A lithium battery negative electrode and preparation method thereof

Abstract

The present invention relates to the technical field of lithium batteries, and in particular to a negative electrode of a lithium battery and a preparation method thereof. The negative electrode of the lithium battery comprises a current collector and a negative electrode slurry layer, the negative electrode slurry layer covers the current collector, the negative electrode slurry layer comprises a first slurry part and a second slurry part, the first slurry part and the second slurry part are multiple, the first slurry part and the second slurry part are alternately arranged, the composition of the first slurry part includes graphene, and the graphene content in the composition of the second slurry part is 0. The preparation method prepares a negative electrode of a lithium battery through a special first mold and a second mold structure. Through the present application, the prepared negative electrode of the lithium battery reduces the obstruction to the diffusion of lithium ions and improves the performance of the lithium battery.

Description

Technical Field

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

[0002] The main structure of a lithium battery includes a positive electrode, a negative electrode, a separator and an electrolyte. The separator is used to separate the positive electrode and the negative electrode to prevent the two electrodes from contacting and short-circuiting, and to allow electrolyte ions to pass through. The electrolyte plays the role of transporting ions and conducting current between the positive and negative electrodes, and is generally a mixed solvent of an organic solvent and a lithium salt. The positive electrode includes a current collector and a positive electrode material, and the negative electrode includes a current collector and a negative electrode material. During the charging process, the lithium ions in the positive electrode material are released and diffuse to the negative electrode and are enriched. During the discharge process, the lithium ions diffuse from the negative electrode to the positive electrode and are embedded in the crystals of the positive electrode material.

[0003] Graphene has high electron mobility and ultra-high charge carrier mobility, which can significantly reduce the internal resistance of the battery, improve the rate performance and cycle life, and is used in the negative electrode of lithium batteries.

[0004] Although adding graphene to the negative electrode can improve the conductivity of the negative electrode and reduce the internal resistance of the current, graphene is a two-dimensional carbon material, so graphene has a typical sheet structure. When sheet graphene is added to the negative electrode of the battery, it will hinder the diffusion of lithium ions, thereby reducing the diffusion efficiency of lithium ions and extending the diffusion path of lithium ions, which is not conducive to improving the performance of lithium batteries and affects the charging and discharging efficiency of the battery. Summary of the invention

[0005] The present invention aims to provide a lithium battery negative electrode and a preparation method thereof, so as to reduce the obstacles to the diffusion of lithium ions and improve the performance of the lithium battery.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a lithium battery negative electrode, including a current collector and a negative electrode slurry layer, the negative electrode slurry layer is located on the current collector, the negative electrode slurry layer includes a first slurry part and a second slurry part, the first slurry part and the second slurry part are multiple, the first slurry part and the second slurry part are alternately arranged, the component of the first slurry part includes graphene, and the graphene content in the component of the second slurry part is 0.

[0007] The principle and advantage of this scheme are: the negative electrode slurry layer formed by this scheme contains graphene. Compared with the negative electrode of the lithium battery without graphene, graphene has high electron mobility and ultra-high charge carrier mobility, which can significantly reduce the internal resistance of the battery, improve the rate performance and cycle life, and thus help improve the performance of the lithium battery. At the same time, since only the first slurry part contains graphene components, and the second slurry part does not contain graphene components, the entire negative electrode slurry layer does not contain graphene, which can avoid the entire negative electrode slurry layer being full of graphene, and the second slurry part will not hinder the diffusion of lithium ions, reducing the impact of flaky graphene on the diffusion of lithium ions. Compared with the distribution of graphene in the entire negative electrode, the performance of the lithium battery is improved, which helps to increase the amount of embedded lithium ions in the negative electrode and optimize the fast charging and discharging performance of the battery.

[0008] The first slurry part and the second slurry part are alternately arranged, so that the first slurry part and the second slurry part in the negative electrode slurry layer are distributed relatively evenly, which is beneficial to improving the performance of the negative electrode of the lithium battery.

[0009] Preferably, as an improvement, the first slurry portion and the second slurry portion are both in strip shape. The strip-shaped first slurry portion and the second slurry portion are convenient for production and processing.

[0010] Preferably, as an improvement, the first slurry part further comprises a binder, a solvent and carbon nanotubes; the second slurry part further comprises graphite, a binder, a conductive agent and a solvent.

[0011] Preferably, as an improvement, the current collector is a copper foil with holes; thus, the current collector can be made of existing copper foil;

[0012] Alternatively, the current collector includes an upper shell and a lower shell, and both the upper shell and the lower shell are provided with an extrusion cavity, and the extrusion cavity on the upper shell and the extrusion cavity on the lower shell are staggered and opposite to each other. In this way, the current collector may not be the existing copper foil, but the mold for forming the negative electrode slurry layer can be used as the current collector. In this way, after the negative electrode slurry layer is formed, there is no need to take it out of the mold and cover it on the copper foil alone. The mold is directly used as the current collector, which is beneficial to reduce the production process and improve the production efficiency. At the same time, the extrusion cavity can be used as a channel for lithium ions to pass through, and the upper shell and the lower shell will not hinder the movement and diffusion of lithium ions.

[0013] A method for preparing a negative electrode of a lithium battery comprises the following steps:

[0014] Step 1: prepare the first slurry, take graphene and carbon nanotubes and grind them evenly, then add a binder and a solvent and stir evenly;

[0015] Prepare the second slurry by mixing graphite, a binder, a conductive agent and a solvent to form the second slurry;

[0016] Step 2: preparing a negative electrode slurry layer, taking a first mold and a second mold, the first mold and the second mold are opposite to each other, a molding cavity is formed between the first mold and the second mold, the first mold is provided with a plurality of first extrusion cavities arranged in sequence, the second mold is provided with a plurality of second extrusion cavities arranged in sequence, and the first extrusion cavities and the second extrusion cavities are staggered and opposite to each other;

[0017] Filling the first slurry into the molding cavity through the first extrusion cavity to form a first slurry portion, and filling the second slurry into the molding cavity through the second extrusion cavity to form a second slurry portion;

[0018] Step 3: Place the negative electrode slurry layer on the current collector and dry it.

[0019] Thus, through this preparation method, a negative electrode slurry layer in which the first slurry part and the second slurry part are alternately arranged can be prepared, thereby forming the negative electrode of the lithium battery in this application. At the same time, the first mold and the second mold in the structure of this scheme are used in this preparation method, the first extrusion cavity is used to squeeze the first slurry into the molding cavity, and the second extrusion cavity is used to squeeze the second slurry into the molding cavity. The first extrusion cavity and the second extrusion cavity are staggered relative to each other, and the first extrusion cavity and the second extrusion cavity are not directly opposite, so that the first slurry and the second slurry can be prevented from colliding with each other during the process of squeezing into the molding cavity, so that the first slurry part and the second slurry part formed can be staggered and alternately arranged.

[0020] Preferably, as an improvement, in step 2, after the first slurry and the second slurry both fill the molding cavity, the extrusion force on the first slurry and the second slurry is increased. Thus, after the first slurry and the second slurry are squeezed into the molding cavity, by increasing the pressure, the first slurry and the second slurry in the molding cavity can be laterally diffused and laterally squeezed against each other, so that the first slurry part and the second slurry part can be tightly adhered together, ensuring the structural stability of the negative electrode slurry layer.

[0021] Preferably, as an improvement, in step 2, the first extrusion chamber and the second extrusion chamber are both arranged vertically; when the first extrusion chamber is located above the second extrusion chamber, the first slurry and the second slurry are filled into the molding chamber in the order of priority; when the second extrusion chamber is located above the first extrusion chamber, the second slurry and the first slurry are filled into the molding chamber in the order of priority. Thus, the material is first fed from the upper extrusion chamber, and then from the lower extrusion chamber, so that the slurry that first enters from the upper extrusion chamber forms a space between adjacent slurries without hindering the subsequent feeding from the lower extrusion chamber, which is conducive to forming a structure in which the first slurry portion and the second slurry portion are alternately arranged.

[0022] Preferably, as an improvement, in step 2, after the negative electrode slurry layer is formed, the negative electrode slurry layer and the slurry in the first mold and the second mold are separated by using an insert plate. Thus, it is easy to separate the first mold and the second mold from the formed negative electrode slurry layer, and the slurry remaining inside the first mold and the second mold will not adhere to the negative electrode slurry layer when the first mold and the second mold are disassembled.

[0023] Preferably, as an improvement, in step 2, a molding frame is detachably connected between the first mold and the second mold, and the molding frame includes a detachably connected frame. Thus, the molding frame and the first mold and the second mold surround to form a molding cavity. The molding frame can be disassembled and assembled to facilitate demolding of the negative electrode slurry layer.

[0024] Preferably, as an improvement, in step three, the first mold and the second mold serve as current collectors, and are respectively the upper shell and the lower shell of the current collector; in this way, the mold for molding the negative electrode slurry layer serves as the current collector, so that after the negative electrode slurry layer is molded, it does not need to be taken out of the mold and is covered on the copper foil alone, and the mold directly serves as the current collector, thereby helping to reduce the production process and improve the production efficiency. At the same time, the extrusion cavity can be used as a channel for lithium ions to pass through, and the upper shell and the lower shell will not hinder the movement and diffusion of lithium ions;

[0025] Alternatively, the current collector is copper foil. Of course, existing copper foil can also be used as the current collector. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the planar structure of the negative electrode slurry layer.

[0027] Figure 2 This is a cross-sectional view of the first mold, the second mold, and the molding frame in use.

[0028] Figure 3 A top view of the molding frame.

[0029] Figure 4 FIG. 4 is a cross-sectional view of a negative electrode of a lithium battery in another embodiment. DETAILED DESCRIPTION

[0030] The following is further described in detail through specific implementation methods:

[0031] The figure marks in the drawings of the specification include: a first slurry part 1, a second slurry part 2, a first extrusion cavity 3, a first partition wall 4, a first mold 5, a first feed port 6, a molding cavity 7, a molding frame 8, an insert plate 9, a second mold 10, a second extrusion cavity 11, a second partition wall 12, a second feed port 13, a first frame 14, a second frame 15, a wedge block 16, and a positioning hole 17.

[0032] Example 1

[0033] Basically as attached Figure 1 As shown: A lithium battery negative electrode, including a current collector and a negative electrode slurry layer, the negative electrode slurry layer is located on the current collector, the negative electrode slurry layer includes a first slurry part 1 and a second slurry part 2, the first slurry part 1 and the second slurry part 2 are multiple, the first slurry part 1 and the second slurry part 2 are alternately arranged, and the first slurry part 1 and the second slurry part 2 are both strip-shaped. The component 1 of the first slurry part includes graphite, graphene, a binder, a solvent and carbon nanotubes, the mass ratio of graphite, graphene, carbon nanotubes and binder is 75:10:2:2, the solvent is water or nmp solvent, and the binder is sodium carboxymethyl cellulose and styrene-butadiene rubber, or polyvinylidene fluoride; the component 2 of the second slurry part includes graphite, a binder, a conductive agent and a solvent, and the mass ratio of graphite, binder and conductive agent is: 90:1:2. The conductive agent is polyaniline and conductive carbon black, the mass ratio of polyaniline to conductive carbon black is 1:3, the binder is sodium carboxymethyl cellulose and styrene-butadiene rubber, or polyvinylidene fluoride, and the solvent is water. Component 2 of the second slurry part does not contain graphene. The current collector is a copper foil with holes.

[0034] A method for preparing a negative electrode of a lithium battery comprises the following steps:

[0035] Step 1: prepare the first slurry, take graphene (powder) and carbon nanotubes and grind them evenly, then add a binder and a solvent and stir evenly, the mass ratio of graphite, graphene, carbon nanotubes and binder is 75:10:2:2;

[0036] The second slurry is prepared by taking graphite, a binder, a conductive agent and a solvent, mixing and stirring to form the second slurry, and the mass ratio of graphite, a binder and a conductive agent is 90:1:2.

[0037] Step 2: Prepare the negative electrode slurry layer. Figure 2 The first mold 5 and the second mold 10 are opposite to each other. The first mold 5 is provided with a plurality of first extrusion cavities 3 arranged in sequence transversely, and adjacent first extrusion cavities 3 are separated by a first partition wall 4. A first feed port 6 is provided at the end of the first mold 5; the second mold 10 is provided with a plurality of second extrusion cavities 11 arranged in sequence transversely, and adjacent second extrusion cavities 11 are separated by a second partition wall 12. A second feed port 13 is provided at the end of the first mold 5; a molding frame 8 is provided between the first mold 5 and the second mold 10, and a molding cavity 7 is formed between the molding frame 8, the end of the first mold 5 away from the first feed port 6, and the end of the second mold 10 away from the second feed port 13, and the molding cavity 7 is formed between the molding frame 8, the end of the first mold 5 away from the first feed port 6, and the end of the second mold 10 away from the second feed port 13. Figure 3As shown, the molding frame 8 includes two first frames 14 and two second frames 15, and the two first frames 14 and the second frames 15 are detachably connected to form a rectangular molding frame 8. Positioning holes 17 are provided on the upper and lower sides of the first frames 14. The end of the first mold 5 away from the first feed port 6 and the end of the second mold 10 away from the second feed port 13 are integrally formed with positioning columns, which can be inserted into the positioning holes 17, so that the first mold 5 and the second mold 10 are respectively assembled on the upper and lower sides of the molding frame 8; Figure 2 As shown, after the first mold 5 and the second mold 10 are installed on the upper and lower sides of the molding frame 8, the first extrusion cavity 3 and the second extrusion cavity 11 are staggered and opposite, that is, the first extrusion cavity 3 and the second partition wall 12 are opposite, and the second extrusion cavity 11 and the first partition wall 4 are opposite; the first feed port 6 and the second feed port 13 are both clamped (such as by a clamping block and a clamping groove structure) with a feed pipe (not shown in the figure); the first extrusion cavity 3 and the second extrusion cavity 11 are both strip-shaped; the thickness of the molding cavity 7 in this embodiment is 0.5-1cm.

[0038] First, the first slurry is charged into the first feed port 6 through the feed pipe, and the first slurry enters the molding cavity 7 through the plurality of first extrusion cavities 3 respectively. The first slurry is formed into a block shape under the action of the first extrusion cavity 3 and falls onto the top of the second partition wall 12, so that there is a gap between adjacent first slurries in the molding cavity 7; then the second slurry is charged into the second feed port 13 through the feed pipe, and the second slurry enters the molding cavity 7 through the plurality of second extrusion cavities 11 respectively. At this time, the second slurry in the molding cavity 7 is located between adjacent first slurries, and the second slurry is formed into a block shape under the action of the second extrusion cavity 11 and falls upward. Move and contact with the bottom of the first partition wall 4; when the second slurry fills the molding cavity 7, the first slurry and the second slurry in the molding cavity 7 are alternately distributed, and then the extrusion force on the first slurry and the second slurry is increased to make the first slurry and the second slurry diffuse laterally in the molding cavity 7, so that the first slurry and the second slurry adhere to each other; in this embodiment, the first mold 5 is located above the second mold 10, and of course the second mold 10 can also be located above the first mold 5. At this time, it is necessary to first extrude the second slurry into the molding cavity 7 through the second mold 10, and then extrude the first slurry into the molding cavity 7 through the first mold 5;

[0039] The first slurry and the second slurry enter the molding cavity 7 and are distributed alternately, thereby forming a first slurry portion 1 and a second slurry portion 2;

[0040] After the negative electrode slurry layer is formed, combine Figure 2As shown, two insertion holes are provided at the right end of the molding frame 8, and the two insertion holes are respectively close to the first mold 5 and the second mold 10. Two plug plates 9 are respectively inserted into the insertion holes, and the left end of the plug plate 9 and the left end of the molding frame 8 are abutted against each other, thereby separating the negative electrode slurry layer in the molding cavity 7 from the slurry in the first mold 5 and the second mold 10. At this time, the first mold 5 and the second mold 10 can be removed from the molding frame 8.

[0041] Step 3: Dry the negative electrode slurry layer in the forming frame 8 until it is half dry, remove the forming frame 8, and laminate the negative electrode slurry layer on the copper foil. In order to improve the bonding firmness between the negative electrode slurry layer and the copper foil, an adhesive (the adhesive is a conductive adhesive) can be applied to the copper foil during lamination, and then it is thoroughly dried to prepare the negative electrode of the lithium battery. The negative electrode of the lithium battery in this embodiment is applied to a square lithium battery.

[0042] In this embodiment, the first frame 14 and the second frame 15 of the molding frame 8 can be detached by: Figure 3 As shown, a wedge-shaped groove is provided on the side of the first frame 14 facing the second frame 15, and a wedge-shaped block 16 is integrally formed on the end of the second frame 15. The wedge-shaped block 16 is stuck in the wedge-shaped groove, thereby realizing the connection between the first frame 14 and the second frame 15. The wedge-shaped block 16 is taken out of the wedge-shaped groove, thereby realizing the separation of the first frame 14 and the second frame 15. In this embodiment, the wedge-shaped block 16 is stuck in the wedge-shaped groove. When the two first frames 14 are away from each other in the length direction of the second frame 15, the wedge-shaped block 16 is stuck with the wedge-shaped groove and the first frame 14 and the second frame 15 cannot be separated. The connection between the first frame 14 and the second frame 15 is relatively stable.

[0043] Comparative Example 1: The entire negative electrode slurry layer is the first slurry, and the rest is the same as the embodiment.

[0044] Comparative Example 2: The entire negative electrode slurry layer is made of the second slurry, and the rest is the same as in the embodiment.

[0045] The samples obtained in the examples and comparative examples were made into square lithium batteries, the length, width and height of which were 217 mm, 53 mm and 98 mm respectively. Celgard 2400 was used as a separator in the lithium battery, and a lithium hexafluorophosphate solution with a concentration of 1.0 mol / L was used as the electrolyte.

[0046] The lithium battery performance was tested using the ITECH ITS5300 battery charge and discharge test system. At a current density of 1C, the first lithium insertion specific capacity of the negative electrode of the embodiment and comparative example 1-2 is as shown in Table 1:

[0047] Table 1

[0048]

[0049] The performance of lithium batteries was tested using the ITECH ITS5300 battery charge and discharge test system. At a current density of 1C, the lithium removal specific capacity and specific capacity retention rate of the negative electrode of the experimental group after 1000 cycles of charge and discharge are shown in Table 2:

[0050] Table 2

[0051]

[0052] At the same time, the internal resistance of the experimental group was tested using the ITECH ITS5300 battery charge and discharge test system. The measured internal resistance is shown in Table 3:

[0053] Table 3

[0054]

[0055] From the above experimental data, it can be seen that the first lithium insertion capacity in this embodiment is significantly better than that in comparative example 1, and is not much different from comparative example 2; the lithium removal capacity of the embodiment after 1000 cycles of negative electrode charge and discharge is significantly better than that in comparative example 1, and is not much different from that in comparative example 2; therefore, compared with comparative example 1 which uses all graphene components, the embodiment has excellent performance and has less influence on the diffusion of lithium ions. At the same time, the internal resistance of the embodiment is not much different from that in comparative example 1, and the internal resistance of the embodiment is significantly smaller than that of comparative example 2. Therefore, the comprehensive performance of the embodiment is better than that of comparative examples 1-2, not only having better conductivity, but also having less influence on the diffusion of lithium ions.

[0056] Example 2

[0057] Combination Figure 4 As shown, the first mold 5 and the second mold 10 in this embodiment are welded and fixed. There is no first feed port on the first mold 5, and there is no second feed port on the second mold. There is no molding frame 8 between the first mold 5 and the second mold 10, and the first mold 5 and the second mold 10 form a molding cavity. In this embodiment, the thickness of the first mold 5 is 2 mm, the bottom thickness of the second mold is 2 mm, and the thickness of the molding cavity is 5 mm. In this embodiment, the first slurry and the second slurry are respectively filled into the first extrusion cavity 3 and the second extrusion cavity 11 by a scraper. After the first slurry and the second slurry are filled into the molding cavity 7, there is no need to disassemble the first mold 5 and the second mold 10. After the negative electrode slurry layer is formed, it does not need to be taken out of the mold and covered on the copper foil separately. The first mold 5 and the second mold 10 are directly used as current collectors (the first mold 5 and the second mold 10 are respectively used as the upper shell and the lower shell, and the material is copper), which is conducive to reducing the production process and improving the production efficiency. At the same time, the first extrusion cavity 3 and the second extrusion cavity 11 can be used as channels for lithium ions to pass through, and the upper shell and the lower shell will not hinder the movement and diffusion of lithium ions. By using the test system in Example 1 to perform tests, the performance of the lithium battery in Example 2 is comparable to that of the lithium battery in Example 1.

[0058] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A lithium battery negative electrode, comprising a current collector and a negative electrode slurry layer, wherein the negative electrode slurry layer is located on the current collector, characterized in that: The negative electrode slurry layer includes a first slurry part and a second slurry part, the first slurry part and the second slurry part are both multiple, the first slurry part and the second slurry part are alternately arranged, the first slurry part includes graphene, and the graphene content in the second slurry part is 0; When preparing the negative electrode slurry layer, a first mold and a second mold are taken, the first mold and the second mold are opposite to each other, a molding cavity is formed between the first mold and the second mold, the first mold is provided with a plurality of first extrusion cavities arranged in sequence, the second mold is provided with a plurality of second extrusion cavities arranged in sequence, and the first extrusion cavities and the second extrusion cavities are staggered and opposite to each other; The first slurry is filled into the molding cavity through the first extrusion cavity to form a first slurry portion, and the second slurry is filled into the molding cavity through the second extrusion cavity to form a second slurry portion; the first slurry and the second slurry in the molding cavity diffuse laterally and squeeze each other laterally, so that the first slurry portion and the second slurry portion can stick together.

2. A lithium battery negative electrode according to claim 1, characterized in that: The first slurry portion and the second slurry portion are both in strip shape.

3. A lithium battery negative electrode according to claim 1, characterized in that: The first slurry part also includes components of a binder, a solvent and carbon nanotubes; the second slurry part includes components of graphite, a binder, a conductive agent and a solvent.

4. A lithium battery negative electrode according to claim 1, characterized in that: The current collector is a copper foil with holes; Alternatively, the current collector comprises an upper shell and a lower shell, both the upper shell and the lower shell are provided with an extrusion cavity, and the extrusion cavity on the upper shell and the extrusion cavity on the lower shell are staggered and opposite to each other.

5. A method for preparing a negative electrode of a lithium battery, characterized in that: The following steps are involved: Step 1: prepare the first slurry, take graphene and carbon nanotubes and grind them evenly, then add a binder and a solvent and stir evenly; Prepare the second slurry by mixing graphite, a binder, a conductive agent and a solvent to form the second slurry; Step 2: preparing a negative electrode slurry layer, taking a first mold and a second mold, the first mold and the second mold are opposite to each other, a molding cavity is formed between the first mold and the second mold, the first mold is provided with a plurality of first extrusion cavities arranged in sequence, the second mold is provided with a plurality of second extrusion cavities arranged in sequence, the first extrusion cavities and the second extrusion cavities are staggered and opposite to each other; The first slurry is charged into the molding cavity through the first extrusion cavity to form a first slurry portion, and the second slurry is charged into the molding cavity through the second extrusion cavity to form a second slurry portion; the first slurry and the second slurry in the molding cavity diffuse laterally and are laterally extruded against each other, so that the first slurry portion and the second slurry portion can be adhered together; Step 3: Place the negative electrode slurry layer on the current collector and dry it.

6. A method for preparing a negative electrode for a lithium battery according to claim 5, characterized in that: In step 2, after the first slurry and the second slurry fill the molding cavity, the extrusion pressure on the first slurry and the second slurry is increased.

7. A method for preparing a negative electrode for a lithium battery according to claim 5, characterized in that: In step 2, the first extrusion chamber and the second extrusion chamber are both arranged vertically; when the first extrusion chamber is located above the second extrusion chamber, the first slurry and the second slurry are filled into the molding chamber in the order of first and second slurries; When the second extrusion cavity is located above the first extrusion cavity, the second slurry and the first slurry are filled into the molding cavity in the order of first and last slurry.

8. A method for preparing a negative electrode for a lithium battery according to claim 7, characterized in that: In step 2, after the negative electrode slurry layer is formed, an insert plate is used to separate the negative electrode slurry layer from the slurries in the first mold and the second mold.

9. A method for preparing a negative electrode for a lithium battery according to claim 5, characterized in that: In step 2, a molding frame is detachably connected between the first mold and the second mold, and the molding frame includes a detachably connected frame.

10. A method for preparing a negative electrode for a lithium battery according to claim 5, characterized in that: In step 3, the first mold and the second mold serve as current collectors, and are respectively the upper shell and the lower shell of the current collector; Alternatively, the current collector is copper foil.

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