Composite negative electrode current collector and preparation method and application thereof

Abstract

The invention relates to the technical field of batteries, in particular to a composite negative electrode current collector and a preparation method and application thereof. The composite negative electrode current collector comprises a high polymer material layer, a lithium supplementing layer and a conductive metal layer, the lithium supplementing layer is located on the surface of at least one side of the high polymer material layer, and the conductive metal layer is located on the surface, away from the high polymer material layer, of the lithium supplementing layer; the lithium supplementing layer comprises a composite lithium material, and the composite lithium material comprises a lithium metal core and a lithium compound coating layer coating the surface of the lithium metal core; the conductive metal layer is provided with a plurality of through hole structures. According to the composite negative electrode current collector disclosed by the invention, through the matching of each layer structure, the storage performance of a negative electrode plate is improved, the battery impedance is reduced, the infiltration time of an electrolyte is shortened, the lithium supplementing capability is improved, lithium dendrites are prevented from being generated, and the safety performance of the battery is improved.

Description

Technical Field

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

[0002] Currently, secondary lithium-ion batteries (LIBs) are widely used in wearable devices, electric vehicles, industrial energy storage and other fields. The rapid development of electric vehicles has led to people's demand for long battery life, long life, high safety and other performance. Therefore, it is urgent to develop a new generation of power batteries with high cycle life, high energy density and high safety.

[0003] Under the current technological status, the main aspects to improve the battery's energy density, cycle life and safety performance are the battery structure and positive and negative electrode materials. In terms of structure, the battery's energy density and safety performance are improved through technologies such as CTP, CTB, blade batteries, and minimalist cover plates; in terms of materials, the energy density of power lithium-ion batteries can be greatly improved through the application of high-nickel ternary materials, high-voltage nickel-manganese materials and other positive electrode materials and silicon-carbon negative electrode materials.

[0004] In addition, the energy density of the battery can also be improved through pre-lithiation technology. During the charge and discharge process of lithium-ion batteries, as the SEI film is formed, the active lithium will produce irreversible loss due to the formation of the SEI film, resulting in a decrease in battery capacity. Eliminating or reducing the loss of active lithium can effectively improve the energy density of the battery. The pre-lithiation lithium replenishment technology can effectively compensate for the loss of active lithium and improve the energy density of the battery. Pre-lithiation technology adds lithium replenishment materials before the first charge and discharge of the battery, and releases them during the charge and discharge process of the battery to compensate for the loss of active lithium during the battery cycle, increase battery capacity, and improve the coulomb efficiency and energy density of the battery. At present, pre-lithiation technology mainly includes positive electrode pre-lithiation and negative electrode pre-lithiation. Negative electrode lithium replenishment is currently mainly achieved by directly compounding metal lithium on the negative electrode sheet or attaching metal lithium to the surface of the negative electrode sheet by magnetron sputtering. Positive electrode lithium replenishment is achieved by adding lithium replenishment materials to the positive electrode of the lithium-ion battery. During the battery charging process, the lithium replenishment materials decompose and release active lithium to compensate for the irreversible active lithium loss caused by the growth of negative electrode SEI.

[0005] However, the lithium metal replenishment method can compensate for the active lithium in the negative electrode material, but the metal lithium is highly active, and the negative electrode sheet formed by the composite lithium metal layer on the surface of the negative electrode sheet has poor storage performance. The lithium replenishment capacity is significantly weakened over time, and the surface lithium metal composite layer will cause the electrolyte to wet for a long time and the battery impedance is large. The positive electrode lithium replenishment material has the disadvantages of high decomposition potential, low irreversible capacity, limited lithium replenishment capacity, and increased battery gas production.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] One object of the present invention is to provide a composite negative electrode current collector to solve the technical problems in the prior art that the lithium-supplemented negative electrode sheet has poor storage performance, increased battery impedance, prolonged electrolyte wetting time, low lithium replenishment capacity and easy generation of lithium dendrites, which affects battery safety.

[0008] Another object of the present invention is to provide a method for preparing the composite negative electrode current collector. The method is simple and easy to implement. By combining the various steps, a composite negative electrode current collector with good mechanical strength and electrochemical performance can be obtained to improve the comprehensive electrochemical performance of the battery.

[0009] Another object of the present invention is to provide a negative electrode sheet.

[0010] Another object of the present invention is to provide a battery.

[0011] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0012] A composite negative electrode current collector comprises a polymer material layer, a lithium supplement layer and a conductive metal layer, wherein the lithium supplement layer is located on at least one side surface of the polymer material layer, and the conductive metal layer is located on the surface of the lithium supplement layer away from the polymer material layer; the lithium supplement layer comprises a composite lithium material, wherein the composite lithium material comprises a lithium metal core and a lithium compound coating layer coated on the surface of the lithium metal core; and the conductive metal layer is provided with a plurality of through-hole structures.

[0013] In some implementations, the plurality of through-hole structures are distributed in a matrix on the conductive metal layer, and a row spacing L1 and a column spacing L2 of the matrix distribution satisfy: L1=L2, and L1 is 0.5-3 mm.

[0014] In some embodiments, the opening area of ​​any of the through-hole structures is 0.5 to 3 mm 2 .

[0015] In some embodiments, the ratio of the total opening area of ​​the plurality of through-hole structures to the single-side surface area of ​​the complete conductive metal layer is (0.5-3):10.

[0016] In some embodiments, the opening shape of the through-hole structure includes a circle and / or a regular polygon.

[0017] In some embodiments, the conductive metal layer includes copper.

[0018] In some embodiments, the thickness of the conductive metal layer is 1 to 3 μm.

[0019] In some embodiments, the polymer material layer includes at least one of polyamide, polyimide, polyethylene terephthalate and polypropylene.

[0020] In some embodiments, the polymer material layer has a thickness of 2 to 5 μm.

[0021] In some embodiments, the lithium compound coating layer includes at least one of lithium fluoride and lithium carbonate.

[0022] In some embodiments, the lithium replenishing layer has a thickness of 0.5 to 1 μm.

[0023] The method for preparing the composite negative electrode current collector as described above comprises the following steps:

[0024] The lithium metal raw material and the lithium compound raw material are subjected to a first vapor deposition to obtain a composite lithium material and form a lithium supplement layer on the surface of the polymer material layer; the conductive metal raw material is subjected to a second vapor deposition to form a conductive metal layer on the surface of the lithium supplement layer; and a through-hole structure is made on the conductive metal layer.

[0025] In some implementations, the first vapor deposition and the second vapor deposition are performed by magnetron sputtering, respectively.

[0026] In some implementations, the through-hole structure is obtained by punching the conductive metal layer using a punching device.

[0027] A negative electrode sheet comprises the composite negative electrode current collector and a negative electrode active layer, wherein the negative electrode active layer comprises a coating layer structure located on the surface of the conductive metal layer and an extension structure accommodated in the through-hole structure.

[0028] A battery comprises the negative electrode sheet.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) In the composite negative electrode current collector of the present invention, the polymer material layer can reduce the amount of metal used, reduce weight and cost, while maintaining good mechanical strength and conductivity, reducing the risk of internal short circuit, and effectively preventing the occurrence of thermal runaway. In addition, the polymer material layer can also prevent lithium dendrites from penetrating the diaphragm, further improving the cycle life and safety of the battery; the lithium replenishment layer can compensate for the lithium ions consumed by the formation of the solid electrolyte interface (SEI) layer during the first charge, which can significantly improve the initial Coulomb efficiency of the battery and increase the energy density and cycle life of the battery; the through-hole structure on the metal conductive layer can improve the stress of the conductive metal layer, which is conducive to the direct contact and connection between the negative electrode active layer and the lithium replenishment layer, and increase the bonding force between the negative electrode active material and the current collector. The advantages of the two can be combined while reducing the shortcomings and safety hazards caused by the lithium metal lithium replenishment method, and improving the battery performance. The composite negative electrode current collector of the present invention, through the coordination of each layer structure, is conducive to improving the storage performance of the negative electrode sheet, reducing the battery impedance, shortening the electrolyte infiltration time, improving the lithium replenishment ability, avoiding the generation of lithium dendrites, and improving the safety performance of the battery.

[0031] (2) The preparation method of the composite negative electrode current collector of the present invention first deposits a lithium replenishing layer formed by a composite lithium material on the surface of a polymer material layer, then deposits metal ions of a conductive metal raw material on the surface of the lithium replenishing layer to form a conductive metal layer, and further makes a through-hole structure on the conductive metal layer. The method of the present invention is simple and easy to implement, and can prepare a composite negative electrode current collector with good comprehensive performance, which is beneficial to improving the liquid storage performance of the negative electrode sheet, reducing the battery impedance, shortening the electrolyte infiltration time, having a good lithium replenishing effect, and improving the safety performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 Schematic diagram of the structure of the composite negative electrode current collector in each embodiment of the present invention.

[0034] 1-polymer material layer, 2-lithium supplement layer, 3-conductive metal layer, 4-through hole structure. DETAILED DESCRIPTION

[0035] The embodiments of the present invention will be described in detail below in conjunction with examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. In the examples, if specific conditions are not specified, the conditions are carried out according to normal conditions or manufacturer recommendations. If the manufacturer is not specified for reagents or instruments used, they are all conventional products that can be obtained commercially. The terms "first", "second", "third", etc. are only used to distinguish descriptions and cannot be interpreted as indicating or suggesting relative importance.

[0036] According to one aspect of the present invention, the present invention relates to a composite negative electrode current collector, comprising a polymer material layer, a lithium replenishing layer and a conductive metal layer, wherein the lithium replenishing layer is located on at least one side surface of the polymer material layer, and the conductive metal layer is located on the surface of the lithium replenishing layer away from the polymer material layer. The composite lithium material comprises a lithium metal core and a lithium compound coating layer coated on the surface of the lithium metal core; the conductive metal layer is provided with a plurality of through-hole structures.

[0037] In the composite negative electrode current collector of the present invention, the polymer material layer can reduce the amount of metal used, thereby reducing weight and cost, while maintaining good mechanical strength and conductivity. When the battery is physically damaged, such as in a needle puncture test, the composite current collector can produce smaller burrs, reduce the risk of internal short circuits, and effectively prevent the occurrence of thermal runaway. In addition, the polymer material layer can also prevent lithium dendrites from penetrating the diaphragm, further improving the cycle life and safety of the battery. The lithium replenishment layer can compensate for the lithium ions consumed by the formation of the solid electrolyte interface (SEI) layer during the first charge, which can significantly improve the initial coulomb efficiency of the battery and increase the energy density and cycle life of the battery. The through-hole structure on the metal conductive layer can improve the stress of the conductive metal layer, which is conducive to the direct contact and connection between the negative electrode active layer and the lithium replenishment layer, and increase the bonding force between the negative electrode active material and the current collector. The advantages of the two can be combined while reducing the shortcomings and safety hazards caused by the lithium metal lithium replenishment method, thereby improving battery performance. The composite negative electrode current collector of the present invention, through the coordination of various layer structures, is conducive to improving the storage performance of the negative electrode sheet, reducing the battery impedance, shortening the electrolyte infiltration time, enhancing the lithium replenishment ability, avoiding the generation of lithium dendrites, and improving the safety performance of the battery.

[0038] In some embodiments, the lithium replenishing layer is located on one side or both sides of the polymer material layer, preferably on both sides, that is, the composite negative electrode current collector includes a conductive metal layer, a lithium replenishing layer, a polymer material layer, a lithium replenishing layer, and a conductive metal layer stacked in sequence. The thickness of the lithium replenishing layer on both sides of the polymer material layer can be the same or different, and the thickness of the conductive metal layer on both sides can be the same or different.

[0039] The through-hole structure of the present invention is evenly distributed on the conductive metal layer. In some embodiments, a plurality of the through-hole structures are distributed in a matrix on the conductive metal layer, and the row spacing L1 and column spacing L2 of the matrix distribution satisfy: L1=L2, and L1 is 0.5-3mm, L1 includes but is not limited to 0.5mm, 0.8mm, 1mm, 1.5mm, 1.8mm, 2mm, 2.2mm, 2.5mm, 2.8mm, 3mm, etc., or any range value between the two. In some embodiments, the opening area of ​​any of the through-hole structures is 0.5-3mm 2 including but not limited to 0.5mm 2 , 0.8mm 2 , 1mm 2 , 1.5mm 2 , 2mm 2 , 2.5mm 2 , 3mm 2 Etc., or any range value between the two. In some embodiments, the ratio of the total opening area of ​​the plurality of through-hole structures to the single-side surface area of ​​the complete conductive metal layer is (0.5-3):10, including but not limited to 0.5:10, 1:10, 1.5:10, 1.8:10, 2:10, 2.2:10, 2.5:10, 2.8:10, 3:10, etc. In some embodiments, the opening shape of the through-hole structure includes a circle and / or a regular polygon, wherein the regular polygon includes a rectangle, a square, a triangle, a pentagon, a hexagon, etc., and one or more combinations thereof may be used, such as a combination of a circle and a square, a combination of a circle and a triangle, etc. The spacing, size and area ratio of the through-hole structure of the present invention are set within the above-mentioned suitable range, which is more conducive to ensuring the positive electrode mechanical properties and electrochemical properties of the composite negative electrode current collector, and is conducive to improving the comprehensive electrochemical properties of the negative electrode sheet prepared therefrom.

[0040] In some embodiments, the conductive metal layer includes copper. In some embodiments, the thickness of the conductive metal layer is 1 to 3 μm, including but not limited to 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, etc., or any range between the two. The conductive metal layer of the present invention has a suitable thickness, which is beneficial to the comprehensive performance of the composite negative electrode current collector.

[0041] In some embodiments, the polymer material layer includes at least one of polyamide (PA), polyimide (PI), polyethylene terephthalate (PET) and polypropylene (PP). The polymer material layer of the present invention can be any one of polyamide, polyimide, polyethylene terephthalate and polypropylene (PP), or a combination of several, or a composite laminate of several. In some embodiments, the thickness of the polymer material layer is 2 to 5 μm, including but not limited to 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm, etc., or any range value between the two. A polymer material layer of appropriate thickness is conducive to ensuring the mechanical strength and conductivity of the composite current collector, and can effectively prevent lithium dendrites from penetrating the diaphragm.

[0042] In some embodiments, the lithium compound coating layer includes one or a combination of lithium fluoride and lithium carbonate.

[0043] In some embodiments, the thickness of the lithium replenishing layer is 0.5-1 μm, including but not limited to 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc., or any range between the two. A lithium replenishing layer of suitable thickness is conducive to ensuring the lithium replenishing effect, thereby improving the initial coulomb efficiency of the battery, and increasing the energy density and cycle life of the battery.

[0044] According to another aspect of the present invention, the present invention also relates to a method for preparing the composite negative electrode current collector as described above, comprising the following steps:

[0045] The lithium metal raw material and the lithium compound raw material are subjected to a first vapor deposition to obtain a composite lithium material and form a lithium supplement layer on the surface of the polymer material layer; the conductive metal raw material is subjected to a second vapor deposition to form a conductive metal layer on the surface of the lithium supplement layer; and a through-hole structure is made on the conductive metal layer.

[0046] The preparation method of the composite negative electrode current collector of the present invention first deposits a lithium supplement layer formed by a composite lithium material on the surface of a polymer material layer, then deposits metal ions of a conductive metal raw material on the surface of the lithium supplement layer to form a conductive metal layer, and further makes a through-hole structure on the conductive metal layer. The method of the present invention is simple and easy to implement, and can prepare a composite negative electrode current collector with good comprehensive performance, which is beneficial to improving the liquid storage performance of the negative electrode sheet, reducing the battery impedance, shortening the electrolyte infiltration time, having a good lithium supplement effect, and improving the safety performance of the battery.

[0047] In some embodiments, the first vapor deposition and the second vapor deposition are each independently performed by magnetron sputtering.

[0048] In some embodiments, during the first vapor deposition process, argon ions (Ar +) bombards lithium metal targets and lithium compound targets, causing the targets to sputter to produce gas-phase lithium ion particles and lithium compound particles. The lithium compound particles are coated on the surface of the lithium ion particles to form a lithium composite material, and are deposited on the surface of the polymer material layer to form a lithium replenishing layer.

[0049] In some embodiments, the second vapor deposition uses argon ions (Ar+) to bombard a conductive metal raw material (such as a copper alloy target) to sputter the target and generate metal ions, which are deposited on the lithium supplement layer to form a conductive metal layer.

[0050] In some implementations, the conductive metal layer is punched to obtain the through-hole structure by using a punching device, and a through-hole structure with a suitable spacing, hole diameter, and number is punched out by the punching device.

[0051] In a preferred embodiment, the method for preparing the composite negative electrode current collector comprises the following steps:

[0052] (a) By magnetron sputtering, argon ions (Ar + ) bombards lithium metal targets and lithium compound targets, causing the targets to sputter to produce gas-phase lithium ion particles and lithium compound particles. The lithium compound particles are coated on the surface of the lithium ion particles to form a lithium composite material, and are deposited on the surface of the polymer material layer to form a lithium replenishing layer.

[0053] (b) Argon ions (Ar+) are used to bombard the metal conductive layer raw material target material, causing the target material to sputter and generate metal ions, which are deposited on the lithium replenishment layer to form a conductive metal layer.

[0054] (c) punching holes on the conductive metal layer using a punching device to form a through-hole structure to obtain a composite negative electrode current collector.

[0055] According to another invention of the present invention, the present invention also relates to a negative electrode sheet, comprising the composite negative electrode current collector and a negative electrode active layer, wherein the negative electrode active layer comprises a coating layer structure located on the surface of the conductive metal layer, and an extension structure accommodated in the through-hole structure.

[0056] The negative electrode sheet of the present invention has a through-hole structure, which enables the extended structure of the negative electrode active layer to directly contact the lithium replenishment layer, thereby reducing the disadvantages and potential safety hazards caused by the lithium metal replenishment method and improving the electrical performance of the negative electrode sheet.

[0057] The negative electrode active layer of the present invention comprises a negative electrode active material, a negative electrode conductive agent and a negative electrode binder. The negative electrode active material comprises at least one of graphite, hard carbon, graphene, soft carbon and silicon-based materials. The negative electrode binder comprises at least one of polyacrylic acid, styrene-butadiene rubber, sodium polyacrylate and polyvinylidene fluoride. The negative electrode conductive agent comprises at least one of conductive carbon black, carbon black, carbon nanotubes and carbon fibers.

[0058] According to another aspect of the present invention, the present invention also relates to a battery, comprising the negative electrode sheet.

[0059] The battery of the present invention has excellent cycle performance, rate performance and safety performance.

[0060] The battery of the present invention comprises the above-mentioned negative electrode sheet, positive electrode sheet, separator and electrolyte. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer located on the surface of the positive electrode current collector, and the positive electrode active layer comprises a positive electrode active material, a positive electrode conductor and a positive electrode binder. The positive electrode active material comprises conventional positive electrode active materials such as high-nickel ternary positive electrode materials and lithium cobalt oxide materials. The positive electrode binder comprises at least one of polyvinyl alcohol binder, polyurethane binder, butyl rubber binder, polyacrylate binder, polyvinylidene fluoride binder, epoxy resin binder, vinyl acetate resin binder and polytetrafluoroethylene binder. The positive electrode conductor comprises at least one of conductive carbon black, conductive graphite, acetylene black and carbon nanotubes. The separator comprises polyethylene (PE), polyethylene terephthalate (PET), and polyimide (PI).

[0061] The following is further explained in conjunction with specific embodiments and comparative examples.

[0062] The structural schematic diagram of the composite negative electrode current collector in each embodiment of the present invention is as follows Figure 1 shown.

[0063] Example 1

[0064] A composite negative electrode current collector includes a polymer material layer 1, a lithium supplement layer 2 and a conductive metal layer 3, wherein the lithium supplement layer 2 is located on both side surfaces of the polymer material layer 1, and the conductive metal layer 3 is located on the surface of the polymer material layer 1 away from the polymer base film. The polymer material layer 1 is PI with a thickness of 4μm. The lithium supplement layer 2 includes a composite lithium material, which includes a lithium metal core and a lithium compound coating layer coated on the surface of the lithium metal core. The lithium compound coating layer is lithium fluoride, and the thickness of the lithium supplement layer 2 is 0.5μm. The thickness of the single-sided conductive metal layer 3 is 1.5μm, and the conductive metal layer 3 is provided with a plurality of circular through-hole structures 4. The plurality of through-hole structures 4 are distributed in a matrix on the conductive metal layer 3, and the row spacing L1 and column spacing L2 of the matrix distribution satisfy: L1=L2=2mm; the opening area of ​​any through-hole structure 4 is 1mm 2 The ratio of the total opening area of ​​the plurality of through-hole structures 4 to the single-side surface area of ​​the complete conductive metal layer 3 is 1.6:10.

[0065] The method for preparing the composite negative electrode current collector of this embodiment comprises the following steps:

[0066] By magnetron sputtering, argon ions (Ar +) bombards lithium metal target and lithium compound target, so that the target sputters to produce gas phase lithium ion particles and lithium compound particles, the lithium compound particles are coated on the surface of the lithium ion particles to form a lithium composite material, and are deposited on the surface of the polymer material layer 1 to form a lithium supplement layer 2. Argon ions (Ar+) are used to bombard the copper alloy target, so that the target is sputtered to produce copper ions, and the copper ions are deposited on the lithium supplement layer 2 to form a conductive metal layer 3. Punching the conductive metal layer 3 with a punching device to form a through-hole structure 4, and a composite negative electrode current collector is obtained.

[0067] Example 2

[0068] A composite negative electrode current collector, which differs from Example 1 in that the polymer material layer 1 is made of PET.

[0069] The method for preparing the composite negative electrode current collector of this embodiment is different from that of Embodiment 1 in that the polymer material layer 1 is made of PET.

[0070] Example 3

[0071] A composite negative electrode current collector, which is different from Example 1 in that: the thickness of the lithium supplement layer 2 is 1 μm.

[0072] The method for preparing the composite negative electrode current collector of this embodiment is different from that of Embodiment 1 in that the lithium composite material is deposited on the surface of the polymer material layer 1 to form a lithium supplement layer 2 with a thickness of 1 μm.

[0073] Example 4

[0074] A composite negative electrode current collector is different from Example 1 in that: the thickness of the polymer material layer 1 is 5 μm, the thickness of the lithium supplement layer 2 is 1 μm, and the thickness of the single-side conductive layer is 2 μm.

[0075] The preparation method of the composite negative electrode current collector of this embodiment is different from that of Embodiment 1 in that: the thickness of the polymer material layer 1 is 5 μm; the lithium composite material is deposited on the surface of the polymer material layer 1 to form a lithium supplement layer 2 with a thickness of 1 μm, and the deposition thickness of the conductive layer is 2 μm.

[0076] Example 5

[0077] A composite negative electrode current collector is different from Example 1 in that: the thickness of the polymer material layer 1 is 3 μm, the thickness of the lithium supplement layer 2 is 1.5 μm, and the thickness of the single-side conductive layer is 2 μm.

[0078] The preparation method of the composite negative electrode current collector of this embodiment is different from that of Embodiment 1 in that: the thickness of the polymer material layer 1 is 3 μm; the lithium composite material is deposited on the surface of the polymer material layer 1 to form a lithium supplement layer 2 with a thickness of 1.5 μm, and the deposition thickness of the conductive layer is 2 μm.

[0079] Example 6

[0080] A composite negative electrode current collector, which differs from Example 1 in that the opening area of ​​any through-hole structure 4 is 3 mm 2 .

[0081] The preparation method of the composite negative electrode current collector of this embodiment is different from that of embodiment 1 in that the aperture of the punching device is adjusted to punch holes on the conductive metal layer 3 to obtain a single through-hole structure 4 with an opening area of ​​3 mm. 2 of through holes.

[0082] Example 7

[0083] A composite negative electrode current collector, which differs from Example 1 in that: a plurality of through-hole structures 4 are distributed in a matrix on the conductive metal layer 3, and the row spacing L1 and column spacing L2 of the matrix distribution satisfy: L1 = L2 = 2 mm; the opening area of ​​any through-hole structure 4 is 2 mm 2 The ratio of the total opening area of ​​the plurality of through-hole structures 4 to the single-side surface area of ​​the complete conductive metal layer 3 is 1.2:10.

[0084] Comparative Example 1

[0085] A conventional composite negative electrode current collector comprises a polymer material layer 1 and copper layers located on both sides of the polymer material layer 1. The polymer material layer 1 is PI with a thickness of 4 μm, and the thickness of the single-side copper layer is 2 μm.

[0086] Comparative Example 2

[0087] A conventional negative electrode current collector is a copper current collector with a thickness of 6 μm.

[0088] Experimental example

[0089] The negative electrode current collectors of the embodiments and comparative examples are respectively prepared into batteries, comprising the following steps:

[0090] The negative electrode active material, the negative electrode conductive agent, the negative electrode binder and the solvent are mixed to obtain a negative electrode slurry, the mass ratio of the negative electrode active material, the negative electrode conductive agent and the negative electrode binder is 95:1:4, the negative electrode active material is graphite, the negative electrode conductive agent is carbon nanotubes, the negative electrode binder is polyvinylidene fluoride, the solvent is NMP, and the solid content of the negative electrode slurry is 54%; the negative electrode slurry is coated on the surface of the negative electrode current collector, and the negative electrode sheet is obtained after drying and rolling. The positive electrode active material, the positive electrode conductive agent, the positive electrode binder and the solvent are mixed to obtain a positive electrode slurry, the mass ratio of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder is 96:1.5:2.5, the positive electrode active material is lithium iron phosphate, the positive electrode conductive agent is conductive carbon black, the positive electrode binder is polyvinylidene fluoride, the solvent is NMP, and the solid content of the positive electrode slurry is 58%. The positive electrode slurry is coated on the surface of the aluminum foil, and the positive electrode sheet is obtained after drying and rolling. The positive electrode sheet, negative electrode sheet and separator are stacked to obtain a battery cell, which is further shelled, welded, baked, injected and formed to obtain a lithium-ion battery, wherein the electrolyte used for injection is Shanshan SS-YQQCHS002.

[0091] The above batteries were subjected to electrochemical performance tests: initial efficiency and cycle performance (45°C, 1000 cycles). The test results are shown in Table 1.

[0092] Table 1 Electrochemical performance test results of the battery

[0093] Group First effect Cycle performance Example 1 86.23％ 82.52％ Example 2 85.89％ 82.47％ Example 3 86.93％ 83.12％ Example 4 86.57％ 84.45％ Example 5 87.13％ 84.06％ Example 6 85.65％ 82.77％ Example 7 85.31％ 82.68％ Comparative Example 1 80.39％ 79.93％ Comparative Example 2 81.74％ 81.84％

[0094] As can be seen from Table 1, the battery further prepared by the composite negative electrode current collector obtained by the method of the present invention has excellent first efficiency and high temperature cycle performance, with the first efficiency being above 85%, and the capacity retention rate at 45°C and 1000 cycles being greater than 82%. The first efficiency and high temperature cycle performance of the battery prepared by the conventional composite current collector of Comparative Example 1 and the conventional copper current collector of Comparative Example 2 are relatively poor.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite negative electrode current collector, characterized in that: It comprises a polymer material layer, a lithium supplement layer and a conductive metal layer, wherein the lithium supplement layer is located on at least one side surface of the polymer material layer, and the conductive metal layer is located on the surface of the lithium supplement layer away from the polymer material layer; The lithium supplement layer includes a composite lithium material, wherein the composite lithium material includes a lithium metal core and a lithium compound coating layer coated on the surface of the lithium metal core; The conductive metal layer is provided with a plurality of through-hole structures.

2. The composite negative electrode current collector according to claim 1, characterized in that: Contains at least one of the following features (1) to (4): (1) The plurality of through-hole structures are distributed in a matrix on the conductive metal layer, and the row spacing L1 and column spacing L2 of the matrix distribution satisfy: L1=L2, and L1 is 0.5-3 mm; (2) The opening area of ​​any of the through-hole structures is 0.5 to 3 mm 2 ; (3) The ratio of the total opening area of ​​the plurality of through-hole structures to the single-side surface area of ​​the complete conductive metal layer is (0.5-3):10; (4) The opening shape of the through hole structure includes a circle and / or a regular polygon.

3. The composite negative electrode current collector according to claim 1, characterized in that: Contains at least one of the following features (1) to (2): (1) The conductive metal layer includes copper; (2) The thickness of the conductive metal layer is 1 to 3 μm.

4. The composite negative electrode current collector according to claim 1, characterized in that: Contains at least one of the following features (1) to (2): (1) The polymer material layer includes at least one of polyamide, polyimide, polyethylene terephthalate and polypropylene; (2) The thickness of the polymer material layer is 2 to 5 μm.

5. The composite negative electrode current collector according to claim 1, characterized in that: Contains at least one of the following features (1) to (2): (1) The lithium compound coating layer comprises at least one of lithium fluoride and lithium carbonate; (2) The thickness of the lithium replenishing layer is 0.5 to 1 μm.

6. The method for preparing a composite negative electrode current collector according to any one of claims 1 to 5, characterized in that: The following steps are involved: Performing a first vapor deposition on a lithium metal raw material and a lithium compound raw material to obtain a composite lithium material and form a lithium supplement layer on the surface of the polymer material layer; Performing a second vapor deposition on a conductive metal raw material to deposit a conductive metal layer on the surface of the lithium supplementing layer; A through-hole structure is fabricated on the conductive metal layer.

7. The method for preparing a composite negative electrode current collector according to claim 6, characterized in that: The first vapor deposition and the second vapor deposition are respectively carried out by magnetron sputtering.

8. The method for preparing a composite negative electrode current collector according to claim 6, characterized in that: The conductive metal layer is punched by a punching device to obtain the through-hole structure.

9. A negative electrode sheet, characterized in that: The invention comprises the composite negative electrode current collector according to any one of claims 1 to 5 and a negative electrode active layer, wherein the negative electrode active layer comprises a coating layer structure located on the surface of the conductive metal layer and an extension structure accommodated in the through-hole structure.

10. A battery, characterized in that: Includes the negative electrode sheet as described in claim 9.

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