Copper cluster array composite current collector, preparation method and battery

Abstract

The embodiment of the present invention provides a copper cluster array composite current collector, a preparation method and a battery, wherein magnetron sputtering is performed on a PET film to obtain a composite film having a sputtered metal layer on the surface; a composite layer containing copper seeds and carbon nanotubes is obtained on the surface of the sputtered metal layer through a first stage of composite electrodeposition; a first height copper cluster array consisting of multiple copper columns is obtained on the surface of the sputtered metal layer through a second stage of composite electrodeposition; the first height does not exceed 2 μm; a second height copper cluster array is obtained by extending and growing on the first height copper cluster array through a third stage of composite electrodeposition; wherein the copper columns are perpendicular to the sputtered metal layer, and the carbon nanotubes are distributed inside the copper columns and are divided into two parts, wherein the first part is distributed on the surface of the sputtered metal layer and the first height copper cluster array, and the second part is distributed on the second height copper cluster array; the content and distribution of carbon nanotubes in the electroplated metal layer are adjusted through the three-stage composite electrodeposition.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium battery materials, and in particular relates to a copper cluster array composite current collector, a preparation method and a battery. Background Art

[0002] Composite current collector is a new type of material composed of polymer film and metal. It mainly collects electrons, gathers current and carries active substances in lithium batteries. Compared with traditional current collectors, composite current collectors can not only reduce the amount of metal used, but also reduce the weight of the current collector, effectively improving the energy density of the battery. In addition, the composite current collector material is soft and has good ductility. It can effectively maintain the stability of the electrode structure when subjected to mechanical loads, thereby improving the safety performance of lithium batteries.

[0003] Designing the surface structure of composite current collectors is an important means to enhance the functions of composite current collectors and improve the performance of lithium batteries. Introducing a three-dimensional structure on the surface of a composite current collector can effectively increase the contact area between the composite current collector and the active material and reduce the interface resistance. At the same time, the three-dimensional structure can also restrict the active materials that have volume expansion during the charge and discharge process, and alleviate the stress caused by volume expansion during the charge and discharge process. However, due to the thin metal layer on the surface of the composite current collector and the soft substrate, the interface bonding force between the three-dimensional structure and the composite current collector is weak, and the introduced three-dimensional structure is difficult to grow stably on the surface of the composite current collector. Summary of the invention

[0004] In view of this, the present invention provides a copper cluster array composite current collector, a preparation method and a battery, which can effectively stabilize the three-dimensional structure on the surface of the composite current collector. The introduction of carbon nanotubes not only enhances the bonding stability between the three-dimensional structure and the composite current collector, improves the overall fracture strength of the composite current collector, but also improves the structural stability of the three-dimensional structure. The composite current collector surface prepared by the method has a stable three-dimensional structure, which can provide a larger contact area for the active material in the lithium battery, and inhibit its volume expansion during the charge and discharge process, which is beneficial to improving the electrochemical performance of the battery.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] In a first aspect, an embodiment of the present invention provides a method for preparing a copper cluster array composite current collector, the method comprising:

[0007] A metal layer is sputtered on the surface of a polyethylene glycol terephthalate (PET) film by magnetron sputtering to obtain a composite film, and the composite film is used as a substrate to perform three-stage composite electrodeposition on the composite film to obtain an electroplated metal layer on its surface; wherein the electroplated metal layer includes a copper cluster array composed of a plurality of copper columns growing perpendicular to the sputtered metal layer, and the copper columns contain carbon nanotubes;

[0008] The content and distribution of carbon nanotubes in the electroplated metal layer were adjusted by three-stage composite electrodeposition, wherein the first part of the carbon nanotubes were distributed in the first height copper cluster array on the surface of the sputtered metal layer, and the second part of the carbon nanotubes were distributed in the second height copper cluster array.

[0009] Preferably, the three-stage composite electrodeposition regulates the content and distribution of carbon nanotubes, including:

[0010] (1) placing a PET composite film with a sputtered metal layer in an electrodeposition solution containing carbon nanotubes, setting the first stage composite electrodeposition voltage to 0.1-0.3 V, the electrodeposition time to 10-30 s, maintaining the electrodeposition temperature to 25-30° C., stirring the process at a stirring speed of 800-900 r / min;

[0011] (2) Setting the voltage of the second composite electrodeposition stage from 0.2 V to 1.8 V, the voltage increase rate is 0.05 V / s, the electrodeposition temperature is maintained at 25°C, and the stirring speed is constant at 50 r / min;

[0012] (3) Add 1% Triton X-100 solution to the electrodeposition solution and stir it thoroughly. The voltage of the third stage of composite electrodeposition is 1.5-2V. The rotation speed is adjusted and gradually reduced from 800-900 r / min. The rotation speed decay rate is 400-600 r / min and lasts for 1-2 minutes. A copper cluster array composite current collector is obtained.

[0013] Preferably, the content of carbon nanotubes in the electrodeposition solution is 0.2 wt.%.

[0014] Preferably, the aspect ratio of each copper pillar in the copper cluster array is 2.5-4:1, the distance between two adjacent copper pillars is 1-5 μm, and the height of each copper pillar is 6-10 μm.

[0015] Preferably, the content of the carbon nanotubes in the first part is 3.7-4.2 vol%, and the content of the carbon nanotubes in the second part is 0.7-0.9 vol%.

[0016] In a second aspect, an embodiment of the present invention provides a copper cluster array composite current collector, which is prepared by the method for preparing a copper cluster array composite current collector described in any embodiment of the present invention.

[0017] In a third aspect, an embodiment of the present invention provides a battery, comprising a battery prepared by the method for preparing a copper cluster array composite current collector described in any embodiment of the present invention.

[0018] The invention provides a method for preparing a copper cluster array composite current collector. A metal layer is sputtered on the surface of a PET film by a magnetron sputtering method to obtain a composite film. The composite film is used as a substrate and three-stage composite electrodeposition is performed on the composite film to obtain an electroplated metal layer on the surface. The electroplated metal layer comprises a copper cluster array composed of a plurality of copper columns growing perpendicular to the sputtered metal layer, and the copper cluster array contains carbon nanotubes. The content and distribution of the carbon nanotubes in the electroplated metal layer are adjusted by the three-stage composite electrodeposition. The first part of the carbon nanotubes are distributed in the first height copper cluster array on the surface of the sputtered metal layer, and the content is 3.7-4.2 vol%. The second part of the carbon nanotubes are distributed in the second height copper cluster array, and the content is 0.7-0.9 vol%.

[0019] Compared with the prior art, it has the following beneficial effects:

[0020] (1) The three-stage composite electrodeposition in the present application is to adjust the content and distribution of carbon nanotubes in the copper cluster array by controlling the matching relationship between the rotation speed and the voltage during the electrodeposition process. The first part of the carbon nanotubes is distributed in the first height copper cluster array, and its content is higher than that of the conventional technology. In addition, this part of the carbon nanotubes enhances the bonding stability between the copper seed metal layer and the sputtered metal layer, improves the fracture strength of the composite film, and effectively improves the structural stability problems such as the three-dimensional metal structure being easy to fall off on the surface of the composite current collector;

[0021] (2) The second part of carbon nanotubes in the present application is distributed in the second height copper cluster array, which effectively enhances the structural stability of the copper cluster array and improves the overall mechanical strength of the copper cluster array. When it is combined with active materials to form a lithium battery electrode, it can effectively inhibit the volume expansion of the active material during the charge and discharge process, thereby improving the stability of the electrode and the cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic structural diagram of a copper cluster array composite current collector provided in Example 1 of the present invention.

[0023] Figure 2 This is a scanning electron microscope image of the surface of the first-height copper cluster array after the second stage of composite electrodeposition in Example 1 of the present invention;

[0024] Figure 3This is a scanning electron microscope image of the surface of the second-height copper cluster array after the third stage of composite electrodeposition in Example 1 of the present invention.

[0025] Among them, there are polyethylene terephthalate film 1, sputtered metal layer 2, copper pillars 3, second height copper cluster array 4, and first height copper cluster array 5. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] Before further describing the present invention in detail, the nouns and terms involved in the embodiments of the present invention are explained. The nouns and terms involved in the embodiments of the present invention are subject to the following explanations.

[0028] Copper seeds: small grains formed on the surface of the composite film after the first stage of composite electrodeposition that can extend and grow into copper cluster arrays;

[0029] First-height copper cluster array: after the second stage of composite electrodeposition, the copper cluster array on the surface of the sputtered metal layer is a first-height copper cluster array, and the height of the copper cluster array does not exceed 2 μm;

[0030] Second-height copper cluster array: After the third stage of composite electrodeposition, the copper cluster array between the top of the first-height copper cluster array and the top of the copper cluster array is the second-height copper cluster array.

[0031] Embodiment 1

[0032] A method for preparing a copper cluster array composite current collector prepared in an embodiment of the present invention is as follows:

[0033] (1) placing a PET film with a thickness of 12.5 μm in a vacuum chamber containing argon gas at a pressure of 0.1 to 10 Pa, and preparing a sputtered metal layer with a thickness of 0.4 μm on the surface of the PET film by applying a direct current negative high voltage radio frequency voltage, thereby completing the metallization treatment of the PET film and obtaining a composite film; then, using an acetone solution to clean the surface of the composite film, and the treatment process adopts an oscillation treatment, with the oscillator speed being 150 r / min and maintained for 3 minutes;

[0034] (2) 0.2 wt.% carbon nanotubes and 0.2 wt.% sodium dodecyl sulfate were added to the electrodeposition solution, and the solution was placed in an ultrasonic machine for intermittent ultrasonic treatment for 5 h, with each ultrasonic treatment lasting 30 min and then paused for 10 min. The cleaned composite film was immersed in a 5% dilute sulfuric acid solution for 20 s, rinsed with deionized water, and then placed in the electrodeposition solution;

[0035] (3) setting the first stage composite electrodeposition voltage to 0.2 V, the electrodeposition time to 20 s, and maintaining the electrodeposition temperature to 25° C., stirring the electrodeposition solution during this process, and the rotor stirring speed to 850 r / min, to obtain a composite layer containing copper seeds and carbon nanotubes on the surface of the composite film;

[0036] (4) The second stage of composite electrodeposition is variable voltage electrodeposition, the voltage is set to 0.2V and then increased to 1.8V, the voltage increase rate is 0.05V / s, the electrodeposition time is 32s, and the electrodeposition temperature is maintained at 25°C. This process is stirred at a constant speed, and the rotor stirring speed is 50r / min, to obtain a composite layer with a certain carbon nanotube content;

[0037] (5) Add 1% Triton X-100 solution to the electrodeposition solution and stir it thoroughly. Set the third stage composite electrodeposition voltage to 1.8 V, the electrodeposition time to 1.5 min, maintain the electrodeposition temperature to 25 ° C, adjust the rotor speed, and gradually decrease from 850 r / min. The rotor speed decay rate is 500 r / min, which lasts for 1 to 2 minutes to obtain a copper cluster array with an aspect ratio of 2.5 to 4:1, an average adjacent spacing of 3 μm, and an average height of 8 μm on the surface of the composite film. Subsequently, the composite film with the copper cluster array is alternately cleaned with anhydrous ethanol and deionized water, and the process is repeated 2 to 3 times. The composite film is placed in a vacuum drying oven and dried at 60 ° C for 6 hours to obtain a copper cluster array composite current collector.

[0038] The first part of the carbon nanotube content refers to the content of carbon nanotubes in the first-height copper cluster array, and the second part of the carbon nanotube content refers to the content of carbon nanotubes contained in the second-height copper cluster array, both of which are characterized by a sulfur-carbon analyzer;

[0039] The fracture strength of the composite film after the second electrodeposition was characterized by a universal testing machine;

[0040] The composite current collector is placed on a smooth and flat press. When the thickness of the composite current collector is reduced by 15%, the applied pressure is used to characterize the structural stability of the copper cluster array itself.

[0041] The bending resistance is characterized by testing the rate of change in resistance of the composite current collector sample after the third stage of electrodeposition before and after bending 100 times.

[0042] Embodiment 2

[0043] The method for preparing a copper cluster array composite current collector prepared in the embodiment of the present invention is consistent with the specific implementation method of Example 1, except that the voltage is adjusted to 0.1V in the "first stage of electrodeposition" step for the experiment.

[0044] Embodiment 3

[0045] The method for preparing a copper cluster array composite current collector prepared in the embodiment of the present invention is consistent with the specific implementation method of Example 1, except that the voltage is adjusted to 0.3V in the "first stage electrodeposition" step for the experiment.

[0046] Embodiment 4

[0047] A method for preparing a copper cluster array composite current collector prepared in an embodiment of the present invention is consistent with the specific implementation method of Example 1, except that the rotor speed is adjusted to 800r / min in the "first stage electrodeposition" step for the experiment.

[0048] Embodiment 5

[0049] A method for preparing a copper cluster array composite current collector prepared in an embodiment of the present invention is consistent with the specific implementation method of Example 1, except that the rotor speed is adjusted to 900 r / min in the "first stage electrodeposition" step for the experiment.

[0050] Embodiment 6

[0051] The method for preparing a copper cluster array composite current collector prepared in the embodiment of the present invention is consistent with the specific implementation method of Example 1, except that the voltage is adjusted to 2.0V in the "third stage electrodeposition" step for experiment.

[0052] Embodiment 7

[0053] This is a method for preparing a copper cluster array composite current collector prepared in an embodiment of the present invention. The specific implementation method is consistent with that of Example 1, except that the voltage is adjusted to 1.5V in the "third stage electrodeposition" step for the experiment.

[0054] Embodiment 8

[0055] A method for preparing a copper cluster array composite current collector prepared in an embodiment of the present invention is consistent with the specific implementation method of Example 1, except that the rotor attenuation rate is adjusted to 400r / min in the "third stage electrodeposition" step for experiment.

[0056] Embodiment 9

[0057] A method for preparing a copper cluster array composite current collector prepared in an embodiment of the present invention is consistent with the specific implementation method of Example 1, except that the rotor attenuation rate is adjusted to 600r / min in the "third stage electrodeposition" step for experiment.

[0058] Comparative Example 1

[0059] A method for preparing a copper cluster array composite current collector prepared in a comparative example of the present invention is consistent with the specific implementation method of Example 1, except that the carbon nanotube content in the electrodeposition solution is changed to 0wt.% for the experiment;

[0060] The content of carbon nanotubes in the composite current collector prepared in this experiment is zero, the structural stability of the copper cluster array is reduced, and the copper cluster array is easily detached from the surface of the composite current collector, which is not conducive to improving the electrochemical performance of the battery.

[0061] Comparative Example 2

[0062] A copper cluster array composite current collector prepared as a comparative example of the present invention, the specific implementation method is consistent with that of Example 1, and only the second electrodeposition step is omitted for the experiment;

[0063] The composite current collector prepared in this experiment has a carbon nanotube content of 2.5 vol% in the first part, which is low. There are not enough carbon nanotubes to improve the stability of the bottom of the copper cluster array and the sputtered metal layer. The fracture strength of the composite current collector is low, which is not conducive to improving the electrochemical performance of the battery.

[0064] Comparative Example 3

[0065] A copper cluster array composite current collector prepared as a comparative example of the present invention, the specific implementation method is consistent with that of Example 1, and only the third electrodeposition step is omitted for the experiment;

[0066] In the composite current collector prepared in this experiment, no copper cluster array was observed to be formed on the surface of the composite film. The composite current collector is difficult to suppress the volume expansion of the active material during the charging and discharging process, which is not conducive to improving the electrochemical performance of the battery.

[0067] See Table 1 and Table 2, which are summaries of the effects of the first electrodeposition voltage, the first rotor speed, the third electrodeposition voltage, and the third rotor decay rate on the performance of the copper cluster array composite current collector in the embodiments of the present invention; the first part of the carbon nanotube content in the table refers to the content of carbon nanotubes in the first-height copper cluster array, and the second part of the carbon nanotube content refers to the content of carbon nanotubes contained in the second-height copper cluster array. It can be seen from Table 1 and Table 2 that:

[0068] (1) In Example 1, the first electrodeposition voltage is 0.2V, the first rotor speed is 850r / min, the third electrodeposition voltage is 1.8V, and the third rotor decay rate is 500r / min. The prepared copper cluster array composite current collector is the optimal parameter composite current collector. The carbon nanotube content of the first part is as high as 4.2vol%, the carbon nanotube content of the second part is 0.9vol%, and the fracture strength of the composite film after the second electrodeposition is 293.4MPa. The pressure applied when the thickness is reduced by 15% is about 312N, and the resistance change rate after 100 bendings is 1.5%;

[0069] (2) Through the comparison of Examples 1, 2, 3, 8, and 9, it can be concluded that the first-stage electrodeposition voltage and the first-stage rotor speed have a greater impact on the carbon nanotube content of the first part, and have a smaller impact on the carbon nanotube content of the second part; increasing the first-stage electrodeposition voltage, the carbon nanotube content increases less, but the copper seed grows more densely, resulting in a reduction in the gap between the final copper cluster array, making it difficult to accommodate more active substances; reducing the first-stage electrodeposition voltage, carbon nanotubes are difficult to stably deposit on the copper seed layer, and the carbon nanotube content of the first part also decreases; reducing the first-stage rotor speed, the carbon nanotube content in the copper seed growth layer decreases, and increasing the first-stage rotor speed, the carbon nanotube content hardly increases, so the speed in Example 1 is the optimal parameter;

[0070] (3) Through comparison of Examples 1, 4, 5, 6, and 7, it can be concluded that the third-stage electrodeposition voltage and the third-stage rotor attenuation rate have a greater impact on the carbon nanotube content in the second part, and have a smaller impact on the carbon nanotube content in the first part; increasing the third-stage electrodeposition voltage does not significantly increase the carbon nanotube content in the second part, but the aspect ratio of the copper column increases, and the pressure applied when the thickness of the composite current collector decreases by 15% also decreases, indicating that its structural stability deteriorates, while reducing the third-stage electrodeposition voltage significantly reduces the carbon nanotube content in the copper cluster array; reducing the third-stage rotor attenuation rate does not significantly increase the carbon nanotube content distributed in the copper cluster array, and increasing the third-stage rotor attenuation speed results in more carbon nanotubes distributed in the gaps between the copper cluster arrays, and less carbon nanotube content inside the copper cluster arrays.

[0071]

[0072] Table 1

[0073]

[0074] Table 2

[0075] See Table 3 and Table 4, which summarize the effects of the content of carbon nanotubes in the electrodeposition solution, the voltage rise rate of the second electrodeposition stage, the rotor speed of the second stage, the electrodeposition voltage of the third stage, and the decay rate of the rotor speed of the third stage on the performance of the copper cluster array composite current collector in the comparative examples of the present invention. Combined with Table 1 and Table 2, it can be seen from Table 3 and Table 4 that:

[0076] (1) It can be concluded from Examples 1, 2, 3, 4, 5, 6, 7, 8, 9 and Comparative Example 1 that when no carbon nanotubes are added to the electrodeposition solution, the fracture strength of the composite current collector is significantly reduced, and the resistance change rate after 100 bends is significantly increased, and the resistance of the copper layer on the surface of the composite current collector increases, indicating that its integrity deteriorates, that is, the structural stability of the copper layer on the surface of the composite current collector deteriorates;

[0077] (2) It can be concluded from Examples 1, 2, 3, 4, 5, 6, 7, 8, 9 and Comparative Example 2 that the second stage variable pressure electrodeposition is crucial to increasing the content of carbon nanotubes in the first part. Without this step, the content of carbon nanotubes in the first part is difficult to be significantly increased. There are not more carbon nanotubes to tightly combine the sputtered metal layer with the bottom metal of the copper cluster array, and the fracture strength of the composite film after the second stage electrodeposition is also reduced.

[0078] (3) It can be concluded from Examples 1, 2, 3, 4, 5, 6, 7, 8, 9 and Comparative Example 3 that the third stage of electrodeposition is a necessary step for the extension growth of copper pillars. Without this step, it is difficult for copper seeds to grow into copper pillars, and it is difficult to form a complete copper cluster array on the surface of the composite current collector.

[0079]

[0080] Table 3

[0081]

[0082] Table 4

[0083] In summary, the present invention provides a method for preparing a copper cluster array composite current collector, which relates to the technical field of lithium batteries. The steps include: using a magnetron sputtering method to complete the metallization treatment of a PET film to obtain a composite film; then using a three-stage composite electrodeposition method to complete the structural design of the copper cluster array on the surface of the composite film, and adjusting the electrodeposition parameters and the stirring speed of the electrodeposition solution to control the content and distribution of carbon nanotubes; the carbon nanotubes distributed in the first height copper cluster array make the copper cluster array stably attached to the surface of the composite film, thereby improving the fracture strength of the composite film, and the carbon nanotubes distributed in the second height copper cluster array enhance the structural stability of the three-dimensional structure, and improve the overall mechanical strength of the copper cluster array. When it forms a lithium battery electrode with an active substance, it can effectively inhibit the volume expansion of the active substance during the charge and discharge process, and improve the stability of the electrode and the cycle performance of the battery.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement and improvement made within the spirit and scope of the present invention are included in the protection scope of the present invention.

Claims

1. A method for preparing a copper cluster array composite current collector, characterized in that: The method comprises: A composite film with a sputtered metal layer on the surface is obtained by magnetron sputtering the PET film; Through the first stage of composite electrodeposition, a composite layer containing copper seeds and carbon nanotubes is obtained on the surface of the sputtered metal layer; Through the second stage of composite electrodeposition, a first-height copper cluster array consisting of a plurality of copper pillars is obtained on the surface of the sputtered metal layer; the first height does not exceed 2 μm; Through the third stage of composite electrodeposition, a second-height copper cluster array is obtained by extending and growing on the first-height copper cluster array; wherein the copper column is perpendicular to the sputtered metal layer, and the carbon nanotubes are distributed inside the copper column and are divided into two parts, wherein the first part is distributed on the surface of the sputtered metal layer and the first-height copper cluster array, and the second part is distributed in the second-height copper cluster array; The method further comprises: (1) Placing the composite film with the sputtered metal layer in an electrodeposition solution containing carbon nanotubes, setting the first stage composite electrodeposition voltage to 0.1-0.3 V, the electrodeposition time to 10-30 s, and the electrodeposition temperature to 25-30 °C. In this process, a magnetic stirrer is used to stir the electrodeposition solution at a stirring speed of 800-900 r / min. (2) The voltage of the second composite electrodeposition was set to 0.2 V and then increased to 1.8 V, the voltage increase rate was 0.05 V / s, the electrodeposition temperature was maintained at 25 °C, and the stirring speed was constant at 50 r / min. (3) Add 1% Triton X-100 solution to the electrodeposition solution and stir thoroughly. The voltage of the third stage of composite electrodeposition is 1.5-2 V. The rotation speed is adjusted from 800-900 r / min to gradually decrease. The speed decay rate is 400-600 r / min and lasts for 1-2 min. A copper cluster array composite current collector is obtained.

2. The method for preparing a copper cluster array composite current collector according to claim 1, characterized in that: The aspect ratio of each copper pillar in the copper cluster array is 2.5-4:1, the distance between two adjacent copper pillars is 1-5 μm, and the height of each copper pillar is 6-10 μm; The content of the carbon nanotubes in the first part is 3.7-4.2 vol%, and the content of the carbon nanotubes in the second part is 0.7-0.9 vol%.

3. The method for preparing a copper cluster array composite current collector according to claim 1, characterized in that: The carbon nanotubes include at least one of hydroxylated carbon nanotubes, multi-walled carbon nanotubes and single-walled carbon nanotubes.

4. The method for preparing a copper cluster array composite current collector according to claim 1, characterized in that: The content of carbon nanotubes in the electrodeposition solution was 0.2 wt.%.

5. A copper cluster array composite current collector, characterized in that: The method comprises preparing the composite current collector by using the method for preparing a copper cluster array composite current collector according to any one of claims 1 to 4.

6. A battery, characterized in that: It includes the copper cluster array composite current collector as described in claim 5.

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