A current collector, pole piece, and a preparation system

Abstract

The application provides a current collector, a pole piece and a preparation system. The current collector has a first surface and a second surface. A plurality of first pits are formed from the first surface to the second surface. A plurality of second pits are formed from the second surface to the first surface. The first pits and the second pits are distributed in a staggered manner. The application changes the traditional structure of the current collector. The pits are arranged on both sides of the current collector. Different active materials can be filled in the pits according to the different positive and negative electrodes. For example, for the positive electrode, the lithium supplementing material of the positive electrode can be filled in the pits of the current collector, so that the high-temperature storage gas production is significantly improved. For the negative electrode, the silicon negative electrode material can be filled in the pits of the current collector, so that the cycle resistance is reduced and the cycle performance is improved.

Description

Technical Field

[0001] This invention belongs to the technical field and relates to a current collector, an electrode, and a preparation system. Background Technology

[0002] As people's demand for mobile terminals and new energy vehicles increases, their requirements for battery range also become higher, which necessitates a significant improvement in the energy density of the supporting batteries.

[0003] For the positive electrode, lithium replenishment materials can effectively compensate for lithium loss caused by the low initial efficiency of the negative electrode. However, the use of positive electrode lithium replenishment materials usually brings many side effects. The most obvious is the generation of a large amount of gas during high-temperature storage, which cannot meet the battery's operating requirements. At the same time, lithium metal salts, as lithium replenishing agents, can increase the dissolution of metal ions, triggering a series of side reactions and deteriorating battery performance. Some positive electrode lithium replenishment materials undergo significant volume changes after releasing a large number of lithium ions, which can also damage the positive electrode structure, increase internal resistance, and deteriorate battery performance.

[0004] For the anode, current silicon anode materials require compounding with graphite and coating onto the current collector. Due to the significant volume expansion and poor electronic conductivity of silicon-based materials, it is necessary to increase the amount of binder and conductive agent used to ensure the battery's thickness expansion, capacity decay, and internal resistance are maintained. Even so, the significant expansion of silicon anode particles during cycling leads to binder failure and conductive agent disconnection, affecting the capacity utilization of silicon materials, deteriorating cell performance, and limiting the amount of silicon material added and the development progress of high-energy-density silicon anode systems.

[0005] Therefore, in order to further improve battery energy density and enhance battery performance, it is necessary to improve the existing electrode structure and solve the technical problems that currently exist in the positive and negative electrodes. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a current collector, an electrode, and a preparation system. The present invention changes the traditional current collector structure by setting pits on both sides of the current collector, which can be used for different positive and negative electrodes. Different active materials can be filled into the pits, thereby significantly improving gas generation during high-temperature storage, reducing internal resistance during circulation, and improving circulation performance.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a current collector having a first surface and a second surface, wherein a plurality of first pits are formed from the first surface toward the second surface, and a plurality of second pits are formed from the second surface toward the first surface, wherein the first pits and the second pits are staggered.

[0009] In a second aspect, the present invention provides an electrode comprising the current collector described in the first aspect, the electrode being divided into a positive electrode and a negative electrode, the current collector being divided into a positive current collector and a negative current collector, the positive electrode comprising the positive current collector and a positive lithium-filling slurry filled in the first pit and / or the second pit; the negative electrode comprising the negative current collector and a silicon negative electrode slurry filled in the first pit and / or the second pit.

[0010] Thirdly, the present invention provides a preparation system for the electrode sheet described in the first aspect, wherein the preparation system comprises, along the current collector conveying direction, an unwinding module, a stamping and casting module, a first coating module, an electrode sheet transmission module, a second coating module, a pressing module, and a winding module arranged sequentially.

[0011] The stamping and casting module includes a first stamping die and a second stamping die arranged at an upper and lower interval. The current collector passes between the first stamping die and the second stamping die. After the first stamping die and the second stamping die are aligned with each other, they stamp the two sides of the current collector to form a first recess and a second recess.

[0012] The first stamping die and the second stamping die are respectively provided with a through first pouring channel and a second pouring channel, and the grout to be poured is injected into the first pit and the second pit through the first pouring channel and the second pouring channel, respectively.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] This invention modifies the traditional current collector structure by creating recesses on both sides of the current collector. Depending on the applicable positive and negative electrodes, different active materials can be filled into these recesses. For example, for the positive electrode, lithium-replenishing materials can be filled into the recesses of the current collector, significantly improving gas generation during high-temperature storage. For the negative electrode, silicon negative electrode materials can be filled into the recesses of the current collector, thereby reducing cycle resistance and improving cycle performance. Attached Figure Description

[0015] Figure 1 A cross-sectional view of a current collector provided for a specific embodiment of the present invention;

[0016] Figure 2 A top view of the current collector provided in a specific embodiment of the present invention;

[0017] Figure 3 A cross-sectional view of a positive current collector provided for a specific embodiment of the present invention;

[0018] Figure 4A cross-sectional view of a negative electrode current collector provided for a specific embodiment of the present invention;

[0019] Figure 5 A schematic diagram of the positive electrode structure provided in a specific embodiment of the present invention;

[0020] Figure 6 A schematic diagram of the negative electrode structure provided in a specific embodiment of the present invention;

[0021] Figure 7 A schematic diagram of the preparation system provided in a specific embodiment of the present invention;

[0022] Figure 8 A schematic diagram of the infusion process provided for a specific embodiment of the present invention;

[0023] Figure 9 A schematic diagram of the electrode sheet after infusion is provided for a specific embodiment of the present invention;

[0024] Among them, 1-current collector; 2-first recess; 3-second recess; 4-positive electrode lithium replenishment slurry; 5-silicon negative electrode slurry; 6-positive electrode active material layer; 7-negative electrode active material layer; 8-first stamping die; 9-second stamping die; 10-first die head; 11-first die head; 12-first casting channel; 13-second casting channel; 14-unwinding module; 15-stamping and casting module; 16-first drying device; 17-first coating module; 18-second drying device; 19-electrode transmission module; 20-second coating module; 21-third drying device; 22-pressing module; 23-rewinding module. Detailed Implementation

[0025] It should be understood that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0026] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0028] In one specific embodiment, the present invention provides a current collector, such as... Figure 1 and Figure 2 As shown, the current collector has a first surface and a second surface, with a plurality of first pits formed from the first surface toward the second surface and a plurality of second pits formed from the second surface toward the first surface, the first pits and the second pits being staggered.

[0029] This invention modifies the traditional current collector structure by creating recesses on both sides of the current collector. Depending on the applicable positive and negative electrodes, different active materials can be filled into these recesses. For example, for the positive electrode, lithium-replenishing materials can be filled into the recesses of the current collector, significantly improving gas generation during high-temperature storage. For the negative electrode, silicon negative electrode materials can be filled into the recesses of the current collector, thereby reducing cycle resistance and improving cycle performance.

[0030] As a preferred embodiment of the present invention, the diameter of the opening of the first recess is from 50 μm to 2000 μm, for example, it can be 50 μm, 100 μm, 200 μm, 400 μm, 600 μm, 800 μm, 1000 μm, 1200 μm, 1400 μm, 1600 μm, 1800 μm or 2000 μm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0031] The depth of the first pit is from 20 μm to 200 μm, for example, it can be 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm or 200 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0032] As a preferred embodiment of the present invention, a plurality of the first pits are distributed in a matrix, including a plurality of rows of first pit groups arranged side by side along the width direction of the current collector.

[0033] The second pits are distributed in a matrix, including a number of rows of second pit groups arranged side by side along the width direction of the current collector.

[0034] The first pit group and the second pit group are alternately arranged along the width direction of the current collector, and adjacent first pit groups and second pit groups are staggered.

[0035] In another specific embodiment, the present invention provides an electrode sheet including the current collector provided in the above specific embodiments, the electrode sheet being divided into a positive electrode and a negative electrode, the current collector being divided into a positive current collector and a negative current collector, the positive electrode including the positive current collector and a positive lithium replenishment slurry (such as...) filling the first pit and / or the second pit. Figure 3 (as shown); the negative electrode includes the negative electrode current collector and a silicon negative electrode paste (such as...) filling the first pit and / or the second pit. Figure 4 (As shown).

[0036] The current collector provided by this invention can be used for both positive and negative electrodes. When used for different types of electrodes, the materials filled in the first and second pits of the current collector are different. When used for positive electrodes, the first and second pits of the current collector are filled with positive electrode lithium replenishment slurry; when used for negative electrodes, the first and second pits of the current collector are filled with silicon negative electrode slurry.

[0037] It should be noted that this invention does not impose specific requirements or limitations on the specific composition and proportions of the positive electrode lithium replenishment slurry. It mainly includes a positive electrode lithium replenishment material, a conductive agent, and a binder. The positive electrode lithium replenishment agent may optionally include Li oxides or organic lithium salts, such as Li₂O, Li₂O₂, LiN₃, Li₂CO₃, Li₂C₂O₄, etc.; lithium-rich compounds such as Li₂NiO₂, Li₅FeO₄, Li₆CoO₆, lithium-rich manganese-based materials, etc. Similarly, this invention does not impose specific requirements or limitations on the specific composition and proportions of the silicon anode slurry. It mainly includes a silicon anode material, a conductive agent, and a binder. The silicon anode material may optionally include a series of silicon-based materials such as Si, Si / C, SiOx, and SiOx / C.

[0038] As a preferred technical solution of the present invention, such as Figure 5 As shown, the positive electrode further includes a positive electrode active material layer disposed on at least one side surface of the positive electrode current collector, the positive electrode active material layer covering the first pit and / or the second pit.

[0039] When the current collector provided by this invention is used as the positive electrode, it is necessary to fill the first and second pits with positive electrode lithium replenishment slurry, and coat the surface of the current collector with positive electrode active slurry to cover the positive electrode lithium replenishment slurry. The positive electrode structure provided by this invention fully combines the characteristics of positive electrode lithium replenishment material and positive electrode active material. By placing the positive electrode lithium replenishment slurry and the positive electrode active slurry in different areas of the current collector and coating them separately, the best positive electrode effect and battery performance can be achieved. Its advantages specifically include:

[0040] (1) The positive electrode lithium replenishment slurry and the positive electrode active slurry can each have their own optimized formulations. Utilizing the high alkalinity and low structural stability of the positive electrode lithium replenishment slurry, the amount of binder and conductive agent added in the positive electrode lithium replenishment slurry can be appropriately increased. Optionally, the binder accounts for 1-20% of the total mass of the positive electrode lithium replenishment slurry, and the conductive agent accounts for 0.5-20% of the total mass of the positive electrode lithium replenishment slurry. Optionally, a coating agent can be added to the positive electrode lithium replenishment slurry to coat the surface of the positive electrode lithium replenishment material, isolating the positive electrode lithium replenishment material from the electrolyte and reducing the impact of the alkalinity of the positive electrode lithium replenishment material on the battery system. At the same time, by covering the positive electrode lithium replenishment slurry with the positive electrode active slurry, the lithium-ion transport impedance can be increased, the irreversible specific capacity of the positive electrode lithium replenishment slurry can be improved, which is beneficial for the lithium-ion replenishment of the positive electrode active material.

[0041] (2) The high-temperature storage gas generation of the battery cell prepared by the positive electrode structure provided by the present invention is significantly improved. Due to the increased amount of binder added in the positive electrode lithium replenishment slurry, the contact between the material surface and the electrolyte is isolated during high-temperature storage. At the same time, the alkalinity of the positive electrode lithium replenishment slurry is also difficult to release, thereby significantly improving the high-temperature storage gas generation.

[0042] It should be noted that the present invention does not impose specific requirements or special limitations on the specific components and the proportions of each component of the positive electrode active slurry. The positive electrode active slurry includes positive electrode active material, positive electrode lithium supplement, conductive agent, binder, dispersant, etc. Optionally, the positive electrode active material can be one or more of NCM, NCA, lithium cobalt oxide, lithium iron phosphate, lithium-rich manganese-based materials, lithium iron manganese phosphate, and binary metal lithium compounds.

[0043] As a preferred technical solution of the present invention, such as Figure 6 As shown, the negative electrode further includes a negative electrode active material layer disposed on at least one side surface of the negative electrode current collector, the negative electrode active material layer covering the first pit and / or the second pit.

[0044] When the current collector provided by this invention is used as the negative electrode, silicon negative electrode slurry needs to be filled into the first and second pits, and negative electrode active material is coated on the surface of the current collector to cover the silicon negative electrode slurry. This fully combines the characteristics of silicon negative electrode slurry and negative electrode active slurry, placing the silicon negative electrode material and negative electrode active material in different areas of the current collector and coating them separately. By adjusting the size and number of pits and the solid content of the silicon negative electrode slurry, the silicon negative electrode / graphite ratio can be controlled to achieve the best positive electrode effect and battery performance. Its advantages specifically include:

[0045] (1) Silicon anode slurry and anode active slurry (mainly including graphite) can each have their own optimized formulations. Taking advantage of the high expansion and low electronic conductivity of silicon anode materials, the amount of binder and conductive agent added in silicon anode slurry can be appropriately increased. Optionally, the binder accounts for 1% to 0% of the total mass of silicon anode slurry, and the conductive agent accounts for 1% to 20% of the total mass of silicon anode slurry. CNT and other conductive agents can be added to improve the electronic conduction network between particles. However, the anode active slurry does not need to add too much conductive agent and binder, nor does it need to add CNT and other conductive agents. This is beneficial to reduce the surface resistance of the anode active material, reduce the risk of lithium plating, and improve cycle performance.

[0046] (2) Compared with traditional silicon / graphite hybrid active materials, the negative electrode structure provided by this invention can reduce the amount of overall conductive agent and binder added, and increase the proportion of negative electrode active material. In addition, it prevents the destruction of the surrounding particle space structure by the expansion of silicon negative electrode material during cycling of traditional silicon / graphite hybrid active materials, and can effectively reduce the cycling resistance;

[0047] (3) The silicon anode paste is placed in the pit on the surface of the current collector, which ensures that the silicon anode material is in close contact with the current collector, so that the silicon anode material with poor electron conduction can successfully complete electron transfer, which is more conducive to the capacity of the silicon anode material.

[0048] It should be noted that the present invention does not impose specific requirements or special limitations on the specific composition and the proportion of each component of the negative electrode active slurry. The negative electrode active slurry includes a negative electrode active material, a binder and a conductive agent. Optionally, the negative electrode active material can be one or more of graphite, Si, SiOx, hard carbon, etc.

[0049] In another specific embodiment, the present invention provides a system for preparing the electrode sheet provided in the above specific embodiments, such as... Figure 7 As shown, the preparation system includes, along the current collector conveying direction, an unwinding module, a stamping and casting module, a first coating module, an electrode transmission module, a second coating module, a pressing module, and a winding module arranged in sequence.

[0050] like Figure 8As shown, the stamping and casting module includes a first stamping die and a second stamping die arranged at an upper and lower interval. The current collector passes between the first stamping die and the second stamping die. After the first stamping die and the second stamping die are aligned with each other, they stamp the two sides of the current collector to form a first recess and a second recess.

[0051] like Figure 9 As shown, the first stamping die and the second stamping die are respectively provided with a through-flow first pouring channel and a second pouring channel, and the grout to be poured is injected into the first pit and the second pit through the first pouring channel and the second pouring channel, respectively.

[0052] The advantages of the preparation system provided by this invention are:

[0053] (1) The stamping-casting technology is used to shape the current collector and coat the positive lithium slurry or silicon negative electrode slurry. It is highly efficient and can accurately control the amount of slurry to be injected, while ensuring that the shape and arrangement of the current collector pits are controllable.

[0054] (2) The active material and the slurry to be injected are coated in separate areas. For the positive electrode, the positive electrode lithium replenishment slurry with strong alkalinity and unstable structure is placed in an independent pit. The optimal ratio of binder and conductive agent can be used in the positive electrode lithium replenishment slurry, and a coating agent can be added optionally. After coating the active material, the positive electrode lithium replenishment material and the electrolyte can be completely isolated, which improves gas generation during high-temperature storage and reduces the cycle resistance. For the negative electrode, the silicon negative electrode slurry with high expansion and poor conductivity is placed in an independent pit. The optimal ratio of binder and conductive agent can be used in the silicon negative electrode slurry, which ensures the spatial electron conduction network and adhesion of the silicon negative electrode slurry, reduces the cycle resistance, and slows down the volume expansion and capacity decay. Since the amount of binder and conductive agent in the silicon negative electrode slurry is increased, the amount of binder and conductive agent in the negative electrode active material can be appropriately reduced, which increases the proportion of negative electrode active material, improves the lithium-ion interface transport performance, reduces the risk of lithium plating and internal resistance, and improves the energy density.

[0055] (3) The surface density and ratio of the electrode preparation are controllable and continuous production can be realized. By adjusting the size and number of pits and the solid content of the slurry to be injected, the ratio of positive lithium supplement material / positive active material and the ratio of silicon negative electrode material / negative active material can be controlled. The electrode is produced by continuous equipment, realizing the efficient preparation of the electrode.

[0056] As a preferred embodiment of the present invention, the first stamping die is provided with a plurality of first die heads on the side near the collector, the first die heads being used to stamp and form the first recess; the first pouring channel passes through the first die head, and the slurry to be poured passes through the first pouring channel and is then injected into the first recess by the first die head.

[0057] The second stamping die has a plurality of second die heads on the side near the collector, and the second die heads are used to stamp and form the second recess; the second pouring channel passes through the first die head, and the slurry to be poured passes through the second pouring channel and is injected into the second recess by the second die head.

[0058] When the current collector is a positive electrode current collector, the grout to be injected is a positive electrode lithium replenishment material.

[0059] When the current collector is a negative electrode current collector, the grout to be injected is a silicon negative electrode material.

[0060] As a preferred embodiment of the present invention, the electrode transmission module includes a first conveying roller and a second conveying roller. The unwinding module, the first conveying roller, the second conveying roller and the winding module are arranged sequentially along the current collector conveying direction to form an inverted U-shaped conveying path. After one side surface of the current collector is coated, it is conveyed by the first conveying roller and the second conveying roller and then flipped.

[0061] As a preferred embodiment of the present invention, a first drying device is further provided on the current collection and conveying path between the stamping and casting module and the first coating module. The first drying device is used to dry the material poured into the first and second recesses.

[0062] A second drying device is provided on the current collector conveying path between the first coating module and the electrode transmission module. The second drying device is used to dry the active slurry coated on the surface of the current collector by the first coating module.

[0063] A third drying device is provided on the current collector transport path between the second coating module and the tableting module. The third drying device is used to dry the active slurry coated by the second coating module on the other side of the current collector.

[0064] Example 1

[0065] This embodiment provides a positive electrode, including a positive electrode current collector. Several first pits and several second pits are respectively formed on both sides of the positive electrode current collector. The first and second pits are filled with a positive electrode lithium supplement agent Li₂NiO₂:PVDF:CNT:SP = 85:6:3:6. A positive electrode active material layer with a thickness of 95 μm is coated on both sides of the positive electrode current collector. The composition of the positive electrode active material layer includes NCM:PVDF:CNT:SP = 95:1.5:1.5:2. In the overall positive electrode system, NCM:L₂NiO₂ = 95:5.

[0066] Comparative Example 1

[0067] This comparative example provides a positive electrode, including a positive electrode current collector. The two sides of the positive electrode current collector are coated with positive electrode active material layers with a thickness of 95 μm. The composition of the positive electrode active material layers includes AM:PVDF:CNT:SP = 94:2:2:2, wherein AM is composed of NCM and Li2NiO2 in a ratio of 95:5.

[0068] Example 2

[0069] This embodiment provides a negative electrode, including a negative electrode current collector. Several first pits and several second pits are respectively provided on both sides of the negative electrode current collector. The first pits and second pits are filled with Si:CNT:SP:PAA = 92:2:2:4. The two sides of the negative electrode current collector are respectively coated with a negative electrode active material layer with a thickness of 100μm. The composition of the negative electrode active material layer includes Gr:SP:CMC:SBR = 96:1:1.5:1.5.

[0070] Comparative Example 2

[0071] This comparative example provides a negative electrode, including a negative electrode current collector. The two sides of the negative electrode current collector are coated with a negative electrode active material layer with a thickness of 100 μm. The composition of the negative electrode active material layer includes AM:SP:CNT:PAA = 94:1.5:1:3.5, wherein AM is composed of Gr and Si in a ratio of 80:20.

[0072] The positive and negative electrodes provided in Examples 1 and 2 were used to assemble the battery cells, which were designated as the experimental group; the positive and negative electrodes provided in Comparative Examples 1 and 2 were used to assemble the battery cells, which were designated as the control group.

[0073] Performance tests were conducted on the experimental and control groups. The test items included DCR (BOL), 25℃ cycling performance (number of cycles with 80% capacity retention), thickness expansion rate, DCR growth rate (EOL), and gas production volume after 30 days of storage at 60℃. The test results are shown in Table 1.

[0074] Table 1

[0075]

[0076]

[0077] As can be seen from the data in Table 1, the electrode structure proposed in this invention can separately coat the components of the positive and negative electrodes with different optimized formulations, thereby reducing the degradation of battery performance caused by the interaction between different components.

[0078] In terms of the positive electrode structure design, since a separate formulation was designed for the lithium replenishing agent and it does not directly contact the NCM, firstly, more polymers can be used to coat the surface of the lithium replenishing agent, isolating it from the oxidation of the electrolyte, and significantly improving gas generation during high-temperature storage; secondly, it improves the impact of the volume change and gas generation caused by the initial delithiation of the lithium replenishing agent and subsequent electrochemical effects on the electrode structure, reduces the increase in DCR caused by the increase of by-products on the conductive network and active material surface, and also has a certain improvement effect on cycle improvement.

[0079] In the negative electrode structure design, a PAA system suitable for Si negative electrode materials with significant volume expansion was designed, and the conductive agent formulation was optimized. Furthermore, this system is isolated from pure graphite material. Firstly, it significantly reduces the impact of material expansion on electrode thickness, and secondly, it improves the connectivity of the overall conductive network of the electrode during cycling, thus improving DCR growth. Simultaneously, the pure graphite system formulation was also optimized, further enhancing initial DCR. This electrode design is highly adaptable to the different characteristics of various negative electrode materials, resulting in significantly improved cycle performance.

[0080] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. An electrode sheet, characterized in that, The electrode is divided into a positive electrode and a negative electrode. The positive electrode includes a positive current collector, and the negative electrode includes a negative current collector. The positive current collector and the negative current collector each have a first surface and a second surface independently. A first pit is formed on the first surface that is recessed into the second surface, and a second pit is formed on the second surface that is recessed into the first surface. The positive electrode further includes a positive electrode lithium replenishment slurry filling the first pit and / or the second pit, and a positive electrode active material layer covering the first pit and / or the second pit; the positive electrode lithium replenishment slurry includes a positive electrode lithium replenishment material, a conductive agent, and a binder, wherein the conductive agent accounts for 0.5-20% of the total mass of the positive electrode lithium replenishment slurry; The negative electrode further includes a silicon negative electrode slurry filled in the first pit and / or the second pit, and a negative electrode active material layer covering the first pit and / or the second pit; the silicon negative electrode slurry includes a silicon negative electrode material, a conductive agent and a binder, wherein the conductive agent accounts for 1 to 20% of the total mass of the silicon negative electrode slurry; the negative electrode active material in the negative electrode active material layer is graphite and / or hard carbon.

2. The electrode sheet according to claim 1, characterized in that, The first and second pits are arranged alternately in a matrix distribution.

3. The electrode sheet according to claim 1, characterized in that, The diameter of the first pit on the first surface is 50 μm to 2000 μm, and the depth of the first pit is 20 μm to 200 μm.

4. An electrode preparation system for preparing the electrode as described in any one of claims 1-3, characterized in that, The electrode preparation system includes, along the current collector conveying direction, an unwinding module, a stamping and casting module, a first coating module, an electrode transmission module, a second coating module, a pressing module, and a winding module arranged in sequence.

5. The preparation system according to claim 4, characterized in that, The stamping and casting module includes a first stamping die and a second stamping die arranged at an upper and lower interval. After the first stamping die and the second stamping die are aligned with each other, they are used to stamp the two sides of the collector to form a first recess and a second recess. The first stamping die and the second stamping die are respectively provided with a through casting channel and a casting channel.

6. The preparation system according to claim 4, characterized in that, The electrode transmission module includes a first conveying roller and a second conveying roller. The unwinding module, the first conveying roller, the second conveying roller and the winding module are arranged sequentially along the current collector conveying direction to form an inverted U-shaped conveying path. After one side surface of the current collector is coated, it is conveyed by the first conveying roller and the second conveying roller and then flipped.

7. The preparation system according to claim 4, characterized in that, A first drying device is provided on the current collector conveying path between the stamping and casting module and the first coating module; a second drying device is provided on the current collector conveying path between the first coating module and the electrode transmission module; and a third drying device is provided on the current collector conveying path between the second coating module and the tablet pressing module.

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