Battery cell and lithium ion battery

Abstract

The utility model discloses a battery cell which comprises an anode piece, a cathode piece and a diaphragm, the anode piece, the diaphragm and the cathode piece are sequentially stacked and wound to form the battery cell, a plane part and a bent part are formed in each winding circle of the anode piece, and the cathode piece comprises a winding starting end located at the innermost circle of the battery cell; the diaphragm comprises a base membrane section and a reinforcing membrane section, the reinforcing membrane section is connected with the base membrane section, the puncture resistance of the reinforcing membrane section is greater than that of the base membrane section, and the reinforcing membrane section is positioned at the bending part of the innermost ring of the battery cell and wraps the winding starting end; the probability of direct contact between the anode plate and the cathode plate due to the fact that burrs at the winding starting end pierce the diaphragm is reduced, and the safety risk caused by short circuit of the battery cell is reduced; and the reinforced membrane section is positioned at the bending part of the innermost ring of the battery cell and does not participate in ion transportation, so that the energy density of the battery cell is not lost, and the performance of the battery cell is not influenced. The utility model further discloses a lithium ion battery which comprises a shell and the battery cell, and the battery cell is arranged in the shell.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium ion batteries, in particular to a battery core and a lithium ion battery. Background Art

[0002] Lithium-ion batteries refer to lithium-ion batteries that contain lithium (including metallic lithium, lithium alloys, lithium ions, and lithium polymers) in their electrochemical systems. In recent years, lithium-ion batteries have been widely used in digital products, electric vehicles, energy storage systems, and other fields due to their many advantages such as long cycle life, good safety performance, and rapid charging and discharging.

[0003] At present, in the lithium battery industry, anode sheets, cathode sheets and separators are generally wound into wound cells. When the head of a wound cell is cut, burrs are easily generated at the cut portion of the cell head. Due to the limited head space of the wound cell, when it is subjected to abnormal conditions such as collision or extrusion, the cut portion of the cell head is likely to touch the corner of the cell, causing the burrs at the cut portion to easily pierce the separator, thereby causing the anode sheet and cathode sheet inside the cell to directly contact each other, causing a short circuit inside the cell, affecting the safe use of the cell. Utility Model Content

[0004] The main purpose of the utility model is to provide a battery cell and a lithium ion battery, aiming to solve the technical problem that the existing battery cell is prone to internal short circuit due to burrs piercing the diaphragm.

[0005] To achieve the above-mentioned object, the utility model provides a battery cell, comprising an anode sheet, a cathode sheet and a separator disposed between the anode sheet and the cathode sheet, wherein the anode sheet, the separator and the cathode sheet are stacked and wound in sequence to form the battery cell, and the anode sheet has a flat portion and a curved portion in each winding circle, and the cathode sheet includes a winding start end located at the innermost circle of the battery cell;

[0006] Among them, the diaphragm includes a base film segment and a reinforcement film segment, the reinforcement film segment is connected to the base film segment, and the puncture resistance of the reinforcement film segment is greater than that of the base film segment, and the reinforcement film segment is located at the bending part of the innermost circle of the battery cell and covers the starting end of the winding.

[0007] In some embodiments, the reinforcement film segment and the base film segment satisfy at least one of the following conditions: the thickness of the reinforcement film segment is greater than the thickness of the base film segment, and the material of the reinforcement film segment is different from that of the base film segment.

[0008] In some embodiments, the reinforcement film segment and the base film segment are integrally formed, and the thickness of the reinforcement film segment is greater than the thickness of the base film segment.

[0009] In some embodiments, the thickness of the reinforcement film segment is 20um-40um.

[0010] In some embodiments, the reinforced membrane segment includes a base membrane layer and a thickened adhesive layer, the base membrane layer and the base membrane segment are integrally formed, the thickness of the base membrane layer is equal to the thickness of the base membrane segment, and the thickened adhesive layer is attached to at least one side of the base membrane layer.

[0011] In some embodiments, the thickened adhesive layer is provided on both sides of the base film layer;

[0012] And / or, the thickened glue layer is green glue.

[0013] In some embodiments, the thickness of the thickened adhesive layer is 10um-30um.

[0014] In some embodiments, the base film segment is one of a polyolefin film, a polylinolenic alcohol film, a glass fiber diaphragm, or a ceramic diaphragm;

[0015] And / or, the reinforcing film segment is one of a PE / PP composite film, a PET / PP composite film, a PE / PET composite film or a PP / PE / PP composite film.

[0016] In some embodiments, the length of the reinforcement film segment is 2 mm-4 mm.

[0017] The utility model also provides a lithium ion battery, comprising a shell and the battery core as described above, wherein the battery core is arranged in the shell.

[0018] In the technical solution of the present application, the diaphragm includes a base film segment and a reinforcement film segment, the reinforcement film segment is connected to the base film segment, and the puncture resistance of the reinforcement film segment is greater than that of the base film segment, the reinforcement film segment is located at the bending portion of the innermost circle of the battery cell, and the coated cathode sheet is located at the starting end of the winding of the innermost circle of the battery cell, thereby reducing the probability of the burrs at the starting end of the winding piercing the diaphragm and causing direct contact between the anode sheet and the cathode sheet, thereby reducing the safety risks caused by a short circuit in the battery cell; and the reinforcement film segment is located at the bending portion of the innermost circle of the battery cell, does not participate in the transport of ions, does not lose the energy density of the battery cell, and thus does not affect the performance of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a cross-sectional schematic diagram of a battery cell in one embodiment of the utility model;

[0020] Figure 2 This is a partial enlarged view of the innermost circle of the battery cell in the first embodiment of the utility model;

[0021] Figure 3 This is a partial enlarged view of the innermost circle of the battery cell in the second embodiment of the utility model.

[0022] Description of Figure Numbers:

[0023] Label name Label name 100 Battery Cell 10 Anode 20 Cathode sheet 30 Diaphragm 101 Plane 102 Bending 21 Winding start end 31 Basement membrane segment 32 Strengthening membrane segment 321 Basement membrane layer 322 Thickened glue layer

[0024] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the scheme in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0026] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0027] It should also be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element at the same time. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0028] In addition, the descriptions of "first", "second", etc. in the present utility model are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0029] Please refer to Figure 1 The utility model proposes a battery cell 100, comprising an anode sheet 10, a cathode sheet 20 and a separator 30 arranged between the anode sheet 10 and the cathode sheet 20. The anode sheet 10, the separator 30 and the cathode sheet 20 are stacked and wound in sequence to form the battery cell 100, and the anode sheet 10 is formed with a flat portion 101 and a curved portion 102 in each winding circle, and the cathode sheet 20 includes a winding starting end 21 located at the innermost circle of the battery cell 100.

[0030] Before the battery cell 100 is wound, the cathode sheet 20 is usually cut by a cutter. During this process, burrs are easily generated at the end of the cathode sheet 20. The burrs can easily cause the cathode sheet 20 to pierce the diaphragm 30 at the winding starting end 21, causing the battery cell 100 to short-circuit.

[0031] In order to prevent the cathode sheet 20 from puncturing the diaphragm 30 at the starting end 21 of winding and causing a short circuit in the battery cell 100, the diaphragm 30 provided by the utility model includes a base film segment 31 and a reinforcement film segment 32. The reinforcement film segment 32 is connected to the base film segment 31, and the puncture resistance of the reinforcement film segment 32 is greater than that of the base film segment 31. The reinforcement film segment 32 is located at the innermost bending portion 102 of the battery cell 100 and covers the starting end 21 of winding. That is, after the anode sheet 10, the cathode sheet 20 and the separator 30 are wound to form the battery cell 100, the reinforcing film segment 32 is located at the corner of the battery cell 100. When the corner of the battery cell 100 is collided or squeezed, the reinforcing film segment 32 contacts the winding starting end 21 of the cathode sheet 20, which greatly reduces the probability that the burrs at the winding starting end 21 pierce the separator 30 and cause the anode sheet 10 to directly contact the cathode sheet 20, thereby reducing the safety risk caused by a short circuit in the battery cell 100; and the reinforcing film segment 32 is located at the innermost curved portion 102 of the battery cell 100, does not participate in the transport of ions, does not lose the energy density of the battery cell 100, and thus does not affect the performance of the battery cell 100.

[0032] In some embodiments, the reinforcing film segment 32 and the base film segment 31 meet at least one of the following conditions: the thickness of the reinforcing film segment 32 is greater than the thickness of the base film segment 31, and the material of the reinforcing film segment 32 is different from the material of the base film segment 31. The reinforcing film segment 32 and the base film segment 31 meet the above conditions, which can improve the puncture resistance of the reinforcing film segment 32, thereby reducing the probability that the burr at the winding starting end 21 punctures the separator 30 and causes the anode sheet 10 to directly contact the cathode sheet 20, thereby ensuring the safety of the battery cell 100.

[0033] Please refer to Figure 2 As a first embodiment, the reinforcing film segment 32 and the base film segment 31 are integrally formed, and the thickness of the reinforcing film segment 32 is greater than the thickness of the base film segment 31. In this embodiment, by increasing the thickness of the separator 30 corresponding to the winding start end 21, the probability of the burr at the winding start end 21 piercing the separator 30 can be reduced, thereby avoiding direct contact between the anode sheet 10 and the cathode sheet 20 to cause a short circuit in the battery cell 100.

[0034] In some embodiments, the thickness of the reinforcing film segment 32 is 20um-40um, for example, the thickness of the thickened adhesive layer 322 is 20um, 30um or 40um, which can be set according to actual needs during use. This thickness range ensures that the reinforcing film segment 32 will not affect its function of protecting the diaphragm 30 from being punctured due to being too thin, nor will it affect the winding of the battery cell 100 due to being too thick.

[0035] Please refer to Figure 3 As a second embodiment, the reinforcement film segment 32 includes a base film layer 321 and a thickened adhesive layer 322. The base film layer 321 is integrally formed with the base film segment 31, and the thickness of the base film layer 321 is equal to the thickness of the base film segment 31. The thickened adhesive layer 322 is attached to at least one side of the base film layer 321. In this embodiment, by adding the thickened adhesive layer 322, the thickened adhesive layer 322 is arranged corresponding to the winding starting end 21, which can reduce the probability of the burr at the winding starting end 21 piercing the diaphragm 30, thereby avoiding the direct contact between the anode sheet 10 and the cathode sheet 20 and causing a short circuit of the battery cell 100.

[0036] In some embodiments, thickened adhesive layers 322 are provided on both sides of the base film layer 321 to further reduce the probability of burrs at the winding starting end 21 piercing the diaphragm 30 .

[0037] In some embodiments, the thickened adhesive layer 322 is green adhesive. Green adhesive is composed of polyester film and silicone adhesive system, and is an adhesive tape used for bonding printed circuit boards and films. It has good heat resistance and does not debond, and can protect the diaphragm 30 from being punctured.

[0038] In some embodiments, the thickness of the thickened adhesive layer 322 is 10um-30um, for example, the thickness of the thickened adhesive layer 322 is 10um, 20um or 30um, which can be set according to actual needs during use. This thickness range ensures that the thickened adhesive layer 322 will not affect its function of protecting the diaphragm 30 from being punctured due to being too thin, nor will it affect the winding of the battery cell 100 due to being too thick.

[0039] In some embodiments, the base film segment 31 is one of a polyolefin film, a polylinolenic alcohol film, a glass fiber diaphragm 30 or a ceramic diaphragm 30. When used, it can be set according to actual needs.

[0040] In some embodiments, the reinforcing film segment 32 is one of a PE (polyethylene) / PP (polypropylene) composite film, a PET (Polyethylene terephthalate) / PP composite film, a PE / PET composite film, or a PP / PE / PP composite film. When used, it can be set according to actual needs. These composite films are polymer composite materials with good puncture resistance, which can reduce the probability that the burrs at the winding starting end 21 pierce the diaphragm 30 and cause the anode sheet 10 to directly contact the cathode sheet 20.

[0041] In some embodiments, the length of the reinforcing film segment 32 is 2 mm-4 mm, such as 2 mm, 3 mm or 4 mm, to ensure that the reinforcing film segment 32 can completely cover the burr at the winding start end 21 to prevent the burr from piercing the diaphragm 30. When used, it can be set according to actual needs.

[0042] The utility model also provides a lithium ion battery, comprising a housing and a battery cell 100 as described above, wherein the battery cell 100 is disposed in the housing. Since the lithium ion battery of the utility model adopts all the technical solutions of all the above embodiments, it at least has all the technical effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0043] The above embodiments of the utility model are merely examples for clearly explaining the utility model, and are not intended to limit the implementation methods of the utility model. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the utility model are still within the scope of protection of the utility model.

Claims

1. A battery cell, characterized in that: The battery cell comprises an anode sheet, a cathode sheet and a separator disposed between the anode sheet and the cathode sheet, wherein the anode sheet, the separator and the cathode sheet are stacked and wound in sequence to form the battery cell, and the anode sheet is formed with a flat portion and a curved portion in each winding circle, and the cathode sheet includes a winding start end located at the innermost circle of the battery cell; Among them, the diaphragm includes a base film segment and a reinforcement film segment, the reinforcement film segment is connected to the base film segment, and the puncture resistance of the reinforcement film segment is greater than that of the base film segment, and the reinforcement film segment is located at the bending part of the innermost circle of the battery cell and covers the starting end of the winding.

2. The battery cell according to claim 1, characterized in that: The reinforcing film segment and the base film segment satisfy at least one of the following conditions: the thickness of the reinforcing film segment is greater than the thickness of the base film segment; the material of the reinforcing film segment is different from the material of the base film segment.

3. The battery cell according to claim 2, characterized in that: The reinforcement film segment and the base film segment are integrally formed, and the thickness of the reinforcement film segment is greater than the thickness of the base film segment.

4. The battery cell according to claim 3, characterized in that: The thickness of the reinforcement membrane segment is 20um-40um.

5. The battery cell according to claim 2, characterized in that: The reinforced membrane segment includes a base membrane layer and a thickened adhesive layer. The base membrane layer and the base membrane segment are integrally formed, and the thickness of the base membrane layer is equal to the thickness of the base membrane segment. The thickened adhesive layer is attached to at least one side of the base membrane layer.

6. The battery cell according to claim 5, characterized in that: The thickened adhesive layer is provided on both sides of the base film layer; And / or, the thickened glue layer is green glue.

7. The battery cell according to claim 5 or 6, characterized in that: The thickness of the thickened adhesive layer is 10um-30um.

8. The battery cell according to claim 2, characterized in that: The base membrane segment is one of a polyolefin membrane, a polylinolenic alcohol membrane, a glass fiber membrane or a ceramic membrane; And / or, the reinforcing film segment is one of a PE / PP composite film, a PET / PP composite film, a PE / PET composite film or a PP / PE / PP composite film.

9. The battery cell according to any one of claims 1 to 6, characterized in that: The length of the reinforcement membrane segment is 2 mm-4 mm.

10. A lithium ion battery, characterized in that: The invention comprises a shell and a battery cell as claimed in any one of claims 1 to 9, wherein the battery cell is arranged in the shell.

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