Winding battery cell and battery

Abstract

The invention relates to a winding battery cell and a battery, the winding battery cell comprises a positive plate, a negative plate and a diaphragm which are laminated, and the negative plate comprises a first layer section and a second layer section which are connected and a first bending part which is formed by bending back; the positive plate comprises a third layer section and a fourth layer section which are connected, and a second bending part formed by bending back; the positive plate is a double-sided coating pole plate, and a negative protection layer is arranged on the inner side of the second bending part; one end, far away from the first bending part, of the first layer section is opposite to the negative electrode protection layer; and the starting end of the first layer section in the negative electrode protection layer is a double-sided coating pole piece. A winding starting end of a negative plate is a double-sided coating pole piece, a first layer section of the negative plate and a third layer section of a positive plate are alternately laminated to form a winding battery cell, and a second bending part of the positive plate is provided with a negative protection layer so as to protect the starting end, opposite to the negative protection layer, of the negative plate; the thickness of the battery cell is not additionally increased while lithium precipitation is avoided, and the energy density of the battery cell is effectively increased.

Description

Technical Field

[0001] The invention belongs to the technical field of battery manufacturing, and in particular relates to a wound battery core and a battery. Background Art

[0002] The charging and discharging of the charge-discharge battery is formed by the migration of lithium ions between the positive and negative electrodes. When the battery is charged, lithium ions are generated on the positive electrode of the battery. The generated lithium ions move to the negative electrode through the electrolyte and are embedded in the negative electrode sheet. The more lithium ions are embedded, the higher the charging capacity. By the same token, when the battery is discharged (that is, the process of using the battery), the lithium ions embedded in the negative electrode are released and move back to the positive electrode. The more lithium ions return to the positive electrode, the higher the discharge capacity. In a wound battery, the battery cell is wound with a positive electrode sheet and a negative electrode sheet. The innermost circle of the lithium battery wound battery cell generally has a single-sided negative electrode area. The single-sided negative electrode area is easy to curl due to the inconsistent stress on both sides of the copper foil, which increases the difficulty of processing and manufacturing; the curled area increases the transmission distance of lithium ions, causing lithium precipitation. Summary of the invention

[0003] The purpose of the present invention is to provide a wound battery cell and a battery in view of the shortcomings of the prior art. By changing the negative electrode single-sided area of ​​the innermost circle of the wound battery cell into a negative electrode with a double-sided coating, and forming a tight overall design with the positive electrode, it can not only solve the problem of easy curling of the inner circle negative electrode single-sided area, but also reduce the waste of copper foil and diaphragm, thereby improving the volume energy density of the battery cell to a certain extent and reducing the material cost.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A wound battery cell, comprising a stacked positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is arranged between the positive electrode sheet and the negative electrode sheet, the negative electrode sheet comprises a first layer segment and a second layer segment, the first layer segment is located at the winding start end of the negative electrode sheet, the second layer segment is connected to the first layer segment and folded back relative to the first layer segment, and the folded portion is a first bending portion;

[0006] The positive electrode sheet comprises a third layer segment and a fourth layer segment, wherein the third layer segment is located at the winding start end of the positive electrode sheet, and the fourth layer segment is connected to the third layer segment and folded back relative to the third layer segment, and the folded back portion is a second bending portion; the positive electrode sheet is a double-sided coated electrode sheet, and a negative electrode protective layer is provided inside the second bending portion;

[0007] The first layer segment is arranged between the third layer segment and the fourth layer segment, the end of the first layer segment away from the first bending portion is arranged opposite to the negative electrode protection layer, the starting end of the first layer segment in the negative electrode protection layer is a double-sided coated electrode sheet, and the third layer segment is arranged between the first layer segment and the second layer segment.

[0008] Preferably, the negative electrode protective layer is any one of single-sided protective adhesive, double-sided protective adhesive or a ceramic insulating layer.

[0009] Preferably, a recessed area is provided on the inner side of the second bent portion, and the negative electrode protection layer is provided in the recessed area.

[0010] Preferably, the recessed area is a thinned active coating area on the surface of the positive electrode sheet, and the thinned thickness T1 of the thinned area and the thickness T of the active coating satisfy the following relationship: 0<T1<T.

[0011] Preferably, the recessed area is a thinned active coating area on the surface of the positive electrode sheet, and the thinned thickness T1 of the thinned area and the thickness T of the active coating satisfy the following relationship: 60%T<T1<80%T.

[0012] Preferably, the recessed area is an empty foil area on the surface of the positive electrode sheet, and the empty foil area has the same size as that of the negative electrode protective layer.

[0013] Preferably, the negative electrode sheet is a double-sided coated electrode sheet, a layer of the diaphragm is provided on both sides of the negative electrode sheet in the thickness direction, a positive electrode protective layer is provided on the inner side of the first bending portion, and the positive electrode protective layer is arranged between the negative electrode sheet and the diaphragm; the positive electrode protective layer is any one of a single-sided protective adhesive, a double-sided protective adhesive or a ceramic insulating layer.

[0014] Preferably, one end of the third layer segment away from the second bending portion is arranged opposite to the positive electrode protection layer on the inner side of the first bending portion.

[0015] Preferably, the first layer segment and the third layer segment are bonded to each other to form the innermost circle of the wound battery core.

[0016] Preferably, an axial spacing distance between the front end of the first layer segment away from one end of the first bending portion and the negative electrode protection layer is A, and the value range of A is 0<A≤50mm.

[0017] Preferably, the front end of the first layer section away from one end of the first bending portion is a double-sided empty foil area, and the empty length thereof is B, and the value range of B is 0<B≤10mm.

[0018] Preferably, the protection length of the negative electrode protection layer after being symmetrically bent and coated at the second bending portion is C, satisfying the following relationship: C≥A+B.

[0019] A battery comprises the wound battery cell described in any one of the above items.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: the winding starting end of the negative electrode sheet is a double-sided coated electrode sheet, which can cover the winding starting end of the positive electrode sheet by forming the first layer and the second layer after only one bending, and the wound battery cell alternately stacked with each other, and the second bending portion of the positive electrode sheet is provided with a negative electrode protection layer to protect the starting end of the negative electrode sheet opposite thereto, which can avoid lithium deposition without additionally increasing the thickness of the battery cell, and effectively increase the energy density of the battery cell. In addition, the problem of curling easily occurring in the single-sided area of ​​the negative electrode in the existing design can be avoided, while reducing the use of copper foil and diaphragm, and reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure of the wound battery cell of the present invention.

[0022] Figure 2 It is a schematic diagram of the partial structure of the wound battery cell of Example 1 and Example 2 of the present invention.

[0023] Figure 3 It is a schematic diagram of the partial structure of the wound battery cell of Example 3 of the present invention.

[0024] Figure 4 It is a schematic diagram of the overall structure of the wound battery cell of Example 4 of the present invention.

[0025] Figure 5 yes Figure 4 A partial enlarged view of point A.

[0026] Figure 6 It is a schematic diagram of the overall structure of the wound battery cell of Example 5 of the present invention.

[0027] Reference numerals:

[0028] 1. positive electrode sheet, 11. third layer segment, 12. fourth layer segment, 13. second bending portion, 14. negative electrode protection layer, 15. recessed area;

[0029] 2. negative electrode sheet, 21. first layer segment, 22. second layer segment, 23. first bending portion, 24. positive electrode protection layer;

[0030] 3. Diaphragm. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Embodiment 1:

[0033] See also Figure 1-2 The present invention provides a wound battery cell, comprising a stacked positive electrode sheet 1, a negative electrode sheet 2 and a separator 3, wherein the separator 3 is arranged between the positive electrode sheet 1 and the negative electrode sheet 2, and the negative electrode sheet 2 comprises a first layer segment 21 and a second layer segment 22, wherein the first layer segment 21 is located at the winding start end of the negative electrode sheet 2, and the second layer segment 22 is connected to the first layer segment 21 and folded back relative to the first layer segment 21, and the folded portion is a first bending portion 23;

[0034] The positive electrode sheet 1 comprises a third layer section 11 and a fourth layer section 12, wherein the third layer section 11 is located at the winding start end of the positive electrode sheet 1, and the fourth layer section 12 is connected to the third layer section 11 and folded back relative to the third layer section 11, and the folded portion is a second bending portion 13; the positive electrode sheet 1 is a double-sided coated electrode sheet, and a negative electrode protective layer 14 is provided inside the second bending portion 13;

[0035] The first layer segment 21 is arranged between the third layer segment 11 and the fourth layer segment 12. The end of the first layer segment 21 away from the first bending portion 23 is arranged opposite to the negative electrode protection layer 14. The starting end of the first layer segment 21 in the negative electrode protection layer 14 is a double-sided coated electrode. The third layer segment 11 is arranged between the first layer segment 21 and the second layer segment 22.

[0036] The negative electrode protective layer 14 is any one of a single-sided protective adhesive, a double-sided protective adhesive or a ceramic insulating layer. When the negative electrode protective layer 14 is a single-sided protective adhesive or a double-sided protective adhesive, the protective adhesive substrate is any one of BOPP, PET or PI. If it is a single-sided protective adhesive, its adhesive layer is bonded to the positive electrode active material layer, and the other non-stick surface faces the first layer segment 21 and covers and protects it. If it is a double-sided protective adhesive, in addition to being bonded to the positive electrode active material layer, it can also be bonded and positioned to the second layer segment 21. The above selections can be appropriately replaced according to actual production. Preferably, the negative electrode protective layer 14 used in this embodiment is a single-sided protective adhesive, and the substrate of the single-sided protective adhesive is PET.

[0037] As described above, the starting end of the negative electrode sheet 2 coated with active material on one side in the original design is changed to a double-sided coating, and the positive electrode sheet 1 and the negative electrode sheet 2 are then bent and stacked in a U-shape, and the negative electrode single-sided area of ​​the innermost circle of the battery cell is cancelled, thereby directly avoiding the problem of curling of the negative electrode single-sided area. That is, in the existing design, the starting end of the negative electrode current collector is only coated with negative electrode active material on one side, and the coated side will have cohesive force on the current collector, while the uncoated side will have no effect on it. Therefore, the starting end of the negative electrode sheet 2 is easy to curl toward the side coated with the negative electrode active material, thereby causing the innermost circle of the battery cell to deform and even cause lithium deposition, while avoiding the useless negative electrode in the innermost circle occupying the battery cell volume, effectively increasing the energy density of the battery cell. The negative electrode protection layer 14 is arranged at the corresponding position of the positive electrode sheet 1 to prevent the first layer segment 21 of the negative electrode sheet 2 from directly contacting the second bending portion 13 of the positive electrode sheet 1 , thereby avoiding the occurrence of adverse conditions such as short circuit or puncture of the positive electrode sheet 1 .

[0038] Specifically, a recessed area 15 is provided on the inner side of the second bent portion 13, and the negative electrode protection layer 14 is provided in the recessed area 15. The thickness of the negative electrode protection layer 14 is the same as the depth of the recessed area 15. After the negative electrode protection layer 14 is embedded in the recessed area 15, the surface of the second bent portion 13 is still a flat surface after being unfolded.

[0039] Specifically, the recessed area 15 is a thinned area of ​​the active coating on the surface of the positive electrode sheet 1, and the thinned thickness T1 of the thinned area is 50%-90% of the thickness T of the active coating. Preferably, the thinned thickness T1 is 50%, 60%, 70%, 80% or 90%, etc. In this embodiment, the thinned thickness T1 is 50%.

[0040] Specifically, the negative electrode sheet 2 is a double-sided coated electrode sheet, and a layer of diaphragm 3 is provided on both sides of the negative electrode sheet 2 in the thickness direction. The positive electrode sheet 1 and the negative electrode sheet 2 are separated by the diaphragm 3 to prevent the third layer segment 11 of the positive electrode sheet 1 from directly contacting the first bending portion 23 of the negative electrode sheet 2 at the starting end of the winding, so as to avoid the occurrence of adverse conditions such as short circuit or puncturing the negative electrode sheet 2. More specifically, a positive electrode protective layer 24 is provided on the inner side of the first bending portion 23, and the positive electrode protective layer 24 is provided between the negative electrode sheet 2 and the diaphragm 3; the positive electrode protective layer 24 is any one of a single-sided protective adhesive, a double-sided protective adhesive or a ceramic insulating layer. In this embodiment, the positive electrode protective layer 24 is a double-sided protective adhesive. The negative electrode sheet 2 is also provided with an active coating thinning area to accommodate the positive electrode protective layer 24.

[0041] Specifically, one end of the third layer segment 11 away from the second bending portion 13 is arranged opposite to the positive electrode protection layer 24 inside the first bending portion 23. The first layer segment 21 and the third layer segment 11 are overlapped at the innermost layer of the battery cell, and this is used as the winding starting position of the entire battery cell, and the second layer segment 22 and the fourth layer segment 12 that follow are wound and formed thereon.

[0042] Specifically, the axial spacing distance between the front end of the first layer segment 21 away from one end of the first bent portion 23 and the negative electrode protective layer 14 is A, and the value range of A is 0<A≤50mm. More specifically, A can be 1mm, 5mm, 8mm, 10mm, 20mm, 25mm, 40mm and 50mm, etc. In this embodiment, A is 10mm.

[0043] Specifically, the protection length of the negative electrode protection layer after the second bending portion is symmetrically bent and coated is C, satisfying the following relationship: C ≥ A. More specifically, C can be 1 mm, 5 mm, 8 mm, 10 mm, 20 mm, 25 mm, 40 mm, 50 mm, etc. In this embodiment, C is 15 mm.

[0044] Embodiment 2:

[0045] See also Figure 1-2 The present invention provides a wound battery cell, comprising a stacked positive electrode sheet 1, a negative electrode sheet 2 and a separator 3, wherein the separator 3 is arranged between the positive electrode sheet 1 and the negative electrode sheet 2, and the negative electrode sheet 2 comprises a first layer segment 21 and a second layer segment 22, wherein the first layer segment 21 is located at the winding start end of the negative electrode sheet 2, and the second layer segment 22 is connected to the first layer segment 21 and folded back relative to the first layer segment 21, and the folded portion is a first bending portion 23;

[0046] The positive electrode sheet 1 comprises a third layer section 11 and a fourth layer section 12, wherein the third layer section 11 is located at the winding start end of the positive electrode sheet 1, and the fourth layer section 12 is connected to the third layer section 11 and folded back relative to the third layer section 11, and the folded portion is a second bending portion 13; the positive electrode sheet 1 is a double-sided coated electrode sheet, and a negative electrode protective layer 14 is provided inside the second bending portion 13;

[0047] The first layer segment 21 is arranged between the third layer segment 11 and the fourth layer segment 12. The end of the first layer segment 21 away from the first bending portion 23 is arranged opposite to the negative electrode protection layer 14. The starting end of the first layer segment 21 in the negative electrode protection layer 14 is a double-sided coated electrode. The third layer segment 11 is arranged between the first layer segment 21 and the second layer segment 22.

[0048] The negative electrode protective layer 14 is any one of a single-sided protective adhesive, a double-sided protective adhesive or a ceramic insulating layer. When the negative electrode protective layer 14 is a single-sided protective adhesive or a double-sided protective adhesive, the protective adhesive substrate is any one of BOPP, PET or PI. If it is a single-sided protective adhesive, its adhesive layer is bonded to the positive electrode active material layer, and the other non-stick surface faces the first layer segment 21 and covers and protects it. If it is a double-sided protective adhesive, in addition to being bonded to the positive electrode active material layer, it can also be bonded and positioned to the second layer segment 21. The above selections can be appropriately replaced according to actual production. Preferably, the negative electrode protective layer 14 used in this embodiment is a double-sided protective adhesive, and the substrate of the double-sided protective adhesive is PET.

[0049] As described above, the starting end of the negative electrode sheet 2 coated with active material on one side in the original design is changed to a double-sided coating, and the positive electrode sheet 1 and the negative electrode sheet 2 are then bent and stacked in a U-shape, and the negative electrode single-sided area of ​​the innermost circle of the battery cell is cancelled, thereby directly avoiding the problem of curling of the negative electrode single-sided area. That is, in the existing design, the starting end of the negative electrode current collector is only coated with negative electrode active material on one side, and the coated side will have cohesive force on the current collector, while the uncoated side will have no effect on it. Therefore, the starting end of the negative electrode sheet 2 is easy to curl toward the side coated with the negative electrode active material, thereby causing the innermost circle of the battery cell to deform and even cause lithium deposition, while avoiding the useless negative electrode in the innermost circle occupying the battery cell volume, effectively increasing the energy density of the battery cell. The negative electrode protection layer 14 is arranged at the corresponding position of the positive electrode sheet 1 to prevent the first layer segment 21 of the negative electrode sheet 2 from directly contacting the second bending portion 13 of the positive electrode sheet 1 , thereby avoiding the occurrence of adverse conditions such as short circuit or puncture of the positive electrode sheet 1 .

[0050] Specifically, a recessed area 15 is provided on the inner side of the second bent portion 13, and the negative electrode protection layer 14 is provided in the recessed area 15. The thickness of the negative electrode protection layer 14 is the same as the depth of the recessed area 15. After the negative electrode protection layer 14 is embedded in the recessed area 15, the surface of the second bent portion 13 is still a flat surface after being unfolded.

[0051] Specifically, the recessed area 15 is a thinned area of ​​the active coating on the surface of the positive electrode sheet 1, and the thinned thickness T1 of the thinned area is 60%-80% of the thickness T of the active coating. Preferably, the thinned thickness T1 is 60%, 65%, 70%, 75% or 80%, etc. In this embodiment, the thinned thickness T1 is 70%.

[0052] Specifically, the negative electrode sheet 2 is a double-sided coated electrode sheet, and a layer of diaphragm 3 is provided on both sides of the negative electrode sheet 2 in the thickness direction. The positive electrode sheet 1 and the negative electrode sheet 2 are separated by the diaphragm 3 to prevent the third layer segment 11 of the positive electrode sheet 1 from directly contacting the first bending portion 23 of the negative electrode sheet 2 at the starting end of the winding, so as to avoid the occurrence of adverse conditions such as short circuit or puncturing the negative electrode sheet 2. More specifically, a positive electrode protective layer 24 is provided on the inner side of the first bending portion 23, and the positive electrode protective layer 24 is provided between the negative electrode sheet 2 and the diaphragm 3; the positive electrode protective layer 24 is any one of a single-sided protective adhesive, a double-sided protective adhesive or a ceramic insulating layer. In this embodiment, the positive electrode protective layer 24 is a double-sided protective adhesive. The negative electrode sheet 2 is also provided with an active coating thinning area to accommodate the positive electrode protective layer 24.

[0053] Specifically, one end of the third layer segment 11 away from the second bending portion 13 is arranged opposite to the positive electrode protection layer 24 inside the first bending portion 23. The first layer segment 21 and the third layer segment 11 are overlapped at the innermost layer of the battery cell, and this is used as the winding starting position of the entire battery cell, and the second layer segment 22 and the fourth layer segment 12 that follow are wound and formed thereon.

[0054] Specifically, the axial spacing distance between the front end of the first layer segment 21 away from one end of the first bent portion 23 and the negative electrode protective layer 14 is A, and the value range of A is 0<A≤50mm. More specifically, A can be 1mm, 5mm, 8mm, 10mm, 20mm, 25mm, 40mm and 50mm, etc. In this embodiment, A is 8mm.

[0055] Specifically, the protection length of the negative electrode protection layer after the second bending portion is symmetrically bent and coated is C, satisfying the following relationship: C ≥ A. More specifically, C can be 1 mm, 5 mm, 8 mm, 10 mm, 20 mm, 25 mm, 40 mm, 50 mm, etc. In this embodiment, C is 10 mm.

[0056] Embodiment 3:

[0057] See also Figure 1 and Figure 3 The present invention provides a wound battery cell, comprising a stacked positive electrode sheet 1, a negative electrode sheet 2 and a separator 3, wherein the separator 3 is arranged between the positive electrode sheet 1 and the negative electrode sheet 2, and the negative electrode sheet 2 comprises a first layer segment 21 and a second layer segment 22, wherein the first layer segment 21 is located at the winding start end of the negative electrode sheet 2, and the second layer segment 22 is connected to the first layer segment 21 and folded back relative to the first layer segment 21, and the folded portion is a first bending portion 23;

[0058] The positive electrode sheet 1 comprises a third layer section 11 and a fourth layer section 12, wherein the third layer section 11 is located at the winding start end of the positive electrode sheet 1, and the fourth layer section 12 is connected to the third layer section 11 and folded back relative to the third layer section 11, and the folded portion is a second bending portion 13; the positive electrode sheet 1 is a double-sided coated electrode sheet, and a negative electrode protective layer 14 is provided inside the second bending portion 13;

[0059] The first layer segment 21 is arranged between the third layer segment 11 and the fourth layer segment 12. The end of the first layer segment 21 away from the first bending portion 23 is arranged opposite to the negative electrode protection layer 14. The starting end of the first layer segment 21 in the negative electrode protection layer 14 is a double-sided coated electrode. The third layer segment 11 is arranged between the first layer segment 21 and the second layer segment 22.

[0060] The negative electrode protective layer 14 is any one of a single-sided protective adhesive, a double-sided protective adhesive or a ceramic insulating layer. When the negative electrode protective layer 14 is a single-sided protective adhesive or a double-sided protective adhesive, the protective adhesive substrate is any one of BOPP, PET or PI. If it is a single-sided protective adhesive, its adhesive layer is bonded to the positive electrode active material layer, and the other non-stick surface faces the first layer segment 21 and covers and protects it. If it is a double-sided protective adhesive, in addition to being bonded to the positive electrode active material layer, it can also be bonded and positioned to the second layer segment 21. The above selections can be appropriately replaced according to actual production. Preferably, the negative electrode protective layer 14 used in this embodiment is a single-sided protective adhesive, and the substrate of the single-sided protective adhesive is PET.

[0061] As described above, by changing the starting end of the negative electrode sheet 2 coated with active material on one side in the original design to double-sided coating, and then bending and stacking the positive electrode sheet 1 and the negative electrode sheet 2 in a U-shaped shape, the negative electrode single-sided area of ​​the innermost circle of the battery cell is cancelled, directly avoiding the problem that the negative electrode single-sided area is prone to occur, that is, in the existing design, the starting end of the negative current collector is only coated with negative active material on one side, and the coated side will have cohesive force on the current collector, while the uncoated side will have no effect on it, so the starting end of the negative electrode sheet 2 is easy to curl toward the side coated with negative active material, so that the innermost circle of the battery cell is deformed and even lithium precipitation occurs, while avoiding the useless negative electrode of the innermost circle occupying the volume of the battery cell, effectively increasing the energy density of the battery cell. By arranging the negative electrode protective layer 14 at the corresponding position of the positive electrode sheet 1, the first layer segment 21 of the negative electrode sheet 2 is prevented from directly contacting the second bending portion 13 of the positive electrode sheet 1, so as to avoid the occurrence of adverse conditions such as short circuit or puncture of the positive electrode sheet 1.

[0062] Specifically, a recessed area 15 is provided on the inner side of the second bent portion 13, and the negative electrode protection layer 14 is provided in the recessed area 15. The thickness of the negative electrode protection layer 14 is the same as the depth of the recessed area 15. After the negative electrode protection layer 14 is embedded in the recessed area 15, the surface of the second bent portion 13 is still a flat surface after being unfolded.

[0063] Specifically, the recessed area 15 is an empty foil area on the surface of the positive electrode sheet 1, and the empty foil area has the same size as the negative electrode protective layer 14. The empty foil area is an area on the current collector of the positive electrode sheet 1 where the positive electrode active material is not coated, and the thickness of the negative electrode protective layer 14 is the same as the thickness of the positive electrode active material layer to form a flat surface. In this embodiment, the empty foil area is arranged on the side of the second bent portion 13 facing the winding start end of the negative electrode sheet 2.

[0064] Specifically, the negative electrode sheet 2 is a double-sided coated electrode sheet, and a layer of diaphragm 3 is provided on both sides of the negative electrode sheet 2 in the thickness direction. The positive electrode sheet 1 and the negative electrode sheet 2 are separated by the diaphragm 3 to prevent the third layer section 11 of the positive electrode sheet 1 from directly contacting the first bending portion 23 of the negative electrode sheet 2 at the starting end of the winding, so as to avoid the occurrence of adverse conditions such as short circuit or puncturing the negative electrode sheet 2. More specifically, a positive electrode protective layer 24 is provided on the inner side of the first bending portion 23, and the positive electrode protective layer 24 is provided between the negative electrode sheet 2 and the diaphragm 3; the positive electrode protective layer 24 is any one of a single-sided protective adhesive, a double-sided protective adhesive or a ceramic insulating layer. In this embodiment, an empty foil area is also provided on the surface of the negative electrode sheet 2 corresponding to the first bending portion 23 to accommodate the positive electrode protective layer 24.

[0065] Specifically, one end of the third layer segment 11 away from the second bent portion 13 is arranged opposite to the diaphragm 3 inside the first bent portion 23. The first layer segment 21 and the third layer segment 11 are overlapped at the innermost layer of the battery cell, and this is used as the winding starting position of the entire battery cell, and the second layer segment 22 and the fourth layer segment 12 that follow are wound and formed thereon.

[0066] Specifically, the axial spacing distance between the front end of the first layer segment 21 away from one end of the first bent portion 23 and the negative electrode protective layer 14 is A, and the value range of A is 0<A≤50mm. More specifically, A can be 1mm, 5mm, 8mm, 10mm, 20mm, 25mm, 40mm and 50mm, etc. In this embodiment, A is 8mm.

[0067] Specifically, the protection length of the negative electrode protection layer after the second bending portion is symmetrically bent and coated is C, satisfying the following relationship: C ≥ A. More specifically, C can be 1 mm, 5 mm, 8 mm, 10 mm, 20 mm, 25 mm, 40 mm, 50 mm, etc. In this embodiment, C is 10 mm.

[0068] Embodiment 4:

[0069] See also Figure 1 , Figure 4 and Figure 5 The present invention provides a wound battery cell, comprising a stacked positive electrode sheet 1, a negative electrode sheet 2 and a separator 3, wherein the separator 3 is arranged between the positive electrode sheet 1 and the negative electrode sheet 2, and the negative electrode sheet 2 comprises a first layer segment 21 and a second layer segment 22, wherein the first layer segment 21 is located at the winding start end of the negative electrode sheet 2, and the second layer segment 22 is connected to the first layer segment 21 and folded back relative to the first layer segment 21, and the folded portion is a first bending portion 23;

[0070] The positive electrode sheet 1 comprises a third layer section 11 and a fourth layer section 12, wherein the third layer section 11 is located at the winding start end of the positive electrode sheet 1, and the fourth layer section 12 is connected to the third layer section 11 and folded back relative to the third layer section 11, and the folded portion is a second bending portion 13; the positive electrode sheet 1 is a double-sided coated electrode sheet, and a negative electrode protective layer 14 is provided inside the second bending portion 13;

[0071] The first layer segment 21 is arranged between the third layer segment 11 and the fourth layer segment 12. The end of the first layer segment 21 away from the first bending portion 23 is arranged opposite to the negative electrode protection layer 14. The starting end of the first layer segment 21 in the negative electrode protection layer 14 is a double-sided coated electrode. The third layer segment 11 is arranged between the first layer segment 21 and the second layer segment 22.

[0072] The negative electrode protective layer 14 is any one of a single-sided protective adhesive, a double-sided protective adhesive or a ceramic insulating layer. When the negative electrode protective layer 14 is a single-sided protective adhesive or a double-sided protective adhesive, the protective adhesive substrate is any one of BOPP, PET or PI. If it is a single-sided protective adhesive, its adhesive layer is bonded to the positive electrode active material layer, and the other non-stick surface faces the first layer segment 21 and covers and protects it. If it is a double-sided protective adhesive, in addition to being bonded to the positive electrode active material layer, it can also be bonded and positioned to the second layer segment 21. The above selections can be appropriately replaced according to actual production. Preferably, the negative electrode protective layer 14 used in this embodiment is a double-sided protective adhesive, and the substrate of the double-sided protective adhesive is PET.

[0073] As described above, the starting end of the negative electrode sheet 2 coated with active material on one side in the original design is changed to a double-sided coating, and the positive electrode sheet 1 and the negative electrode sheet 2 are then bent and stacked in a U-shape, and the negative electrode single-sided area of ​​the innermost circle of the battery cell is cancelled, thereby directly avoiding the problem of curling of the negative electrode single-sided area. That is, in the existing design, the starting end of the negative electrode current collector is only coated with negative electrode active material on one side, and the coated side will have cohesive force on the current collector, while the uncoated side will have no effect on it. Therefore, the starting end of the negative electrode sheet 2 is easy to curl toward the side coated with the negative electrode active material, thereby causing the innermost circle of the battery cell to deform and even cause lithium deposition, while avoiding the useless negative electrode in the innermost circle occupying the battery cell volume, effectively increasing the energy density of the battery cell. The negative electrode protection layer 14 is arranged at the corresponding position of the positive electrode sheet 1 to prevent the first layer segment 21 of the negative electrode sheet 2 from directly contacting the second bending portion 13 of the positive electrode sheet 1 , thereby avoiding the occurrence of adverse conditions such as short circuit or puncture of the positive electrode sheet 1 .

[0074] Specifically, a recessed area 15 is provided on the inner side of the second bent portion 13, and the negative electrode protection layer 14 is provided in the recessed area 15. The thickness of the negative electrode protection layer 14 is the same as the depth of the recessed area 15. After the negative electrode protection layer 14 is embedded in the recessed area 15, the surface of the second bent portion 13 is still a flat surface after being unfolded.

[0075] Specifically, the recessed area 15 is a thinned area of ​​the active coating on the surface of the positive electrode sheet 1, and the thinned thickness T1 of the thinned area is 60%-80% of the thickness T of the active coating. Preferably, the thinned thickness T1 is 60%, 65%, 70%, 75% or 80%, etc. In this embodiment, the thinned thickness T1 is 70%.

[0076] Specifically, the negative electrode sheet 2 is a double-sided coated electrode sheet, and a layer of diaphragm 3 is provided on both sides of the negative electrode sheet 2 in the thickness direction. The positive electrode sheet 1 and the negative electrode sheet 2 are separated by the diaphragm 3 to prevent the third layer segment 11 of the positive electrode sheet 1 from directly contacting the first bending portion 23 of the negative electrode sheet 2 at the starting end of the winding, so as to avoid the occurrence of adverse conditions such as short circuit or puncturing the negative electrode sheet 2. More specifically, a positive electrode protective layer 24 is provided on the inner side of the first bending portion 23, and the positive electrode protective layer 24 is provided between the negative electrode sheet 2 and the diaphragm 3; the positive electrode protective layer 24 is any one of a single-sided protective adhesive, a double-sided protective adhesive or a ceramic insulating layer. In this embodiment, the positive electrode protective layer 24 is a double-sided protective adhesive. The negative electrode sheet 2 is also provided with an active coating thinning area to accommodate the positive electrode protective layer 24.

[0077] Specifically, one end of the third layer segment 11 away from the second bending portion 13 is arranged opposite to the positive electrode protection layer 24 inside the first bending portion 23. The first layer segment 21 and the third layer segment 11 are overlapped at the innermost layer of the battery cell, and this is used as the winding starting position of the entire battery cell, and the second layer segment 22 and the fourth layer segment 12 that follow are wound and formed thereon.

[0078] Specifically, the axial spacing distance between the front end of the first layer segment 21 away from one end of the first bent portion 23 and the negative electrode protective layer 14 is A, and the value range of A is 0<A≤50mm. More specifically, A can be 1mm, 5mm, 8mm, 10mm, 20mm, 25mm, 40mm and 50mm, etc. In this embodiment, A is 10mm.

[0079] Specifically, a double-sided empty foil area is provided at the starting end of the first layer section 21 away from the first bending portion 23, and its empty length is B, and the value range of B is 0<B≤10mm. More specifically, C can be 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 8mm and 10mm, etc. In this embodiment, A is 5mm.

[0080] Specifically, the protection length of the negative electrode protection layer after the second bending portion is symmetrically bent and coated is C, satisfying the following relationship: C ≥ A + B. More specifically, C can be 2 mm, 5 mm, 8 mm, 10 mm, 20 mm, 25 mm, 40 mm, 50 mm and 60 mm, etc. In this embodiment, C is 20 mm.

[0081] Embodiment 5:

[0082] See also Figure 6 The present invention provides a wound battery cell, comprising a stacked positive electrode sheet 1, a negative electrode sheet 2 and a separator 3, wherein the separator 3 is arranged between the positive electrode sheet 1 and the negative electrode sheet 2, and the negative electrode sheet 2 comprises a first layer segment 21 and a second layer segment 22, wherein the first layer segment 21 is located at the winding start end of the negative electrode sheet 2, and the second layer segment 22 is connected to the first layer segment 21 and folded back relative to the first layer segment 21, and the folded portion is a first bending portion 23;

[0083] The positive electrode sheet 1 comprises a third layer section 11 and a fourth layer section 12, wherein the third layer section 11 is located at the winding start end of the positive electrode sheet 1, and the fourth layer section 12 is connected to the third layer section 11 and folded back relative to the third layer section 11, and the folded portion is a second bending portion 13; the positive electrode sheet 1 is a double-sided coated electrode sheet, and a negative electrode protective layer 14 is provided inside the second bending portion 13;

[0084] The first layer segment 21 is arranged between the third layer segment 11 and the fourth layer segment 12. The end of the first layer segment 21 away from the first bending portion 23 is arranged opposite to the negative electrode protection layer 14. The starting end of the first layer segment 21 in the negative electrode protection layer 14 is a double-sided coated electrode. The third layer segment 11 is arranged between the first layer segment 21 and the second layer segment 22.

[0085] The negative electrode protective layer 14 is any one of a single-sided protective adhesive, a double-sided protective adhesive or a ceramic insulating layer. When the negative electrode protective layer 14 is a single-sided protective adhesive or a double-sided protective adhesive, the protective adhesive substrate is any one of BOPP, PET or PI. If it is a single-sided protective adhesive, its adhesive layer is bonded to the positive electrode active material layer, and the other non-stick surface faces the first layer segment 21 and covers and protects it. If it is a double-sided protective adhesive, in addition to being bonded to the positive electrode active material layer, it can also be bonded and positioned to the second layer segment 21. The above selections can be appropriately replaced according to actual production. Preferably, the negative electrode protective layer 14 used in this embodiment is a single-sided protective adhesive, and the substrate of the single-sided protective adhesive is PET.

[0086] As described above, the starting end of the negative electrode sheet 2 coated with active material on one side in the original design is changed to a double-sided coating, and the positive electrode sheet 1 and the negative electrode sheet 2 are then bent and stacked in a U-shape, and the negative electrode single-sided area of ​​the innermost circle of the battery cell is cancelled, thereby directly avoiding the problem of curling of the negative electrode single-sided area. That is, in the existing design, the starting end of the negative electrode current collector is only coated with negative electrode active material on one side, and the coated side will have cohesive force on the current collector, while the uncoated side will have no effect on it. Therefore, the starting end of the negative electrode sheet 2 is easy to curl toward the side coated with the negative electrode active material, thereby causing the innermost circle of the battery cell to deform and even cause lithium deposition, while avoiding the useless negative electrode in the innermost circle occupying the battery cell volume, effectively increasing the energy density of the battery cell. The negative electrode protection layer 14 is arranged at the corresponding position of the positive electrode sheet 1 to prevent the first layer segment 21 of the negative electrode sheet 2 from directly contacting the second bending portion 13 of the positive electrode sheet 1 , thereby avoiding the occurrence of adverse conditions such as short circuit or puncture of the positive electrode sheet 1 .

[0087] Specifically, a recessed area 15 is provided on the inner side of the second bent portion 13, and the negative electrode protection layer 14 is provided in the recessed area 15. The thickness of the negative electrode protection layer 14 is the same as the depth of the recessed area 15. After the negative electrode protection layer 14 is embedded in the recessed area 15, the surface of the second bent portion 13 is still a flat surface after being unfolded.

[0088] Specifically, the recessed area 15 is a thinned area of ​​the active coating on the surface of the positive electrode sheet 1, and the thinned thickness T1 of the thinned area is 50%-90% of the thickness T of the active coating. Preferably, the thinned thickness T1 is 50%, 60%, 70%, 80% or 90%, etc. In this embodiment, the thinned thickness T1 is 50%.

[0089] Specifically, the negative electrode sheet 2 is a double-sided coated electrode sheet, and a layer of separator 3 is provided on both sides of the thickness direction of the negative electrode sheet 2. The separator 3 separates the positive electrode sheet 1 and the negative electrode sheet 2 to prevent the winding start end of the third layer segment 11 of the positive electrode sheet 1 from directly contacting the first bent portion 23 of the negative electrode sheet 2, thereby avoiding the occurrence of adverse conditions such as short circuit or puncture of the negative electrode sheet 2.

[0090] Specifically, one end of the third layer segment 11 away from the second bent portion 13 is arranged opposite to the diaphragm 3 inside the first bent portion 23. The first layer segment 21 and the third layer segment 11 are overlapped at the innermost layer of the battery cell, and this is used as the winding starting position of the entire battery cell, and the second layer segment 22 and the fourth layer segment 12 that follow are wound and formed thereon.

[0091] Specifically, the axial spacing distance between the front end of the first layer segment 21 away from one end of the first bent portion 23 and the negative electrode protective layer 14 is A, and the value range of A is 0<A≤50mm. More specifically, A can be 1mm, 5mm, 8mm, 10mm, 20mm, 25mm, 40mm and 50mm, etc. In this embodiment, A is 10mm.

[0092] Specifically, the protection length of the negative electrode protection layer after the second bending portion is symmetrically bent and coated is C, satisfying the following relationship: C ≥ A. More specifically, C can be 1 mm, 5 mm, 8 mm, 10 mm, 20 mm, 25 mm, 40 mm, 50 mm, etc. In this embodiment, C is 15 mm.

[0093] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs can also change and modify the above embodiment. Therefore, the present invention is not limited to the above specific embodiment, and any obvious improvement, replacement or modification made by those skilled in the art on the basis of the present invention belongs to the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A wound battery cell, comprising a positive electrode sheet (1), a negative electrode sheet (2) and a separator (3) which are stacked, wherein the separator (3) is arranged between the positive electrode sheet (1) and the negative electrode sheet (2), characterized in that: The negative electrode sheet (2) comprises a first layer segment (21) and a second layer segment (22), wherein the first layer segment (21) is located at the winding start end of the negative electrode sheet (2), and the second layer segment (22) is connected to the first layer segment (21) and folded back relative to the first layer segment (21), and the folded portion is a first bending portion (23); The positive electrode sheet (1) comprises a third layer segment (11) and a fourth layer segment (12), wherein the third layer segment (11) is located at the winding start end of the positive electrode sheet (1), and the fourth layer segment (12) is connected to the third layer segment (11) and folded back relative to the third layer segment (11), and the folded back portion is a second bending portion (13); the positive electrode sheet (1) is a double-sided coated electrode sheet, and a negative electrode protective layer (14) is provided on the inner side of the second bending portion (13); The first layer segment (21) is arranged between the third layer segment (11) and the fourth layer segment (12); one end of the first layer segment (21) away from the first bent portion (23) is arranged opposite to the negative electrode protection layer (14); the starting end of the first layer segment (21) in the negative electrode protection layer (14) is a double-sided coated electrode sheet; and the third layer segment (11) is arranged between the first layer segment (21) and the second layer segment (22).

2. The wound battery cell according to claim 1, characterized in that: The negative electrode protective layer (14) is any one of a single-sided protective adhesive, a double-sided protective adhesive or a ceramic insulating layer.

3. The wound battery cell according to claim 1, characterized in that: A recessed area (15) is provided on the inner side of the second bent portion (13), and the negative electrode protection layer (14) is provided in the recessed area (15).

4. The wound battery cell according to claim 3, characterized in that: The recessed area (15) is a thinned active coating area on the surface of the positive electrode sheet (1), and the thinned thickness T1 of the thinned area and the thickness T of the active coating satisfy the following relationship: 0<T1<T.

5. The wound battery cell according to claim 4, characterized in that: The recessed area (15) is a thinned active coating area on the surface of the positive electrode sheet (1), and the thinned thickness T1 of the thinned area and the thickness T of the active coating satisfy the following relationship: 60%T<T1<80%T.

6. The wound battery cell according to claim 3, characterized in that: The recessed area (15) is an empty foil area on the surface of the positive electrode sheet (1), and the empty foil area has the same size as the negative electrode protective layer (14).

7. The wound battery cell according to claim 1, characterized in that: The negative electrode sheet (2) is a double-sided coated electrode sheet, a layer of the diaphragm (3) is provided on both sides of the negative electrode sheet (2) in the thickness direction, a positive electrode protection layer (24) is provided on the inner side of the first bent portion (23), and the positive electrode protection layer (24) is provided between the negative electrode sheet (2) and the diaphragm (3); the positive electrode protection layer (24) is any one of a single-sided protective adhesive, a double-sided protective adhesive or a ceramic insulating layer.

8. The wound battery cell according to claim 7, characterized in that: One end of the third layer segment (11) away from the second bent portion (13) is arranged opposite to the positive electrode protection layer (24) inside the first bent portion (23).

9. The wound battery cell according to claim 1, characterized in that: The first layer segment (21) and the third layer segment (11) are bonded to each other to form the innermost circle of the wound battery core.

10. The wound battery cell according to claim 1, characterized in that: The axial spacing distance between the front end of the first layer segment (21) away from one end of the first bent portion (23) and the negative electrode protective layer (14) is A, and the value range of A is 0<A≤50mm.

11. The wound battery cell according to claim 10, characterized in that: A double-sided empty foil area is provided at the starting end of the first layer section (21) away from one end of the first bent portion (23), and the empty length thereof is B, and the value range of B is 0<B≤10mm.

12. The wound battery cell according to claim 11, characterized in that: The protection length of the negative electrode protection layer (14) after being symmetrically bent and coated on the second bent portion (13) is C, satisfying the following relationship: C≥A+B.

13. A battery, characterized in that: The invention comprises a wound battery cell as described in any one of claims 1 to 12.

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