A prelithiated electrode, a method for preparing a prelithiated electrode, and a lithium-ion battery

Abstract

The present invention discloses a prelithiated electrode, a preparation method of the prelithiated electrode, and a lithium ion battery, relating to the technical field of lithium ion batteries; the preparation method of the prelithiated electrode includes the steps of: S1, making a metal film; S2, forming a sandwich-shaped film; S3, forming a metallic lithium layer, using an ion milling technique to etch a plurality of array-distributed areas to be plated on the surfaces of the upper and lower thin film substrates, and the areas to be plated penetrate through the thin film substrates and the active material layer; plating metallic lithium on the surface of the thin film substrate, and the metallic lithium fills the areas to be plated to form a metallic lithium layer on the outer surface of the thin film substrate; S4, peeling the thin film substrate, realizing peeling between the thin film substrate and the active material layer on the upper surface of the metal film and between the thin film substrate and the active material layer on the lower surface of the metal film to obtain the prelithiated electrode; the beneficial effects of the present invention are: higher safety performance, and it can also provide a continuous lithium source for the lithium battery, achieving a perfect balance between safety and energy density.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries. More specifically, the present invention relates to a prelithiated electrode sheet, a preparation method of the prelithiated electrode sheet, and a lithium-ion battery. Background Art

[0002] During the first charging process of a polymer lithium battery, the organic electrolyte will be reduced and decomposed on the surface of the negative electrode such as graphite to form a solid electrolyte interphase (SEI) film, permanently consuming a large amount of lithium from the positive electrode, resulting in a low coulombic efficiency (ICE) in the first cycle and reducing the capacity and energy density of the polymer lithium battery. To solve this problem, people began to study prelithiation technology. After continuous research, the current prelithiation process mainly includes the following four types: electrochemical prelithiation method, chemical prelithiation method, metal lithium patch method, and stable metal lithium powder method.

[0003] The existing processes using these methods can achieve the function of supplementing lithium to the lithium-ion battery, but due to the defects of the processes themselves, they cannot achieve continuous lithium supplementation for the lithium-ion battery, and the safety performance and strength are not very good. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a prelithiated electrode sheet, a preparation method of the prelithiated electrode sheet, and a lithium-ion battery to solve the problems in the prior art that the lithium-supplementing electrode sheet cannot achieve continuous lithium supplementation, and the safety performance and strength are insufficient.

[0005] The technical solution adopted by the present invention to solve its technical problems is: a preparation method of a prelithiated electrode sheet, which is improved in that the preparation method includes the following steps:

[0006] S1. Preparation of a metal thin film: Metal layers are respectively plated on both sides of a thin film substrate to form a metal thin film. An active material slurry is coated on the upper surface and the lower surface of the metal thin film and baked, and the active material slurry forms an active material layer;

[0007] S2. Molding of a sandwich-shaped thin film: Two thin film substrates are taken and respectively arranged on the active material layers on the upper surface and the lower surface of the metal thin film, and are compounded by a coating compounding machine to form a sandwich-structured thin film;

[0008] S3. Molding of a metal lithium layer: The surfaces of the upper and lower thin film substrates are etched with a plurality of array-distributed areas to be plated by using ion milling technology, and the areas to be plated penetrate through the thin film substrate and the active material layer; Metal lithium is plated on the surface of the thin film substrate, and the metal lithium fills the areas to be plated to form a metal lithium layer on the outer surface of the thin film substrate;

[0009] S4. Stripping of the thin film substrate: Using a stripping machine, stripping is achieved between the thin film substrate on the upper surface of the metal thin film and the active material layer, and between the thin film substrate on the lower surface of the metal thin film and the active material layer, forming multiple lithium supplement areas distributed in an array on the active material layer to obtain a prelithiated electrode sheet.

[0010] Further, in step S1, a metal layer is plated on both sides of the thin film substrate by vacuum coating, and the active material slurry is coated on the upper surface and the lower surface of the metal thin film using a coating and compounding device.

[0011] Further, in steps S1 and S2, the thin film substrate is PP, PE or PET, and the thickness of the thin film substrate is 3 - 4 μm.

[0012] Further, the metal layer is a copper layer, and the thickness of the metal layer is 600 - 1000 nm.

[0013] Further, in step S1, the baking temperature is 80 - 90 °C, and the baking time is 1 - 2 minutes.

[0014] Further, after step S2, there is also a step of high-temperature curing of the sandwich-structured thin film.

[0015] Further, in step S3, the thickness of the metal lithium layer on the outer surface of the thin film substrate is 100 - 200 nm.

[0016] Further, in step S4, the lithium supplement area is rectangular, with a length of 100 nm, a width of 30 nm, and the spacing between adjacent lithium supplement areas is 20 - 30 nm.

[0017] Further, in step S4, the thickness of the active material layer is the same as that of the lithium supplement area, which is 50 - 100 nm.

[0018] Further, after step S4, there is also a step:

[0019] S5. Formation of the protective layer: Under the condition of dry inert gas, a protective layer is coated on the outer surface of the active material layer and the lithium supplement area, and the protective layer is porous nano-zirconia.

[0020] Further, the thickness of the protective layer is 1 - 2 μm.

[0021] In addition, the present invention also provides a prelithiated electrode sheet, which is improved in that it includes a thin film substrate, a metal layer, an active material layer, and a lithium supplement area;

[0022] The upper surface and the lower surface of the thin film substrate are both coated with metal layers. An active material layer is attached to the outer surface of the metal layer, and through holes are arrayed and distributed on the active material layer. The lithium supplement area is arranged in the through holes of the active material layer and is in contact with the outer surface of the metal layer.

[0023] Further, the lithium supplement area is rectangular, and the length of the rectangle is more than three times the distance between adjacent lithium supplement areas.

[0024] Further, the length of the lithium supplement area is 100 nm, the width is 30 nm, and the distance between adjacent lithium supplement areas is 20 - 30 nm.

[0025] Further, the active material layer and the lithium supplement area have the same thickness, which is 50 - 100 nm.

[0026] Further, a protective layer is arranged on the outer surfaces of the active material area and the lithium supplement area, and the material of the protective layer is porous nano zirconia.

[0027] Further, the thickness of the protective layer is 1 - 2 μm.

[0028] Further, the material of the lithium supplement area is metallic lithium.

[0029] Further, the material of the thin film substrate is PP, PE or PET.

[0030] Further, the thickness of the thin film substrate is 3 - 4 μm.

[0031] Further, the metal layer is a copper layer, and the thickness of the metal layer is 600 - 1000 nm.

[0032] In addition, the present invention also provides a lithium ion battery, and the improvement lies in that the negative electrode sheet of the lithium ion battery is obtained by the preparation method of the pre-lithiated electrode sheet described above.

[0033] The beneficial effects of the present invention are as follows: Compared with the traditional methods of supplementing lithium by spraying Li powder through electrostatic control and covering a thin Li foil on the negative electrode surface, as well as the method of directly using metallic lithium as the negative electrode of the lithium battery, the lithium ion battery of the present invention has higher safety performance, can also provide a rich lithium source for the lithium battery, realizes a perfect balance between safety and energy density, and by adopting the method of arranging the active material area and the lithium supplement area at intervals and coating the surface of the lithium supplement area with porous nano zirconia, the strength of the electrode sheet is also greatly improved. Brief Description of the Drawings

[0034] Figure 1 It is a schematic flow chart of a preparation method of a pre-lithiated electrode sheet of the present invention.

[0035] Figure 2 Schematic structural diagram of the active material slurry-coated metal thin film of the present invention.

[0036] Figure 3 Schematic cross-sectional view of the sandwich-shaped thin film of the present invention.

[0037] Figure 4 Schematic structural diagram of the formed lithium metal layer of the present invention.

[0038] Figure 5 Schematic structural diagram of the peeled thin film substrate of the present invention.

[0039] Figure 6 Schematic structural diagram of the prelithiated electrode sheet with the formed protective layer of the present invention.

[0040] Figure 7 Schematic structural diagram of the surface of the active material layer of the prelithiated electrode sheet of the present invention. Detailed implementation manners

[0041] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0042] The concept, specific structure and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments and the accompanying drawings to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative efforts shall fall within the scope of protection of the present invention. In addition, all the connection / connection relationships involved in the patent do not simply refer to the direct connection of components, but refer to the more optimal connection structure that can be formed by adding or reducing connection accessories according to the specific implementation situation. The various technical features in the present invention can be combined with each other without conflicting with each other.

[0043] Embodiment 1

[0044] Referring to Figure 1 As shown, the present invention discloses a preparation method of a prelithiated electrode sheet. The prelithiated electrode sheet prepared by this preparation method can overcome the problems in the prior art that the lithium supplementing electrode sheet cannot achieve continuous lithium supplementing, and the safety performance and strength are insufficient. Specifically, in this embodiment, the preparation method of the prelithiated electrode sheet includes the following steps:

[0045] S1. Preparation of the metal thin film: Metal layers 20 are respectively plated on both sides of the thin film substrate 10 to form a metal thin film. An active material slurry is coated on the upper surface and the lower surface of the metal thin film, and it is baked at a baking temperature of 80°C for 2 minutes; the active material slurry forms an active material layer 30; As Figure 2As shown, it is a cross-sectional schematic diagram of the semi-finished product obtained in step S1;

[0046] In this solution, a metal layer 20 is plated on both sides of the thin film substrate 10 by vacuum coating method. The metal layer 20 is a copper layer, and the thickness of the copper layer is 600 nm. An active material slurry is coated on the upper surface and the lower surface of the metal thin film by a coating and compounding device. Since the vacuum coating method and the coating and compounding device are relatively common technologies in the prior art, the vacuum coating method and the coating and compounding device will not be described in detail in this embodiment.

[0047] In addition, in step S1, the active material slurry is composed of a lithium-insertable active material, a conductive agent, a binder, and a solvent N-methylpyrrolidone, and their mass ratio is 2:1:1:2. Among them, the lithium-insertable active material is one of artificial graphite, natural graphite, lithium titanate, and silicon-carbon material, the conductive agent is one of acetylene black and carbon nanotubes, and the binder is PVDF.

[0048] S2. Formation of a sandwich-shaped thin film. Take two thin film substrates 10 and respectively arrange them on the active material layers 30 on the upper surface and the lower surface of the metal thin film, and form a sandwich-structured thin film through a coating and compounding machine. In this embodiment, the thin film substrates 10 in step S1 and step S2 are the same, both are PET, and the thickness of the thin film substrate 10 is 3 μm. As Figure 3 shown, it is a cross-sectional schematic diagram of the sandwich-shaped thin film;

[0049] S3. Formation of the metallic lithium layer. Use ion milling technology to etch multiple array-distributed areas to be plated on the surfaces of the upper and lower thin film substrates 10, and the areas to be plated penetrate through the thin film substrate 10 and the active material layer 30. Plate metallic lithium on the surface of the thin film substrate 10, and the metallic lithium fills the areas to be plated, forming a metallic lithium layer 40 on the outer surface of the thin film substrate 10. As Figure 4 shown, it is a structural schematic diagram after the formation of the metallic lithium layer 40. After the metallic lithium layer 40 covers the thin film substrate 10 and fills the areas to be plated, it can be directly in contact with the metal layer 30;

[0050] It should be noted that before step S3, there is also a step of high-temperature aging of the sandwich-structured thin film to facilitate the etching of the areas to be plated on the surface of the thin film substrate 10;

[0051] In this step, the thickness of the metallic lithium layer 40 on the outer surface of the thin film substrate 10 is 100 nm;

[0052] S4. Stripping of the thin film substrate 10. Using a stripping machine, stripping is achieved between the thin film substrate 10 on the upper surface of the metal thin film and the active material layer 30, and between the thin film substrate 10 on the lower surface of the metal thin film and the active material layer 30, forming a plurality of lithium supplement regions 401 distributed in an array on the active material layer 30 to obtain a prelithiated electrode sheet; as Figure 5 shown, which is the schematic structural diagram after the stripping of the thin film substrate 10;

[0053] In this embodiment, the lithium supplement region 401 is rectangular, with a length of 100 nm, a width of 30 nm, and a spacing of 20 nm between adjacent lithium supplement regions 401; in addition, the active material layer 30 and the lithium supplement region 401 have the same thickness of 50 nm.

[0054] In addition, after the step S4, the following steps are further included:

[0055] S5. Formation of the protective layer. Under the condition of dry inert gas, a protective layer is coated on the outer surface of the active material layer 30 and the lithium supplement region 401, and the protective layer is porous nanozirconia 60; the thickness of the protective layer is 1 μm. The purpose of coating a porous carbon nano-film is that, on the one hand, it can prevent the reaction of metallic lithium with water in the air, and on the other hand, the porous nanozirconia can also increase the strength of the positive electrode sheet. As Figure 6 shown, which is the schematic structural diagram of the prelithiated electrode sheet after the formation of the protective layer.

[0056] Example 2

[0057] Referring to Figure 1 shown, the present invention discloses a preparation method of a prelithiated electrode sheet. The prelithiated electrode sheet obtained by this preparation method can overcome the problems in the prior art that the lithium supplement electrode sheet cannot achieve continuous lithium supplementation, and has insufficient safety performance and strength. Specifically, in this embodiment, the preparation method of the prelithiated electrode sheet includes the following steps:

[0058] S1. Preparation of the metal thin film. Metal layers 20 are respectively plated on both sides of the thin film substrate 10 to form a metal thin film. An active material slurry is coated on the upper surface and the lower surface of the metal thin film, and it is baked, with a baking temperature of 90 °C and a baking time of 1 minute; the active material slurry forms the active material layer 30; as Figure 2 shown, which is the schematic cross-sectional view of the semi-finished product obtained in step S1;

[0059] In this solution, a metal layer 20 is plated on both sides of the thin film substrate 10 by vacuum coating. The metal layer 20 is a copper layer with a thickness of 1000 nm. An active material slurry is coated on the upper and lower surfaces of the metal film by a coating and compounding device. Since the vacuum coating method and the coating and compounding device are relatively common techniques in the prior art, the vacuum coating method and the coating and compounding device will not be described in detail in this embodiment.

[0060] In addition, in step S1, the active material slurry is composed of a lithium-insertable active material, a conductive agent, a binder, and a solvent N-methylpyrrolidone, and their mass ratio is 2:1:1:2. Among them, the lithium-insertable active material is one of artificial graphite, natural graphite, lithium titanate, and silicon-carbon materials, the conductive agent is one of acetylene black and carbon nanotubes, and the binder is PVDF.

[0061] S2. Formation of a sandwich-shaped thin film. Take two thin film substrates 10 and respectively place them on the active material layers 30 on the upper and lower surfaces of the metal film, and form a sandwich-structured thin film through compounding by a coating and compounding machine. In this embodiment, the thin film substrates 10 in step S1 and step S2 are the same, both are PE, and the thickness of the thin film substrate 10 is 4 μm. As Figure 3 shown, it is a schematic cross-sectional view of the sandwich-shaped thin film.

[0062] S3. Formation of the metallic lithium layer 40. Use ion milling technology to etch multiple array-distributed areas to be plated on the surfaces of the upper and lower thin film substrates 10, and the areas to be plated penetrate through the thin film substrate 10 and the active material layer 30. Deposit metallic lithium on the surface of the thin film substrate 10, and the metallic lithium fills the areas to be plated to form a metallic lithium layer 40 on the outer surface of the thin film substrate 10. As Figure 4 shown, it is a schematic structural view after the formation of the metallic lithium layer 40.

[0063] It should be noted that before step S3, there is also a step of high-temperature curing the sandwich-structured thin film to facilitate the etching of the areas to be plated on the surface of the thin film substrate 10.

[0064] In this step, the thickness of the metallic lithium layer 40 on the outer surface of the thin film substrate 10 is 200 nm.

[0065] S4. Peeling of the thin film substrate 10. Use a peeling machine to peel between the thin film substrate 10 and the active material layer 30 on the upper surface of the metal film and between the thin film substrate 10 and the active material layer 30 on the lower surface of the metal film, and form multiple array-distributed lithium compensation areas 401 on the active material layer 30 to obtain a prelithiated electrode sheet 50. As Figure 5 shown, it is a schematic structural view after the peeling of the thin film substrate 10.

[0066] In this embodiment, the lithium supplementation region 401 is rectangular, with a length of 100 nm, a width of 30 nm, and a spacing of 30 nm between adjacent lithium supplementation regions 401; in addition, the active material layer 30 has the same thickness as the lithium supplementation region 401, which is 100 nm.

[0067] In addition, after the step S4, the following steps are further included:

[0068] S5. Formation of the protective layer. Under the condition of dry inert gas, a protective layer is coated on the outer surface of the active material layer 30 and the lithium supplementation region 401. The protective layer is porous nanozirconia 60; the thickness of the protective layer is 2 μm. The purpose of coating a porous carbon nanofilm is that, on the one hand, it can prevent metallic lithium from reacting with water in the air, and on the other hand, the porous nanozirconia can also increase the strength of the positive electrode sheet. As Figure 6 shown, it is a schematic structural diagram of the prelithiated electrode sheet 50 after the formation of the protective layer.

[0069] Embodiment 3

[0070] Based on the above preparation method of the prelithiated electrode sheet, the present invention provides a prelithiated electrode sheet. Referring to Figure 6 、 Figure 7 shown, the prelithiated electrode sheet includes a thin film substrate 10, a metal layer 20, an active material layer 30, and a lithium supplementation region 401; both the upper surface and the lower surface of the thin film substrate 10 are plated with a metal layer 20. The material of the thin film substrate 10 is PP, and its thickness is 3.5 μm. The metal layer 20 is a copper layer, and the thickness of the metal layer 20 is 800 nm. An active material layer 30 is attached to the outer surface of the metal layer 20, and through holes are arrayed and distributed on the active material layer 30. The lithium supplementation region 401 is arranged in the through holes of the active material layer 30 and is in contact with the outer surface of the metal layer 20; in this embodiment, the active material layer 30 has the same thickness as the lithium supplementation region 401, which is 75 nm; and the material of the lithium supplementation region 401 is metallic lithium.

[0071] Among them, the active material layer 30 is prepared from an active material slurry, and the active material slurry is composed of a lithium-intercalatable active material, a conductive agent, a binder, and a solvent N-methylpyrrolidone, and their mass ratio is 2:1:1:2; among them, the lithium-intercalatable active material is one of artificial graphite, natural graphite, lithium titanate, and silicon-carbon material, the conductive agent is one of acetylene black and carbon nanotubes, and the binder is a conventional PVDF.

[0072] As a preferred embodiment, as Figure 7As shown, the lithium compensation region 401 is rectangular, and the length of the rectangle is more than three times the spacing between adjacent lithium compensation regions 401; in this embodiment, the length of the lithium compensation region 401 is 100 nm, the width is 30 nm, and the spacing between adjacent lithium compensation regions 401 is 25 nm. In addition, a protective layer is provided on the outer surfaces of the active material region and the lithium compensation region 401, and the material of the protective layer is porous nano zirconia 60; the thickness of the protective layer is 1.5 μm.

[0073] Example 4

[0074] Based on the above method for preparing a prelithiated electrode, the present invention provides a prelithiated electrode, referring to Figure 6 , Figure 7 As shown, the prelithiated electrode includes a thin film substrate 10, a metal layer 20, an active material layer 30, and a lithium compensation region 401; metal layers 20 are plated on both the upper surface and the lower surface of the thin film substrate 10. The material of the thin film substrate 10 is PP, and its thickness is 3.75 μm. The metal layer 20 is a copper layer, and the thickness of the metal layer 20 is 700 nm. An active material layer 30 is attached to the outer surface of the metal layer 20, and through holes are arrayed in the active material layer 30. The lithium compensation region 401 is provided in the through holes of the active material layer 30 and is in contact with the outer surface of the metal layer 20; in this embodiment, the active material layer 30 and the lithium compensation region 401 have the same thickness, which is 80 nm; and the material of the lithium compensation region 401 is metallic lithium.

[0075] Among them, the active material layer 30 is prepared from an active material slurry, and the active material slurry is composed of a lithium-insertable active material, a conductive agent, a binder, and a solvent N-methylpyrrolidone. Among them, the lithium-insertable active material is one of artificial graphite, natural graphite, lithium titanate, and silicon-carbon material, the conductive agent is one of acetylene black and carbon nanotubes, and the binder is a conventional PVDF.

[0076] As a preferred embodiment, as Figure 7 shown, the lithium compensation region 401 is rectangular, and the length of the rectangle is more than three times the spacing between adjacent lithium compensation regions 401; in this embodiment, the length of the lithium compensation region 401 is 100 nm, the width is 30 nm, and the spacing between adjacent lithium compensation regions 401 is 28 nm. In addition, a protective layer is provided on the outer surfaces of the active material region and the lithium compensation region 401, and the material of the protective layer is porous nano zirconia 60; the thickness of the protective layer is 1 μm.

[0077] Based on the above embodiments, the present invention further provides a lithium-ion battery, and the negative electrode of the lithium-ion battery is obtained by the method for preparing the prelithiated electrode.

[0078] The prelithiated electrode of the present invention, on the one hand, compared with the traditional methods of lithium supplementation by spraying Li powder through electrostatic control and covering a thin Li foil on the negative electrode surface, as well as the method of directly using metallic lithium as the negative electrode of the lithium battery, the lithium-ion battery of the present invention has higher safety performance, can also provide a continuous lithium source for the lithium battery, achieving a perfect balance between safety and energy density. Moreover, by adopting the method of arranging the active material region and the lithium supplementation region 401 at intervals and coating the surface of the lithium supplementation region 401 with porous nanozirconia 60, the strength of the electrode is also greatly improved.

[0079] In addition, the present invention also provides relevant data on safety performance testing and energy density testing.

[0080] Preparation of the experimental battery of the present invention:

[0081] Among them, the negative electrode uses the above-mentioned prelithiated electrode of the present invention, and the positive electrode is composed of lithium iron phosphate, positive electrode conductive agent acetylene black, binder PVDF, and positive electrode current collector aluminum foil; the electrolyte is composed of lithium salt LiPF6, solvent dimethyl carbonate, and additive fluoroethylene carbonate; thereafter, a lithium-ion battery is made according to the normal lithium-ion battery production process.

[0082] Preparation of the comparative battery:

[0083] The negative electrode is completely covered with active material, without the structure of the prelithiated electrode of the present invention, and the others are exactly the same, and an experimental battery for comparison is assembled.

[0084] Needle-punch test method: Using the conventional test method, after the battery is fully charged, a high-temperature resistant steel needle with a diameter of Φ7mm is used to penetrate from the direction perpendicular to the battery electrode plate at a speed of 23mm / s, and the steel needle stays in the battery for 1h. No abnormal phenomenon is qualified.

[0085] Overcharge test: Using the conventional test method, at 25°, first charge the battery at 0.5C until it is half full, and then charge it at a constant current of 1C for 2h and then stop. The battery does not smoke or catch fire is qualified.

[0086] The experimental data are as follows:

[0087] Experimental product Overcharge experiment Pinprick experiment 1 No abnormal phenomenon No smoking, no fire 2 No abnormal phenomenon No smoking, no fire 3 No abnormal phenomenon No smoking, no fire

[0088] The test method for energy density is: at room temperature of 25°C, after the battery is left standing for 30 minutes, first charge it at a constant current of 0.7C to 4.35V, and then charge it at a constant voltage until the current is 0.05C; leave it standing for 3 minutes, and discharge it at a constant current of 0.5C to 3.0V, and measure the energy at this time. The calculation formula for energy density is: energy density = energy of the battery divided by the volume of the battery.

[0089] The test data are as follows:

[0090] Sample Energy density Experimental product 1 810 Wh / L Experimental product 2 823 Wh / L Comparative example 1 730 Wh / L Comparative example 2 742 Wh / L

[0091] Strength test:

[0092] Fix the prelithiated sample of the present invention to the clips at the upper and lower ends of the tensile strength measuring instrument. Measure the tensile strength at a speed of 100 mm / min. Apply force along the upper and lower directions, and mark the strength when the test piece is broken as the tensile strength, with the unit of kgf / cm2. The test results are shown in the following table.

[0093] Sample Tensile strength Experimental product 1 5.213 Experimental product 2 5.734 Comparative example 1 3.445 Comparative example 2 3.673

[0094] Combined with the experimental data, it can be seen that the prelithiated electrode sheet of the present invention has good performance in terms of energy density, tensile strength and safety performance.

[0095] The above is a specific description of the preferred embodiment of the present invention, but the present invention is not limited to the described embodiment. Those skilled in the art can also make various equivalent deformations or substitutions without departing from the spirit of the present invention, and these equivalent deformations or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A method for preparing a prelithiated electrode sheet, characterized in that, The preparation method includes the following steps: S1. Preparation of the metal film: Metal layers are respectively plated on both sides of the film substrate to form a metal film. An active material slurry is coated on the upper and lower surfaces of the metal film and baked, and the active material slurry forms an active material layer. S2. Molding of the sandwich-shaped film: Two film substrates are taken and respectively arranged on the active material layers on the upper and lower surfaces of the metal film, and a sandwich-structured film is formed after being compounded by a coating compounding machine. S3. Molding of the lithium metal layer: The surfaces of the upper and lower two film substrates are etched with a plurality of array-distributed areas to be plated by using ion milling technology, and the areas to be plated penetrate through the film substrate and the active material layer; Lithium metal is plated on the surface of the film substrate, and the lithium metal fills the areas to be plated, and a lithium metal layer is formed on the outer surface of the film substrate. S4. Peeling of the film substrate: By using a peeling machine, peeling is achieved between the film substrate and the active material layer on the upper surface of the metal film and between the film substrate and the active material layer on the lower surface of the metal film, and a plurality of array-distributed lithium supplement areas are formed on the active material layer to obtain a prelithiated electrode sheet.

2. The preparation method of a prelithiated electrode sheet according to claim 1, wherein, In step S1, the metal layers are respectively plated on both sides of the film substrate by using vacuum coating, and the active material slurry is coated on the upper and lower surfaces of the metal film by using a coating compounding device.

3. The preparation method of a prelithiated electrode sheet according to claim 1, characterized in that, In steps S1 and S2, the film substrate is PP, PE or PET, and the thickness of the film substrate is 3 - 4 μm.

4. The preparation method of a prelithiated electrode sheet according to claim 3, wherein The metal layer is a copper layer, and the thickness of the metal layer is 600 - 1000 nm.

5. The preparation method of a prelithiated electrode sheet according to claim 1, characterized in that, In step S1, the baking temperature is 80 - 90 °C, and the baking time is 1 - 2 minutes.

6. The preparation method of a prelithiated electrode sheet according to claim 1, wherein, After step S2, there is also a step of high-temperature aging of the sandwich-structured film.

7. The preparation method of a prelithiated electrode sheet according to claim 1, characterized in that, In step S3, the thickness of the lithium metal layer on the outer surface of the film substrate is 100 - 200 nm.

8. A method for preparing a prelithiated electrode sheet according to claim 1, characterized in that, In step S4, the lithium supplement areas are rectangular, with a length of 100 nm, a width of 30 nm, and the spacing between adjacent lithium supplement areas is 20 - 30 nm.

9. The preparation method of a prelithiated electrode sheet according to claim 1 or 8, characterized in that, In step S4, the active material layer and the lithium supplement areas have the same thickness, which is 50 - 100 nm.

10. The preparation method of a prelithiated electrode sheet according to claim 1, characterized in that, After step S4, there is also a step: S5. Molding of the protective layer: Under the condition of dry inert gas, a protective layer is coated on the outer surface of the active material layer and the lithium supplement areas, and the protective layer is porous nano zirconia.

11. A method for preparing a prelithiated electrode sheet according to claim 10, characterized in that, The thickness of the protective layer is 1 - 2 μm.

12. A prelithiated electrode sheet, characterized in that: The prelithiated electrode sheet is obtained by the preparation method of the prelithiated electrode sheet according to any one of claims 1 - 11, and the prelithiated electrode sheet includes a film substrate, a metal layer, an active material layer and lithium supplement areas; Metal layers are plated on both the upper and lower surfaces of the film substrate, an active material layer is attached to the outer surface of the metal layer, and through holes are array-distributed on the active material layer, and the lithium supplement areas are arranged in the through holes of the active material layer and are in contact with the outer surface of the metal layer.

13. A prelithiated electrode sheet according to claim 12, characterized in that: The lithium supplement areas are rectangular, and the length of the rectangle is more than three times the spacing between adjacent lithium supplement areas.

14. A prelithiated electrode sheet according to claim 13, characterized in that: The length of the lithium supplement areas is 100 nm, the width is 30 nm, and the spacing between adjacent lithium supplement areas is 20 - 30 nm.

15. A prelithiated electrode sheet according to claim 12, characterized in that: The thickness of the active material layer is the same as that of the lithium supplement area, which is 50-100 nm.

16. A prelithiated electrode sheet according to claim 12, characterized in that: A protective layer is provided on the outer surfaces of the active material area and the lithium supplement area, and the material of the protective layer is porous nano zirconia.

17. A prelithiated electrode sheet according to claim 16, characterized in that: The thickness of the protective layer is 1-2 μm.

18. A prelithiated electrode sheet according to claim 12, characterized in that: The material of the lithium supplement area is metallic lithium.

19. A prelithiated electrode sheet according to claim 12, characterized in that: The material of the thin film substrate is PP, PE or PET.

20. A prelithiated electrode sheet according to claim 12, characterized in that: The thickness of the thin film substrate is 3-4 μm.

21. A prelithiated electrode sheet according to claim 12, characterized in that: The metal layer is a copper layer, and the thickness of the metal layer is 600-1000 nm.

22. A lithium-ion battery, characterized in that, The negative electrode sheet of the lithium ion battery is obtained by the preparation method of the prelithiated electrode sheet according to any one of claims 1-11.

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