A wound cell structure

Abstract

The utility model relates to the technical field of lithium ion battery, especially relates to a winding electric core structure. Winding electric core structure includes positive sheet, negative sheet and diaphragm. Positive sheet, negative sheet and diaphragm are formed arc region and flat region after winding, and the arc region formed by the first bending of positive sheet in the winding process is first arc region, and the inner side of first arc region is opposite to the starting end of negative sheet, and the inner side of first arc region is provided with insulating layer. The insulating layer includes framework layer and first adhesion layer, and the first adhesion layer is towards positive sheet, and the framework layer has first surface and second surface, and the second surface is towards the starting end of negative sheet. First surface and adhesion layer are bonded, can avoid the relative displacement between insulating layer and positive sheet in the winding electric core structure during charge and discharge, thereby can avoid the short circuit of electric core in the use process, and enhances the safety performance of electric core.

Description

Technical Field

[0001] This utility model relates to the field of lithium-ion battery technology, and in particular to a wound cell structure. Background Technology

[0002] Batteries are widely used in portable electronic devices, electric vehicles, power tools, drones, energy storage devices, and other fields. As application environments and conditions become increasingly complex, higher demands are being placed on the energy density of battery cells. Currently, there are methods to improve battery energy density by optimizing the space utilization of wound cell structures. For example, a plug-in cell structure is used, with an insulating layer placed between the inner side of the first arc region of the positive electrode and the starting end of the negative electrode. However, this insulating layer lacks adhesive properties and undergoes relative displacement with the positive electrode during repeated charging and discharging. This fails to provide the intended protection for the wound cell structure, easily leading to performance problems and safety risks.

[0003] Developing a wound cell structure that can improve safety performance without sacrificing battery energy density has become a technical problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0004] The purpose of this invention is to provide a wound battery cell structure that solves the problem of relative displacement between the insulating layer and the positive electrode sheet during the use of the wound battery cell structure after electrolyte injection. This prevents short circuits during battery cell use and enhances the safety performance of the battery cell. To address the problems and shortcomings of the prior art, this invention provides a wound battery cell structure, including a positive electrode sheet, a negative electrode sheet, and a separator.

[0005] The positive electrode, the negative electrode, and the separator are wound to form an arc region and a straight region. The arc region formed by the first bending of the positive electrode during the winding process is the first arc region. The inner side of the first arc region is opposite to the starting end of the negative electrode. An insulating layer is provided on the inner side of the first arc region. The insulating layer is used to block the diffusion of some lithium ions deintercalated from the positive electrode to the starting end of the negative electrode.

[0006] The insulating layer includes a skeleton layer and a first adhesive layer. The skeleton layer has pores. The first adhesive layer faces the positive electrode. The skeleton layer has a first surface and a second surface. The first surface is bonded to the first adhesive layer, and the second surface faces the starting end of the negative electrode.

[0007] Optionally, the insulating layer further includes a second adhesive layer located on the second surface, the second adhesive layer having an adhesion strength of 1.0~3.5N / 25mm, the insulating layer being located between the first arc region and the diaphragm, and the second adhesive layer being bonded to the diaphragm.

[0008] Optionally, the second surface is rough.

[0009] Optionally, when the insulating layer is in a straightened state, the distance between the highest point and the lowest point of the second surface in the direction of the thickness of the insulating layer is 3μm to 5μm.

[0010] Optionally, the skeleton layer has pores;

[0011] The porosity of the insulating layer is 20% to 50%.

[0012] Optionally, the pores are regularly distributed; the distance between any two adjacent pores in the width direction of the diaphragm is 0.5 mm to 2.0 mm; the distance between any two adjacent pores in the length direction of the diaphragm is 1 mm to 2.5 mm.

[0013] Optionally, the cross-section of the pore is circular, and the radius of the pore is 0.05 mm to 0.2 mm.

[0014] Optionally, the length of the insulating layer along the length direction of the diaphragm is not less than the arc length of the first arc region;

[0015] The width of the insulating layer along the width direction of the diaphragm is not less than the width of the first arc region.

[0016] Optionally, the positive electrode has a groove that covers the first arcuate region;

[0017] The depth of the groove is less than or equal to the thickness of the active material layer on the positive electrode sheet;

[0018] The insulating layer is located within the groove and completely covers the first arc area;

[0019] The thickness of the insulating layer is less than or equal to the depth of the groove.

[0020] Optionally, both ends of the groove extend to the flat area adjacent to the first arc area, and the length of either end of the groove extending to the flat area is 0.1 mm to 1.0 mm.

[0021] Optionally, the arc region formed by the first bending of the negative electrode during the winding process is the second arc region; the head of the separator is pre-wound in the gap between the second arc region and the head of the positive electrode.

[0022] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0023] The first adhesion layer of the insulating layer faces the positive electrode and is bonded to the positive electrode. This can prevent relative displacement between the insulating layer and the positive electrode during the charging and discharging process of the wound cell structure, thereby avoiding short circuits during use and enhancing the safety performance of the wound cell structure. Furthermore, the pores in the skeleton layer can increase the liquid retention capacity of the cell, thereby improving the long-term cycle performance of the cell.

[0024] The above and other objects, advantages and features of this utility model will become more apparent to those skilled in the art from the following detailed description of specific embodiments of this utility model in conjunction with the accompanying drawings. Attached Figure Description

[0025] The following sections will describe some specific embodiments of the present invention in a detailed manner by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or components. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0026] Figure 1 This is a schematic diagram of the structure of one embodiment of the present invention;

[0027] Figure 2 This is a structural schematic diagram of yet another embodiment of the present utility model;

[0028] Figure 3 This is a partial structural schematic diagram of one embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the insulating layer structure of one embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of the insulating layer structure of another embodiment of the present invention;

[0031] Figure 6 This is a structural schematic diagram of one embodiment of the present invention.

[0032] In the diagram: 10-wound cell structure, 101-arc region, 102-flat region; 11-positive electrode sheet, 111-first arc region, 112-groove; 12-negative electrode sheet, 121-second arc region; 13-separator; 14-insulating layer, 141-skeleton layer, 142-first adhesion layer, 143-second adhesion layer. Detailed Implementation

[0033] The following reference Figures 1 to 6This invention describes a wound battery cell structure according to an embodiment of the present invention. In this description, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature, that is, include one or more of that feature. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. When a feature "includes or contains" one or more of the features it encompasses, unless otherwise specifically described, this indicates that other features are not excluded and may be further included.

[0034] In the description of this embodiment, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0035] Figure 1 This is a schematic diagram of a wound battery cell structure according to an embodiment of the present invention. Figure 1 As shown, this utility model discloses a wound battery cell structure. The wound battery cell structure 10 includes a positive electrode 112, a negative electrode 12, and a separator 13. The positive electrode 112, the negative electrode 12, and the separator 13 are wound to form an arc region 101 and a straight region 102. The arc region 101 formed by the first bending of the positive electrode 112 during the winding process is the first arc region 111. The inner side surface of the first arc region 111 (i.e., the bent inner side surface) is opposite to the starting end of the negative electrode 12, and an insulating layer 14 is provided on the inner side surface of the first arc region 111. The insulating layer 14 is used to prevent some lithium ions extracted from the positive electrode 112 from diffusing to the starting end of the negative electrode 12. The insulating layer 14 includes a skeleton layer 141 and a first adhesive layer 142. The skeleton layer 141 has pores. The first adhesive layer 142 faces the positive electrode 112. The skeleton layer 141 has a first surface and a second surface. The first surface is bonded to the first adhesive layer 142, and the second surface faces the starting end of the negative electrode 12.

[0036] Specifically, the first arc region 111 formed during the winding process of the positive electrode 112 is opposite to the starting end of the negative electrode 12, forming an interlocking wound cell structure 10. An insulating layer 14, including a skeleton layer 141 and a first adhesive layer 142, is provided on the inner side of the first arc region 111. The first adhesive layer 142 faces the positive electrode 112, the first surface of the skeleton layer 141 is bonded to the first adhesive layer 142, and the second surface of the skeleton layer 141 faces the starting end of the negative electrode 12.

[0037] In this embodiment, the first adhesion layer 142 of the insulating layer 14 faces the positive electrode 112 and is bonded to the positive electrode 112. This prevents relative displacement between the insulating layer 14 and the positive electrode 112 during charging and discharging of the wound cell structure 10, thereby preventing short circuits during use and enhancing the safety performance of the cell. Pores in the skeleton layer 141 increase the cell's liquid retention capacity, thus improving its long-term cycle performance. Furthermore, the insulating layer 14 in the first arc region 111 also prevents some lithium ions extracted from the positive electrode 112 from diffusing to the starting end of the negative electrode 12, reducing the risk of lithium deposition on the inner surface of the wound cell structure 10 in the first arc region 111, thereby improving the safety of the wound cell structure 10.

[0038] In some embodiments of the present invention, the insulating layer 14 further includes a second adhesive layer 144, which is located on the second surface of the skeleton layer 141. The adhesive force of the second adhesive layer 144 is 1.0~3.5N / 25mm. The insulating layer 14 is located between the first arc region 111 and the diaphragm 13, and the second adhesive layer 144 is bonded to the diaphragm 13.

[0039] In this embodiment, the insulating layer 14 has a three-layer structure, including a middle skeleton layer 141, and a first adhesive layer 142 and a second adhesive layer 144 located on both sides of the skeleton layer 141. The first adhesive layer 142 faces the positive electrode 112, and the second adhesive layer 144 faces the separator 13 and is bonded to the separator 13. The second adhesive layer 144 increases the adhesion of the insulating layer 14 to the first arc region 111 in the wound cell structure 10, reducing the risk of slippage of the insulating layer 14 and thus achieving better insulation.

[0040] In a further embodiment of this invention, the skeleton layer 141 is a PET film or a polyimide film, which increases the selectivity and diversity of all materials for the skeleton layer 141.

[0041] In some embodiments of this invention, the first adhesive layer 142 is either epoxy resin or acrylate.

[0042] In some other embodiments of this invention, the second adhesive layer 144 is either epoxy resin or acrylate.

[0043] In some other embodiments of the present invention, the first adhesive layer 142 and the second adhesive layer 144 are both epoxy resin or acrylate.

[0044] In the above embodiments, the materials used for the first adhesive layer 142 / second adhesive layer 144 can be selected from epoxy resin and acrylate, which increases the selectivity and diversity of all materials for the first adhesive layer 142 and the second adhesive layer 144.

[0045] In some embodiments of this invention, the second surface of the skeleton layer 141 is rough. Specifically, the second surface of the skeleton layer 141 is not smooth. That is, when the insulating layer 14 is in a straightened state, the surfaces of the skeleton layer 141 are not on the same horizontal plane.

[0046] In this embodiment, the second surface of the skeleton layer 141 is rough, which increases the friction between the skeleton layer 141 and the diaphragm 13, making it less likely for the insulating layer 14 to undergo relative displacement when it is in the first arc region 111, further reducing the risk of the insulating layer 14 sliding, thereby improving the insulating effect of the insulating layer 14.

[0047] In some other embodiments of this invention, the second surface of the skeleton layer 141 is rough, and a second adhesive layer 144 is adhered to the second surface. In this embodiment, the roughness of the second surface on which the second adhesive layer 144 is adhered increases the bonding area of ​​the second adhesive layer 144 on the second surface, thereby improving the stability of the insulating layer 14.

[0048] In some embodiments of this utility model, when the insulating layer 14 is in a straightened state, the distance between the highest point and the lowest point of the second surface in the thickness direction of the insulating layer 14 is 3μm~5μm.

[0049] Appropriate roughness can significantly increase the actual contact area between the skeleton layer 141 and the second adhesive layer 144. When the surface of the skeleton layer 141 has certain unevenness, the material of the second adhesive layer 144 can better fill these microscopic depressions, forming a mechanical interlock. If the surface of the skeleton layer 141 is too smooth, the actual contact area is limited, and the second adhesive layer 144 and the skeleton layer 141 are only bonded by intermolecular forces, resulting in low bonding strength and easy peeling under external force. If the surface roughness is too large, excessively high protrusions and deep depressions may prevent the second adhesive layer 144 from uniformly covering and filling the second surface of the skeleton layer 141, thereby forming gaps or bubbles between the second adhesive layer 144 and the second surface, which will also reduce the bonding effect.

[0050] In this embodiment, the distance between the highest and lowest points of the second surface in the thickness direction of the insulating layer 14 is 3μm to 5μm, which is beneficial to increase the bonding area of ​​the second adhesive layer 144 and the second surface, and improve the adhesion and bonding force between them.

[0051] In some embodiments of this invention, the porosity of the insulating layer 14 is 20% to 50%. Specifically, it can be any value between 20% and 50%, such as 20%, 25%, 30%, 35%, 50%, etc. The porosity of the insulating layer 14 refers to the percentage of the pore volume of the insulating layer 14 to the total volume of the insulating layer 14 under natural conditions. It should be noted that the porosity of the insulating layer 14 refers to the effective porosity, that is, the ratio of the sum of the volumes of those interconnected pores that allow electrolyte flow under normal pressure conditions to the total volume of the insulating layer 14.

[0052] If the porosity of the insulating layer 14 is too small, it will limit the wetting range of the electrolyte; if the porosity of the insulating layer 14 is too large, it will reduce the strength of the insulating layer 14. In this embodiment, the porosity of the insulating layer 14 is between 20% and 50%, which can both adsorb and store the electrolyte to improve the performance of the battery cell, and also enable the insulating layer 14 to maintain a high strength.

[0053] In some embodiments of this invention, the pores in the insulating layer 14 are regularly distributed. In this embodiment, the regularly distributed pores in the insulating layer 14 enable the insulating layer 14 to maintain relatively good strength, while also allowing full utilization of the pores in the insulating layer 14, thereby increasing the liquid storage capacity of the insulating layer 14.

[0054] In a further embodiment of the present invention, the distance between any two adjacent pores of the insulating layer 14 in the width direction of the diaphragm 13 is 0.5 mm to 2.0 mm; the distance between any two adjacent pores of the insulating layer 14 in the length direction of the diaphragm 13 is 1.0 mm to 2.5 mm.

[0055] Specifically, the distance between any two adjacent pores in the insulating layer 14 in the width direction of the diaphragm 13 is any value between 0.5 mm and 2.0 mm, such as 0.5 mm, 0.53 mm, 0.85 mm, 1.02 mm, 1.29 mm, 1.5 mm, 1.89 mm, 1.94 mm, etc. Similarly, the distance between any two adjacent pores in the insulating layer 14 in the length direction of the diaphragm 13 is any value between 1.0 mm and 2.5 mm, such as 1.02 mm, 1.29 mm, 1.5 mm, 1.89 mm, 1.94 mm, 2.35 mm, etc.

[0056] If the distance between any two adjacent pores in the insulating layer 14 is too large, the number of pores that can be distributed on the insulating layer 14 will be limited, affecting the porosity of the insulating layer 14. If the distance between any two adjacent pores in the insulating layer 14 is too small, the strength of the insulating layer 14 will decrease. In this embodiment, the distance between any two adjacent pores is set within a suitable range, so that the overall porosity and strength of the insulating layer 14 are balanced.

[0057] In some embodiments of this utility model, the cross-section of the pores in the insulating layer 14 is circular.

[0058] The circular pores allow the stress in the insulating layer 14 to be evenly distributed around the pores when subjected to external forces, thereby avoiding stress concentration and helping to improve the overall strength and stability of the object, and reducing the risk of breakage caused by the pore structure.

[0059] In this embodiment, the cross-section of the pores in the insulating layer 14 is set to be circular, which can improve the strength and overall stability of the insulating layer 14.

[0060] In a further embodiment of this invention, the radius of the pores in the insulating layer 14 is 0.05 mm to 0.2 mm. If the radius of the pores in the insulating layer 14 is too large, it will lead to an increase in the internal pore structure, a decrease in load-bearing capacity, and will also disrupt the internal continuity of the material, reducing its toughness. Furthermore, if the pore size of the insulating layer 14 is too large, the capillary force generated will be smaller, making it easier for liquid to flow out of the pores under gravity, resulting in relatively poor liquid storage stability. If the pore size of the insulating layer 14 is too small, the internal pore structure of the material will be too dense, leading to increased brittleness. Also, if the pore size of the insulating layer 14 is too small, the entry of liquid molecules into the pores may be restricted.

[0061] In this embodiment, the selection of a suitable pore radius for the insulating layer 14 can improve the strength and toughness of the material and allow the electrolyte to be stably stored in the pores.

[0062] In some embodiments of this invention, the length of the insulating layer 14 along the length direction of the diaphragm 13 is not less than the arc length of the first arc region 111. The width of the insulating layer 14 along the width direction of the diaphragm 13 is not less than the width of the first arc region 111.

[0063] In this embodiment, the length and width of the insulating layer 14 are set to increase the coverage area of ​​the insulating layer 14, which better restricts the movement of lithium ions in the first arc region 111 of the positive electrode 112 to the starting end of the negative electrode 12, further reducing the risk of lithium deposition at the starting end of the negative electrode 12 of the wound cell structure 10, and improving the safety performance of the cell.

[0064] In some embodiments of this invention, the positive electrode 112 has a groove 112 that covers the first arc region 111. The depth of the groove 112 is less than or equal to the thickness of the active material layer on the positive electrode 112. An insulating layer 14 is located within the groove 112 and completely covers the first arc region 111. The thickness of the insulating layer 14 is less than or equal to the depth of the groove 112.

[0065] Specifically, a groove 112 is provided on the inner side of the first arc region 111, and the insulating layer 14 is located within the groove 112. This helps to alleviate the problem of excessive enlargement of the wound cell structure 10 due to the presence of the insulating layer 14, thereby mitigating the problem of reduced energy density of the wound cell structure 10 caused by the presence of the insulating layer 14. It should be noted that the depth of the groove 112 can be equal to or less than the thickness of the active material layer on the positive electrode 112.

[0066] In some embodiments of this utility model, the two ends of the groove 112 extend to the flat area 102 adjacent to the first arc area 111, and the length of any end of the groove 112 extending to the flat area 102 is 0.1 mm to 1.0 mm.

[0067] Specifically, one end of the groove 112 can extend into the flat region 102, or both ends of the groove 112 can extend into the flat region 102, with the extension length into the flat region 102 being 0.1 mm to 1.0 mm. In actual production, the extension length can be any value between 0.1 mm and 1.0 mm, such as 0.1 mm, 0.2 mm, or 0.5 mm. If the extension length into the flat region 102 is too long, wrinkles or deformation may occur during the winding process, causing damage to the insulation layer 14, resulting in direct contact between the positive and negative electrode sheets 12 and increasing the risk of short circuits; in addition, it will reduce the length of the positive electrode active material layer, thereby reducing the overall energy density of the wound cell structure 10. If the extension is too short, it cannot completely cover the area that needs insulation, and leakage may occur at the junction of the first arc region 111 and the flat region 102 during cell operation.

[0068] In this embodiment, the extended length setting can reduce the risk of short circuits and avoid leakage.

[0069] In some embodiments of this utility model, the arc region 101 formed by the initial bending of the negative electrode 12 during the winding process is the second arc region 121101. The head of the separator 13 is pre-wound in the gap between the second arc region 121101 and the head of the positive electrode 112.

[0070] In this embodiment, the pre-wound portion of the separator 13 is located between the second arc region 121101 and the head of the positive electrode 112, opposite to the position where the insulating layer 14 is attached to the first arc region 111. Pre-winding the separator 13 helps to balance the thickness of the wound cell structure 10, thereby improving the energy density of the battery.

[0071] Therefore, those skilled in the art should recognize that although many exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and recognized as covering all such other variations or modifications.

Claims

1. A wound battery cell structure, comprising a positive electrode, a negative electrode, and a separator, characterized in that, The positive electrode, the negative electrode, and the separator are wound to form an arc region and a straight region. The arc region formed by the first bending of the positive electrode during the winding process is the first arc region. The inner side of the first arc region is opposite to the starting end of the negative electrode. An insulating layer is provided on the inner side of the first arc region. The insulating layer is used to block the diffusion of some lithium ions deintercalated from the positive electrode to the starting end of the negative electrode. The insulating layer includes a skeleton layer and a first adhesive layer. The skeleton layer has pores. The first adhesive layer faces the positive electrode. The skeleton layer has a first surface and a second surface. The first surface is bonded to the first adhesive layer, and the second surface faces the starting end of the negative electrode.

2. The wound cell structure according to claim 1, characterized in that, The insulating layer further includes a second adhesive layer located on the second surface. The adhesive force of the second adhesive layer is 1.0~3.5N / 25mm. The insulating layer is located between the first arc region and the diaphragm, and the second adhesive layer is bonded to the diaphragm.

3. The wound cell structure according to claim 1 or 2, characterized in that, The second surface is rough.

4. The wound cell structure according to claim 3, characterized in that, When the insulating layer is in a straightened state, the distance between the highest and lowest points of the second surface in the direction of the thickness of the insulating layer is H, where H = 3 μm ~ 5 μm.

5. The wound cell structure according to claim 1, characterized in that, The porosity of the insulating layer is 20% to 50%.

6. The wound cell structure according to claim 5, characterized in that, The pores are regularly distributed; the distance between any two adjacent pores in the width direction of the diaphragm is D1, where D1 = 0.5 mm to 2.0 mm; the distance between any two adjacent pores in the length direction of the diaphragm is D2, where D2 = 1 mm to 2.5 mm.

7. The wound cell structure according to claim 5, characterized in that, The cross-section of the pore is circular, and the radius of the pore is R, where R = 0.05 mm to 0.2 mm.

8. The wound cell structure according to claim 1, characterized in that, The length of the insulating layer along the length direction of the diaphragm is not less than the arc length of the first arc region; The width of the insulating layer along the width direction of the diaphragm is not less than the width of the first arc region.

9. The wound cell structure according to claim 1, characterized in that, The positive electrode sheet has a groove that covers the first arc region; The depth of the groove is less than or equal to the thickness of the active material layer on the positive electrode sheet; The insulating layer is located within the groove and completely covers the first arc area; The thickness of the insulating layer is less than or equal to the depth of the groove.

10. The wound cell structure according to claim 9, characterized in that, The two ends of the groove extend to the straight area adjacent to the first arc area, and the length of the groove extending to the straight area from any end of the groove is L, where L = 0.1 mm to 1.0 mm.

11. The wound cell structure according to claim 1, characterized in that, The arc region formed by the first bending of the negative electrode during the winding process is the second arc region; the head of the diaphragm is pre-wound in the gap between the second arc region and the head of the positive electrode.

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