Battery roll core structure and secondary battery

Abstract

The invention discloses a battery roll core structure and a secondary battery, the battery roll core comprises a first pole piece and a second pole piece opposite to the first pole piece in polarity, and the first pole piece comprises a first winding starting section; the second pole piece comprises a second winding starting section; the first winding starting section is arranged in the first direction, the second winding starting section is arranged in the second direction, and the first direction is opposite to the second direction. Compared with the prior art, the battery roll core structure provided by the invention has the advantages that by changing the winding mode of the innermost ring of the battery roll core, the problem that the pole piece of the innermost ring of the battery roll core is easy to curl is effectively improved, the processing difficulty of the battery roll core is reduced, meanwhile, the thickness of the battery core is reduced, and the volume energy density of a secondary battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary batteries, and in particular to a battery core structure and a secondary battery. Background Art

[0002] Secondary batteries generally include battery cells, electrolytes and battery cases. Among them, battery cells can be divided into laminated battery cells and rolled battery cells. In the field of power lithium batteries, rolled battery cells have certain advantages. As a common battery cell structure, wound battery cells have the advantages of high production efficiency and stable quality, and are widely used in small conventional square batteries and cylindrical batteries. However, in the manufacturing process of wound battery cells, the positive and negative electrodes are wound in the same direction, and the innermost negative electrode often adopts a single-sided coating structure. Although this structural form simplifies the process to a certain extent, it also brings a series of technical problems and challenges:

[0003] 1) When the innermost negative electrode of the wound lithium battery cell adopts a single-sided coating structure, due to the unevenness of the coating and the particularity of the single-sided coating structure, it is easy to cause capacity loss, performance degradation and lithium deposition in this area.

[0004] 2) Due to the particularity of the single-sided coating structure, the stress on both sides of the current collector is inconsistent, which makes it easy to curl. The pole piece and the diaphragm are prone to misalignment and wrinkles during the bonding process, which increases the difficulty of processing and manufacturing, thereby affecting the internal structure and stability of the battery cell.

[0005] 3) Although the negative electrode single-sided coating structure simplifies the process to a certain extent, due to the performance problems and safety hazards it brings, additional process steps and quality control measures are often required to compensate. This not only increases the complexity of the process, but also increases the production cost.

[0006] Therefore, faced with these problems exposed by battery roll cores in practical applications, researchers urgently need to provide a new technical solution to solve the above problems. Summary of the invention

[0007] The purpose of the present invention is to provide a battery core structure, which improves the winding method of the innermost circle of the battery core in the prior art, effectively improves the problem of easy curling of the innermost circle electrode of the battery core, and improves the volume energy density of the battery core.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A battery core structure, comprising:

[0010] A first pole piece and a second pole piece with opposite polarity to the first pole piece, wherein the first pole piece includes a first winding start section; and the second pole piece includes a second winding start section;

[0011] The first winding starting section is arranged along a first direction, and the second winding starting section is arranged along a second direction, and the first direction is opposite to the second direction.

[0012] Preferably, the first pole piece and the second pole piece are both double-sided coating structures.

[0013] Preferably, the first pole piece further includes a first bending section, the first bending section is connected to the first winding start section along the winding direction, and the second winding start section is arranged on the inner side of the first bending section.

[0014] Preferably, the second pole piece further includes a second bending section, the second bending section is connected to the second winding start section along the winding direction, and the first winding start section is arranged on the inner side of the second bending section.

[0015] Preferably, a double-sided protective adhesive is provided on the first bending section, and the double-sided protective adhesive is provided with an A surface and an oppositely arranged B surface, and the A surface is connected to the first bending section.

[0016] Preferably, the battery core structure further includes a first diaphragm and a second diaphragm, and the first diaphragm and the second diaphragm are respectively arranged on two opposite surfaces of the second electrode sheet.

[0017] Preferably, one end of the B surface is connected to the first diaphragm, and the other end is connected to the second diaphragm;

[0018] Alternatively, the B surface is connected to the second diaphragm.

[0019] Preferably, a groove is provided on the surface of the first bending section opposite to the double-sided protective adhesive, and the double-sided protective adhesive is embedded in the groove.

[0020] Preferably, the heat-resistant temperature range of the double-sided protective adhesive is ≥150°C.

[0021] The present invention also provides a secondary battery, comprising the battery core structure described above.

[0022] The beneficial effects of the present invention are as follows: the battery core structure provided by the present invention effectively improves the problem of easy curling of the innermost circle of the battery core by changing the winding method of the innermost circle of the battery core, reduces the processing difficulty of the battery core, and at the same time reduces the thickness of the battery core, thereby improving the volume energy density of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of a battery roll core in one embodiment of the present invention.

[0024] Among them: 1. first pole piece; 11. first winding starting section; 12. first bending section; 2. second pole piece; 21. second winding starting section; 22. second bending section; 3. first diaphragm; 4. second diaphragm; 5. double-sided protective adhesive. DETAILED DESCRIPTION

[0025] In order to make the technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. 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.

[0026] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by technicians in the technical field of this application; the terms used in the specification of this application are only for the purpose of describing specific implementation methods and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned drawings and any variations thereof are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship.

[0027] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0028] The following is combined with Figure 1 The present invention is further described in detail with specific implementation modes, but is not intended to limit the present invention.

[0029] According to a first aspect of the present invention, the present invention provides a battery roll core structure, comprising:

[0030] A first pole piece 1 and a second pole piece 2 having a polarity opposite to that of the first pole piece 1, wherein the first pole piece 1 comprises a first winding start section 11; and the second pole piece 2 comprises a second winding start section 21;

[0031] The first winding start section 11 is arranged along the first direction, and the second winding start section 21 is arranged along the second direction, and the first direction is opposite to the second direction. The present invention effectively improves the problem of easy curling of the innermost circle of the battery core by changing the winding method of the innermost circle of the battery core, reduces the processing difficulty of the battery core, and reduces the thickness of the battery core, thereby improving the volume energy density of the secondary battery.

[0032] In one embodiment of the present invention, the first pole piece 1 and the second pole piece 2 are both double-sided coating structures.

[0033] The first pole piece 1 and the second pole piece 2 both have double-sided coating structures, which have the following advantages:

[0034] 1) Double-sided coating can make full use of both sides of the pole piece, so that the active material coating area is increased, thereby improving the capacity and energy density of the battery. Compared with the structure of the innermost pole piece of the battery core in the prior art with a single-sided coating, the double-sided coating can more effectively utilize the pole piece material and improve the overall performance of the battery. The double-sided coating makes the electron transmission between the positive and negative electrodes more uniform and efficient during the charge and discharge process of the battery, which helps to reduce the internal resistance of the battery, improve the charge and discharge efficiency, and thus extend the service life of the battery.

[0035] 2) In terms of the preparation of battery electrodes, compared with electrodes with alternating single-sided coating and double-sided coating, electrodes with double-sided coating do not require multiple coating and drying operations, thereby saving time and cost, helping to reduce errors and defective rates in the preparation process, and improving the quality and stability of the battery.

[0036] 3) During the battery cell winding process, the double-sided coating structure of the electrode can reduce the misalignment and wrinkling of the battery electrode during the winding or stacking process, thereby reducing the risk of internal short circuits and helping to improve the safety and reliability of the battery.

[0037] In one embodiment of the present invention, the first pole piece 1 further includes a first bending section 12, the first bending section 12 is connected to the first winding start section 11 along the winding direction, and the second winding start section 21 is arranged on the inner side of the first bending section 12. The second winding start section 21 is close to the inner side of the first bending section 12, so that a corresponding active material layer can be provided for the active material layer of the first winding start section 11 to perform subsequent electrode reactions, thereby improving the energy density of the battery.

[0038] In one embodiment of the present invention, the second pole piece 2 further includes a second bending section 22, the second bending section 22 is connected to the second winding start section 21 along the winding direction, and the first winding start section 11 is arranged on the inner side of the second bending section 22. The first winding start section 11 is arranged on the inner side of the second bending section 22, so that a corresponding active material layer can be provided for the active material layer of the second winding start section 21 to perform subsequent electrode reactions, thereby improving the energy density of the battery.

[0039] In one embodiment of the present invention, a double-sided protective adhesive 5 is provided on the first bending section 12 . The double-sided protective adhesive 5 includes a surface A and an opposite surface B. The surface A is connected to the first bending section 12 .

[0040] In one embodiment of the present invention, the battery core structure further includes a first diaphragm 3 and a second diaphragm 4 , and the first diaphragm 3 and the second diaphragm 4 are respectively disposed on two opposite surfaces of the second electrode sheet 2 .

[0041] In one embodiment of the present invention, one end of the B surface is connected to the first diaphragm 3, and the other end is connected to the second diaphragm 4;

[0042] Or, the B surface is connected to the second diaphragm 4. When the first diaphragm 3 and the second diaphragm 4 are respectively connected to the two ends of the B surface of the double-sided protective adhesive 5, the starting ends of the first diaphragm 3 and the second diaphragm 4 are flush with the starting position of the second pole piece 2, and the diaphragm at the starting position of the second pole piece 2 is attached with double-sided adhesive, and the two layers of diaphragms are fixed to cover the second pole piece, which can effectively prevent the diaphragm from wrinkling and shrinking. When only the second diaphragm 4 is connected to the B surface of the double-sided protective adhesive 5, the starting ends of the first diaphragm 3 and the second diaphragm 4 are not flush with the starting position of the second pole piece 2, and the parts of the first diaphragm 3 and the second diaphragm 4 that are longer than the second pole piece 2 are wound in the innermost circle. At this time, it is more commonly used because when the first diaphragm 3 and the second diaphragm 4 are long, on the one hand, it can be convenient for processing and manufacturing, and the existing equipment can be adapted with minor changes; on the other hand, it can increase the safety performance of the battery cell. Since the inner circle diaphragm is long enough, the positive and negative electrodes will not be directly overlapped and short-circuited due to the shrinkage of the diaphragm during the cycle expansion of the battery cell.

[0043] In one embodiment of the present invention, a groove is provided on the surface of the first bending section 12 opposite to the double-sided protective adhesive 5, and the double-sided protective adhesive 5 is embedded in the groove. The double-sided protective adhesive 5 is embedded in the groove, fixing the diaphragm while achieving the effect of not increasing the thickness of the battery cell.

[0044] In one embodiment of the present invention, the heat-resistant temperature range of the double-sided protective adhesive 5 is ≥150°C.

[0046] According to a second aspect of the present invention, a secondary battery is further provided, comprising the battery roll core structure described above.

[0047] According to a third aspect of the present invention, there is also provided an electrical device comprising the above-mentioned secondary battery.

[0048] The electrical device may be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, etc. The vehicle may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc.; the spacecraft includes an airplane, a rocket, a space shuttle and a spacecraft, etc.; the electric toy includes a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy and an electric airplane toy, etc.; the electric tool includes a metal cutting electric tool, a grinding electric tool, an assembly electric tool and an electric tool for railways, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact drill, a concrete vibrator and an electric planer, etc. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical devices.

[0049] The present invention is further described below by means of specific embodiments. The following specific embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0050] Example 1

[0051] The positive electrode sheet with a double-sided coating structure, the negative electrode sheet with a double-sided coating structure, the first separator and the second separator are stacked in sequence and wound to obtain an electrode assembly; the electrode assembly is placed in a packaging shell, and an electrolyte is injected into the packaging shell and packaged to finally obtain a lithium-ion battery. The winding start section of the positive electrode sheet is arranged along a first direction, and the winding start section of the negative electrode sheet is arranged along a second direction, and the first direction is opposite to the second direction.

[0052] Comparative Example 1

[0053] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order and wound to obtain an electrode assembly; the electrode assembly is placed in a packaging shell, and the electrolyte is injected into the packaging shell and packaged to finally obtain a lithium-ion battery. The winding starting sections of the positive electrode sheet and the negative electrode sheet are in the same direction, and the negative electrode sheet in the innermost circle of the battery core is a single-sided coating structure.

[0054] Performance Test:

[0055] The lithium ion batteries of Example 1 and Comparative Example 1 were tested for battery volume energy density. The test results are shown in Table 1.

[0056] Table 1

[0057]

[0058] It can be seen from the test results in Table 1 that the volume energy density of the lithium-ion battery of Example 1 is higher than that of Comparative Example 1, which indicates that the present invention improves the winding method of the innermost circle of the battery core in the prior art, effectively improves the problem of easy curling of the innermost circle electrode of the battery core, and improves the volume energy density of the battery core.

[0059] 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 battery core structure, characterized in that: include: A first pole piece and a second pole piece having a polarity opposite to that of the first pole piece, wherein the first pole piece includes a first winding start section; The second pole piece includes a second winding start section; The first winding starting section is arranged along a first direction, and the second winding starting section is arranged along a second direction, and the first direction is opposite to the second direction.

2. The battery roll core structure according to claim 1, characterized in that: The first pole piece and the second pole piece are both double-sided coating structures.

3. The battery roll core structure according to claim 1, characterized in that: The first pole piece further includes a first bending section, the first bending section is connected to the first winding start section along a winding direction, and the second winding start section is arranged on the inner side of the first bending section.

4. The battery core structure according to claim 1, characterized in that: The second pole piece further includes a second bending section, the second bending section is connected to the second winding start section along the winding direction, and the first winding start section is arranged on the inner side of the second bending section.

5. The battery roll core structure according to claim 3, characterized in that: The first bending section is provided with a double-sided protective adhesive, the double-sided protective adhesive is provided with an A surface and an oppositely arranged B surface, and the A surface is connected to the first bending section.

6. The battery roll core structure according to claim 1, characterized in that: The battery core structure further includes a first diaphragm and a second diaphragm, wherein the first diaphragm and the second diaphragm are respectively disposed on two opposite surfaces of the second pole piece.

7. The battery roll core structure according to claim 6, characterized in that: One end of the B surface is connected to the first diaphragm, and the other end is connected to the second diaphragm; Alternatively, the B surface is connected to the second diaphragm.

8. The battery roll core structure according to claim 5, characterized in that: A groove is arranged on the surface of the first bending section opposite to the double-sided protective adhesive, and the double-sided protective adhesive is embedded in the groove.

9. The battery roll core structure according to claim 5, characterized in that: The heat-resistant temperature range of the double-sided protective adhesive is ≥150°C.

10. A secondary battery, characterized in that: It comprises the battery roll core structure as claimed in any one of claims 1 to 9.

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