Composite copper current collector and preparation method therefor

Abstract

The present application relates to the technical field of current collectors, specifically to a composite copper current collector and a preparation method therefor. In the present application, a modified polymer film is obtained by means of subjecting a polymer and an active material to heating and melting, extrusion, casting, and biaxial stretching processes; copper layers are formed on the upper and lower sides of the modified polymer film, respectively, using a chemical plating method; finally, an anti-oxidation layer is prepared on the copper layers, thereby obtaining a composite copper current collector. The composite copper current collector prepared by means of the present application realizes one-step preparation of a composite copper current collector, namely a chemical plating method, successfully solving the problems of high energy consumption and low yield caused by physical vapor deposition process in conventional preparation processes. Compared with conventional methods, the performance of the composite copper current collector prepared by the present application is not degraded, while energy consumption is greatly reduced and yield is increased.

Description

Composite copper current collector and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of current collectors, in particular to a composite copper current collector and a preparation method thereof. BACKGROUND

[0002] At present, the composite copper current collector based on the high polymer film has been widely concerned and applied in the new energy industry. The preparation process of the composite copper current collector is generally divided into two steps: first, a layer of copper is deposited on the polymer film (such as polypropylene, polyethylene, polyester, etc.) by physical vapor deposition (magnetron sputtering or evaporation), and a composite copper current collector semi-finished product with certain conductive capacity is prepared. Then, the composite copper current collector semi-finished product is further treated by electroplating to thicken the conductive copper layer, so as to prepare a composite copper current collector with conductivity. Compared with the traditional current collector (copper foil), the composite copper current collector based on the high polymer film has the characteristics of low cost, light weight, good insulation of the inner polymer film layer, etc. These characteristics enable the composite current collector to reduce the cost of the battery and improve the energy density of the battery when applied in the battery, prevent the short circuit of the positive and negative electrodes, and increase the safety.

[0003] At present, the preparation of the composite copper current collector has the following problems: since the surface of the polymer film does not have conductivity, the preparation of the composite current collector cannot be completed by one-step electroplating. In order to solve this problem, a physical vapor deposition process is needed before electroplating to deposit a thin conductive copper layer on the surface of the polymer film to complete the preparation of the composite copper current collector. However, the introduction of the physical vapor deposition process will increase the energy consumption and lead to the increase of the preparation cost. In addition, during the preparation of the composite current collector semi-finished product by magnetron sputtering, hole defects are easily generated, resulting in a low yield of the composite copper current collector.

[0004] Therefore, in view of the above problems, it is necessary to develop a new preparation method of the composite copper current collector, so as to prepare a low-cost composite copper current collector, thereby promoting the popularization and application of the composite copper current collector. SUMMARY

[0005] The following is a summary of the subject matter described in detail in this document. This summary is not intended to limit the scope of protection of the claims.

[0006] The purpose of the present application is to provide a composite copper current collector and a preparation method thereof to solve the problems raised in the background art.

[0007] In order to solve the above technical problems, the present application provides the following technical solutions:

[0008] A preparation method of a composite copper current collector, comprising the following steps:

[0009] Step S1: doping an active material in a polymer, and preparing a modified polymer film by bidirectional stretching; the active material is one or more of carbon, cadmium sulfide, silver iodide, silver oxide, nickel oxide, conductive fiber, nickel, chromium, tin, nickel-chromium alloy, tin-nickel-copper alloy, lead-tin alloy, and palladium-copper alloy;

[0010] Step S2: forming a copper layer on the upper and lower sides of the modified polymer film by using a chemical plating method;

[0011] Step S3: preparing an oxidation-resistant layer on the copper layer to obtain a composite copper current collector.

[0012] In one embodiment, the preparation method of the modified polymer film is as follows:

[0013] Step (1): melt extrusion: adding the polymer and the active material into a double-screw extruder, and performing heating melting and extrusion to obtain a molten raw material;

[0014] Step (2): casting: casting the molten raw material onto a casting roller, and performing cooling treatment to form a casting sheet;

[0015] Step (3): stretching: performing bidirectional stretching on the casting sheet to obtain the modified polymer film.

[0016] In the above technical solution, by introducing the nano metal active material into the modified polymer film, active deposition sites can be provided for chemical copper plating, thereby promoting the chemical copper plating and improving the adhesion between the chemical copper layer and the polymer film, and the adhesion and stability of the copper plating layer. At the same time, by using this technical solution, the cumbersome activation, sensitization, and degumming pretreatment processes are not required in the chemical copper plating process, and the modified polymer film can be directly put into the chemical copper plating tank for chemical copper plating, thereby greatly shortening the process flow of the chemical copper plating process and improving the production efficiency.

[0017] In one embodiment, the modified polymer film comprises the following raw materials: 90-99 wt% of the polymer and 1-10 wt% of the active material.

[0018] In one embodiment, the polymer is one or more of polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polypropylene ethylene (EPR), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polyphenylene sulfide (PPS).

[0019] In one embodiment, the particle size of the active material is 10-100 nm.

[0020] In one embodiment, the temperature of the heating and melting in step (1) is higher than the melting point of the polymer.

[0021] In one embodiment, the cooling medium in step (2) is water, and the cooling temperature is 10-50℃.

[0022] In one embodiment, the stretching ratio in step (3) is 2-6, and the stretching temperature is 80-160℃, which is lower than the melting point of the polymer.

[0023] In one embodiment, the thickness of the modified polymer film is 3-12μm.

[0024] In one embodiment, the main components of the electroless plating solution are: sodium pyrrolidine dithiocarbamate 0.08g / L-0.12g / L, benzyl triphenyl phosphonium bromide 0.16g / L-0.24g / L, 2-(hydroxymethyl) thiophene 0.24g / L-0.36g / L, Cu 2+ 10g / L-15g / L, potassium sodium tartrate 18g / L-24g / L, EDTA 8g / L-12g / L, α, α-dipyridyl 0.008g / L-0.012g / L, potassium ferrocyanide 0.02g / L-0.03g / L, formaldehyde 2.5g / L-3.5g / L, sodium hydroxide 6g / L-7g / L, and sodium carbonate 3g / L-6g / L, pH=11-12.

[0025] In one embodiment, the process conditions of the electroless plating are: temperature 40-60℃, time 6-8min, and the relative movement speed of the film is 3-10m / min.

[0026] In one embodiment, the thickness of the copper layer is 500-2000nm, and further optionally 700-1200nm.

[0027] In the above technical solution, the copper layer is located on the upper and lower surfaces of the modified polymer film, and functions as a conductor.

[0028] In one embodiment, the material of the antioxidant layer is one or more of copper chromate, copper chromite, and chromium oxide.

[0029] In one embodiment, the preparation method of the antioxidant layer is one or more of dip coating, physical vapor deposition, and chemical vapor deposition.

[0030] In one embodiment, the thickness of the antioxidant layer is 5-100nm, and the thickness of the antioxidant layer cannot exceed one-tenth of the thickness of the copper layer.

[0031] In the above technical solution, the material and thickness of the antioxidant layer should be consistent. The main function of the antioxidant layer is to prevent the metal conductor layer from being chemically corroded or physically damaged. The thickness of the antioxidant layer cannot exceed one-tenth of the thickness of the copper layer. If the protective layer is too thin, it will not effectively play a protective role, and if the protective layer is too thick, it may affect the conductivity. Therefore, the material and thickness of the protective layer need to be reasonably selected and controlled to maximize its protective effect on the conductive layer.

[0032] Compared with the prior art, the beneficial effects of the present application are as follows:

[0033] The composite copper current collector and the preparation method thereof realize the preparation of the composite copper current collector by one-step chemical plating method, solve the problems of high energy consumption and low yield caused by the physical vapor deposition process in the conventional preparation process of the composite copper current collector. Compared with the composite copper current collector prepared by the traditional method, the performance of the composite copper current collector prepared by the present application is not reduced, which further promotes the popularization and application of the composite current collector.

[0034] Other aspects can be appreciated upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0036] In the present embodiment, PP: the grade is M800E of Shanghai Petrochemical; nickel-chromium alloy: the particle size is 50 nm, the grade is Ni80Cr20.

[0037] Embodiment 1: A preparation method of a composite copper current collector, comprising the following processes:

[0038] Step S1: doping an active material in a polymer, and preparing a modified polymer film with a thickness of 4.5 μm by bidirectional stretching;

[0039] Step S2: placing the modified polymer film in a plating solution (the main components of the chemical plating solution are: sodium pyrrolidine dithiocarbamate 0.08 g / L, benzyl triphenyl phosphonium bromide 0.16 g / L, 2-(hydroxymethyl) thiophene 0.24 g / L, Cu 2+10 g / L, potassium sodium tartrate 18 g / L, EDTA 8 g / L, α,α-dipyridyl 0.008 g / L, potassium ferrocyanide 0.02 g / L, formaldehyde 2.5 g / L, sodium hydroxide 6 g / L and sodium carbonate 3 g / L, pH = 12), a copper layer is formed on both sides of the modified polymer film by using a chemical copper plating process (temperature 40℃, time 6 min, relative movement speed of film 10 m / min);

[0040] Step S3: an oxidation-resistant layer (material: copper chromite) is prepared on the copper layer by using a chemical vapor deposition method, to obtain a composite copper current collector;

[0041] The preparation method of the modified polymer film is as follows:

[0042] Step (1): melt extrusion: taking PP as the polymer and nickel-chromium alloy as the active material, 950 g of PP and 50 g of nickel-chromium are added into a double-screw extruder, melted (temperature 165℃) and extruded to obtain a molten raw material;

[0043] Step (2): casting: the molten raw material is cast onto a casting roller and shaped by cooling treatment (cooling medium: water, cooling temperature: 10℃) to obtain a casting sheet;

[0044] Step (3): stretching: the casting sheet is stretched by a two-way stretching process (stretching ratio: 2, stretching temperature: 80℃) to obtain a modified polymer film.

[0045] Example 2: a preparation method of a composite copper current collector, comprising the following processes:

[0046] Step S1: doping an active material in a polymer, and preparing a modified polymer film with a thickness of 4.5 μm by two-way stretching;

[0047] Step S2: placing the modified polymer film in a plating solution (the main components of the chemical plating solution are: sodium pyrrolidine dithiocarbamate 0.10 g / L, benzyl triphenyl phosphonium bromide 0.2 g / L, 2-(hydroxymethyl) thiophene 0.3 g / L, Cu 2+ 12 g / L, potassium sodium tartrate 20 g / L, EDTA 10 g / L, α,α-dipyridyl 0.01 g / L, potassium ferrocyanide 0.025 g / L, formaldehyde 3 g / L, sodium hydroxide 6.5 g / L and sodium carbonate 5 g / L, pH = 11), a copper layer is formed on both sides of the modified polymer film by using a chemical copper plating process (temperature 45℃, time 7 min, relative movement speed of film 7 m / min);

[0048] Step S3: an oxidation-resistant layer (material: copper chromite) is prepared on the copper layer by using a chemical vapor deposition method, to obtain a composite copper current collector;

[0049] The preparation method of the modified polymer film is as follows:

[0050] Step (1): melt extrusion: taking PP as the polymer and nickel-chromium alloy as the active material, 940 g of PP and 60 g of nickel-chromium are added into a double screw extruder, melted by heating (the temperature is 165°C), and extruded to obtain a molten raw material;

[0051] Step (2): cast sheet: the molten raw material is cast onto a cast roll, and shaped by cooling treatment (the cooling medium is water, and the cooling temperature is 20°C) to obtain a cast sheet;

[0052] Step (3): stretching: the cast sheet is stretched by a two-way stretching process (the stretching ratio is 3, and the stretching temperature is 90°C) to obtain a modified polymer film.

[0053] Example 3: a preparation method of a composite copper current collector, comprising the following processes:

[0054] Step S1: doping an active material in a polymer, and preparing a modified polymer film with a thickness of 4.5 μm by two-way stretching;

[0055] Step S2: placing the modified polymer film in a plating solution (the main components of the chemical plating solution are: sodium pyrrolidine dithiocarbamate 0.12 g / L, benzyl triphenyl phosphonium bromide 0.24 g / L, 2-(hydroxymethyl) thiophene 0.36 g / L, Cu 2+ 15 g / L, potassium sodium tartrate 24 g / L, EDTA 12 g / L, α, α-dipyridyl 0.012 g / L, potassium ferrocyanide 0.03 g / L, formaldehyde 3.5 g / L, sodium hydroxide 7 g / L, and sodium carbonate 6 g / L, pH = 12), and adopting a chemical copper plating process (the temperature is 50°C, the time is 7 min, and the relative movement speed of the film is 6 m / min) to form copper layers on the upper and lower sides of the modified polymer film;

[0056] Step S3: adopting a chemical vapor deposition method to prepare an oxidation-resistant layer (the material is copper chromite) on the copper layer to obtain a composite copper current collector;

[0057] The preparation method of the modified polymer film is as follows:

[0058] Step (1): melt extrusion: taking PP as the polymer and nickel-chromium alloy as the active material, 930 g of PP and 70 g of nickel-chromium are added into a double screw extruder, melted by heating (the temperature is 165°C), and extruded to obtain a molten raw material;

[0059] Step (2): cast sheet: the molten raw material is cast onto a cast roll, and shaped by cooling treatment (the cooling medium is water, and the cooling temperature is 30°C) to obtain a cast sheet;

[0060] Step (3): Stretching: the cast sheet is subjected to a biaxial stretching process (stretching ratio of 4, stretching temperature of 100°C) to obtain the modified polymer film.

[0061] Example 4: A preparation method of a composite copper current collector, comprising the following processes:

[0062] Step S1: doping an active material in a polymer, and biaxial stretching to prepare a modified polymer film with a thickness of 4.5 μm;

[0063] Step S2: placing the modified polymer film in a plating solution (the main components of the chemical plating solution are: sodium pyrrolidine dithiocarbamate 0.12 g / L, benzyl triphenyl phosphonium bromide 0.24 g / L, 2-(hydroxymethyl) thiophene 0.36 g / L, Cu 2+ 15 g / L, potassium sodium tartrate 24 g / L, EDTA 12 g / L, α, α-dipyridyl 0.012 g / L, potassium ferrocyanide 0.03 g / L, formaldehyde 3.5 g / L, sodium hydroxide 7 g / L, and sodium carbonate 6 g / L, pH = 12), and adopting a chemical copper plating process (temperature 55°C, time 8 min, and relative movement speed of the film 4 m / min) to form copper layers on the upper and lower sides of the modified polymer film, respectively;

[0064] Step S3: adopting a chemical vapor deposition method to prepare an oxidation-resistant layer (material: copper chromite) on the copper layer to obtain a composite copper current collector;

[0065] The preparation method of the modified polymer film is as follows:

[0066] Step (1): melt extrusion: taking PP as the polymer and nickel-chromium alloy as the active material, 920 g of PP and 80 g of nickel-chromium alloy are added into a double-screw extruder, heated and melted (temperature 165°C), and extruded to obtain a molten raw material;

[0067] Step (2): cast sheet: the molten raw material is cast onto a cast roll and shaped through cooling treatment (cooling medium: water, cooling temperature: 40°C) to obtain a cast sheet;

[0068] Step (3): stretching: the cast sheet is subjected to a biaxial stretching process (stretching ratio of 5, stretching temperature of 110°C) to obtain the modified polymer film.

[0069] Example 5: A preparation method of a composite copper current collector, comprising the following processes:

[0070] Step S1: doping an active material in a polymer, and biaxial stretching to prepare a modified polymer film with a thickness of 4.5 μm;

[0071] Step S2: placing the modified polymer film into a plating solution (the main components of the chemical plating solution are: sodium pyrrolidine dithiocarbamate 0.12 g / L, benzyl triphenyl phosphonium bromide 0.24 g / L, 2-(hydroxymethyl) thiophene 0.36 g / L, Cu 2+ 15 g / L, potassium sodium tartrate 24 g / L, EDTA 12 g / L, α, α-dipyridyl 0.012 g / L, potassium ferrocyanide 0.03 g / L, formaldehyde 3.5 g / L, sodium hydroxide 7 g / L, and sodium carbonate 6 g / L, pH = 12), using a chemical copper plating process (temperature 60°C, time 8 min, thin film relative motion speed 3 m / min), to form a copper layer on the upper and lower sides of the modified polymer film, respectively;

[0072] Step S3: using a chemical vapor deposition method to prepare an oxidation-resistant layer (material is copper chromite) on the copper layer, to obtain a composite copper current collector;

[0073] The preparation method of the modified polymer film is as follows:

[0074] Step (1): melt extrusion: taking PP as the polymer and nickel-chromium alloy as the active material, 900 g of PP and 100 g of nickel-chromium are added into a double-screw extruder, heated and melted (temperature 165°C), and extruded to obtain a molten raw material;

[0075] Step (2): casting: the molten raw material is cast onto a casting roller and shaped by cooling treatment (cooling medium is water, cooling temperature is 50°C) to obtain a cast sheet;

[0076] Step (3): stretching: the cast sheet is stretched by a two-way stretching process (stretching ratio is 6, stretching temperature is 120°C) to obtain a modified polymer film.

[0077] Comparative Example 1: a preparation method of a composite copper current collector, comprising the following processes:

[0078] Compared with Example 5, no active material is added in the modified polymer film of Comparative Example 1, and the other steps are the same as those of Example 5.

[0079] Comparative Example 2: a preparation method of a composite copper current collector, comprising the following processes:

[0080] The preparation method of the modified polymer film is as follows:

[0081] Step (1): melt extrusion: taking PP as the polymer and nickel-chromium alloy as the active material, 900 g of PP and 100 g of nickel-chromium are added into a double-screw extruder, heated and melted (temperature 165°C), and extruded to obtain a molten raw material;

[0082] Step (2): Casting: casting the molten raw material onto a casting roll, and shaping by cooling treatment (cooling medium is water, and cooling temperature is 50℃), to obtain a cast sheet;

[0083] Step (3): Stretching: stretching the cast sheet by a two-way stretching process (stretching ratio is 6, and stretching temperature is 120℃), to obtain a modified polymer film;

[0084] Compared with Example 5, the modified polymer film of Comparative Example 2 comprises the following raw materials: 80wt% of polymer, 20wt% of active material, and other steps are the same as Example 5.

[0085] Experiment: Bonding force test: test the bonding force between the modified polymer film and the copper layer obtained in Examples 1-5 and Comparative Examples 1-2, after baking the copper layer at 150℃ for 3min, use 3M tape for adhesion and separation test, i.e. paste the 3M tape on the copper layer, and then tear off quickly, by observing whether there is film falling phenomenon on the tape, the bonding force between the modified polymer film and the copper layer can be evaluated.

[0086] Pre-plating sheet resistance test: take the modified polymer film obtained in Examples 1-5 and Comparative Examples 1-2, place it on the sample stage, and use a four-probe sheet resistance meter to test the sheet resistance of the sample.

[0087] Sheet resistance test: take the composite copper current collector obtained in Examples 1-5 and Comparative Examples 1-2, place it on the sample stage, and use a four-probe sheet resistance meter to test the sheet resistance of the sample.

[0088] Test results

[0089] According to the data in the above table, the following conclusions can be clearly obtained:

[0090] 1. Compared with Comparative Example 2, the pre-plating sheet resistance of the modified polymer film of Examples 1-5 is very high, and the conductivity cannot be measured, which shows that when the content of active material in the modified polymer film is low, the material cannot meet the conductivity condition without subsequent copper plating treatment, which ensures the insulation of the non-metallic layer in the composite current collector. Therefore, only in the case of subsequent copper plating treatment, the performance of the film will change qualitatively, so as to realize the conductivity condition.

[0091] 2. Compared with Examples 1-5, the composite copper current collector of Comparative Example 1 has almost no copper deposition on the surface, and the sheet resistance is very high, which is because in the case of no active material added, there is a lack of active deposition sites required for electroless copper plating on the modified polymer film, therefore, the modified polymer film surface cannot provide enough conductive sites to effectively adsorb copper ions for deposition. At the same time, due to the lack of copper deposition on the surface of the film, the surface resistance of the film is very high, and the conductivity is poor.

[0092] 3、Compared with examples 1-5, the sheet resistance of the composite copper current collector of comparative example 2 decreased, which indicated that when the content of active material in the modified polymer film was too high, the intermediate polymer film layer had conductivity, which did not meet the requirements of the intermediate polymer film layer itself in the composite current collector, and could not prevent the short circuit of the positive and negative electrodes and increase the safety, therefore, when preparing the modified polymer film, the mass ratio should be selected within the range to ensure that the bonding force and insulation performance between the modified polymer film and other layers meet the requirements of the composite current collector.

[0093] It should be noted that, in this document, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0094] Finally, it should be noted that: the above only describes the preferred embodiments of the present application, and is not used to limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a composite copper current collector, comprising the following steps: Step S1: doping an active material in a polymer, and preparing a modified polymer film by biaxial stretching; the active material is one or more of carbon, cadmium sulfide, silver iodide, silver oxide, nickel oxide, conductive fiber, nickel, chromium, tin, nickel-chromium alloy, tin-nickel-copper alloy, lead-tin alloy, and palladium-copper alloy; Step S2: forming a copper layer on both upper and lower sides of the modified polymer film by using a chemical plating method; Step S3: preparing an oxidation-resistant layer on the copper layer to obtain a composite copper current collector.

2. The method of claim 1, wherein: The method for preparing the modified polymer film is as follows: Step (1): melt extrusion: adding the polymer and the active material into a double-screw extruder, and heating and melting and extruding to obtain a molten raw material; Step (2): casting: casting the molten raw material onto a casting roller, and forming by cooling treatment to obtain a casting sheet; Step (3): stretching: obtaining the modified polymer film by a biaxial stretching process.

3. The method of claim 2, wherein: The modified polymer film comprises the following raw materials: 90-99 wt% of the polymer and 1-10 wt% of the active material.

4. The method of claim 3, wherein: The polymer is one or more of polypropylene, polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, and polyphenylene sulfide.

5. The method of claim 2, wherein: In the step (2), the process conditions for the cooling treatment are as follows: the cooling medium is water, and the cooling temperature is 10-50℃.

6. The method of claim 2, wherein: In the step (3), the process conditions for the biaxial stretching process are as follows: the stretching ratio is 2-6, and the stretching temperature is 80-160℃, and the temperature is lower than the melting point of the polymer.

7. The method of claim 1, wherein: The thickness of the copper layer is 500-2000 nm.

8. The method of claim 1, wherein: The material of the oxidation-resistant layer is one or more of copper chromate, copper chromite, and chromium oxide.

9. The method of claim 1, wherein: The preparation method of the oxidation-resistant layer is one or more of dip coating, physical vapor deposition, and chemical vapor deposition.

10. The method of claim 1, wherein: The thickness of the oxidation-resistant layer is 5-100 nm, and the thickness of the oxidation-resistant layer cannot exceed one-tenth of the thickness of the copper layer.

Images