Current collector, negative pole piece, preparation method of negative pole piece, battery and electric equipment

Abstract

The invention provides a current collector, a negative pole piece, a preparation method of the negative pole piece, a battery and electric equipment, the current collector comprises a copper foil and copper particles, the copper particles grow on the surface of the copper foil and form a three-dimensional structure on the surface of the copper foil, the current collector is used for enabling a silicon-based material to form a three-dimensional interactive structure on the surface of the current collector, the surface structure of the copper foil can provide a buffer space for the expansion of the silicon-based material, the volume change of the silicon-based material is controlled, the rapid increase of impedance is avoided, and the performance of the battery is improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a current collector, a negative electrode sheet and a preparation method thereof, a battery and an electrical device. Background Art

[0002] Lithium batteries have high charge and discharge performance and are widely used in electric vehicles and other products. Currently, commercial lithium batteries mainly use graphite as the negative electrode material. Graphite has a theoretical capacity of 372mAh / g. After years of research and development and engineering optimization, the existing graphite materials have fully utilized the capacity close to this theoretical limit, and are increasingly unable to meet the needs of modern electronic products for high energy density.

[0003] Silicon material has a theoretical gram capacity of up to 3579mAh / g and a suitable charge and discharge voltage. However, silicon negative electrode materials will produce up to 300% volume expansion during the lithium insertion and delithiation process, which will cause the electrode material particles to be damaged or even pulverized, the material to be peeled off from the conductive network, and even the electrode layer to be separated from the current collector, resulting in loss of electrical contact, leading to a sharp deterioration in cycle performance and rapid decay of battery capacity, which seriously restricts the industrial application of silicon negative electrode materials.

[0004] Mixing silicon materials with other negative electrode materials can control the volume change of silicon materials during the charging and discharging process, but the problem of silicon material expansion and separation from the current collector after expansion has not been alleviated, making it difficult to meet the needs of high capacity and long service life of the battery. Summary of the invention

[0005] The purpose of the present application is to provide a current collector, a negative electrode plate and a preparation method thereof, a battery and an electrical device, which solve the problem of rapid impedance growth caused by the expansion of silicon materials.

[0006] To achieve the purpose of this application, this application provides the following technical solutions:

[0007] In a first aspect, the present application provides a current collector, comprising a copper foil substrate and copper particles, wherein the copper particles are attached to a surface of the copper foil substrate and form a three-dimensional structure on the surface of the copper foil substrate.

[0008] In one embodiment, the number of the copper particles is plural, and the plurality of copper particles form a plurality of protrusions on the surface of the copper foil substrate, and the plurality of protrusions are arranged in an array on the surface of the copper foil substrate.

[0009] In one embodiment, a single protrusion includes a plurality of copper particles, and the protrusion extends in a direction perpendicular to the surface of the copper foil substrate.

[0010] In the second aspect, the present application also provides a negative electrode plate, comprising: a current collector as described in any embodiment of the first aspect; a silicon-containing material layer, comprising a silicon-based material, and the side of the silicon-containing material layer close to the current collector forms a first three-dimensional interactive structure on the surface of the current collector.

[0011] In one embodiment, the silicon-containing material layer further includes graphite material.

[0012] In one embodiment, the negative electrode plate further includes a graphite layer, the graphite layer is disposed on a side of the silicon-containing material layer away from the current collector, and the graphite layer includes a graphite material.

[0013] In one embodiment, the graphite layer forms a second three-dimensional interactive structure on the surface of the silicon material layer away from the current collector.

[0014] In the third aspect, the present application also provides a method for preparing a negative electrode plate, comprising: converting the copper ions into copper particles, allowing the copper particles to adhere to the surface of the copper foil substrate to form a three-dimensional structure, and obtaining a current collector; applying a silicon-containing electrode slurry on the surface of the current collector to form a silicon-containing material layer, wherein the silicon-containing material layer comprises a silicon-based material, and a side of the silicon-containing material layer close to the current collector forms a first three-dimensional interactive structure on the surface of the current collector, and obtaining a negative electrode plate.

[0015] In one embodiment, the current collector is placed in an inert gas for heat treatment.

[0016] In one embodiment, the silicon-containing electrode slurry also includes graphite material.

[0017] In one embodiment, a graphite electrode slurry is further provided, and the graphite electrode slurry is coated on the surface of the silicon-containing material layer to form a graphite layer.

[0018] In a fourth aspect, the present application also provides a battery, comprising a shell and a negative electrode plate as described in any embodiment of the second aspect, or comprising a shell and a negative electrode plate prepared by the method for preparing a negative electrode plate as described in any embodiment of the third aspect, wherein the negative electrode plate is accommodated inside the shell.

[0019] In a fifth aspect, the present application also provides an electrical device, comprising the battery as described in the fourth aspect.

[0020] In the current collector provided by the present application, copper particles grow on the surface of the copper foil. The copper particles protrude from the surface of the copper foil and form a three-dimensional structure. When the silicon-based material is covered on the three-dimensional structure formed by the copper particles, a silicon-containing material layer with a three-dimensional interactive structure is formed based on the three-dimensional structure. The three-dimensional structure on the current collector provides a buffer space and a conductive path for volume expansion of the silicon-based material. At the same time, it can also increase the stability of the connection between the silicon-containing material layer and the current collector, alleviate the separation of the silicon-containing material layer from the current collector, avoid the rapid increase of the impedance of the negative electrode sheet, and improve the stability of the silicon-containing material layer during the cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 is a cross-sectional view of a negative electrode sheet according to an embodiment;

[0023] Figure 2 The present invention is a flow chart of preparing a negative electrode sheet according to an embodiment of the present invention.

[0024] Description of reference numerals:

[0025] 10-current collector, 20-silicon-containing material layer, 30-graphite layer;

[0026] 11- copper foil base, 12- convex part. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0028] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there can be a central component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there can be a central component at the same time.

[0029] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in this application and in the specification are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this application includes any and all combinations of one or more of the related listed items.

[0030] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0031] The present application embodiment provides a current collector 10, see Figure 1 The current collector 10 includes a copper foil substrate 11 and copper particles. The copper foil substrate 11 has a flat surface. The copper particles grow on the surface of the copper foil substrate 11. The copper particles themselves have a certain volume, so that the copper particles protrude from the surface of the copper foil substrate 11 and form a three-dimensional structure on the surface of the copper foil substrate 11.

[0032] There are multiple copper particles, and the multiple copper particles form multiple protrusions 12 on the surface of the copper foil substrate 11. The protrusions 12 protrude from the surface of the copper foil substrate 11 to form a three-dimensional structure. A single protrusion 12 is composed of multiple copper particles. The multiple protrusions 12 are arranged at intervals, and a recessed area is formed between two adjacent protrusions 12.

[0033] The current collector 10 is used to make the silicon-based material cover the surface of the current collector 10 , and the silicon-based material forms a three-dimensional interactive structure on the surface of the current collector 10 .

[0034] Copper particles grow on the surface of the copper foil. The copper particles protrude from the surface of the copper foil and form a three-dimensional structure. When the silicon-based material is covered on the three-dimensional structure formed by the copper particles, a silicon-containing material layer 20 with a three-dimensional interactive structure is formed based on the three-dimensional structure. The three-dimensional structure on the current collector 10 provides a buffer space and a conductive path for volume expansion of the silicon-based material. At the same time, it can increase the stability of the connection between the silicon-containing material layer 20 and the current collector 10, alleviate the separation of the silicon-containing material layer 20 and the current collector 10, avoid the rapid increase of the impedance of the negative electrode sheet, and improve the stability of the silicon-containing material layer 20 during the cycle.

[0035] In one implementation, see Figure 1 A single protrusion 12 includes multiple copper particles, and the multiple copper particles of the same protrusion 12 are arranged in a direction perpendicular to the surface of the copper foil substrate 11 to form a skeleton, so that the protrusion 12 protrudes vertically from the surface of the copper foil substrate 11 to form a three-dimensional structure.

[0036] The plurality of protrusions 12 are disposed at intervals, and the plurality of protrusions 12 are arranged in an array on the surface of the copper foil substrate 11 .

[0037] By arranging the plurality of protrusions 12 in an array on the surface of the copper foil substrate 11, it is beneficial for the plurality of protrusions 12 to form an ordered three-dimensional structure on the surface of the copper foil substrate 11, so that the electrical contact between the silicon-based material and the current collector 10 is more uniform, the impedance of the negative electrode sheet is reduced, and a buffer space for volume expansion of the silicon-based material is provided, thereby suppressing the expansion of the silicon-based material during the charge and discharge process and improving the stability of the silicon-containing material layer 20 during the cycle process.

[0038] The present application also provides a negative electrode plate. Figure 1 The negative electrode plate includes the current collector 10 and the silicon-containing material layer 20 described in any one of the above embodiments, and the silicon-containing material layer 20 covers the surface of the current collector 10.

[0039] The silicon-containing material layer 20 includes a silicon-based material, which covers the surface of the current collector 10 , and a first three-dimensional interactive structure is formed on the surface of the current collector 10 at a side of the silicon-containing material layer 20 close to the current collector 10 .

[0040] The silicon-containing material layer 20 also includes a graphite material, and the silicon-containing material layer 20 composed of the silicon-based material and the graphite material covers the surface of the current collector 10. The silicon-based material and the graphite material can be covered on the surface of the current collector 10 in sequence; or the silicon-based material and the graphite material can be mixed first, and then the mixture of the silicon-based material and the graphite material is covered on the surface of the current collector 10 at the same time.

[0041] Graphite material has higher stability than silicon-based material. Silicon-based material and graphite material are sequentially covered on the surface of the current collector 10, that is, graphite material is covered on the surface of the silicon-based material facing away from the current collector 10, which can protect the silicon-based material and increase the resistance encountered by the silicon-based material during expansion, thereby improving the stability of the silicon-containing material layer 20.

[0042] There is a spacing distance between adjacent convex portions 12 , so that there is a concave area between adjacent convex portions 12 . The convex portions 12 protrude from the surface of the copper foil substrate 11 , so that the current collector 10 forms an uneven surface.

[0043] When the silicon-containing material layer 20 covers the surface of the current collector 10, the silicon-based material can be embedded in the recessed area between the protrusions 12 and cover the surface of the protrusions 12. The surface of the current collector 10 has an uneven structure, and the side of the silicon-containing material layer 20 close to the current collector 10 also forms an uneven structure, and forms a first three-dimensional interactive structure.

[0044] Optionally, the side of the silicon-containing material layer 20 away from the current collector 10 also forms an uneven structure. The graphite material is embedded in the concave area between the convex parts 12 and covers the surface of the convex parts 12, and the graphite material is located on the surface of the silicon-containing material layer 20 facing away from the current collector 10. The graphite material forms a graphite layer 30 on the surface of the silicon-containing material layer 20, and the side of the graphite layer 30 close to the silicon-containing material layer 20 also forms an uneven structure, and the surface of the graphite layer 30 facing away from the silicon-containing material layer 20 can be a planar structure.

[0045] When the silicon-containing material layer 20 covers the surface of the current collector 10, it can also be a mixture of silicon-based material and graphite material that is embedded in the recessed area between the protrusions 12 and covers the surface of the protrusions 12. The mixture of silicon-based material and graphite material forms a silicon-containing material layer 20 on the surface of the current collector 10.

[0046] The copper particles form a plurality of protrusions 12 on the surface of the copper foil substrate 11, and the plurality of protrusions 12 constitute a three-dimensional structure protruding from the surface of the copper foil substrate 11, and a recessed area is formed between two adjacent protrusions 12. The silicon-based material and the graphite material form a covering structure on the surface of the current collector 10, and the covering structure is based on the above three-dimensional structure, so that the silicon-based material and the graphite material form a three-dimensional interactive structure on the surface of the current collector 10.

[0047] During the charge and discharge process, the silicon-based material will expand in volume. The recessed area between the protrusions 12 provides a buffer space for the volume expansion of the silicon-based material, and the expansion of the silicon-based material in the recessed area is limited by the size of the recessed area, which is beneficial to controlling the volume change of the silicon-based material during the charge and discharge process, and can also improve the electrical connection interruption caused by the separation of the silicon-based material from the current collector 10 after expansion; the graphite material has a high stability. When the graphite material is mixed or stacked with the silicon-based material, the graphite material can limit the volume change of the silicon-based material during the charge and discharge process, which is beneficial to improving the stability of the silicon-containing material layer 20.

[0048] By growing copper particles on the surface of the copper foil substrate 11, the copper particles protrude from the surface of the copper foil substrate 11 and form a three-dimensional structure by themselves, which is beneficial for the silicon-based material to cover the three-dimensional structure formed by the copper particles, and form a silicon-containing material layer with a three-dimensional interactive structure based on the three-dimensional structure. The three-dimensional structure of the copper particles provides a buffer space and a conductive path for volume expansion of the silicon-based material. At the same time, the three-dimensional structure of the copper particles can also increase the stability of the connection between the silicon-containing material layer and the current collector 10, alleviate the separation of the silicon-containing material layer from the current collector 10, avoid the rapid increase of the impedance of the negative electrode sheet, and improve the stability of the silicon-containing material layer during the cycle.

[0049] By making the silicon-containing material layer 20 also include graphite material, the graphite material has higher stability, which is beneficial to inhibiting the expansion of silicon-based materials, avoiding the rapid growth of negative electrode impedance, and improving the stability of the silicon-containing material layer 20 during the cycle process; at the same time, using silicon-based materials and graphite materials as raw materials can be connected with the existing electrode preparation process, simplifying the preparation process and reducing production costs.

[0050] In one implementation, see Figure 1 , the silicon-based material and the graphite material are sequentially covered on the surface of the current collector 10 .

[0051] The silicon-based material is in contact with the surface of the current collector 10. Since the copper particles form a plurality of protrusions 12 on the surface of the copper foil substrate 11, and the protrusions 12 have a three-dimensional structure, the silicon-based material is embedded in the gaps between the plurality of protrusions 12 on the surface of the current collector 10, so that the silicon-based material forms a first three-dimensional interactive structure based on the three-dimensional structure of the protrusions 12, and forms a silicon-containing material layer 20 having a first three-dimensional interactive structure on the surface of the current collector 10.

[0052] The protrusions 12 on the surface of the copper foil substrate 11 support and conduct electricity for the silicon-based material. The gaps between the multiple protrusions 12 are beneficial for buffering the volume expansion of the silicon-based material during the charging and discharging process, shortening the conductive path between the current collector 10 and the silicon-based material, thereby reducing the internal resistance and increasing the specific capacity and cycle life.

[0053] The graphite material covers the surface of the silicon-containing material layer 20 facing away from the current collector 10, and the graphite material contacts the surface of the silicon-containing material layer 20 facing away from the current collector 10. The graphite material fills the gaps between the plurality of protrusions 12 not filled by the silicon material, and covers the silicon-containing material layer 20, so that the graphite material forms a second three-dimensional interactive structure based on the structure of the silicon-containing material layer 20, and forms a graphite layer 30 having a second three-dimensional interactive structure on the surface of the silicon-containing material layer 20 facing away from the current collector 10.

[0054] The graphite layer 30 protects the silicon-containing material layer 20 and suppresses the volume expansion of the silicon-based material. At the same time, the graphite layer 30 can construct a flat electrode surface, which is conducive to forming a stable interface between the electrode and other structures in the lithium battery.

[0055] The silicon-containing material layer 20 having the first three-dimensional interactive structure and the graphite layer 30 having the second three-dimensional interactive structure both form a three-dimensional interactive structure, which is beneficial for preparing a negative electrode sheet with high capacity and high stability.

[0056] By making the silicon-based material form a silicon-containing material layer 20 with a first three-dimensional interactive structure on the surface of the current collector 10, it is beneficial to increase the conductivity and adhesion of the silicon-based material to the current collector 10. The graphite material forms a graphite layer 30 on the surface of the silicon-containing material layer 20, which is beneficial for the graphite material to protect the silicon-based material, provide a buffer space and a conductive path for the volume expansion of the silicon-based material, inhibit the expansion of the silicon-based material, avoid rapid impedance growth, and improve the stability of the silicon-containing material layer 20 during the cycle.

[0057] This application also provides a method for preparing a negative electrode sheet, please refer to Figure 2 The method for preparing the negative electrode sheet comprises:

[0058] Step S10: converting copper ions into copper particles, so that the copper particles adhere to the surface of the copper foil substrate 11 to form a three-dimensional structure, thereby obtaining a current collector 10;

[0059] Step S20: coating the silicon-containing electrode slurry on the surface of the current collector 10 to form a silicon-containing material layer 20, wherein the silicon-containing material layer 20 includes a silicon-based material, and the side of the silicon-containing material layer 20 close to the current collector 10 forms a first three-dimensional interactive structure on the surface of the current collector 10 to obtain a negative electrode sheet.

[0060] Specifically, multiple copper ions are converted into multiple copper particles, and the multiple copper particles grow on the surface of the copper foil substrate 11, and multiple protrusions 12 are formed on the surface of the copper foil substrate 11. The multiple protrusions 12 protrude from the surface of the copper foil substrate 11, and form a three-dimensional structure on the surface of the copper foil substrate 11, thereby obtaining a current collector 10 with a three-dimensional structure on the surface.

[0061] In step S10, the copper foil substrate 11 is immersed in a solution containing copper ions, and pulse electrodeposition is used to convert the copper ions into copper particles. The copper particles grow on the surface of the copper foil substrate 11 to obtain a current collector with a three-dimensional structure on the surface.

[0062] Optionally, a plurality of protrusions 12 are arranged in an array on the surface of the copper foil.

[0063] Optionally, in step S20 , the silicon-containing electrode slurry further includes a graphite material, and the silicon-based material and the graphite material form a three-dimensional interactive structure on the surface of the current collector 10 , and the silicon-based material and the graphite material together constitute a silicon-containing material layer 20 .

[0064] The silicon-based material and the graphite material can also be sequentially covered on the surface of the current collector 10, the silicon-based material forming a silicon-containing material layer 20 having a first three-dimensional interactive structure, and the graphite material forming a graphite layer 30 having a second three-dimensional interactive structure; the silicon-based material and the graphite material can also be mixed and jointly covered on the surface of the current collector 10, and the mixture of the silicon-based material and the graphite material forms a silicon-containing material layer 20 having a three-dimensional interactive structure on the surface of the current collector 10.

[0065] Copper particles can grow in an orderly manner on the surface of the copper foil substrate 11, so that a plurality of protrusions 12 are arranged in an array on the surface of the copper foil substrate 11, and a recessed area is formed between two adjacent protrusions 12. The silicon material and the graphite material are both embedded in the recessed area between the protrusions 12 and cover the surface of the protrusions 12 facing away from the copper foil substrate 11.

[0066] In one implementation, see Figure 2 In step S10, after the copper particles grow on the surface of the copper foil substrate 11, the current collector 10 is placed in an inert gas for heat treatment, so that the copper particles are solidified on the surface of the copper foil substrate 11, which is conducive to a stronger combination of the copper particles and the copper foil substrate 11, preventing the copper particles from falling off the surface of the copper foil substrate 11, and improving the stability of the three-dimensional structure of the surface of the current collector 10.

[0067] Before placing the copper foil substrate 11 in an inert gas for heat treatment, the current collector 10 may be cleaned with a cleaning agent, which may be at least one of water, kerosene, trichloroethylene, chloroform, alcohol and acetone.

[0068] In one implementation, see Figure 2 In step S20 , the conductive agent, the adhesive and the silicon-based material form a silicon-containing electrode slurry which is then coated on the surface of the current collector 10 , and the silicon-containing electrode slurry forms a silicon-containing material layer 20 on the surface of the current collector 10 .

[0069] The conductive agent includes but is not limited to carbon black powder, and the silicon-based material is a material with silicon as the main active substance, including but not limited to silicon powder, silicon oxide powder or silicon alloy material, etc. The silicon-based material constitutes the main part of the silicon-containing material layer 20, the conductive agent is used to increase the conductivity of the silicon-containing material layer 20, and the adhesive is used to increase the adhesion between the silicon-containing material layer 20 and the current collector 10. The adhesion between the silicon-based material and the current collector 10 can be adjusted by selecting different adhesives.

[0070] In one embodiment, the silicon-based material accounts for 50%-90% of the solid matter mass of the silicon-containing electrode slurry, the conductive agent accounts for 5%-30% of the solid matter mass of the silicon-containing electrode slurry, and the adhesive accounts for 5%-20% of the solid matter mass of the silicon-containing electrode slurry.

[0071] By ensuring that the proportions of various materials in the silicon-containing electrode slurry meet the above range, it is beneficial to reasonably configure the proportions of the conductive agent, adhesive and silicon-based material, thereby ensuring the conductivity and adhesion of the silicon-based material to the current collector 10. At the same time, the introduction of an appropriate amount of silicon-based material is beneficial to meeting the high capacity requirements of the battery.

[0072] In one embodiment, the silicon-containing electrode slurry is coated on the surface of the current collector 10 by at least one of transfer coating, extrusion coating and spin coating.

[0073] In one implementation, see Figure 2 Graphite material is a material with carbon as the main active substance, including but not limited to natural graphite, artificial graphite, carbon microspheres or mixed graphite. In step S20, the graphite material is coated on the surface of the silicon-containing material layer 20 by spraying or double-layer coating. The silicon-based material first forms a silicon-containing material layer 20 with a first three-dimensional interactive structure on the surface of the current collector 10, and the graphite material then forms a graphite layer 30 with a second three-dimensional interactive structure on the surface of the silicon-containing material layer 20 away from the current collector 10.

[0074] In one embodiment, graphite material, conductive carbon black powder, adhesive and dispersant form graphite slurry and then apply the slurry, wherein the graphite material accounts for 80%-95% of the solid matter mass of the graphite slurry, the conductive carbon black powder accounts for 1%-10% of the solid matter mass of the graphite slurry, and the adhesive and dispersant account for 1%-10% of the solid matter mass of the graphite slurry.

[0075] In one embodiment, in step S20, the silicon-based material and the graphite material are first mixed to form a mixed slurry, and then the mixed slurry is coated on the surface of the current collector 10, and the silicon-based material and the graphite material together form a silicon-containing material layer 20 having a first three-dimensional interactive structure on the surface of the current collector 10. Optionally, the silicon-based material accounts for 25%-45% of the mass of the solid matter of the mixed slurry, and the graphite material accounts for 35%-48% of the mass of the solid matter of the mixed slurry.

[0076] The present application also provides a battery, comprising a shell and a negative electrode plate as described in any one of the above embodiments, or a negative electrode plate prepared by the method for preparing a negative electrode plate as described in any one of the above embodiments, wherein the negative electrode plate is accommodated inside the shell.

[0077] It can be understood that the battery in this embodiment has the negative electrode plate in the above embodiment. Therefore, the battery in this embodiment has all the technical effects of the negative electrode plate in the above embodiment. Since the technical effects of the negative electrode plate have been fully explained in the above embodiment, they will not be repeated here.

[0078] The present application also provides an electrical device, comprising the above-mentioned battery.

[0079] It can be understood that the electrical equipment in this embodiment has the battery in the above embodiment. Therefore, the electrical equipment in this embodiment has all the technical effects of the battery in the above embodiment. Since the technical effects of the battery have been fully explained in the above embodiment, they will not be repeated here.

[0080] The technical solution of the present invention is described in detail below through specific embodiments.

[0081] Example 1

[0082] This embodiment provides a negative electrode sheet and a method for preparing the same. The method for preparing the negative electrode sheet forms a graphite / silicon / copper layered negative electrode, and the silicon-based material and the graphite material are coated separately. The method for preparing the negative electrode sheet includes the following steps:

[0083] (1) immersing a copper foil substrate having a thickness of 6 μm to 30 μm in a solution containing copper ions, and using pulse electrodeposition to convert the copper ions into copper particles having a particle size of 100 nm to 500 nm. The copper particles grow on the surface of the copper foil substrate to obtain a current collector having a three-dimensional structure on the surface;

[0084] (2) Silicon powder with a particle size of 0.5 μm is mixed with carbon black powder, polyacrylic acid (PAA) and a certain amount of solvent, and stirred to form a silicon-containing electrode slurry. In the solid matter of the silicon-containing electrode slurry, the content of silicon powder is 85%, the content of carbon black is 10%, and the content of polyacrylic acid binder is 5%.

[0085] (3) The silicon-containing electrode slurry prepared in step (2) is coated on a copper foil substrate, and dried to obtain a Si / Cu negative electrode. The coating surface density is controlled to obtain a suitable Cu / Si interface and capacity.

[0086] (4) artificial graphite, conductive carbon black powder, sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) are mixed in a certain proportion with a certain amount of solvent to prepare graphite slurry. In the solid matter of the graphite slurry, the content of artificial graphite is 90%, the content of conductive carbon black powder is 5%, and the content of CMC and SBR binders is 5%;

[0087] (5) The graphite slurry obtained in step (4) is coated on the Si / Cu electrode obtained in step (3) to obtain a layered graphite / Si / Cu negative electrode, thereby obtaining a negative electrode sheet Z1.

[0088] In this embodiment, the coating content of the silicon-containing electrode slurry and the graphite slurry is adjusted so that the mass fraction of silicon in the final negative electrode Z1 is 3.88%, and the mass fraction of graphite is 90.39%. The mass fraction of silicon in the negative electrode Z1 is the percentage of the mass of silicon in the negative electrode Z1 to the total mass of the silicon-containing material layer of the negative electrode Z1, and the mass fraction of graphite in the negative electrode Z1 is the percentage of the mass of graphite in the negative electrode Z1 to the total mass of the silicon-containing material layer of the negative electrode Z1. The copper particles on the current collector are randomly distributed to form a three-dimensional structure, and the particle size of the copper particles is 1 μm.

[0089] Example 2

[0090] This embodiment provides a negative electrode sheet and a preparation method thereof. The difference from the negative electrode sheet and the preparation method thereof provided in Embodiment 1 is that: silicon oxide powder (SiO x) is a silicon material, the particle size of silicon oxide powder is 1 μm, the content of silicon oxide powder is 90%, the content of carbon black is 5%, and the content of polyacrylic acid binder is 5%, and the negative electrode plate Z2 is obtained. The mass fraction of silicon in the final negative electrode plate Z1 is 4.5%, and the mass fraction of graphite is 88.8%.

[0091] Example 3

[0092] This embodiment provides a negative electrode plate and a preparation method thereof, which is different from the negative electrode plate and a preparation method thereof provided in Example 1 in that: the copper particles on the current collector are distributed in an orderly manner to form an array structure, thereby obtaining a negative electrode plate Z3.

[0093] Example 4

[0094] This embodiment provides a negative electrode plate and a preparation method thereof, which is different from the negative electrode plate and a preparation method thereof provided in Example 1 in that: the particle size of the copper particles on the current collector is about 0.5 μm, and a negative electrode plate Z4 is obtained.

[0095] Example 5

[0096] This embodiment provides a negative electrode plate and a preparation method thereof, which is different from the negative electrode plate and a preparation method thereof provided in Example 1 in that: a silicon-containing electrode slurry made of a silicon-based material and a graphite slurry made of a graphite material are mixed and coated at the same time to obtain a negative electrode plate Z5.

[0097] Comparative Example 1

[0098] The negative electrode sheet and its preparation method provided in this comparative example are different from the negative electrode sheet and its preparation method provided in Example 1 in that: silicon-based material and graphite material are coated on the surface of untreated ordinary copper foil to obtain negative electrode sheet D1.

[0099] Comparative Example 2

[0100] The negative electrode sheet and its preparation method provided in this comparative example are different from the negative electrode sheet and its preparation method provided in Example 2 in that: silicon-based material and graphite material are coated on the surface of untreated ordinary copper foil to obtain negative electrode sheet D2.

[0101] Comparative Example 3

[0102] The negative electrode sheet and its preparation method provided in this comparative example are different from the negative electrode sheet and its preparation method provided in Example 5 in that: silicon-based material and graphite material are coated on the surface of untreated ordinary copper foil to obtain negative electrode sheet D3.

[0103] In order to illustrate the performance of the negative electrode sheets provided in Examples 1 to 5, the following test steps were performed:

[0104] (1) The negative electrode sheets prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were cut into round sheets with a diameter of 14 mm. The cut negative electrode sheets were vacuum dried and assembled into 2032 button batteries, and the performance of the formed button batteries was tested.

[0105] (2) The negative electrode sheets prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were cut into 74*63 mm sheets, and the cut negative electrode sheets were vacuum dried and assembled into 2.5 Ah soft-pack batteries. The formed soft-pack batteries were subjected to cycle life and expansion tests.

[0106] The test steps are as follows:

[0107] Normal temperature cycle test: Place the assembled soft-pack battery in the blue power test cabinet for charge and discharge test: charge to 4.2V at a rate of 1 / 2C; discharge to 2.75V at a rate of 1C, cycle in sequence, and record the number of cycles when the battery capacity retention rate is 80%.

[0108] Normal temperature specific capacity test: The assembled 2032 button cell was placed in a blue power test cabinet for charge and discharge test: charged to 4.2V at a rate of 0.2C; the discharge process was discharged to 2.75V at a rate of 0.2C, and the first discharge efficiency was recorded.

[0109] Negative electrode sheet change rate: record the initial electrode sheet thickness H0 of the negative electrode sheet, and the electrode sheet thickness H1 when the capacity retention rate after disassembly cycle is 80%. Negative electrode sheet change rate = (H1-H0) / H0.

[0110] The test results are shown in Table 1 below:

[0111] Table 1

[0112]

[0113] It can be seen from the test results of Examples 1 to 5 and Comparative Examples 1 to 3 in Table 1 that by forming a three-dimensional interactive structure on the surface of the negative electrode plate, the battery's initial charging capacity and the number of cycles corresponding to 80% of the remaining capacity can be significantly improved, and the battery thickness change rate when the number of cycles corresponding to 80% of the remaining capacity is reduced, ensuring that the battery has good energy density and service life.

[0114] In the description of the embodiments of the present application, it should be noted that the orientation or positional relationship of terms such as "center", "up", "down", "left", "right", "vertical", "horizontal", "inside" and "outside" are based on the orientation or positional relationship of the accompanying drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or original referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0115] What is disclosed above is only a preferred embodiment of the present application, and it certainly cannot be used to limit the scope of rights of the present application. Ordinary technicians in this field can understand that all or part of the processes of implementing the above embodiment and equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. A current collector, characterized in that: The invention comprises a copper foil substrate and copper particles. The copper particles are attached to the surface of the copper foil substrate and form a three-dimensional structure on the surface of the copper foil substrate.

2. The current collector according to claim 1, characterized in that There are multiple copper particles, and the multiple copper particles form multiple protrusions on the surface of the copper foil substrate. The multiple protrusions are arranged in an array on the surface of the copper foil substrate.

3. The current collector according to claim 2, characterized in that: A single protrusion includes a plurality of copper particles, and the protrusion extends in a direction perpendicular to a surface of the copper foil substrate.

4. A negative electrode plate, characterized in that: include: The current collector according to any one of claims 1 to 3; The silicon-containing material layer comprises a silicon-based material, and a first three-dimensional interactive structure is formed on the surface of the current collector at one side of the silicon-containing material layer close to the current collector.

5. The negative electrode sheet according to claim 4, characterized in that: The silicon-containing material layer further includes graphite material.

6. The negative electrode sheet according to any one of claims 4 or 5, characterized in that: The negative electrode plate further includes a graphite layer, which is disposed on a side of the silicon-containing material layer away from the current collector, and the graphite layer includes a graphite material.

7. The negative electrode sheet according to claim 6, characterized in that: The graphite layer forms a second three-dimensional interactive structure on a surface of the silicon-containing material layer away from the current collector.

8. A method for preparing a negative electrode sheet, characterized in that: include: Converting copper ions into copper particles, and making the copper particles adhere to the surface of the copper foil substrate to form a three-dimensional structure, thereby obtaining a current collector; The silicon-containing electrode slurry is coated on the surface of the current collector to form a silicon-containing material layer, wherein the silicon-containing material layer includes a silicon-based material, and a first three-dimensional interactive structure is formed on the surface of the current collector on one side of the silicon-containing material layer close to the current collector to obtain a negative electrode sheet.

9. The method for preparing a negative electrode sheet according to claim 8, characterized in that: The current collector is placed in an inert gas for heat treatment.

10. The method for preparing a negative electrode sheet according to claim 8 or 9, characterized in that: The silicon-containing electrode slurry also includes graphite material.

11. The method for preparing a negative electrode sheet according to claim 8 or 9, characterized in that: A graphite electrode slurry is further provided, and the graphite electrode slurry is coated on the surface of the silicon-containing material layer to form a graphite layer.

12. A battery, characterized in that: It comprises a shell and a negative electrode sheet as claimed in any one of claims 4 to 7, or comprises a shell and a negative electrode sheet made by the method for making a negative electrode sheet as claimed in any one of claims 8 to 11, wherein the negative electrode sheet is accommodated inside the shell.

13. An electrical equipment, characterized in that: Comprising the battery of claim 12.

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