Preparation method of roll core and monomer cell

Abstract

The invention discloses a preparation method of a roll core and a single cell, and relates to the technical field of lithium batteries. The preparation method of the roll core comprises the following steps: preparing a first pole piece: coating two sides of a first current collector with slurry to form the first pole piece; the front face and the back face of a second current collector are coated with slurry to form the second pole piece, and in the length direction of the second pole piece, the slurry on the front face is longer than the slurry on the back face by a first length, so that a blank area and a coating area are formed on the back face; the first pole piece, the diaphragm and the second pole piece are stacked, the second pole piece is located on the outer ring of the first pole piece to be wound to form a winding core, the reverse side is arranged away from the first pole piece, and the blank area is located on the outermost layer of the winding core. According to the preparation method of the roll core, the coating amount of the slurry of the second pole piece can be reduced on the basis of not influencing the effective area of the roll core and not influencing the electric quantity capable of being carried by the single battery core, so that the waste of the slurry is avoided, and the cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a method for preparing a winding core and a single battery cell. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, high average output voltage, low self-discharge, no memory effect and long cycle life, and are widely used in electronic equipment, energy storage devices and new energy vehicles. In order to improve the energy density of lithium-ion batteries, both the positive and negative electrodes of lithium-ion batteries are coated on both sides.

[0003] Generally speaking, when the positive electrode sheet, separator and negative electrode sheet are wound, the negative electrode sheet is located on the outer circle of the positive electrode sheet. As a result, at the end of winding, the slurry coated on the outer layer of the outermost circle of the negative electrode sheet does not have the corresponding positive electrode sheet slurry, and ion exchange cannot be carried out, resulting in slurry waste and increased costs. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a winding core and a single battery cell, which can reduce the coating amount of the slurry of the second pole piece without affecting the effective area of ​​the winding core and the amount of electricity that the single battery cell can carry, thereby avoiding waste of slurry and reducing costs.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] A method for preparing a roll core, comprising:

[0007] Preparing a first pole piece: coating the slurry on both sides of the first current collector to form the first pole piece;

[0008] Preparing a second pole piece: coating the front and back surfaces of the second current collector with slurry to form the second pole piece, and along the length direction of the second pole piece, the slurry on the front surface is longer than the slurry on the back surface by a first length, so as to form a blank area and a coating area on the back surface;

[0009] Winding: The first pole piece, the diaphragm and the second pole piece are stacked, and the second pole piece is located on the outer circle of the first pole piece for winding to form a winding core, and the reverse side is arranged away from the first pole piece, and the blank area is located at the outermost layer of the winding core.

[0010] As an optional solution of the method for preparing the above-mentioned winding core, the first length is 350 mm to 400 mm.

[0011] As an optional solution of the method for preparing the winding core, the end of the slurry on the reverse side is longer than the end of the first pole piece by a second length to form an overhang area.

[0012] As an optional solution of the method for preparing the core, along the length direction of the second current collector, the size of the overhang area is 10 mm to 20 mm.

[0013] As an optional scheme for the preparation method of the above-mentioned winding core, the reverse side of the second current collector is intermittently coated to form a plurality of coating areas and gaps between the plurality of coating areas, and the gaps of the coated second current collector are cut to form a plurality of second pole pieces.

[0014] As an optional solution of the method for preparing the core roll, along the length direction of the second current collector, the size of the gap is equal to the first length, and the cutting position is the edge of the coating area so that the gap forms the blank area.

[0015] As an alternative to the method for preparing the core, gap coating is performed using a high-speed gap valve.

[0016] As an optional scheme for the preparation method of the above-mentioned core roll, after completing the gap coating, a pole ear is set on one side of the second current collector in the coating area along the width direction of the second current collector, and a simulated pole ear is set on one side of the second current collector in the blank area.

[0017] As an optional solution of the method for preparing the above-mentioned core, it also includes:

[0018] Preparing a single cell: placing the core into a housing, injecting liquid to form a single cell, and performing a formation operation on the single cell;

[0019] Check: disassemble the single cell and confirm whether the first length is appropriate. If not, adjust the value of the first length and repeat the above steps.

[0020] A single cell comprises a shell, an electrolyte and a core prepared by the core preparation method, wherein the core and the electrolyte are both arranged in the shell.

[0021] Beneficial effects of the present invention:

[0022] The present invention provides a method for preparing a winding core and a single cell. In the preparation method, when the second pole piece is coated with slurry, the slurry on the reverse side is coated less for a certain distance, so that the slurry on the reverse side forms a blank area, and when winding, the first pole piece is located inside the second pole piece, and the reverse side of the second pole piece is wound as an outer circle, and at the end of winding, the blank area is located at the outermost layer of the winding core. In other words, the area of ​​the second pole piece that does not correspond to the first pole piece is not coated with slurry, which can reduce the amount of slurry applied to the second pole piece without affecting the effective area of ​​the winding core and the amount of electricity that the single cell can carry, thereby avoiding waste of slurry and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the winding core provided by the present invention;

[0024] Figure 2 is a flow chart of a method for preparing a roll core provided by the present invention;

[0025] Figure 3 It is a partial schematic diagram of the negative electrode sheet provided by the present invention;

[0026] Figure 4 It is a partial schematic diagram of the interval coating of the negative electrode sheet provided by the present invention.

[0027] In the figure:

[0028] 1. Positive electrode;

[0029] 2. Negative electrode; 21. Second current collector; 22. Front side; 23. Back side; 24. Coating area; 25. Blank area;

[0030] 3. Diaphragm. DETAILED DESCRIPTION

[0031] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0032] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions.

[0033] Unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; 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. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] Unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include the first feature being in direct contact with the second feature, or may include the first feature being in contact with the second feature through another feature between them instead of being in direct contact. Moreover, a first feature being "above", "above" and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0035] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0036] This embodiment also provides a single cell, which includes a shell, an electrolyte and a winding core, wherein the winding core and the electrolyte are both arranged in the shell. The winding core includes a first pole piece, a second pole piece and a diaphragm arranged between the first pole piece and the second pole piece, and the first pole piece, the second pole piece and the diaphragm are wound to form a winding core.

[0037] In order to increase the capacity of the single cell, both the first pole piece and the second pole piece are coated on both sides.

[0038] like Figure 1 As shown, the first pole piece can be a positive pole piece 1 or a negative pole piece 2, and the second pole piece can be a positive pole piece 1 or a negative pole piece 2. It is only necessary to ensure that the electrical properties of the first pole piece and the second pole piece are opposite. In current lithium-ion batteries, the cost of the positive electrode slurry is higher than the cost of the negative electrode slurry, so it is necessary to ensure that the positive electrode slurry is fully involved in the charging and discharging process. In this embodiment, the first pole piece is a positive pole piece 1 and the second pole piece is a negative pole piece 2 as an example for explanation.

[0039] Generally speaking, when the positive electrode sheet 1, the separator 3 and the negative electrode sheet 2 are wound, the negative electrode sheet 2 is located on the outer circle of the positive electrode sheet 1. This results in that at the end of the winding, the slurry coated on the outer layer of the outermost circle of the negative electrode sheet 2 does not have the corresponding slurry of the positive electrode sheet 1, and ion exchange cannot be performed, resulting in slurry waste and increased cost.

[0040] like Figure 1 to Figure 3 As shown, in order to solve the above problems, this embodiment provides a method for preparing a core, the preparation method comprising:

[0041] Prepare positive electrode sheet 1: apply slurry to both sides of the first current collector to form positive electrode sheet 1;

[0042] Prepare the negative electrode sheet 2: apply slurry to the front side 22 and the back side 23 of the second current collector 21 to form the negative electrode sheet 2, and along the length direction of the negative electrode sheet 2, the slurry on the front side 22 is longer than the slurry on the back side 23 by a first length, so as to form a blank area 25 and a coating area 24 on the back side 23;

[0043] Winding: The positive electrode sheet 1, the separator 3 and the negative electrode sheet 2 are stacked, and the negative electrode sheet 2 is located on the outer circle of the positive electrode sheet 1 and wound to form a winding core, with the reverse side 23 facing away from the positive electrode sheet 1, and the blank area 25 is located at the outermost layer of the winding core.

[0044] In the preparation method, when the negative electrode sheet 2 is coated with slurry, the slurry on the back side 23 is coated less for a distance, so that the slurry on the back side 23 forms a blank area 25, and when winding, the positive electrode sheet 1 is located inside the negative electrode sheet 2, and the back side 23 of the negative electrode sheet 2 is wound as the outer circle. At the end of winding, the blank area 25 is located at the outermost layer of the winding core (the range from A to B in the figure). In other words, the area of ​​the negative electrode sheet 2 that does not correspond to the positive electrode sheet 1 is not coated with slurry, which can reduce the amount of slurry applied to the negative electrode sheet 2 without affecting the effective area of ​​the winding core and the amount of electricity that the single battery cell can carry, thereby avoiding slurry waste and reducing costs.

[0045] In this embodiment, in the inner layer of the winding core, each layer of positive electrode sheet 1 has negative electrode sheets 2 on both sides, and each layer of negative electrode sheet 2 has positive electrode sheets 1 on both sides. Therefore, in order to avoid short circuit caused by direct contact between the positive electrode sheet 1 and the negative electrode sheet 2, the winding core needs to be provided with two layers of separators 3. In other words, the layers of the winding core are positive electrode sheet 1, separator 3, negative electrode sheet 2, and separator 3 in sequence. After winding, the ends of the two layers of separators 3 exceed the positive electrode sheet 1 and the negative electrode sheet 2 to ensure insulation.

[0046] Specifically, the length of the separator 3 exceeding the positive electrode sheet 1 or the negative electrode sheet 2 is 400 mm to 500 mm, and the end of the separator 3 is located on the flat surface of the winding core, so as to facilitate the pasting and fixing of the end of the separator 3. In this embodiment, the length of the separator 3 exceeding the positive electrode sheet 1 or the negative electrode sheet 2 can be 400 mm, 410 mm, 420 mm, 430 mm, 440 mm, 450 mm, 460 mm, 470 mm, 480 mm, 490 mm or 500 mm.

[0047] In this embodiment, after winding to form a winding core, the method further includes:

[0048] Prepare a single cell: put the core into the shell and inject liquid to form a single cell;

[0049] Check: Disassemble the single cell and confirm whether the first length is appropriate.

[0050] It is understandable that, due to the different sizes of the winding core under different process parameters, the sizes of the blank area 25 are also different. If the blank area 25 is too large, it will in turn cause the inner part of the outermost positive electrode sheet 1 to lack the corresponding negative electrode sheet 2 slurry, thereby affecting the maximum amount of electricity that the single cell can carry.

[0051] To solve this problem, after the single cell is made, it is necessary to undergo processes such as formation. After the single cell completes a charge and discharge cycle, the condition of the winding core is checked to confirm whether the size of the blank area 25 is in an appropriate state, that is, the entire area of ​​the positive electrode sheet 1 has the corresponding negative electrode sheet 2 slurry facing it.

[0052] Preferably, during the formation operation, the battery cell is fully charged so that the positive electrode sheet 1 and the negative electrode sheet 2 react fully, making the color change of the negative electrode sheet 2 more obvious and easy to distinguish.

[0053] In this embodiment, the first length is 350 mm to 400 mm. Under this length, it can be ensured that the entire area of ​​the positive electrode sheet 1 has the corresponding slurry of the negative electrode sheet 2 facing it, and at the same time, the slurry of the negative electrode sheet 2 will not exceed the outer side of the outermost positive electrode sheet 1 too much, thereby saving negative electrode slurry to the maximum extent.

[0054] After checking, if the size of the blank area 25 is not appropriate, the value of the first length is adjusted and the above steps are repeated until the size of the blank area 25 is appropriate. Specifically, the first length can be 350mm, 355mm, 360mm, 365mm, 370mm, 375mm, 380mm, 385mm, 390mm, 395mm or 400mm.

[0055] If the size of the blank area 25 is appropriate, the cores are mass-produced according to the data in the above steps.

[0056] like Figure 4 As shown, in order to improve the coating efficiency, the second current collector 21 is in the shape of a long strip, and the reverse side 23 of the second current collector 21 is intermittently coated to form a plurality of coating areas 24 and gaps between the plurality of coating areas 24 , and the gaps in the coated second current collector 21 are cut to form a plurality of negative electrode sheets 2 .

[0057] That is to say, the coating is applied at intervals on the long strip of the second current collector 21, and a structure in which the coating areas 24 and the blank areas 25 are alternately arranged is formed along the length direction of the second current collector 21. Then, the coated negative electrode sheet 2 can be obtained by simply cutting at the blank areas 25, without the need to coat each section of the second current collector 21, which greatly improves the continuity and efficiency of the coating process.

[0058] Furthermore, along the length direction of the second current collector 21, the size of the gap is equal to the first length, and the cutting position is the edge of the coating area 24 so that the gap forms a blank area 25. The first length has been determined during the test process, so after calculating the size of each coating area 24 according to the total length required for the negative electrode sheet 2, the gap coating can be performed according to the size of the coating area 24 and the size of the blank area 25, and the coating area 24 and the blank area 25 are cut at the connection position to obtain a negative electrode sheet 2 that meets the requirements.

[0059] It is worth noting that, in this embodiment, the coater is a continuous coater. In order to form the blank area 25 during continuous coating, a high-speed gap valve needs to be provided on the coater, and gap coating is performed using the high-speed gap valve.

[0060] When coating the second current collector 21, the front side 22 of the second current collector 21 is first fully coated. After drying, the back side 23 of the second current collector 21 is intermittently coated. The high-speed gap valve can control the time of coating interruption. In combination with the transmission speed of the conveyor belt, the size of the blank area 25 can be accurately controlled.

[0061] After coating the second current collector 21, it is necessary to set a tab on one side of the width direction of the second current collector 21. It is worth noting that a tab is set on one side of the second current collector 21 in the coating area 24, and a simulated tab is set on one side of the second current collector 21 in the blank area 25. The function of the simulated tab is to prevent the blank area 25 from being cut off as copper foil or aluminum foil during slitting.

[0062] like Figure 1 As shown, generally speaking, the end slurry of the negative electrode sheet 2 needs to exceed the end slurry of the positive electrode sheet 1 to ensure that all the slurry of the positive electrode sheet 1 has the slurry of the negative electrode sheet 2 corresponding thereto. To achieve the above purpose, the end of the slurry on the back side 23 of the negative electrode sheet 2 is longer than the end of the positive electrode sheet 1 by a second length to form an overhang area (the range from A to C in the figure). The setting of the overhang area can ensure that the slurry of the negative electrode sheet 2 can still cover the slurry of the positive electrode sheet 1 when deviation occurs during the winding process.

[0063] Preferably, along the length direction of the second current collector 21, the second length is 10 mm to 20 mm. This length should not be too long or too short. If it is too long, it will lead to waste of slurry. If it is too short, it will easily cause errors after winding, resulting in the end of the slurry on the back side 23 of the negative electrode sheet 2 being shorter than the end of the positive electrode sheet 1.

[0064] Specifically, the second length may be 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm or 20 mm.

[0065] The above contents are only preferred embodiments of the present invention. For ordinary technicians in this field, according to the concept of the present invention, there will be changes in the specific implementation methods and application scopes. The content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing a core, characterized in that: include: Preparing a first pole piece: coating the slurry on both sides of the first current collector to form the first pole piece; Preparing a second pole piece: coating the front side (22) and the back side (23) of the second current collector (21) with slurry to form the second pole piece, and along the length direction of the second pole piece, the slurry on the front side (22) is longer than the slurry on the back side (23) by a first length, so as to form a blank area (25) and a coating area (24) on the back side (23); Winding: The first pole piece, the diaphragm (3) and the second pole piece are stacked, and the second pole piece is located on the outer circle of the first pole piece and is wound to form a winding core, and the reverse side (23) is arranged away from the first pole piece, and the blank area (25) is located at the outermost layer of the winding core.

2. The method for preparing a winding core according to claim 1, characterized in that: The first length is 350 mm to 400 mm.

3. The method for preparing a winding core according to claim 1, characterized in that: The end of the slurry on the reverse side (23) is longer than the end of the first pole piece by a second length to form an overhang area.

4. The method for preparing a winding core according to claim 3, characterized in that: Along the length direction of the second current collector (21), the size of the overhang area is 10 mm to 20 mm.

5. The method for preparing a winding core according to claim 1, characterized in that: The reverse side (23) of the second current collector (21) is intermittently coated to form a plurality of coating areas (24) and gaps between the plurality of coating areas (24); the gaps of the coated second current collector (21) are cut to form a plurality of second pole pieces.

6. The method for preparing a winding core according to claim 5, characterized in that: Along the length direction of the second current collector (21), the size of the gap is equal to the first length, and the cutting position is the edge of the coating area (24) so ​​that the gap forms the blank area (25).

7. The method for preparing a winding core according to claim 6, characterized in that: Gap coating with high-speed gap valve.

8. The method for preparing a winding core according to claim 5, characterized in that: After gap coating is completed, a pole ear is arranged on one side of the second current collector (21) in the coating area (24) along the width direction of the second current collector (21), and a simulated pole ear is arranged on one side of the second current collector (21) in the blank area (25).

9. The method for preparing a winding core according to any one of claims 1 to 8, characterized in that: Also includes: Preparing a single cell: placing the core into a housing, injecting liquid to form a single cell, and performing a formation operation on the single cell; Check: disassemble the single cell and confirm whether the first length is appropriate. If not, adjust the value of the first length and repeat the above steps.

10. A single cell, characterized in that: The single battery cell comprises a shell, an electrolyte, and a core prepared by the method for preparing a core according to any one of claims 1 to 9, wherein the core and the electrolyte are both arranged in the shell.

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