Device and compounding method for lithium surface protection layer of lithium-copper clad sheet

Abstract

The invention discloses a device and a compounding method for a lithium surface protection layer of a lithium copper clad sheet, and relates to the technical field of battery cell pre-lithiation, the device comprises a winding device and a clamp for clamping the protection layer, and the winding device is sequentially provided with a compounding assembly, a fixed cutting assembly and a material receiving assembly in the unwinding direction; the composite assembly comprises a first vacuum suction plate for containing the lithium strip, a pressing roller and a CCD detection device are installed above the first vacuum suction plate, a material taking box is installed on one side of the first vacuum suction plate, a second vacuum suction device used for transferring the lithium strip is installed above the material taking box, and the protective layer is located between the lithium strip and the pressing roller. The difference between the first effect and the capacity retention rate of the baked battery cell and the tested battery is small, which shows that the lithium strip can still be protected by changing the formula of the protective layer and the pre-lithium battery cell produced by the composite method does not influence the performance data of the pre-lithium battery.

Description

Technical Field

[0001] The invention belongs to the technical field of pre-lithiation of battery cells, and in particular relates to a device and a composite method for a lithium surface protective layer of a lithium-copper composite sheet. Background Art

[0002] With the development of electronic products, new energy vehicles and energy storage industries, human beings have higher and higher requirements for the energy density of lithium batteries. In recent years, people have become more and more urgent to develop batteries with high energy density, so the lithium replenishment technology of lithium-ion batteries has been paid more and more attention by scientific research institutions and enterprises. When lithium-ion batteries are charged for the first time, lithium ions are released from the positive electrode through the electrolyte and the diaphragm to the surface of the negative electrode, and a layer of SEI film (solid electrolyte interface film) will be formed on the surface of the negative electrode. The formation of SEI film will consume a large amount of lithium ions. Due to the non-dense growth of SEI film and the large volume expansion and contraction of positive and negative electrode materials during the cycle, some components of SEI film can be dissolved in the electrolyte, resulting in the continuous growth of SEI film on the surface of positive and negative electrodes, which continuously consumes lithium ions in the battery. Therefore, if lithium ions can be continuously replenished for the battery during the first charge and discharge of the battery and the subsequent charge and discharge cycles to reduce the loss of active lithium in the lithium battery, scientific research institutions and enterprises have begun to develop various pre-lithium technologies to replenish lithium batteries.

[0003] At present, there are several types of pre-lithiation technologies: in-situ doping pre-lithiation, contact pre-lithiation, electrochemical pre-lithiation and chemical pre-lithiation. Among them, the use of lithium metal to electrochemically pre-lithiate the negative electrode is a pre-lithiation strategy that is currently widely studied and adopted, including direct contact pre-lithiation, external short-circuit pre-lithiation, external power supply pre-lithiation and other methods. The electrochemical pre-lithiation of lithium metal composited on the negative electrode of the outermost battery cell will undergo multiple processes such as bare battery cell baking, liquid injection, static, and formation during the production line production process. In the vacuum steps of these processes, they will be exposed to nitrogen and moisture in the air. Especially in the baking process, under high temperature environment, lithium is very easy to react with nitrogen and water to nitride, causing the function of lithium to be destroyed. Therefore, people proposed to add a protective layer on the surface of lithium to protect it, so that the pre-lithium battery cell will not react with nitrogen and water during the production process. At the same time, the protective layer cannot affect the electrical performance and safety performance of the lithium battery during the charging and discharging process.

[0004] However, currently, manual lamination is usually used to produce the surface protective layer of lithium-copper composite belts. Manual lamination will cause problems such as poor effect and low efficiency, and is not suitable for industrial production. Summary of the invention

[0005] In view of the problems mentioned in the background technology, the purpose of the present invention is to provide a composite method and device for a surface protective layer of a lithium-copper composite strip in an electrochemical pre-lithium battery cell to solve the problems mentioned in the background technology.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions:

[0007] A device for forming a lithium surface protective layer of a lithium-copper composite sheet comprises a winding device and a clamp for clamping the protective layer, wherein the winding device is provided with a composite component, a fixed cutting component and a material receiving component in sequence along the unwinding direction; the composite component comprises a vacuum suction plate 1 for placing a lithium strip, a pressure roller and a CCD detection device are installed above the vacuum suction plate 1, a material picking box is installed on one side of the vacuum suction plate 1, a vacuum suction device 2 for transferring the lithium strip is installed above the material picking box, and the protective layer is located between the lithium strip and the pressure roller.

[0008] As a preferred technical solution, the two sides of the lithium strip are respectively a copper foil side and a lithium side, and the lithium side is composited with the protective layer.

[0009] As a preferred technical solution, the protective layer includes a barrier substrate and an adhesive layer coated on the barrier substrate and loses adhesion when immersed in an electrolyte, and one side of the adhesive layer of the protective layer is composited with the lithium side of the lithium strip.

[0010] As a preferred technical solution, the protective layer extends 0-2CM beyond the edges of both sides of the lithium strip.

[0011] As a preferred technical solution, the outermost layer material of the pressure roller is a soft buffer material, and a pressure sensor is installed inside the pressure roller.

[0012] As a preferred technical solution, the fixed cutting assembly includes a clamping plate for fixing the protective layer, a position movement detection device and a cutter, and the clamping plate, the position movement detection device and the cutter are successively close to the material receiving assembly.

[0013] As a preferred technical solution, the material receiving assembly includes a vacuum suction plate 2, a material receiving box is installed on one side of the vacuum suction plate 2, and also includes a vacuum suction device 1 that can transfer the product from the vacuum suction plate 2 to the material receiving box.

[0014] As a preferred technical solution, both vacuum suction plate 1 and vacuum suction plate 2 are made of conductive metal materials and are grounded.

[0015] A composite method for a lithium copper composite sheet lithium surface protection layer, the steps are as follows:

[0016] S1: Place the device in a low humidity and dry environment;

[0017] S2: The vacuum suction device sucks the lithium tape from the material box and drives the lithium tape to be transferred from E to the vacuum suction plate at D, and makes the long side of the lithium tape perpendicular to the unwinding direction of the protective layer and the narrow side parallel to the unwinding direction of the protective layer;

[0018] S3: The clamp pulls the protective layer through the lithium belt;

[0019] S4: The CCD detection device detects the relative position of the lithium ribbon and the protective layer: the protective layer is -CM at the edges of both sides of the lithium ribbon, and ensures that the copper foil is left as the tab at the same position as the narrow edge of the lithium ribbon and the negative tab of the battery cell;

[0020] S5: After the test is qualified, the pressing roller descends from position A to press the protective layer and the lithium belt tightly, and then rolls from left to right to position B to complete the protective layer compounding;

[0021] S6: The clamp takes the composite product and passes it through the clamp and the position movement detection device. After the position movement detection device detects the quality of the product, the clamp holds the protective layer and the cutter cuts off the protective layer;

[0022] S7: The fixture clamps the product and transfers it to the vacuum suction plate 2, and the vacuum suction device 1 sucks the product on the vacuum suction plate 2 and transfers it to the receiving box.

[0023] As a preferred technical solution, the temperature of the low humidity environment described in S1 is -40°C or below.

[0024] Beneficial Effects

[0025] There is little difference in the initial efficiency and capacity retention rate of the cells after baking and battery testing, indicating that changing the formula of the protective layer and using this method can still protect the lithium ribbon and the pre-lithium cells produced by this composite method do not affect the pre-lithium battery performance data.

[0026] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of the composite device with lithium strip protective layer in the electrochemical pre-lithiation application.

[0028] Figure 2 This is a comparison chart of the cycle performance of the lithium-ion battery with protection in Example 1 and the lithium-ion battery with no protection in Example 5.

[0029] Figure numerals: 1. Unwinding device; 2. Protective layer; 3. Guide roller; 4. Pressure roller; 5. Lithium belt; 6. Vacuum suction plate 1; 7. CCD detection device (an instrument that detects the appearance of an object through a display through a photosensitive coupling component); 8. Clamp; 9. Position movement detection device; 10. Cutter; 11. Vacuum suction plate device 1; 12. Vacuum suction plate 2; 13. Clamp; 14. Material box; 15. Vacuum suction plate device 2; 16. Material receiving box. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below in conjunction with specific embodiments and the accompanying drawings. A person of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention.

[0031] Unless otherwise specified, the raw materials used in the examples of the present invention are all commercially available or available to those skilled in the art; unless otherwise specified, the methods used in the examples of the present invention are all methods known to those skilled in the art.

[0032] refer to Figure 1 A device for forming a lithium surface protective layer of a lithium copper composite sheet, comprising a winding device 1 for winding a protective layer 2 and a clamp 13 for clamping the protective layer 2, and a composite component, a fixed cutting component and a material receiving component are sequentially arranged on the right side of the winding device 1. The composite component comprises a vacuum suction plate 6, and a pressure roller 4 for pressing and compounding the protective layer 2 and the lithium strip 5 and a CCD detection device 7 for detecting the relative position of the lithium strip 5 and the protective layer 2 are installed above the vacuum suction plate 6 to ensure that the protective layer 2 is wider than the edge of the lithium strip 5, and a material box 14 for holding the lithium strip 5 is installed at E on one side of the vacuum suction plate 6, and a vacuum suction device 2 15 for transferring the lithium strip 5 from the material box 14 to the vacuum suction plate 6 is installed above the material box 14, and the protective layer 2 is located between the lithium strip 5 and the pressure roller 4.

[0033] Preferably, two groups of guide rollers 3 are installed between the winding device 1 and the composite component, and the bottom end of the lower group of guide rollers 3 is higher than the top of the vacuum suction plate 6 and lower than the bottom end of the guide roller 4.

[0034] The clamp 13 pulls the protective layer 2 through the two sets of guide rollers 3 to the composite assembly in turn to composite the lithium strip 5 and the protective layer 2 into a product, the fixed cutting assembly cuts and separates the product from the protective layer 2, and the clamp 13 transfers the separated product to the receiving assembly for collection. Composite process: The vacuum suction device 15 absorbs the lithium strip 5 from the material box 14, and drives the lithium strip 5 to transfer from E to the vacuum suction plate 6 at D (vacuum suction plate 1 6), the CCD detection device 7 detects the relative position of the lithium strip 5 and the protective layer 2, and then the pressure roller 4 descends from position A (CCD detection device 7 close to the winding device 1 side) to press the protective layer 2 and the lithium strip 5, and then rolls from left to right to position B (CCD detection device 7 close to the fixed cutting assembly side) to complete the protective layer composite process, and after the composite is completed, the pressure roller 4 returns to position A, where the horizontal distance between A and B is not less than the length of the lithium strip 5.

[0035] The two sides of the lithium strip 5 are respectively a copper foil side and a lithium side, and the lithium side is composited with the protective layer 2 .

[0036] The lithium surface is located between the protective layer 2 and the copper foil surface and is not in contact with the air, which can ensure that it is not in contact with the air during assembly processes such as baking, thereby playing a protective role.

[0037] The protective layer 2 includes a barrier substrate and an adhesive layer coated on the barrier substrate and loses adhesion when immersed in an electrolyte. One side of the adhesive layer of the protective layer 2 is composited with the inside of the lithium strip 5 .

[0038] The adhesive layer is compounded with the lithium surface to make the protective layer 2 and the lithium strip 5 firmly bonded, ensuring that the lithium strip 5 does not come into contact with the air during the assembly process such as baking. However, in the battery cell after assembly, the protective layer 2 loses adhesion and falls off under the immersion of electrolyte to ensure that the lithium strip 5 can normally replenish lithium in the battery cell.

[0039] Preferably, the width of the protective layer 2 is 0-2 cm wider than the edges of the lithium ribbon 5 on both sides.

[0040] The extra portion of the protective layer 2 on both sides of the lithium strip can effectively protect the metallic lithium and prevent the lithium surface from coming into contact with the air and reacting.

[0041] Preferably, the outermost layer material of the pressure roller 4 is a soft cushioning material, and the soft cushioning material includes but is not limited to rubber, sponge, flannel, etc.; a pressure sensor is installed inside the pressure roller 4.

[0042] The outermost layer of the pressing roller 4 is made of soft buffer material to ensure that there is buffering when the protective layer and the lithium strip are pressed without damaging the thickness of the protective layer and the lithium strip; the pressure sensor feeds back the pressure when the pressing roller 4 descends and presses the protective layer 2 and the lithium strip 5, so as to compare the pressure parameters set for the protective layer 2 and the lithium strip 5.

[0043] The fixed cutting assembly includes a clamping plate 8 for fixing the protective layer 2, a position movement detection device 9 and a cutter 10. The clamping plate 8, the position movement detection device 9 and the cutter 10 are sequentially close to the material receiving assembly.

[0044] After the compounding is completed, the clamp 13 clamps the product through the clamping plate 8 and the position movement detection device 9. After the position movement detection device 9 detects the protective layer 2, the clamping plate 8 clamps the protective layer 2 and the cutter 10 cuts off the protective layer 2.

[0045] The material receiving assembly includes a vacuum suction plate 12 , a material receiving box 16 is installed on one side of the vacuum suction plate 12 , and also includes a vacuum suction device 11 that can transfer the product from the vacuum suction plate 12 to the material receiving box 16 .

[0046] The clamp 13 clamps the product and transfers it to the vacuum suction plate 12 , and the vacuum suction device 11 sucks the product on the vacuum suction plate 12 and transfers it to the material receiving box 16 .

[0047] As a preferred solution, the vacuum suction device 11 and the vacuum suction device 2 15 use vacuum suction disks.

[0048] The vacuum suction device 11 and the vacuum suction device 2 15 avoid damaging the lithium belt 5 by vacuum suction.

[0049] The vacuum suction plate 1 6 and the vacuum suction plate 2 12 are both made of conductive metal materials and are grounded. The metal materials include but are not limited to common metal materials such as stainless steel and aluminum alloy.

[0050] The metal material and grounded vacuum suction plate 1 6 and vacuum suction plate 2 12 can remove the static electricity generated when the protective layer 2 is close to the metal lithium, and prevent the protective layer 2 from automatically adsorbing on the lithium belt 5 under the action of static electricity, causing the protective layer 2 to wrinkle.

[0051] refer to Figure 1 , a composite method for a lithium copper composite sheet lithium surface protection layer, the steps are as follows:

[0052] S1: Place the device in a low humidity and dry environment;

[0053] S2: The vacuum suction device 15 sucks the lithium ribbon 5 from the material box 14, and drives the lithium ribbon 5 to be transferred from position E to the vacuum suction plate 6 at position D, and makes the long side of the lithium ribbon 5 perpendicular to the unwinding direction of the protective layer 2, and the narrow side is parallel to the unwinding direction of the protective layer 2;

[0054] S3: The clamp 13 pulls the protective layer 2 through two sets of guide rollers 3 and then passes over the lithium belt 5;

[0055] S4: The CCD detection device 7 detects the relative position of the lithium ribbon 5 and the protective layer 2, ensuring that the protective layer 2 is 0-2CM more than the edges of the two sides of the lithium ribbon 5, and ensuring that the copper foil is left as the tab at the same position as the narrow side of the lithium ribbon 5 and the negative tab of the battery cell;

[0056] S5: After the test is qualified, the pressing roller 4 descends from position A to press the rubber layer of the protective layer 2 and the lithium surface of the lithium belt 5 tightly, and then rolls from left to right to position B to complete the protective layer compounding;

[0057] S6: The clamp 13 takes the composite product and passes it through the clamp 8 and the position movement detection device 9. After the position movement detection device 9 detects the quality of the product, the clamp 8 clamps the protective layer 2, and the cutter 10 cuts off the protective layer 2;

[0058] S7: The clamp 13 clamps the product and transfers it to the vacuum suction plate 12, and the vacuum suction device 11 sucks the product on the vacuum suction plate 12 and transfers it to the material receiving box 16.

[0059] The temperature of the low humidity environment described in S1 should control the dew point to be -40°C or below to ensure the normal performance of the lithium ribbon material used.

[0060] Hereinafter, the present invention will be described in more detail by the following examples. However, the following examples and test examples are provided for illustrating the present invention, and the scope of the present invention is not limited by these examples and test examples.

[0061] Example 1

[0062] <Battery Preparation>

[0063] The composited protective layer lithium strip product is collected for use, wherein the size of lithium strip 5 is 144*63mm, the thickness of lithium strip 5 is 100μm, and the weight is 0.6g; the battery cell system adopts a stacked core LFP / C system, wherein LFP is lithium iron phosphate and C is graphite; the formula of protective layer 2 is PET-AA (polyethylene terephthalate barrier substrate-acrylic pressure-sensitive adhesive layer), wherein the thickness of the polyethylene terephthalate substrate is 12μm, and the thickness of the acrylic pressure-sensitive adhesive layer is 6μm.

[0064] The width of the protective layer 2 is 154 mm. When compounded, the width of the protective layer 2 is 5 mm more than the upper and lower sides of the lithium belt 5 with a length of 144 mm, and the length of the protective layer 2 is 73 mm more than the left and right sides of the lithium belt 5 with a width of 63 mm.

[0065] The composite protective layer lithium strip product and the battery cell composite method are as follows: the copper pole ear on the lithium strip 5 is welded with the negative electrode of the battery cell, and the assembled battery cell is baked. After baking, the protective layer 2 is checked for the effect of protecting the lithium strip 5 and the moisture content, and the liquid is injected and packaged into a soft pack battery with a nominal capacity of 22Ah; after high-temperature pre-lithiation, it is formed and aged at a temperature of (45±3)℃; after the second injection, the capacity is divided and the cycle test is carried out at room temperature (25±3)℃, and the cycle test current is 1C (22A). If the protection is unqualified, the lithium strip 5 reacts with nitrogen at high temperature during the baking process to generate lithium nitride in reddish brown, and loses the pre-lithiation effect; the lithium strip 5 protection records the first coulomb efficiency after capacity division, the cycle capacity retention rate performance, and the disassembly of the fully charged battery cell after 800 cycles.

[0066] Example 2

[0067] The difference from Example 1 is that the lithium ribbon 5 has a thickness of 200 μm and a weight of 1.2 g.

[0068] Example 3

[0069] The difference from Example 1 is that the formula of the protective layer 2 is PET-PU (polyethylene terephthalate barrier substrate-polyurethane pressure-sensitive adhesive layer), wherein the polyethylene terephthalate substrate has a thickness of 12 μm and the polyurethane pressure-sensitive adhesive layer has a thickness of 6 μm.

[0070] Example 4

[0071] The difference from Example 1 is that the lithium strip 5 is 200 μm thick and weighs 1.2 g; the formula of the protective layer 2 is PET-PU, wherein the polyethylene terephthalate substrate is 12 μm thick and the polyurethane pressure-sensitive adhesive layer is 6 μm thick.

[0072] Example 5

[0073] The difference from Example 1 is that the lithium strip 5 is not subjected to the protective layer composite process;

[0074] The process of pre-lithium battery cell trial production is to first bake the battery cell to record the moisture content, and then perform the pre-lithium process of combining the lithium strip 5 with the battery cell. The other processes thereafter are the same as those in Example 1.

[0075] Example 6

[0076] The difference from Example 1 is that the lithium strip 5 is not subjected to the protective layer composite process, and the thickness of the lithium strip 5 is 200 μm and the weight is 1.2 g;

[0077] The process of pre-lithium battery cell trial production is to first bake the battery cell to record the moisture content, and then perform the pre-lithium process of combining the lithium strip 5 with the battery cell. The other processes thereafter are the same as those in Example 1.

[0078] The conditions of the above embodiments are recorded, and the parameters are recorded under the same conditions and organized into a table, as shown in the following Table 1:

[0079]

[0080] In Examples 1-4, after the cells were baked, the lithium ribbon 5 was observed to be silver-white in color, and no reaction of the lithium ribbon occurred after baking, indicating that the protective layer lithium ribbon product obtained by compounding the lithium ribbon 5 using this method can protect the lithium ribbon 5 .

[0081] In Examples 1 and 2, the thickness of the lithium ribbons used were different, but the cells remained unreacted after baking, indicating that lithium ribbons 5 of different thicknesses within a certain range can be protected by this composite method.

[0082] Examples 1, 2 and Examples 3, 4 use different adhesive layers in the formula of the protective layer 2. There is little difference in the first efficiency and capacity retention rate of the battery cells after baking and the battery test, indicating that changing the formula of the protective layer 2 and using this method can still protect the lithium strip 5 without affecting the battery performance.

[0083] In terms of the first effect and the disassembly after 800 cycles, the first effect and the consumption of lithium strip 5 of Examples 1-4 with lithium strip protection and Examples 5-6 without lithium strip protection are roughly the same, indicating that the pre-lithium battery cells produced by this composite method do not affect the pre-lithium battery performance data.

[0084] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0085] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0086] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0087] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0088] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0089] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A device for protecting the lithium surface of a lithium copper composite sheet, characterized in that: The invention comprises a winding device (1) and a clamp (13) for clamping a protective layer (2); the winding device (1) is provided with a composite component, a fixed cutting component and a material receiving component in sequence in the unwinding direction; the composite component comprises a vacuum suction plate (6) for placing a lithium strip (5); a pressure roller (4) and a CCD detection device (7) are installed above the vacuum suction plate (6); a material taking box (14) is installed on one side of the vacuum suction plate (6); a vacuum suction device (15) for transferring the lithium strip (5) is installed above the material taking box (14); and the protective layer (2) is located between the lithium strip (5) and the pressure roller (4).

2. The device for lithium surface protection layer of lithium copper composite sheet according to claim 1, characterized in that: The two sides of the lithium strip (5) are respectively a copper foil side and a lithium side, and the lithium side is composited with the protective layer (2).

3. The device for lithium surface protection layer of lithium copper composite sheet according to claim 2, characterized in that: The protective layer (2) comprises a barrier substrate and an adhesive layer coated on the barrier substrate and which loses adhesion when immersed in an electrolyte. One side of the adhesive layer of the protective layer (2) is composited with the lithium side of the lithium strip (5).

4. The device for lithium surface protection layer of lithium copper composite sheet according to claim 1, characterized in that: The protective layer (2) extends beyond the edges of both sides of the lithium strip (5) by 0-2CM.

5. The device for lithium surface protection layer of lithium copper composite sheet according to claim 1, characterized in that: The outermost layer material of the pressure roller (4) is a soft buffer material, and a pressure sensor is installed inside the pressure roller (4).

6. The device for lithium surface protection layer of lithium copper composite sheet according to claim 1, characterized in that: The fixed cutting assembly comprises a clamping plate (8) for fixing the protective layer (2), a position movement detection device (9) and a cutter (10), wherein the clamping plate (8), the position movement detection device (9) and the cutter (10) are sequentially close to the material receiving assembly.

7. The device for lithium surface protection layer of lithium copper composite sheet according to claim 1, characterized in that: The material receiving assembly comprises a second vacuum suction plate (12), a material receiving box (16) is installed on one side of the second vacuum suction plate (12), and also comprises a first vacuum suction device (11) which can transfer the product from the second vacuum suction plate (12) to the material receiving box (16).

8. The device for lithium surface protection layer of lithium copper composite sheet according to claim 7, characterized in that: The vacuum suction plate 1 (6) and the vacuum suction plate 2 (12) are both made of conductive metal material and are grounded.

9. A composite method for a lithium copper composite sheet lithium surface protection layer, the steps are as follows: S1: Place the device in a low humidity and dry environment; S2: The vacuum suction device (15) sucks the lithium tape (5) from the material box (14) and drives the lithium tape (5) to be transferred from position E to the vacuum suction plate (6) at position D, and makes the long side of the lithium tape (5) perpendicular to the unwinding direction of the protective layer (2) and the narrow side parallel to the unwinding direction of the protective layer (2); S3: The clamp (13) pulls the protective layer (2) through the top of the lithium belt (5); S4: The CCD detection device (7) detects the relative position of the lithium strip (5) and the protective layer (2): the protective layer (2) is 0-2CM beyond the edges of both sides of the lithium strip (5), and ensures that the copper foil is left as the tab at the same position of the narrow side of the lithium strip (5) and the negative tab of the battery cell; S5: After the test is qualified, the pressing roller (4) descends from position A to press the protective layer (2) and the lithium belt (5) tightly, and then rolls from left to right to position B to complete the protective layer bonding; S6: The clamp (13) clamps the composite product and passes it through the clamp (8) and the position movement detection device (9). After the position movement detection device (9) detects the quality of the product, the clamp (8) clamps the protective layer (2) and the cutter (10) cuts off the protective layer (2); S7: The clamp (13) clamps the product and transfers it to the second vacuum suction plate (12), and the first vacuum suction device (11) sucks the product on the second vacuum suction plate (12) and transfers it to the receiving box (16).

10. The composite method for the lithium surface protection layer of the lithium copper composite sheet according to claim 9, characterized in that: The temperature of the low humidity environment described in S1 is -40°C or lower.

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