A functional current collector with low residual stress, its preparation method and application

Abstract

The present application specifically discloses a functional current collector with low residual stress, a preparation method thereof, and an application. A functional current collector with low residual stress includes two metal layers and a polymer layer disposed between the two metal layers; wherein, the range from the surface of the polymer layer to 2 - 3 μm away from the metal layer in the polymer layer is denoted as region A, and the range from the surface of the metal layer close to the polymer layer to 100 nm away from the polymer layer in the metal layer is denoted as region B, and regions A and B are the junction regions between the polymer layer and the metal layer; the functional current collector contains nitrogen ions, and the nitrogen ion concentration in the junction region between the polymer layer and the metal layer accounts for more than 80% of the total nitrogen ion concentration in the functional current collector. The present application has the advantages of weakening the residual stress of the functional current collector, improving the stability of the functional current collector to improve the cycle life and safety performance of the battery.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and particularly relates to a functional current collector with low residual stress, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of new energy technologies and electronic technologies, batteries are gradually becoming a research hotspot. How to improve the cycle life, safety performance, energy density, etc. of batteries has become a top priority. As an important part of the battery structure, the current collector can collect the current generated by the active substances in the battery to form a larger external current output. The quality of the current collector will directly affect the cycle life, safety performance, energy density, etc. of the battery.

[0003] Currently, aluminum foils and copper foils are mostly used as current collectors for the positive and negative electrode sheets in lithium batteries and sodium batteries. Such current collectors have relatively high costs, which is not conducive to the control of battery costs and the improvement of energy density. The functional current collector has obvious advantages compared with the traditional foil current collector. The functional current collector is usually a "sandwich" structure, with a polymer polymer layer in the inner layer and metal conductive layers deposited on the polymer polymer layer on both sides. The metal conductive layer on the surface of the functional current collector is thinner, and the polymer polymer layer in the inner layer is lighter, which can well reduce the overall weight of the functional current collector, thereby helping to improve the energy density of the lithium battery. At the same time, the thinner metal conductive layer on the surface of the functional current collector is more likely to break than the traditional foil current collector when the lithium battery undergoes thermal runaway, thereby isolating the connection between the active substances and the current collector and preventing the continuous progress of the thermal runaway of the lithium battery, which helps to improve the safety performance of the lithium battery.

[0004] Although the functional current collector has the advantages of low cost and light weight, it is found in actual application that when the deposition rate of the metal conductive layer in the functional current collector on the surface of the polymer polymer layer is too fast, residual stress will be generated, which will cause stress deformation of the functional current collector, increasing the risk of the metal conductive layer peeling off from the polymer polymer layer, which is not conducive to the improvement of the battery cycle life and safety performance. Summary of the Invention

[0005] In order to reduce the residual stress of the functional current collector and improve the stability of the functional current collector to improve the cycle life and safety performance of the battery, the present application provides a functional current collector with low residual stress, a preparation method thereof, and an application thereof.

[0006] In a first aspect, the present application provides a functional current collector with low residual stress, adopting the following technical solution:

[0007] A functional current collector with low residual stress, the functional current collector includes two metal layers and a polymer layer disposed between the two metal layers;

[0008] Among them, the range from the surface of the polymer layer to 2 - 3 μm away from the metal layer in the polymer layer is denoted as region A, and the range from the surface of the metal layer close to the polymer layer to 100 nm away from the polymer layer in the metal layer is denoted as region B. Regions A and B are the junction regions between the polymer layer and the metal layer;

[0009] The functional current collector contains nitrogen ions, and the nitrogen ion concentration in the junction region between the polymer layer and the metal layer accounts for more than 80% of the total nitrogen ion concentration in the functional current collector.

[0010] By injecting nitrogen ions into the functional current collector and controlling the proportion of the nitrogen ion concentration in the junction region between the polymer layer and the metal layer, first, on the one hand, the nitrogen ions injected into the functional current collector can form a large number of compounds such as copper nitride at the junction region. These compounds can serve as reinforcing agents, enhancing the stability and durability of the metal layer by forming a firm bond with the copper layer. On the other hand, the generation of copper nitride can also improve the structure at the junction region between the metal layer and the polymer layer, making the part of the junction region located in the metal layer more dense and uniform, thereby reducing the residual stress generated due to uneven structure at the interface between the polymer layer and the metal layer, changing the crystal structure and mechanical properties of the functional current collector, and thus reducing the residual stress and improving the bonding stability of the metal layer on the surface of the polymer layer. Second, after the nitrogen ions are injected into the metal layer of the functional current collector, defects and dislocations will be generated in the metal layer, which can both provide stress release paths, thereby adjusting the residual stress in the metal layer to a relatively low level. Third, a part of the nitrogen ions injected into the functional current collector will also penetrate into the polymer layer and collide and interact with the macromolecules in the polymer layer, generating certain energy transfer and damage, which will lead to the breakage, rearrangement, and cross-linking of the molecular chains, thereby changing the internal structure and stress distribution of the material, and further reducing the overall residual stress of the functional current collector. Based on this, the functional current collector with low residual stress is used in lithium batteries, which helps to improve the cycle life and safety performance of lithium batteries.

[0011] Preferably, the thickness of the polymer layer is 4 - 6 μm.

[0012] Preferably, the thickness of any one of the metal layers is 1 - 2 μm.

[0013] By controlling the thicknesses of the polymer layer and the metal layer, and controlling the thickness of the metal layer within a suitable range, while ensuring that the current collector has sufficient conductivity, the material usage is reduced, which helps to improve the energy density of the lithium battery. Moreover, controlling the thickness of the polymer layer within a suitable range can effectively prevent internal short circuits in the battery, further enhancing the insulation of the polymer layer and avoiding potential safety hazards during battery use.

[0014] Preferably, the polymer layer comprises at least one of a polypropylene (PP) film, a polyetheretherketone (PEEK) film, a polyphenylene sulfide (PPS) film, a polyethylene naphthalate (PEN) film, and a polyimide (PI) film.

[0015] Preferably, the metal layer comprises any one of a copper foil and an aluminum foil.

[0016] In a second aspect, the present application provides a method for preparing a functional current collector with low residual stress, adopting the following technical solution:

[0017] A method for preparing a functional current collector with low residual stress, comprising the following steps:

[0018] S1. A metal layer is compounded on two surfaces of the polymer layer to obtain a finished current collector. The finished current collector is placed in a vacuum atmosphere, and a nitrogen ion beam is injected onto the surfaces of the two metal layers of the finished current collector to obtain a pretreated current collector;

[0019] S2. After the injection operation is completed, the pretreated current collector is subjected to heat preservation treatment and then cooled to obtain the functional current collector.

[0020] Preferably, the pressure in the vacuum atmosphere in S1 is 6×10 -4 -2×10 -3 Pa.

[0021] Performing the nitrogen ion implantation operation in the above vacuum atmosphere can ensure the high-speed movement of electrons and ions, achieve the purpose of processing workpieces, avoid the speed attenuation of electron beams and ion beams, and ensure the processing effect and processing quality.

[0022] Preferably, in S1, the metal layer is prepared by magnetron sputtering, electron beam evaporation or laser pulse deposition.

[0023] Preferably, during the injection operation in S1, the injection energy of the nitrogen ion beam is 50 - 150 keV, the ion beam current intensity of the nitrogen ion beam is 5 - 20 mA, and the injection dose of the nitrogen ion beam is 5×10 16 -5×10 17 ions / cm 2 .

[0024] By controlling the implantation energy of the nitrogen ion beam, the penetration depth of nitrogen ions in the functional current collector can be adjusted, enabling the nitrogen ions to mainly concentrate in the junction region between the polymer layer and the metal layer, so as to achieve the effect of reducing the residual stress in the metal layer and improving the stability of the metal layer on the surface of the polymer layer. When the implantation energy is too low, the nitrogen ions may only be distributed in the shallow surface layer of the functional current collector and cannot effectively affect the internal residual stress, resulting in an insignificant effect of eliminating the residual stress in the functional current collector. While when the implantation energy is too high, it may cause excessive damage to the internal structure of the functional current collector and even change the original performance of the functional current collector. Although the residual stress can be eliminated to a certain extent, new performance problems will be generated.

[0025] By controlling the intensity of the ion beam current of the nitrogen ion beam, the number of nitrogen ions implanted into the functional current collector per unit time can be adjusted to generate a sufficient number of nitrides, dislocations, defects, etc. to eliminate the residual stress in the functional current collector. Too high an ion beam current intensity means that a higher number of nitrogen ions are implanted into the functional current collector per unit time, which can improve the processing efficiency, but it will also cause problems such as local overheating and surface sputtering, affecting the surface quality and performance uniformity of the functional current collector; correspondingly, when the ion beam current intensity is weak, the processing efficiency is low, and it may take a longer processing time to achieve the expected effect of eliminating the residual stress.

[0026] By controlling the implantation dose of the nitrogen ion beam, the interaction between the nitrogen ions and the metal layer and the polymer layer can be adjusted, changing the structure and performance of the junction region between the polymer layer and the metal layer to relieve the residual stress in the functional current collector. When the implantation dose is too low, the interaction between the nitrogen ions and the internal atoms of the functional current collector is insufficient, making it difficult to fully change the structure and performance of the junction region and unable to effectively eliminate the residual stress; when the implantation dose is too high, it may cause severe distortion of the material lattice and a large number of defects in the functional current collector, and even form a new phase. Although the residual stress can be eliminated, it will also cause adverse changes in other properties of the material such as hardness and toughness, which is not conducive to the improvement of the comprehensive performance of the functional current collector.

[0027] Preferably, in S2, the heat preservation temperature is 80 - 90 °C, the heat preservation time is 3 - 5 min; the cooling rate is 1 - 3 °C / min until it is cooled to 20 - 25 °C.

[0028] By controlling the heat preservation temperature and heat preservation time in S2, it can promote the better combination, migration of nitrogen ions with the internal structure of the material, promote stress elimination and structural stability, and will not have an adverse impact on other properties of the functional current collector.

[0029] In a third aspect, the present application provides a pole piece, adopting the following technical solution:

[0030] A pole piece, which includes the functional integrated fluid as described above or the functional integrated fluid prepared by the method as described above, and an electrode active material located above the functional integrated fluid.

[0031] In a fourth aspect, the present application provides a lithium battery cell, adopting the following technical solution:

[0032] A lithium battery cell includes the pole piece as described above.

[0033] In a fifth aspect, the present application provides a battery pack, adopting the following technical solution:

[0034] A battery pack includes the lithium battery cell as described above.

[0035] In a sixth aspect, the present application provides an electrical device, adopting the following technical solution:

[0036] An electrical device includes the lithium battery cell as described above or the battery pack as described above.

[0037] In summary, the present application has the following beneficial effects:

[0038] Since in the present application, by injecting nitrogen ions into the functional integrated fluid and controlling the concentration of nitrogen ions in the junction region between the polymer layer and the metal layer to be more than 80% of the total concentration of nitrogen ions injected into the integrated fluid, first, not only can compounds such as copper nitride as a strengthening agent be formed in the junction region to enhance the stability of the metal layer, but also the presence of copper nitride can improve the structural uniformity and density in the junction region, reducing the residual stress generated due to non-uniform structure in the junction region; second, the nitrogen ions injected into the metal layer can generate dislocations and defects in the metal layer, providing a release path for stress release in the metal layer, thereby reducing the residual stress level in the metal layer and contributing to reducing the overall residual stress of the functional integrated fluid; third, some of the nitrogen ions injected into the integrated fluid will also penetrate into the polymer layer, resulting in the breakage, rearrangement and crosslinking of polymer molecular chains, changing the internal structure and stress distribution of the polymer layer, and contributing to reducing the overall residual stress of the functional integrated fluid. Detailed implementation manners

[0039] For better understanding and implementation, the technical solutions of the present application will be clearly and completely described below in combination with embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used in the specification of the present application herein are only for the purpose of describing specific embodiments, and are not intended to limit the present application.

[0041] Unless otherwise indicated, all numerical values of ingredients, reaction conditions, etc. used in the specification and claims are understood to be modified by the term "about". Accordingly, unless otherwise indicated, the numerical parameters set forth herein are approximations that can vary depending upon the desired properties sought to be obtained.

[0042] As used herein, "and / or" refers to one or all of the recited elements.

[0043] As used herein, "comprising" and "including" cover both cases where only the recited elements are present and cases where there are also other unrecited elements in addition to the recited elements.

[0044] All percentages in this application are by weight, unless otherwise indicated.

[0045] Unless otherwise indicated, the articles "a", "an", "one" and "the" as used in this specification are intended to include "at least one" or "one or more". For example, "a component" means one or more components, and thus more than one component may be contemplated and may be employed or used in the practice of the described embodiments.

[0046] Example 1

[0047] A method for preparing a functional current collector with low residual stress, comprising the following steps:

[0048] S1, electroplating a metal layer on two surfaces of a polymer layer to obtain a finished current collector, placing the above-mentioned finished current collector in a vacuum atmosphere with a pressure of 2×10 -3 Pa, using a nitrogen ion implantation device to inject a nitrogen ion beam into two surfaces of the above-mentioned finished current collector (the injection energy of the nitrogen ion beam is 50 keV, the ion beam current intensity of the nitrogen ion beam is 5 mA, and the injection dose of the nitrogen ion beam is 5×10 16 ions / cm 2 ), to obtain a pretreated current collector;

[0049] S2, after the injection operation is completed, keeping the above-mentioned pretreated current collector at 80 °C for 3 min and then cooling it to 20 °C at a cooling rate of 1 °C / min to obtain the functional current collector.

[0050] In the functional current collector, the thickness of the polymer layer (polypropylene film) is 5 μm, the thickness of the metal layer (copper) is 1 μm, and the mass ratio of the nitrogen ion concentration in the junction region to the total nitrogen ion concentration in the functional current collector is 80%.

[0051] Example 2

[0052] A method for preparing a functional current collector with low residual stress, comprising the following steps:

[0053] S1. Electroplate metal layers on two surfaces of the polymer layer to obtain a finished current collector. Place the above-mentioned finished current collector in a vacuum atmosphere with a pressure of 9×10 -4 Pa, and use a nitrogen ion implantation device to inject a nitrogen ion beam into two surfaces of the above-mentioned finished current collector (the implantation energy of the nitrogen ion beam is 100 keV, the ion beam current intensity of the nitrogen ion beam is 15 mA, and the implantation dose of the nitrogen ion beam is 5×10 17 ions / cm 2 ), to obtain a pretreated current collector;

[0054] S2. After the injection operation is completed, keep the above-mentioned pretreated current collector at 85 °C for heat treatment for 4 min and then cool it to 20 °C at a cooling rate of 2 °C / min, thus obtaining the above-mentioned functional current collector.

[0055] In the functional current collector, the thickness of the polymer layer (polypropylene film) is 4 μm, the thickness of the metal layer (copper) is 1.2 μm, and the mass percentage of the concentration of nitrogen ions in the junction region in the total concentration of nitrogen ions in the functional current collector is 85%.

[0056] Example 3

[0057] A preparation method of a functional current collector with low residual stress, comprising the following steps:

[0058] S1. Electroplate metal layers on two surfaces of the polymer layer to obtain a finished current collector. Place the above-mentioned finished current collector in a vacuum atmosphere with a pressure of 6×10 -4 Pa, and use a nitrogen ion implantation device to inject a nitrogen ion beam into two surfaces of the above-mentioned finished current collector (the implantation energy of the nitrogen ion beam is 150 keV, the ion beam current intensity of the nitrogen ion beam is 20 mA, and the implantation dose of the nitrogen ion beam is 5.5×10 16 ions / cm 2 ), to obtain a pretreated current collector;

[0059] S2. After the injection operation is completed, keep the above-mentioned pretreated current collector at 90 °C for heat treatment for 5 min and then cool it to 22 °C at a cooling rate of 3 °C / min, thus obtaining the above-mentioned functional current collector.

[0060] In the functional current collector, the thickness of the polymer layer (polypropylene film) is 6 μm, the thickness of the metal layer (copper) is 2 μm, and the mass percentage of the concentration of nitrogen ions in the junction region in the total concentration of nitrogen ions in the functional current collector is 80%.

[0061] Example 4

[0062] The difference between this example and Example 1 is that the implantation dose of the nitrogen ion beam in S2 is 5×10 17 ions / cm², and other steps and parameter settings are the same as those in Example 1.

[0063] In the functionalized current collector, the thickness of the polymer layer (polypropylene film) is 5 μm, the thickness of the metal layer (copper) is 1 μm, and the mass percentage of the nitrogen ion concentration in the junction region in the total nitrogen ion concentration in the functionalized current collector is 90%.

[0064] Example 5

[0065] The difference between this example and Example 1 is that in S2, the pretreated current collector is heat-insulated at 80 °C for 5 min and then cooled to 20 °C at a cooling rate of 1 °C / min to obtain the functionalized current collector; other steps and parameter settings are the same as those in Example 1.

[0066] In the functionalized current collector, the thickness of the polymer layer (polypropylene film) is 5 μm, the thickness of the metal layer (copper) is 1 μm, and the mass percentage of the nitrogen ion concentration in the junction region in the total nitrogen ion concentration in the functionalized current collector is 80%.

[0067] Example 6

[0068] The difference between this example and Example 1 is that in S2, the pretreated current collector is heat-insulated at 90 °C for 3 min and then cooled to 20 °C at a cooling rate of 2 °C / min to obtain the functionalized current collector; other steps and parameter settings are the same as those in Example 1.

[0069] In the functionalized current collector, the thickness of the polymer layer (polypropylene film) is 5 μm, the thickness of the metal layer (copper) is 1 μm, and the mass percentage of the nitrogen ion concentration in the junction region in the total nitrogen ion concentration in the functionalized current collector is 85%.

[0070] Example 7

[0071] The difference between this example and Example 1 is that in S2, the implantation energy of the nitrogen ion beam is 20 keV, and other steps and parameter settings are the same as those in Example 1.

[0072] Example 8

[0073] The difference between this example and Example 1 is that in S2, the implantation energy of the nitrogen ion beam is 200 keV, and other steps and parameter settings are the same as those in Example 1.

[0074] Example 9

[0075] The difference between this example and Example 1 is that in S2, the ion beam current intensity of the nitrogen ion beam is 2 mA, and other steps and parameter settings are the same as those in Example 1.

[0076] Example 10

[0077] The difference between this embodiment and Embodiment 1 is that in S2, the ion beam current intensity of the nitrogen ion beam is 30 mA, and the other steps and parameter settings are the same as those in Embodiment 1.

[0078] Embodiment 11

[0079] The difference between this embodiment and Embodiment 1 is that in S2, the implantation dose of the nitrogen ion beam is 5×10 15 ions / cm², and the other steps and parameter settings are the same as those in Embodiment 1.

[0080] Embodiment 12

[0081] The difference between this embodiment and Embodiment 1 is that in S2, the implantation dose of the nitrogen ion beam is 5×10 18 ions / cm², and the other steps and parameter settings are the same as those in Embodiment 1.

[0082] Embodiment 13

[0083] The difference between this embodiment and Embodiment 1 is that in S2, the implantation energy of the nitrogen ion beam is 150 keV, and the other steps and parameter settings are the same as those in Embodiment 1.

[0084] In the functional current collector, the thickness of the polymer layer (polypropylene film) is 5 μm, the thickness of the metal layer (copper) is 1 μm, and the mass ratio of the nitrogen ion concentration in the junction region to the total nitrogen ion concentration in the functional current collector is 55%.

[0085] Embodiment 14

[0086] The difference between this embodiment and Embodiment 1 is that in S2, the ion beam current intensity of the nitrogen ion beam is 20 mA, and the other steps and parameter settings are the same as those in Embodiment 1.

[0087] In the functional current collector, the thickness of the polymer layer (polypropylene film) is 5 μm, the thickness of the metal layer (copper) is 1 μm, and the mass ratio of the nitrogen ion concentration in the junction region to the total nitrogen ion concentration in the functional current collector is 65%.

[0088] Comparative Example 1

[0089] The difference between this comparative example and Embodiment 1 is that the functional current collector does not contain nitrogen ions.

[0090] Testing Method

[0091] I. Residual Stress Test

[0092] The residual stress of the functional current collectors provided in the above embodiments and comparative examples was tested by an X-ray residual stress tester of model μ-360s from QUANTUM Quantum Science Instruments Trading (Beijing) Co., Ltd.

[0093] II. Adhesion Test

[0094] Use the Elcometer 510 automatic pull-off adhesion tester produced by Elcometer Company in the UK to test the adhesion between the metal layer and the polymer layer in the functional current collectors provided in the above-mentioned examples and comparative examples.

[0095] Table 1

[0096]

[0097] Combined with Examples 1-6, Examples 13-14, Comparative Example 1 and Table 1, it can be seen that in this solution, by controlling the proportion of the nitrogen ion concentration in the junction area between the polymer layer and the metal layer in the total nitrogen ions in the functional current collector, the residual stress in the functional current collector can be eliminated to a great extent, avoiding the deformation of the functional current collector or the peeling off of the surface metal layer, which helps to improve the cycle performance and safety performance of lithium batteries.

[0098] Combined with Example 1, Examples 7-8 and Table 1, it can be seen that if the implantation energy of the nitrogen ion beam is too low, the nitrogen ions cannot effectively penetrate into the junction area between the polymer layer and the metal layer in the functional current collector, which is not conducive to eliminating the residual stress in the functional current collector; while when the implantation energy of the nitrogen ion beam is too high, although the residual stress in the functional current collector can be eliminated, it may cause structural damage inside the functional current collector. On the one hand, too high implantation energy may generate large impact force and stress on the material surface, exceeding the bearing capacity of the material, resulting in cracks, spalling or other damages on the material surface. On the other hand, although the purpose of nitrogen ion implantation is to remove residual stress, if the implantation energy is too high, new residual stress may be generated inside the material, and these residual stresses may have an adverse impact on the performance and service life of the material.

[0099] Combined with Example 1, Examples 9-10 and Table 1, it can be seen that if the ion beam current intensity of the nitrogen ion beam is too low, the operation time for implanting nitrogen ions is too long, and the processing efficiency is low; while if the ion beam current intensity of the nitrogen ion beam is too high, it will cause local overheating and surface sputtering, affecting the quality of the metal layer surface and the performance uniformity of each region in the functional current collector.

[0100] Combined with Example 1, Examples 11-12 and Table 1, it can be seen that if the implantation dose of the nitrogen ion beam is too low, the residual stress in the functional current collector cannot be effectively eliminated; while if the implantation dose of the nitrogen ion beam is too high, it may cause serious distortion and a large number of defects in the material lattice of the functional current collector, reducing the hardness and toughness of the functional current collector and affecting the applicable range of the functional current collector to a certain extent.

[0101] The above embodiments are only used to illustrate the technical solutions of the present application rather than to limit the protection scope of the present application. Although the present application has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can be modified or equivalently replaced, but such modifications or replacements are all within the protection scope of the present application.

Claims

1. A functional current collector with low residual stress, characterized in that: The functional current collector comprises two metal layers and a polymer layer disposed between the two metal layers; The range from the surface of the polymer layer to the 2-3 μm away from the metal layer in the polymer layer is recorded as region A, and the range from the surface of the metal layer close to the polymer layer to the 100 nm away from the polymer layer in the metal layer is recorded as region B, and the region A and the region B are the boundary regions between the polymer layer and the metal layer; The functional current collector contains nitrogen ions, and the nitrogen ion concentration in the interface area between the polymer layer and the metal layer accounts for more than 80% of the total nitrogen ion concentration in the functional current collector.

2. The functional current collector with low residual stress according to claim 1, characterized in that: The thickness of the polymer layer is 4-6 μm.

3. The functional current collector with low residual stress according to claim 1, characterized in that: The thickness of any one of the metal layers is 1-2 μm.

4. The functional current collector with low residual stress according to claim 2, characterized in that: The polymer layer includes at least one of a polypropylene film, a polyetheretherketone film, a polyphenylene sulfide film, a polyethylene naphthalate film, and a polyimide film.

5. The functional current collector with low residual stress according to claim 3, characterized in that: The metal layer includes any one of copper foil and aluminum foil.

6. The method for preparing a functional current collector with low residual stress according to any one of claims 1 to 5, characterized in that: The steps include: S1, compounding the metal layer on the two surfaces of the polymer layer to obtain a finished current collector, placing the finished current collector in a vacuum atmosphere, and injecting nitrogen ion beams into the surfaces of the two metal layers of the finished current collector to obtain a pretreated current collector; S2, after the injection operation is completed, the pre-treated current collector is subjected to heat preservation treatment and then cooled to obtain the functional current collector.

7. The method for preparing a functional current collector with low residual stress according to claim 6, characterized in that: The pressure of the vacuum atmosphere in S1 is 6×10 -4 -2×10 -3 Pa.

8. The method for preparing a functional current collector with low residual stress according to claim 6, characterized in that: In S1, the metal layer is prepared by magnetron sputtering, electron beam evaporation or laser pulse deposition.

9. The method for preparing a functional current collector with low residual stress according to claim 6, characterized in that: During the implantation operation of S1, the implantation energy of the nitrogen ion beam is 50-150 keV, the ion beam current intensity of the nitrogen ion beam is 5-20 mA, and the implantation dose of the nitrogen ion beam is 5×10 16 -5×10 17 Ions / cm 2 .

10. The method for preparing a functional current collector with low residual stress according to claim 6, characterized in that: In S2, the holding temperature is 80-90°C, the holding time is 3-5min, and the cooling rate is 1-3°C / min, until it cools to 20-25°C.

11. A pole piece, characterized in that: The invention comprises a functional current collector as described in any one of claims 1 to 5 or a functional current collector prepared by the method as described in any one of claims 6 to 10, and an electrode active material located on the functional current collector.

12. A lithium battery cell, characterized in that: Comprising the pole piece as claimed in claim 11.

13. A battery pack, characterized in that: Comprising the lithium battery cell as claimed in claim 12.

14. An electrical equipment, characterized in that: It comprises the lithium battery cell as claimed in claim 12 or the battery pack as claimed in claim 13.

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