite part at 180℃ for 30 minutes, then passivate the surface using silane passivation solution at 25℃ for 18 minutes, and then air dry to obtain the copper-aluminum bipolar current collector.

[0017] Example 3: This example provides a method for preparing a copper-aluminum bipolar current collector, including the following preparation steps: S1: Take copper and aluminum parts, and perform alkaline degreasing and acid degreasing sequentially, followed by acid activation. Aluminum parts are activated with a 15% nitric acid solution for 40 seconds, and copper parts are activated with a 3% nitric acid solution for 25 seconds. The activated copper and aluminum parts are then subjected to oxygen plasma cleaning at 250W for 5 minutes, and a 0.8% trisodium citrate solution is added. The alkaline solution used for alkaline degreasing consists of the following components: deionized water as solvent, 60 g / L sodium hydroxide, and 25 g / L sodium carbonate. The alkaline degreasing process parameters are: temperature 60℃, immersion time 10 minutes. The acidic solution used for acid degreasing is 15% sulfuric acid. The acidic degreasing process parameters are: temperature 50℃, immersion time 8 minutes. S2: Take the cleaned copper and aluminum parts and perform chemical plating to obtain a nickel barrier layer with a thickness of 6μm; the plating solution used for chemical plating includes the following raw material components: deionized water as solvent, 25g / L nickel sulfate heptahydrate, 28g / L sodium hypophosphite monohydrate, and 20g / L sodium acetate; the process parameters for chemical plating are: pH of the plating solution is 4.5, and the temperature is 90℃; S3: An evaporation process is used on the surface of the nickel barrier layer, with an evaporation temperature of 350℃ and a vacuum degree of 5×10⁻⁶. -3 Pa deposition yielded a 10 μm thick tin-bismuth-zinc alloy layer as a sacrificial layer; the sacrificial layer contained 6% bismuth, 3% zinc, and the remainder tin; S4: The copper and aluminum parts after the above treatment are stacked and bonded by low-temperature diffusion. Step-by-step diffusion bonding is used to obtain copper-aluminum composite parts. S5: Anneal the copper-aluminum composite part at 180℃ for 30 minutes, then passivate it using a phosphate passivation solution at 60℃ for 12 minutes, and then dry it at 120℃ for 10 minutes to obtain a copper-aluminum bipolar current collector. The phosphate passivation solution includes the following raw material components: 80 g / L zinc dihydrogen phosphate and 30 g / L nickel nitrate, with deionized water as the solvent. The process parameters for stepwise diffusion bonding are: S1 Preliminary wetting stage: Under nitrogen atmosphere, heat to 190℃ and hold for 25 minutes; S2 interface diffusion stage: heat up to 240℃ and hold for 40 min; S3 Stress relief stage: Cool down to 200℃ and hold for 20 minutes.

[0018] Example 4: Referring to Example 3, except that the thickness of the nickel barrier layer and the sacrificial layer are adjusted; the preparation steps include the following: S1: Take copper and aluminum parts, and perform alkaline degreasing and acid degreasing sequentially, followed by acid activation. Aluminum parts are activated with a 15% nitric acid solution for 40 seconds, and copper parts are activated with a 3% nitric acid solution for 25 seconds. The activated copper and aluminum parts are then subjected to oxygen plasma cleaning at 250W for 5 minutes, and a 0.8% trisodium citrate solution is added. The alkaline solution used for alkaline degreasing consists of the following components: deionized water as solvent, 60 g / L sodium hydroxide, and 25 g / L sodium carbonate. The alkaline degreasing process parameters are: temperature 60℃, immersion time 10 minutes. The acidic solution used for acid degreasing is 15% sulfuric acid. The acidic degreasing process parameters are: temperature 50℃, immersion time 8 minutes. S2: Take the cleaned copper and aluminum parts and perform chemical plating to obtain a nickel barrier layer with a thickness of 8μm; the plating solution used for chemical plating includes the following raw material components: deionized water as solvent, 25g / L nickel sulfate heptahydrate, 28g / L sodium hypophosphite monohydrate, and 20g / L sodium acetate; the process parameters for chemical plating are: pH of the plating solution is 4.5, and the temperature is 90℃; S3: An evaporation process is used on the surface of the nickel barrier layer, with an evaporation temperature of 350℃ and a vacuum degree of 5×10⁻⁶. -3 Pa deposition yielded a 12 μm thick tin-bismuth-zinc alloy layer as a sacrificial layer; the sacrificial layer contained 6% bismuth, 3% zinc, and the remainder tin; S4: The copper and aluminum parts after the above treatment are stacked and bonded by low-temperature diffusion. Step-by-step diffusion bonding is used to obtain copper-aluminum composite parts. S5: Anneal the copper-aluminum composite part at 180℃ for 30 minutes, then passivate it using a phosphate passivation solution at 60℃ for 12 minutes, and then dry it at 120℃ for 10 minutes to obtain a copper-aluminum bipolar current collector. The phosphate passivation solution includes the following raw material components: 80 g / L zinc dihydrogen phosphate and 30 g / L nickel nitrate, with deionized water as the solvent. The process parameters for stepwise diffusion bonding are: S1 Preliminary wetting stage: Under nitrogen atmosphere, heat to 190℃ and hold for 25 minutes; S2 interface diffusion stage: heat up to 240℃ and hold for 40 min; S3 Stress relief stage: Cool down to 200℃ and hold for 20 minutes.

[0019] Example 5: Referring to Example 3, except that the process parameters combining annealing and diffusion were adjusted, including the following preparation steps: S1: Take copper and aluminum parts, and perform alkaline degreasing and acid degreasing sequentially, followed by acid activation. Aluminum parts are activated with a 15% nitric acid solution for 40 seconds, and copper parts are activated with a 3% nitric acid solution for 25 seconds. The activated copper and aluminum parts are then subjected to oxygen plasma cleaning at 250W for 5 minutes, and a 0.8% trisodium citrate solution is added. The alkaline solution used for alkaline degreasing consists of the following components: deionized water as solvent, 60 g / L sodium hydroxide, and 25 g / L sodium carbonate. The alkaline degreasing process parameters are: temperature 60℃, immersion time 10 minutes. The acidic solution used for acid degreasing is 15% sulfuric acid. The acidic degreasing process parameters are: temperature 50℃, immersion time 8 minutes. S2: Take the cleaned copper and aluminum parts and perform chemical plating to obtain a nickel barrier layer with a thickness of 6μm; the plating solution used for chemical plating includes the following raw material components: deionized water as solvent, 25g / L nickel sulfate heptahydrate, 28g / L sodium hypophosphite monohydrate, and 20g / L sodium acetate; the process parameters for chemical plating are: pH of the plating solution is 4.5, and the temperature is 90℃; S3: An evaporation process is used on the surface of the nickel barrier layer, with an evaporation temperature of 350℃ and a vacuum degree of 5×10⁻⁶. -3 Pa deposition yielded a 10 μm thick tin-bismuth-zinc alloy layer as a sacrificial layer; the sacrificial layer contained 6% bismuth, 3% zinc, and the remainder tin; S4: The copper and aluminum parts after the above treatment are stacked and bonded by low-temperature diffusion. Step-by-step diffusion bonding is used to obtain copper-aluminum composite parts. S5: Anneal the copper-aluminum composite part at 190℃ for 40 minutes, then passivate it using a phosphate passivation solution at 60℃ for 12 minutes, and then dry it at 120℃ for 10 minutes to obtain a copper-aluminum bipolar current collector. The phosphate passivation solution includes the following raw material components: 80 g / L zinc dihydrogen phosphate and 30 g / L nickel nitrate, with deionized water as the solvent. The process parameters for stepwise diffusion bonding are: S1 Preliminary wetting stage: Under nitrogen atmosphere, heat to 200℃ and hold for 20 minutes; S2 interface diffusion stage: heat up to 240℃ and hold for 35 minutes; S3 Stress relief stage: Cool down to 200℃ and hold for 20 minutes.

[0020] Comparative Example 1: As a control experiment for Example 3, no chemical activation, plasma cleaning, or nickel barrier layer was added; the following steps were included: S1: Take copper and aluminum parts, and perform alkaline degreasing and acid degreasing in sequence. Then rinse and dry the degreased copper and aluminum parts with deionized water. The alkaline solution used for alkaline degreasing includes the following raw material components: 60 g / L sodium hydroxide and 25 g / L sodium carbonate, with deionized water as the solvent. The process parameters for alkaline degreasing are: temperature 60℃ and soaking time 10 min. The acid solution used for acid degreasing is 15% sulfuric acid (volume concentration). The process parameters for acid degreasing are: temperature 50℃ and soaking time 8 min. S2: Take the cleaned and dried copper and aluminum parts, stack them together and perform low-temperature diffusion bonding. Use step-by-step diffusion bonding to obtain copper-aluminum composite parts; S3: Anneal the copper-aluminum composite part at 180℃ for 30 minutes, then passivate it using a phosphate passivation solution at 60℃ for 12 minutes, and then dry it at 120℃ for 10 minutes to obtain a copper-aluminum bipolar current collector. The phosphate passivation solution includes the following raw material components: 80 g / L zinc dihydrogen phosphate and 30 g / L nickel nitrate, with deionized water as the solvent. The process parameters for stepwise diffusion bonding are: S1 Preliminary wetting stage: Under nitrogen atmosphere, heat to 190℃ and hold for 25 minutes; S2 interface diffusion stage: heat up to 240℃ and hold for 40 min; S3 Stress relief stage: Cool down to 200℃ and hold for 20 minutes.

[0021] Comparative Example 2: As a control experiment for Example 3, no nickel barrier layer was added, and the following steps were included: S1: Take copper and aluminum parts, and perform alkaline degreasing and acid degreasing sequentially, followed by acid activation. Aluminum parts are activated with a 15% nitric acid solution for 40 seconds, and copper parts are activated with a 3% nitric acid solution for 25 seconds. The activated copper and aluminum parts are then subjected to oxygen plasma cleaning at 250W for 5 minutes, and a 0.8% trisodium citrate solution is added. The alkaline solution used for alkaline degreasing consists of the following components: deionized water as solvent, 60 g / L sodium hydroxide, and 25 g / L sodium carbonate. The alkaline degreasing process parameters are: temperature 60℃, immersion time 10 minutes. The acidic solution used for acid degreasing is 15% sulfuric acid. The acidic degreasing process parameters are: temperature 50℃, immersion time 8 minutes. S2: Take the cleaned copper and aluminum parts, stack them together and perform low-temperature diffusion bonding. Use step-by-step diffusion bonding to obtain copper-aluminum composite parts; S3: Anneal the copper-aluminum composite part at 180℃ for 30 minutes, then passivate it using a phosphate passivation solution at 60℃ for 12 minutes, and then dry it at 120℃ for 10 minutes to obtain a copper-aluminum bipolar current collector. The phosphate passivation solution includes the following raw material components: 80 g / L zinc dihydrogen phosphate and 30 g / L nickel nitrate, with deionized water as the solvent. The process parameters for stepwise diffusion bonding are: S1 Preliminary wetting stage: Under nitrogen atmosphere, heat to 190℃ and hold for 25 minutes; S2 interface diffusion stage: heat up to 240℃ and hold for 40 min; S3 Stress relief stage: Cool down to 200℃ and hold for 20 minutes.

[0022] Comparative Example 3: As a control experiment for Example 3, no sacrificial layer was added, and the following steps were included: S1: Take copper and aluminum parts, and perform alkaline degreasing and acid degreasing sequentially, followed by acid activation. Aluminum parts are activated with a 15% nitric acid solution for 40 seconds, and copper parts are activated with a 3% nitric acid solution for 25 seconds. The activated copper and aluminum parts are then subjected to oxygen plasma cleaning at 250W for 5 minutes, and a 0.8% trisodium citrate solution is added. The alkaline solution used for alkaline degreasing consists of the following components: deionized water as solvent, 60 g / L sodium hydroxide, and 25 g / L sodium carbonate. The alkaline degreasing process parameters are: temperature 60℃, immersion time 10 minutes. The acidic solution used for acid degreasing is 15% sulfuric acid. The acidic degreasing process parameters are: temperature 50℃, immersion time 8 minutes. S2: Take the cleaned copper and aluminum parts and perform chemical plating to obtain a nickel barrier layer with a thickness of 6μm. The plating solution used for chemical plating includes the following raw material components: deionized water as solvent, 25g / L nickel sulfate heptahydrate, 28g / L sodium hypophosphite monohydrate, and 20g / L sodium acetate. The process parameters for chemical plating are: pH of the plating solution is 4.5, temperature is 90℃, and plating time is 30min. S3: Anneal the copper-aluminum composite part at 180℃ for 30 minutes, then passivate it using a phosphate passivation solution at 60℃ for 12 minutes, and then dry it at 120℃ for 10 minutes to obtain a copper-aluminum bipolar current collector. The phosphate passivation solution includes the following raw material components: 80 g / L zinc dihydrogen phosphate and 30 g / L nickel nitrate, with deionized water as the solvent. The process parameters for stepwise diffusion bonding are: S1 Preliminary wetting stage: Under nitrogen atmosphere, heat to 190℃ and hold for 25 minutes; S2 interface diffusion stage: heat up to 240℃ and hold for 40 min; S3 Stress relief stage: Cool down to 200℃ and hold for 20 minutes.

[0023] Performance testing: 1. Place the copper-aluminum bipolar current collectors prepared in Examples 1-5 and Comparative Examples 1-3 in a clamp with a clamping distance of 100mm and perform tensile tests at a loading rate of 300mm / min. Repeat the measurement 5 times for each group and take the average value to record its tensile strength. 2. The copper-aluminum bipolar current collectors prepared in Examples 1-5 and Comparative Examples 1-3 were placed in a simulated sulfur-containing environment (50ppm SO2, the rest being air) for 30 days before tensile testing was performed. Each group was measured 5 times and the average value was taken. The tensile strength was recorded. Table 1

[0024] Conclusion: Compared with Examples 1 and 2, Example 3 added a sulfur removal agent during plasma cleaning and adopted double barrier and distributed diffusion to achieve reliable copper-aluminum interface bonding; Example 4 adjusted the thickness of the nickel barrier layer and sacrificial layer based on Example 3, further improving performance; Example 5 adjusted the step diffusion temperature and time according to Example 3, but the performance was slightly insufficient; then, a control experiment was conducted on Example 3. Comparative Example 1 did not perform acid activation, plasma cleaning, or nickel barrier layer on the copper and aluminum parts, and the tensile strength was much lower than that of Example 3. Moreover, embrittlement occurred after being placed in a sulfur-containing environment for 10 days, indicating severe sulfur contamination; Comparative Example 2 did not have a nickel barrier layer, and the tensile strength was insufficient, and the sulfur resistance was much lower than that of Example 3; Comparative Example 3 did not have a sacrificial layer, and the sulfur resistance decreased accordingly.

[0025] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a copper-aluminum bipolar current collector, characterized in that, The preparation steps include the following: S1: Take copper and aluminum parts for pre-surface cleaning; S2: Take any one or two of the cleaned copper and aluminum parts and prepare a nickel barrier layer by electroplating or chemical plating. S3: A sacrificial layer is coated or evaporated onto the surface of the nickel barrier layer, and then low-temperature diffusion bonding is performed after stacking to obtain a copper-aluminum composite. S4: Post-process the copper-aluminum composite to obtain a copper-aluminum bipolar current collector; The sacrificial layer comprises the following components by mass percentage: 75-100% Sn, 0-10% Zn, and 0-15% Bi.

2. The method for preparing a copper-aluminum bipolar current collector according to claim 1, characterized in that, The pre-surface treatment includes solvent degreasing, chemical activation, and plasma cleaning; the plasma cleaning includes adding a sulfur removal agent; the sulfur removal agent is a 0.5~1% (v / v) trisodium citrate solution.

3. The method for preparing a copper-aluminum bipolar current collector according to claim 1, characterized in that, The electroplating in S2 uses a sulfate nickel plating system; the sulfate nickel plating system comprises the following raw material components: deionized water as solvent, 250-300 g / L nickel sulfate heptahydrate, 40-50 g / L nickel chloride hexahydrate, and 30-40 g / L boric acid; the electroplating process parameters are: current density 2-3 A / dm³. 2 Electroplating time: 15-25 minutes.

4. The method for preparing a copper-aluminum bipolar current collector according to claim 1, characterized in that, The plating solution used in S2 for chemical plating includes the following raw material components: deionized water as solvent, 20-25 g / L nickel sulfate heptahydrate, 25-30 g / L sodium hypophosphite monohydrate, and 15-20 g / L sodium acetate; the process parameters for chemical plating are: pH of the plating solution is 4.5-5.0, temperature is 85-90℃, and plating time is 20-30 min.

5. The method for preparing a copper-aluminum bipolar current collector according to claim 1, characterized in that, The thickness of the nickel barrier layer is 2-10 μm, and the thickness of the sacrificial layer is 3-20 μm; the coating in S3 is carried out by thermal spraying; the thermal spraying temperature is 280-320℃; the process parameters for evaporation deposition in S3 are: evaporation temperature 350-400℃, vacuum degree 5×10 -3 Pa.

6. The method for preparing a copper-aluminum bipolar current collector according to claim 1, characterized in that, The low-temperature diffusion bonding in S3 includes single-step low-temperature diffusion bonding and step-by-step low-temperature diffusion bonding; the process parameters for single-step low-temperature diffusion bonding are: under a controlled atmosphere, the temperature is 220-230℃, the holding time is 30-40min, and the applied pressure is 0.5-1MPa; the controlled atmosphere is 5%H2, and the balance is N2 or Ar.

7. The method for preparing a copper-aluminum bipolar current collector according to claim 6, characterized in that, The process parameters for the stepwise low-temperature diffusion bonding are as follows: s1 Initial wetting stage: Under a nitrogen atmosphere, the temperature is raised to 180-200℃ and held for 20-25 minutes; S2 interface diffusion stage: heat to 230-240℃ and hold for 35-45 minutes; S3 stress relief stage: Cool down to 200-210℃ and hold for 15-20 minutes.

8. The method for preparing a copper-aluminum bipolar current collector according to claim 1, characterized in that, The structure of the copper-aluminum composite is any combination of copper-nickel barrier layer-sacrificial layer-aluminum, copper-sacrificial layer-nickel barrier layer-aluminum, and copper-nickel barrier layer-sacrificial layer-sacrificial layer-nickel barrier layer-aluminum; the post-treatment in S4 includes annealing and passivation; the process parameters of the annealing treatment are: temperature 150-200℃, holding time 20-40min.

9. The method for preparing a copper-aluminum bipolar current collector according to claim 8, characterized in that, The passivation treatment uses either a phosphate passivation solution or a silane passivation solution. The phosphate passivation solution comprises the following raw material components: 80-100 g / L zinc dihydrogen phosphate and 20-30 g / L nickel nitrate, with deionized water as the solvent. The process parameters for passivation treatment using the phosphate passivation solution are: temperature 50-60℃ and passivation time 10-15 min. The process parameters for passivation treatment using the silane passivation solution are: temperature 25-30℃ and passivation time 15-20 min.

10. A copper-aluminum bipolar current collector, characterized in that, It is prepared according to any one of claims 1-9.

Images