A composite current collector and its preparation method

Abstract

The present invention discloses a composite current collector, comprising: a base film made of a polymer material; a conductive layer disposed on the base film; the conductive layer sequentially includes a first aluminum layer, an alloy diffusion layer, and a second aluminum layer in a direction away from the base film; the alloy diffusion layer includes multiple layers of inserted metal layers and aluminum plating layers stacked alternately; each inserted metal layer includes at least one plating layer formed by adding elements, and the adding elements include at least one of metal elements with a metal diffusion rate greater than that of aluminum. The added metals in the present invention can occupy the active sites first, inhibit the growth of aluminum crystals, so that the intermetallic compounds formed by these metals and aluminum are distributed in the form of spheres and short rods at the grain boundaries or within the grains, and there are a large number of dislocations distributed in the metal structure, thereby improving the bonding strength and tensile strength of the metal plating layer, and also improving the corrosion resistance, which can solve the problems of coating delamination and peeling during pulling or rolling of the composite film.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a composite current collector and a preparation method thereof. Background Art

[0002] The composite aluminum foil is a "sandwich" structure formed by vacuum evaporation plating process, with 1 micron of aluminum plated on the upper and lower surfaces of a 6-micron PET base film. The mainstream process of the composite aluminum foil is evaporation plating. By using vacuum evaporation coating, aluminum wire is fed onto a high-temperature evaporation boat, and in an electric heating manner (heated to 1000 - 1200 °C), solid aluminum is transformed into gaseous aluminum. Oxygen is simultaneously introduced into the diffusion channel of the aluminum vapor, so that oxygen reacts with aluminum molecules to form a metal compound, which is deposited on the surface of the substrate to form a 5 - 15 nm auxiliary layer with good compactness and corrosion resistance. Although the aluminum-plated composite film prepared by this evaporation plating process has good metal properties. However, compared with traditional aluminum foil, the composite film prepared by physical vapor deposition has poor adhesion between its polymer substrate and metal coating, resulting in easy shedding of the metal coating. At the same time, the gaps between the aluminum layers will cause it to be easily corroded. Especially for the case of multiple evaporation platings, the atomic voids between the aluminum layers will lead to low adhesion. In the actual production process, the adhesion between several aluminum layers in the middle of the conductive layer is lower than that of other layers, which causes the coating layer to delaminate and fall off when the composite film is pulled or rolled, seriously affecting its use. Summary of the Invention

[0003] In order to improve the situation of coating layer delamination and shedding when the composite film is pulled or rolled, the present invention proposes a composite current collector. The above object can be achieved by the following implementation manners of technical solutions:

[0004] A composite current collector, comprising:

[0005] A base film, which is made of a polymer material;

[0006] A conductive layer, which is disposed on the base film; the conductive layer sequentially includes a first aluminum layer, an alloy diffusion layer, and a second aluminum layer along the direction away from the base film;

[0007] The alloy diffusion layer includes multiple layers of inserted metal layers and aluminum plating layers stacked alternately; each inserted metal layer includes at least one coating layer formed by adding elements, and the adding elements include at least one of metal elements with a metal diffusion rate greater than that of aluminum.

[0008] Optionally, the adding elements include at least one rare earth element.

[0009] Optionally, the adding elements include at least one of rhenium, erbium, gadolinium, and manganese.

[0010] Optionally, the alloy diffusion layer includes at least three inserted metal layers.

[0011] Optionally, the thickness of the inserted metal layer in the alloy diffusion layer is 40 - 70 nanometers.

[0012] Optionally, as the distance between the inserted metal layer and the first aluminum layer increases, the thickness of the inserted metal layer first increases and then decreases.

[0013] Optionally, the thickness of each aluminum plating layer in the alloy diffusion layer is 40 - 70 nm.

[0014] Optionally, both the first aluminum layer and the second aluminum layer are formed by stacking multiple layers of aluminum plating layers; the thickness ratio of the first aluminum layer to the second aluminum layer is 2 - 2.6:1;

[0015] Optionally, the first aluminum layer includes 5 - 15 layers of aluminum plating layers, and the thickness of each aluminum plating layer is 50 - 70 nm;

[0016] The second aluminum layer includes 1 - 8 layers, and the thickness of each aluminum plating layer is 40 - 55 nm.

[0017] Optionally, an alumina layer is provided between the base film and the conductive layer.

[0018] A method for preparing a composite current collector includes the following steps:

[0019] Step 1) Deposit multiple layers of aluminum plating layers on the base film by vacuum evaporation to form the first aluminum layer;

[0020] Step 2) Alternately deposit multiple layers of inserted metal layers and aluminum plating layers on the first aluminum layer by vacuum evaporation to form an alloy diffusion layer;

[0021] Step 3) Deposit multiple layers of aluminum plating layers on the alloy diffusion layer by vacuum evaporation to form the second aluminum layer.

[0022] Optionally, the temperature for vacuum evaporating the aluminum plating layer is 1000 - 1200 °C, 10 -3 ~5*10 -2 Pa; and / or

[0023] In step 2), erbium is used as an additive element to prepare the inserted metal layer, the vacuum evaporation temperature is 1000 - 1200 °C, and the vacuum degree is 10 -3 ~5*10 -2 Pa; and / or

[0024] In step 2), gadolinium is used as an additive element to prepare the inserted metal layer, the vacuum evaporation temperature is 1500 - 1700 °C, and the vacuum degree is 10 -3 ~5*10 -2 Pa; and / or

[0025] In step (ii), manganese is used as an additive element to prepare the inserted metal layer, and the vacuum evaporation temperature is 1400 - 1600 °C, and the vacuum degree is 10 -3 ~5×10 -2 Pa.

[0026] The technical solution of the present invention has the following advantages:

[0027] By introducing a variety of inserted metals into the original composite aluminum current collector, the metal diffusion rate of the selected inserted metals is greater than that of aluminum, such as manganese and rare earth metals, which can occupy the active sites first and inhibit the growth of aluminum crystals, so that the intermetallic compounds formed by these inserted metals and aluminum are distributed in the form of spheres and short rods at the grain boundaries or within the boundaries, and there are a large number of dislocations distributed in the metal structure, thereby improving the bonding strength and tensile strength of the metal coating, and also improving the corrosion resistance.

[0028] By introducing a variety of inserted metals in the middle several layers to construct crystal misalignment and increase the resistance to dislocation slip, the tensile capacity of the current collector is improved, and the delamination and peeling of the coating during the rolling process are reduced. Rare earth has the effect of reducing the contents of hydrogen, oxygen and sulfur in aluminum and aluminum alloys, which helps to better remove harmful impurities, refine impurities or change their morphology, making the grains refined and evenly distributed; it can eliminate the coarse massive phases distributed in the original crystal and form spherical phases, significantly reducing the strip-shaped and fragmented compounds at the grain boundaries. Usually, the atomic radius of rare earth is larger than that of aluminum atoms, and its properties are relatively active. When it melts in the aluminum liquid, it is very easy to fill the surface defects of the alloy phase, reducing the surface tension at the interface between the new and old phases and increasing the growth rate of crystal nuclei; at the same time, it can also form a surface active film between the grains and the molten liquid to prevent the grown grains from growing and refine the alloy structure; in addition, the large increase in the number of crystal nuclei when the compound formed by aluminum and rare earth crystallizes also makes the alloy structure refined.

[0029] The thickness of the inserted metal layer introduced by the present invention shows a certain change trend from the base film to the surface of the aluminum layer, so as to improve the consistency of the bonding strength of the multi-layer aluminum layer in the thickness direction and further improve the problem of uneven internal and external stresses caused by subsequent rolling of the electrode sheet and use in the battery;

[0030] The inserted metal layer introduced by the present invention can select a variety of metal combinations to introduce the performance advantages of a variety of metals, and at the same time improve the tensile performance, corrosion resistance and thermal conductivity of the current collector. Compared with introducing other metal layers between each layer of aluminum layer, this solution can reduce the influence of other metals on the sheet resistance of the current collector, ensure the electrical conductivity of the current collector, and reduce the repeated replacement of evaporation materials in the process preparation and the cleaning of the evaporation equipment. Description of the Drawings

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 It is a schematic diagram of the current collector structure of the present invention. Specific embodiments

[0033] Now, various exemplary embodiments of the present invention will 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, characteristics, and implementation schemes of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0034] In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0035] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0036] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention.

[0037] In the prior art, generally 15 - 25 layers of aluminum plating are deposited on the alumina layer to make the performance indicators reach the process set values. The present invention introduces a variety of inserted metals into the original composite aluminum current collector by means of vacuum plating. The selected inserted metals have a metal diffusion rate greater than that of aluminum. For example, rare earth metals are selected, which can occupy the active sites first, inhibit the growth of aluminum crystals, so that the intermetallic compounds formed by these inserted metals and aluminum are distributed in the form of spheres and short rods at the grain boundaries or within the grains, and there are a large number of dislocations distributed in the metal structure, thereby improving the bonding strength and tensile strength of the metal plating, and also improving the corrosion resistance.

[0038] Example 1

[0039] Compared with the existing aluminum coating, a single-layer manganese metal and aluminum are plated between the 6-7, 7-8, and 8-9 layers to form an alloy coating. The specific steps are as follows:

[0040] Fix the base film to the winding trolley, perform threading for unwinding and rewinding, and then adjust the tension. The unwinding end is at 120 N and the rewinding end is at 100 N. After the winding trolley enters the evaporation chamber, evacuate to 5×10 -3 Pa, start the winding trolley, control the speed at 280 - 300 m / min, heat the evaporation boat and feed the aluminum wire at the same time, the wire feeding speed is 300 - 350 mm / min, and start the oxygen inlet at the same time to apply an alumina primer on the surface of the base film, and control the vacuum degree at 5×10 -2 Pa. Then break the vacuum and plate a layer of aluminum in the same way. The heating temperature is 1000 - 1200 °C. After plating aluminum 5 times on both sides, replace the metal wire and plate a layer of manganese metal under the same conditions. The heating temperature is 1400 - 1600 °C. Plate aluminum for the 8th layer, plate manganese metal for the 9th layer, plate aluminum for the 10th layer, plate manganese metal for the 11th layer, and then keep plating aluminum until the surface sheet resistance is about 40 mΩ·□. Take samples of each coating to test the coating adhesion amount, and the average coating thickness is about 53 nm by testing and calculation. The adhesion amount of aluminum is about 162 mg / m 2 , and the adhesion amount of manganese is 440 mg / m 2 . Obtain the current collector structure as Figure 1 shown. An alumina layer 2, a first aluminum layer 3, an alloy diffusion layer 4, and a second aluminum layer 5 are sequentially provided on the base film 1. The alloy diffusion layer 4 is formed by alternately arranging the inserted metal layer 41 and the aluminum coating layer 42.

[0041] Example 2

[0042] Compared with the existing aluminum coating, a single-layer rhenium metal and aluminum are plated between the 6-7 layer, 7-8 layer, and 8-9 layer to form an alloy coating. The specific steps are as follows:

[0043] Fix the base film to the winding trolley, perform threading for unwinding and rewinding, and then adjust the tension. The unwinding end is at 120 N and the rewinding end is at 100 N. After the winding trolley enters the evaporation chamber, evacuate to 5×10 -3 Pa, start the winding trolley, control the speed at 280 - 300 m / min, heat the evaporation boat and feed the aluminum wire at the same time, the wire feeding speed is 300 - 350 mm / min, and start the oxygen inlet at the same time to apply an alumina primer on the surface of the base film, and control the vacuum degree at 5×10 -2Pa. After breaking the vacuum, a layer of aluminum is deposited in the same manner, with a heating temperature of 1000 - 1200 °C. After depositing aluminum 5 times on both sides, the wire is replaced, and a layer of rhenium metal is deposited under the same conditions, with a heating temperature of 3200 - 3700 °C. Aluminum is deposited on the 8th layer, rhenium metal on the 9th layer, aluminum on the 10th layer, and rhenium metal on the 11th layer. Then, aluminum is continuously deposited until the surface sheet resistance is approximately 40 mΩ·□. Samples are taken from each coating layer to test the coating adhesion amount. The average thickness of the coating layer is calculated to be approximately 53 nm through testing, the adhesion amount of aluminum is approximately 162 mg / m 2 , and the adhesion amount of rhenium is approximately 1260 mg / m 2 .

[0044] Example 3

[0045] In this example, compared with the existing aluminum coating layer, a single-layer erbium metal and aluminum are deposited between the 6 - 7th layer, 7 - 8th layer, and 8 - 9th layer to form an alloy coating layer. The specific steps are as follows:

[0046] Fix the base film to the winding trolley, perform winding and unwinding threading, and then adjust the tension. The unwinding end is at 120 N, and the winding end is at 100 N. After the winding trolley enters the evaporation chamber, evacuate to 5×10 -3 Pa, start the winding trolley, control the speed at 280 - 300 m / min, heat the evaporation boat and feed the aluminum wire simultaneously, with the wire feeding speed at 300 - 350 mm / min. At the same time, start the oxygen intake to perform alumina primer on the surface of the base film, and control the vacuum degree at 5×10 -2 Pa. After breaking the vacuum, a layer of aluminum is deposited in the same manner, with a heating temperature of 1000 - 1200 °C. After depositing aluminum 5 times on both sides, the wire is replaced, and a layer of erbium metal is deposited under the same conditions, with a heating temperature of 1700 - 2000 °C. Aluminum is deposited on the 8th layer, erbium metal on the 9th layer, aluminum on the 10th layer, and erbium metal on the 11th layer. Then, aluminum is continuously deposited until the surface sheet resistance is approximately 40 mΩ·□. Samples are taken from each coating layer to test the coating adhesion amount. The average thickness of the coating layer is calculated to be approximately 60 nm through testing, the adhesion amount of aluminum is approximately 162 mg / m 2 , and the adhesion amount of erbium is approximately 530 mg / m 2 .

[0047] Example 4

[0048] In this example, compared with the existing aluminum coating layer, a single-layer gadolinium metal and aluminum are deposited between the 6 - 7th layer, 7 - 8th layer, and 8 - 9th layer to form an alloy coating layer. The specific steps are as follows:

[0049] Fix the base film to the winding trolley, perform winding and unwinding threading, and then adjust the tension. The unwinding end is at 120 N, and the winding end is at 100 N. After the winding trolley enters the evaporation chamber, evacuate to 5×10 -3Pa, start the winding trolley, control the speed at 280 - 300 m / min, simultaneously heat the evaporation boat and feed the aluminum wire, the wire feeding speed is 300 - 350 mm / min, simultaneously turn on the oxygen intake, perform alumina priming on the surface of the base film, and control the vacuum degree at 5×10 -2 Pa. Then break the vacuum and deposit a layer of aluminum in the same way, the heating temperature is 1000 - 1200 °C. After plating aluminum 5 times on both sides, replace the metal wire, deposit a layer of gadolinium metal under the same conditions, and the heating temperature is 1500 - 1700 °C. Deposit aluminum on the 8th layer, deposit gadolinium metal on the 9th layer, deposit aluminum on the 10th layer, deposit gadolinium metal on the 11th layer, and then keep depositing aluminum until the surface sheet resistance is about 40 mΩ·□. Take samples of each coating to test the coating adhesion amount, and through testing and calculation, the average coating thickness is about 52 nm, the adhesion amount of aluminum is about 162 mg / m 2 , the adhesion amount of gadolinium is about 475 mg / m 2 .

[0050] Example 5

[0051] In this example, compared with the existing aluminum coating, a single layer of manganese metal is deposited between the 6th - 7th layers and the 8th - 9th layers. Among them, five layers of erbium metal and aluminum are deposited on the 7th - 8th layers to form an alloy coating. The specific steps are as follows:

[0052] Fix the base film to the winding trolley, perform film threading for winding and unwinding, and then adjust the tension. The film unwinding end is at 120 N, and the winding end is at 100 N. After the winding trolley enters the evaporation chamber, evacuate to 5×10 -3 Pa, start the winding trolley, control the speed at 280 - 300 m / min, simultaneously heat the evaporation boat and feed the aluminum wire, the wire feeding speed is 300 - 350 mm / min, simultaneously turn on the oxygen intake, perform alumina priming on the surface of the base film, and control the vacuum degree at 5×10 -2 Pa. Then break the vacuum and deposit a layer of aluminum in the same way, the heating temperature is 1000 - 1200 °C. After plating aluminum 5 times on both sides, replace the metal wire, deposit a layer of manganese metal under the same conditions, and the heating temperature is 1400 - 1600 °C. Deposit aluminum on the 8th layer, then continuously deposit 5 layers of the second metal, deposit aluminum on the 14th layer, deposit the second metal on the 15th layer, and then keep depositing aluminum until the surface sheet resistance is about 40 mΩ·□. Take samples of each coating to test the coating adhesion amount, and through testing and calculation, the average coating thickness is about 60 nm, the adhesion amount of aluminum is about 162 mg / m 2 , the adhesion amount of erbium is about 530 mg / m 2 , the adhesion amount of gadolinium is about 475 mg / m 2 , the adhesion amount of manganese is 440 mg / m 2 .

[0053] Example 6

[0054] In this implementation, compared with the existing aluminum coating, a single layer of manganese metal is plated between the 6th - 7th layers and the 8th - 9th layers. Among them, five layers of erbium metal and aluminum are plated on the 7th - 8th layers to form an alloy coating. The specific steps are as follows:

[0055] Fix the base film to the winding trolley, perform threading for unwinding and rewinding, and then adjust the tension. The unwinding end is at 120N and the rewinding end is at 100N. After the winding trolley enters the evaporation chamber, evacuate to 5×10 -3 Pa, start the winding trolley, control the speed at 280 - 300 m / min, heat the evaporation boat and feed the aluminum wire simultaneously, with the wire feeding speed at 300 - 350 mm / min. At the same time, start the oxygen intake to apply an alumina primer on the surface of the base film, and control the vacuum degree at 5×10 -2 Pa. Then break the vacuum and plate a layer of aluminum in the same way, with the heating temperature at 1000 - 1200 °C. After plating aluminum 5 times on both sides, replace the metal wire and plate a layer of manganese metal under the same conditions, with the heating temperature at 1400 - 1600 °C (for manganese). Plate aluminum on the 8th layer, and then continuously plate five layers of erbium metal, with the heating temperature at 1700 - 2000 °C. Plate aluminum on the 14th layer and manganese metal on the 15th layer, and then keep plating aluminum until the surface sheet resistance is about 40 mΩ·□. Take samples for each coating layer to test the coating adhesion amount. Through testing and calculation, the average coating thickness is about 53 nm, the adhesion amount of aluminum is about 162 mg / m 2 ², the adhesion amount of erbium is about 530 mg / m 2 ², and the adhesion amount of manganese is 440 mg / m 2 .

[0056] Example 7

[0057] In this implementation, compared with the existing aluminum coating, a single layer of manganese metal is plated between the 6th - 7th layers and the 8th - 9th layers. Among them, five layers of gadolinium metal and aluminum are plated on the 7th - 8th layers to form an alloy coating. The specific steps are as follows:

[0058] Fix the base film to the winding trolley, perform threading for unwinding and rewinding, and then adjust the tension. The unwinding end is at 120N and the rewinding end is at 100N. After the winding trolley enters the evaporation chamber, evacuate to 5×10 -3 Pa, start the winding trolley, control the speed at 280 - 300 m / min, heat the evaporation boat and feed the aluminum wire simultaneously, with the wire feeding speed at 300 - 350 mm / min. At the same time, start the oxygen intake to apply an alumina primer on the surface of the base film, and control the vacuum degree at 5×10 -2Pa. After breaking the vacuum, aluminum is deposited in the same way, with the heating temperature being 1000 - 1200 °C. When the aluminum has been deposited 5 times on both sides, the wire is replaced, and manganese metal is deposited under the same conditions, with the heating temperature being 1400 - 1600 °C (for manganese). Aluminum is deposited on the 8th layer, and then 5 layers of gadolinium metal are continuously deposited, with the heating temperature being 1500 - 1700 °C. Aluminum is deposited on the 14th layer, and manganese metal is deposited on the 15th layer. Then, aluminum is continuously deposited until the surface sheet resistance is approximately 40 mΩ·□. Samples are taken from each coating layer to test the coating adhesion amount. After testing and calculation, the average coating thickness is approximately 53 nm, the adhesion amount of aluminum is approximately 162 mg / m 2 , the adhesion amount of gadolinium is approximately 475 mg / m 2 , and the adhesion amount of manganese is 440 mg / m 2 .

[0059] Example 8

[0060] In this example, compared with the existing aluminum coating, a single layer of manganese metal is deposited between the 6th - 7th and 8th - 9th layers. Between the 7th - 8th layers, a single layer of erbium and gadolinium metals (erbium is deposited first and then gadolinium) is deposited to form an alloy coating with aluminum. The specific steps are as follows:

[0061] Fix the base film to the winding trolley, perform threading for winding and unwinding, and then adjust the tension. The unwinding end is at 120 N, and the winding end is at 100 N. After the winding trolley enters the evaporation chamber, vacuum is pumped to 5×10 -3 Pa. The winding trolley is started, and the speed is controlled at 280 - 300 m / min. At the same time, the evaporation boat is heated and aluminum wire is fed, with the wire - feeding speed being 300 - 350 mm / min. At the same time, oxygen intake is started to deposit a layer of alumina on the surface of the base film, and the vacuum degree is controlled at 5×10 -2 Pa. After breaking the vacuum, aluminum is deposited in the same way, with the heating temperature being 1000 - 1200 °C. When the aluminum has been deposited 5 times on both sides, the wire is replaced, and manganese metal is deposited under the same conditions, with the heating temperature being 1400 - 1600 °C. Aluminum is deposited on the 8th layer, and erbium and gadolinium metals are deposited on the 9th and 10th layers, with erbium being deposited first and then gadolinium, and the heating temperatures being 1700 - 2000 °C (for erbium) / 1500 - 1700 °C (for gadolinium) / 1400 - 1600 °C. Aluminum is deposited on the 11th layer, and manganese metal is deposited on the 12th layer. Then, aluminum is continuously deposited until the surface sheet resistance is approximately 40 mΩ·□. Samples are taken from each coating layer to test the coating adhesion amount. After testing and calculation, the average coating thickness is approximately 60 nm, the adhesion amount of aluminum is approximately 162 mg / m 2 , the adhesion amount of erbium is approximately 530 mg / m 2 , the adhesion amount of gadolinium is approximately 475 mg / m 2 , and the adhesion amount of manganese is 440 mg / m 2 .

[0062] Example 9

[0063] In this implementation, a single layer of manganese metal is plated between 6 - 7 layers and 8 - 9 layers compared with the existing aluminum coating. An alloy coating of erbium, gadolinium, rhenium and aluminum is formed between the original 7 - 8 layers. The specific steps are as follows:

[0064] Fix the base film to the winding carriage, perform threading for unwinding and rewinding, and then adjust the tension. The unwinding end is at 120N and the rewinding end is at 100N. After the winding carriage enters the evaporation chamber, evacuate to 5×10 -3 Pa, start the winding carriage, control the speed at 280 - 300 m / min, heat the evaporation boat and feed the aluminum wire simultaneously, with the wire feeding speed of 300 - 350 mm / min. At the same time, open the oxygen inlet to form an alumina primer on the surface of the base film, and control the vacuum degree at 5×10 -2 Pa. Then break the vacuum and plate a layer of aluminum in the same way, with the heating temperature of 1000 - 1200 °C. After plating aluminum 5 times on both sides, replace the metal wire and plate a layer of manganese metal under the same conditions, with the heating temperature of 1400 - 1600 °C. Plate aluminum for the 8th layer, and plate a layer of erbium, gadolinium, and rhenium respectively for the 9th / 10th / 11th layers. Plate aluminum for the 12th layer and manganese metal for the 13th layer, and then keep plating aluminum until the surface sheet resistance is about 40 mΩ·□. Take samples of each coating to test the coating adhesion amount, and the average coating thickness is calculated to be about 60 nm through testing. The adhesion amount of aluminum is about 162 mg / m 2 , the adhesion amount of erbium is about 530 mg / m 2 , the adhesion amount of gadolinium is about 475 mg / m 2 , the adhesion amount of rhenium is about 1260 mg / m 2 , and the adhesion amount of manganese is 440 mg / m 2 .

[0065] Comparative Example 1

[0066] Compared with Example 1, this comparative example is an original aluminum - plated sample without adding a second metal. The specific steps are as follows:

[0067] Fix the base film to the winding carriage, perform threading for unwinding and rewinding, and then adjust the tension. The unwinding end is at 120N and the rewinding end is at 100N. After the winding carriage enters the evaporation chamber, evacuate to 5×10 -3 Pa, start the winding carriage, control the speed at 280 - 300 m / min, heat the evaporation boat and feed the aluminum wire simultaneously, with the wire feeding speed of 300 - 350 mm / min. At the same time, open the oxygen inlet to form an alumina primer on the surface of the base film, and control the vacuum degree at 5×10 -2Pa. After breaking the vacuum, a layer of aluminum is plated in the same manner, with the heating temperature being 1000 - 1200 °C. Then, aluminum is continuously plated until the surface sheet resistance is approximately 40 mΩ·□. Samples are taken from each plating layer to test the plating adhesion amount. Through testing and calculation, the average thickness of the plating layer is approximately 53 nm, and the adhesion amount of aluminum is approximately 162 mg / m 2 。

[0068] Comparative Example 2

[0069] Compared with Example 1, in this comparative example, a single layer of manganese metal is plated between the alumina layer - layer 1, layer 1 - layer 2, and layer 2 - layer 3. The specific steps are as follows:

[0070] Fix the base film to the winding trolley, perform threading for winding and unwinding, and then adjust the tension. The unwinding end is at 120 N, and the winding end is at 100 N. After the winding trolley enters the evaporation chamber, evacuate to 5 * 10 -3 Pa, start the winding trolley, control the speed at 280 - 300 m / min. At the same time, heat the evaporation boat and feed the aluminum wire, with the wire feeding speed being 300 - 350 mm / min. At the same time, start the oxygen intake to perform alumina priming on the surface of the base film, and control the vacuum degree at 5 * 10 -2 Pa. After breaking the vacuum, a layer of manganese metal is plated in the same manner, with the heating temperature being 1400 - 1600 °C. Then, a layer of aluminum and a layer of manganese are successively plated. After plating 3 layers of manganese in total, aluminum is continuously plated until the surface sheet resistance is approximately 40 mΩ·□. Samples are taken from each plating layer to test the plating adhesion amount. Through testing and calculation, the average thickness of the plating layer is approximately 53 nm, the adhesion amount of aluminum is approximately 162 mg / m2, and the adhesion amount of manganese is 440 mg / m 2 。

[0071] In the above examples, the meanings of the number of layers such as 1 layer, 7 layers, 8 layers, etc. are as follows: The aluminum plating layer closest to the base film is recorded as layer 1, and each aluminum plating layer is sequentially counted according to the distance from the base film.

[0072] Test Example

[0073] The surface sheet resistance, tensile strength MD, tensile strength TD, peel strength, and thickness of the above composite current collector materials are tested. The test results are shown in Table 1. The specific test methods are as follows:

[0074] Surface sheet resistance: The sheet resistance is measured using a four - probe resistivity tester. According to the lateral width of the product, determine the number of square resistance tests. One point is tested every 100 mm, and other requirements are tested according to the method specified in GBIT 22638.6 - 2016.

[0075] Tensile strength: The tensile strength and elongation at break of the composite aluminum foil at room temperature were measured using an electronic universal material testing machine. The test conditions were a gauge length of 10 mm, a tensile speed of 100 mm / min, a width of 15 mm, and other requirements were determined according to the method specified in GB / T 1040.3-2006.

[0076] Peel strength: Take a test sample with dimensions of 15 * 100 mm. Stick the 3M - 9080A - 15 mm tape on a stainless - steel plate, then evenly stick the measurement sample on the double - sided tape. Use a 2 kg standard small pressure roller to squeeze back and forth 2 times. Then stick the 3M - 9080A - 14 mm tape on the surface of the sample and use a 2 kg standard small pressure roller to squeeze back and forth 2 times. Subsequently, take the pressed sample to the tensile machine for 180° stretching at a speed of 100 mm / min and a width setting of 14 mm, and take the maximum value of the result.

[0077] Table 1 Physical data of the composite film in the examples

[0078]

[0079] By comparing Examples 1 - 4 with Comparative Example 1, it can be seen that inserting a second metal into the original aluminum layer in the present invention can effectively improve the tensile strength and peel strength of the composite aluminum current collector. It can be seen that the staggered distribution of multiple metals strengthens the bonding force between the metal layers. By comparing each example with Comparative Example 2, it can be known that the bonding force between the newly added metal and the alumina underlayer is poor. Therefore, at least one layer of aluminum needs to be plated on the underlayer first and then the second metal coating is applied;

[0080] In Examples 8 and 9, the types of added metals are expanded to 2 or 3. The dislocation effect between different metals is further enhanced. At the same time, due to the different atomic radii of the metals, the positions of interlayer defects are filled by other small - radius atoms, preventing the growth of generated grains and refining the alloy structure, further improving the bonding force between the metal layers.

[0081] Obviously, the above - mentioned examples are only for clearly illustrating the examples and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A composite current collector, characterized in that: include: A base film, wherein the base film is made of a polymer material; A conductive layer, the conductive layer is arranged on the base film; the conductive layer comprises a first aluminum layer, an alloy diffusion layer, and a second aluminum layer in sequence in a direction away from the base film; The alloy diffusion layer comprises a plurality of alternately stacked inserted metal layers and aluminum coatings; each inserted metal layer comprises at least one coating formed by an additive element, wherein the additive element comprises at least one of metal elements having a metal diffusion rate greater than that of aluminum; The additional element includes at least one of rhenium, erbium, gadolinium and manganese.

2. The composite current collector according to claim 1, characterized in that: The additional element includes at least one rare earth element.

3. The composite current collector according to claim 1, characterized in that: The alloy diffusion layer includes at least three inserted metal layers.

4. The composite current collector according to claim 1, characterized in that: The thickness of the inserted metal layer in the alloy diffusion layer is 40-70 nanometers.

5. The composite current collector according to claim 1, characterized in that: As the distance between the inserted metal layer and the first aluminum layer increases, the thickness of the inserted metal layer first increases and then decreases.

6. The composite current collector according to claim 1, characterized in that: The thickness of each aluminum coating layer in the alloy diffusion layer is 40-70 nm.

7. The composite current collector according to claim 1, characterized in that: The first aluminum layer and the second aluminum layer are both formed by stacking multiple aluminum plating layers; the thickness ratio of the first aluminum layer to the second aluminum layer is 2-2.6:

1.

8. The composite current collector according to claim 1, characterized in that: The first aluminum layer comprises 5 to 15 aluminum coating layers, and the thickness of each aluminum coating layer is 50 to 70 nm; The second aluminum layer comprises 1 to 8 layers, and the thickness of each aluminum coating layer is 40-55 nm.

9. The composite current collector according to any one of claims 1 to 8, characterized in that: An aluminum oxide layer is provided between the base film and the conductive layer.

10. The method for preparing a composite current collector according to any one of claims 1 to 9, characterized in that: The steps include: Step 1) depositing multiple layers of aluminum coating on the base film by vacuum evaporation to form a first aluminum layer; Step 2) alternately depositing multiple layers of inserted metal layers and aluminum plating layers on the first aluminum layer by vacuum evaporation to form an alloy diffusion layer; Step 3) Depositing multiple aluminum coatings on the alloy diffusion layer by vacuum evaporation to form a second aluminum layer.

11. The preparation method according to claim 10, characterized in that The temperature of vacuum evaporation aluminum coating is 1000-1200℃, and the vacuum degree is 10 -3 ~5*10 -2 Pa; and / or In the step 2), erbium is used as an additive element to prepare an inserted metal layer, and the vacuum evaporation temperature is 1000-1200°C and the vacuum degree is 10 -3 ~5*10 -2 Pa; and / or In the step 2), gadolinium is used as an additive element to prepare an inserted metal layer, and the vacuum evaporation temperature is 1500-1700°C and the vacuum degree is 10 -3 ~5*10 -2 Pa; and / or In the step 2), manganese is used as an additive element to prepare the inserted metal layer, and the vacuum evaporation temperature is 1400-1600°C and the vacuum degree is 10 -3 ~5*10 -2 Pa.

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