Winding battery cell and battery

Abstract

The utility model discloses a winding battery cell and a battery. The winding battery cell comprises two pole pieces and two diaphragms, the two pole pieces and the two diaphragms are alternately overlapped and wound to form a wound battery cell main body, the wound battery cell main body is provided with a straight area and a corner area, each pole piece comprises a current collector and an active substance layer arranged on the current collector, the active substance layer comprises graphite, each pole piece comprises at least two non-magnetized sections and at least two magnetized sections, and the non-magnetized sections are arranged in the corner area. All the non-magnetized sections and all the magnetized sections are alternately arranged in sequence along the length direction of the pole piece; in each pole piece, the non-magnetized section is located in the straight area, at least part of the magnetized section is located in the corner area, and the graphite orientation degree of the magnetized section is smaller than that of the non-magnetized section, so that the expansion amount of the pole piece in the thickness direction is reduced, lithium precipitation caused by corner extrusion is reduced, namely lithium precipitation in the corner area in the charge-discharge cycle process is reduced, and the charge-discharge performance of the pole piece is improved. And moreover, the arrangement direction of the graphite is changed, so that embedding and separation of lithium ions are facilitated, and the charge-discharge performance is improved.

Description

Technical Field

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

[0002] Some common lithium-ion batteries have wound cells, which consist of two electrodes and two separators. These electrodes and separators are alternately stacked and wound a certain number of times to form the main body of the wound cell. The two electrodes are the positive electrode and the negative electrode. The wound cell has straight areas and corners. During the battery's charge and discharge cycles, lithium deposition is prone to occur in these corners, affecting charge and discharge performance. Utility Model Content

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a wound battery cell that can reduce lithium deposition in the corner area during the charge and discharge cycle and improve the charge and discharge performance.

[0004] The utility model also provides a battery having the wound battery core.

[0005] According to an embodiment of the first aspect of the present invention, a wound battery cell comprises two pole pieces and two separators. The two pole pieces and the two separators are alternately stacked and wound to form a wound battery cell body, wherein the wound battery cell body has a straight region and a corner region, each pole piece comprises a current collector and an active material layer disposed on the current collector, wherein the active material layer comprises graphite, and each pole piece comprises at least two non-magnetized segments and at least two magnetized segments, wherein all the non-magnetized segments and all the magnetized segments are alternately arranged in sequence along the length direction of the pole piece; in each pole piece, the non-magnetized segment is located in the straight region, and the magnetized segment is at least partially located in the corner region, and the graphite orientation degree of the magnetized segment is less than the graphite orientation degree of the non-magnetized segment.

[0006] According to the wound battery cell of the embodiment of the first aspect of the present invention, there are at least the following beneficial effects: the graphite orientation degree of the magnetized segment is less than that of the non-magnetized segment, so that the graphite perpendicular to the current collector in the magnetized segment increases. Since the magnetized segment is at least partially located in the corner area, during the charge and discharge cycle, the original expansion of the pole piece along the thickness direction is partially changed to expansion along the length and width directions of the pole piece, thereby reducing the expansion of the pole piece along the thickness direction and reducing lithium deposition caused by squeezing the corner, that is, reducing lithium deposition in the corner area during the charge and discharge cycle, and changing the arrangement direction of the graphite, which is conducive to the insertion and extraction of lithium ions, thereby improving the charge and discharge performance.

[0007] According to some embodiments of the present invention, one end or both ends of the magnetized segment are located in the straight region.

[0008] According to some embodiments of the present invention, the length of the magnetized segment is A, and the corner radius corresponding to the magnetized segment is R, satisfying: A=πR+0.5mm.

[0009] According to some embodiments of the present invention, both ends of the magnetized segment respectively have extension portions of the same length, and the extension portions are located in the straight region.

[0010] According to some embodiments of the present invention, the lengths of the magnetized segments increase sequentially along the length direction of the pole pieces.

[0011] According to some embodiments of the present invention, the graphite orientation degrees of all the magnetized segments are the same.

[0012] According to some embodiments of the present invention, the graphite orientation degree of the same magnetized segment is the same everywhere.

[0013] According to some embodiments of the present invention, the active material layer is provided on at least one side of the current collector.

[0014] According to some embodiments of the present invention, the corner areas are respectively provided on two opposite sides of the straight area.

[0015] A battery according to an embodiment of the second aspect of the present invention includes the aforementioned wound battery cell.

[0016] The battery according to the embodiment of the second aspect of the present invention has at least the following beneficial effects: due to the use of the above-mentioned wound battery cell, the problem of lithium plating during the charge and discharge cycle is reduced, and the charge and discharge performance is improved.

[0017] Additional aspects and advantages of the present invention will be given in part in the following description and will become apparent from the following description or learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0019] Figure 1 This is a cross-sectional schematic diagram of a wound battery cell according to an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of a pole piece according to an embodiment of the present utility model;

[0021] Figure 3 This is a schematic diagram of a pole piece in a non-magnetized section according to an embodiment of the present invention;

[0022] Figure 4 Schematic diagram of the magnetized segment of the pole piece according to an embodiment of the present invention.

[0023] Reference numerals:

[0024] Pole piece 100, non-magnetized section 110, magnetized section 120, extension portion 121;

[0025] diaphragm 200;

[0026] 300 in the flat area;

[0027] Corner area 400. DETAILED DESCRIPTION

[0028] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0029] In the description of the present invention, it should be understood that descriptions involving orientation, such as the orientation or positional relationship indicated by up, down, etc., are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0030] In the description of this utility model, "a plurality" means more than two. The use of "first" or "second" is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features indicated, or implicitly indicating the order of the technical features indicated.

[0031] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0032] Lithium-ion batteries are widely used in various digital products and mobile devices due to their advantages, such as high energy density, low self-discharge, wide operating temperature range, and low environmental pollution. Lithium-ion batteries include wound lithium-ion batteries and laminated lithium-ion batteries. With the increase of charging rate, existing wound lithium-ion batteries have increasingly obvious battery interface problems, especially those at the corners of the electrode 100. In the wound cells of wound lithium-ion batteries, problems such as the electrode 100 expanding and squeezing the corners and difficulty in lithium ion deintercalation occur at the corners. These problems can cause abnormalities such as lithium deposition at the interface of the wound cell corners, affecting the life of the wound lithium-ion battery.

[0033] Reference Figures 1 to 4The wound battery cell of the embodiment of the present invention includes two pole pieces 100 and two separators 200. The two pole pieces 100 and the two separators 200 are alternately stacked and wound to form a wound battery cell body. The wound battery cell body has a straight region 300 and a corner region 400. Each pole piece 100 includes a current collector and an active material layer disposed on the current collector. The active material layer includes graphite. Each pole piece 100 includes two or more non-magnetized segments 110 and two or more magnetized segments 120. All non-magnetized segments 110 and all magnetized segments 120 are alternately arranged along the length direction of the pole piece 100. In each pole piece 100, the non-magnetized segments 110 are located in the straight region 300, and the magnetized segments 120 are partially or entirely located in the corner region 400. The graphite orientation degree of the magnetized segments 120 is lower than that of the non-magnetized segments 110.

[0034] The graphite orientation degree of the magnetized segment 120 is less than that of the non-magnetized segment 110, so that the graphite perpendicular to the current collector in the magnetized segment 120 increases. Since the magnetized segment 120 is at least partially located in the corner area 400, during the charge and discharge cycle, the original expansion of the pole piece 100 along the thickness direction is partially changed to expansion along the length and width directions of the pole piece 100, thereby reducing the expansion amount of the pole piece 100 along the thickness direction, reducing lithium deposition caused by squeezing the corner, that is, reducing lithium deposition in the corner area 400 during the charge and discharge cycle, and changing the arrangement direction of the graphite, which is conducive to the insertion and extraction of lithium ions, thereby improving the charge and discharge performance.

[0035] Specifically, the degree of graphite orientation is the OI value. When testing the sample, the pole piece 100 is placed in an XRD diffractometer for testing. X-rays are irradiated on the sample and diffracted. The diffraction signal of the

[110] crystal plane collected comes from the graphite perpendicular to the current collector, and the diffraction signals of the

[002] crystal plane and the

[004] crystal plane collected come from the graphite parallel to the current collector. Therefore, the degree of graphite orientation can be obtained by using the ratio of the diffraction peak intensity of the

[002] crystal plane to the diffraction peak intensity of the

[110] crystal plane, OI = I

[002] /

[110] ; or the orientation degree of graphite is obtained by the ratio of the integral area of ​​the

[002] crystal plane to the integral area of ​​the

[110] crystal plane, OI = I

[002] /

[110] ; or the orientation degree of graphite is obtained by the ratio of the diffraction peak intensity of the

[004] crystal plane to the diffraction peak intensity of the

[110] crystal plane, OI = I

[004] /

[110] ; or the orientation degree of graphite is obtained by the ratio of the integral area of ​​the

[004] crystal plane to the integral area of ​​the

[110] crystal plane, OI = I

[004] /

[110] .

[0036] Specifically, when producing the pole piece 100, a wet active material layer is first applied to the current collector. The current collector is then moved along its length through a magnetizing device before being baked in an oven to set its shape. The magnetizing device includes an energized coil that generates a magnetic field when powered on. When the magnetizing device is activated, the graphite in the portion of the pole piece 100 that passes through the magnetizing device is magnetized and undergoes a change in orientation, forming a magnetized segment 120. When the magnetizing device is deactivated, the graphite in the portion of the pole piece 100 that passes through the magnetizing device is not magnetized, forming a non-magnetized segment 110. This results in alternating non-magnetized segments 110 and magnetized segments 120 along the length of the pole piece 100.

[0037] When the magnetizing device magnetizes the graphite in the active material layer, the intensity of the magnetic field has a certain influence on the graphite orientation value. The following example illustrates this:

[0038]

[0039] As can be seen from the table above, when the magnetic field strength is 10,000 gs or above, the graphite orientation of the pole piece 100 decreases significantly. As the magnetic field strength continues to increase, the graphite orientation continues to decrease, but the decrease is not significant. When the magnetic field strength is reduced to 5,000 gs, the change in graphite orientation before and after magnetization is relatively small; when the magnetic field strength is reduced to 3,000 gs, the change in graphite orientation before and after magnetization is even smaller. This shows that magnetic field strength can affect graphite orientation to a certain extent, but if the magnetic field strength is too low, the change in graphite orientation is relatively small.

[0040] Specifically, the number of magnetized segments 120 and non-magnetized segments 110 on the pole piece 100 can be two, three, four or more, and should be selected according to actual production requirements; usually the number of magnetized segments 120 and non-magnetized segments 110 is the same or differs by one, so that the pole piece 100 can be wound in a shape similar to a runway to produce a wound battery cell body; for each full circle increase in the number of winding turns of the wound battery cell body, the pole piece 100 should correspondingly add two magnetized segments 120 and two non-magnetized segments 110.

[0041] Specifically, the above-mentioned graphite is preferably layered graphite.

[0042] In an embodiment, both ends of the magnetizing segment 120 are located in the straight area 300, that is, the length of the magnetizing segment 120 needs to be greater than the corresponding corner length of the pole piece 100 in the corner area 400, so that the magnetizing segment 120 can completely cover the corner area 400, avoiding the problem of insufficient length of the magnetizing segment 120, which leads to lithium deposition at the end. If the length of the magnetizing segment 120 is equal to the corner length, the winding accuracy of the winding device is required to be very precise so that the magnetizing segment 120 and the corner area 400 are exactly aligned when winding. Therefore, the above structure is also conducive to the winding device to wind the production battery cell, reduce excessive winding accuracy requirements, and improve the yield rate. It is understandable that one end of the magnetizing segment 120 can also be located in the straight area 300, and the other end can be located at the junction of the straight area 300 and the corner area 400, so that the magnetizing segment 120 can be partially located in the corner area 400.

[0043] In the embodiment, the length of the magnetized segment 120 is A, and the corresponding corner radius of the magnetized segment 120 is R, satisfying: A = πR + 0.5mm. Since the corner of the magnetized segment 120 in the corner region 400 is a semicircular arc, the calculated length is πR. After testing, it was found that when the length of the magnetized segment 120 is 0.5mm greater than the corresponding corner length, the above requirements can be met, reducing the impact on the winding accuracy of the winding device. That is, the magnetized segment 120 can cover the entire corner region 400 during the winding production process without the magnetized segment 120 being excessively long, thereby reducing production costs. It is understood that the value of the length of the magnetized segment 120 greater than the corresponding corner length can be other values, and those skilled in the art can make specific selections based on actual needs.

[0044] In this embodiment, the magnetized segment 120 has extensions 121 of the same length at each end. The extensions 121 are located in the straight region 300, allowing the magnetized segment 120 to be evenly distributed throughout the corner region 400. Furthermore, the extensions 121 extending from the corner region 400 are of the same length, resulting in a better performance. It is understood that the two extensions 121 of the magnetized segment 120 may also be of different lengths, i.e., the two ends of the magnetized segment 120 may extend from the corner region 400 by different lengths.

[0045] In the embodiment, the length of the magnetized segments 120 increases gradually along the length direction of the pole piece 100. Since the magnetized segments 120 are located in the corner regions 400, during the winding process of the wound battery cell, the radius of the winding corners of the different magnetized segments 120 gradually increases with the number of winding turns. Accordingly, if the magnetized segments 120 need to cover the entire corner regions 400, the length of the magnetized segments 120 should also be gradually increased.

[0046] In the embodiment, the graphite orientation of all the magnetized segments 120 is the same, which makes the production process relatively simple, the process controllability is good, and the use effect is stable.

[0047] In the embodiment, the graphite orientation degree of the same magnetized segment 120 is the same everywhere, which makes the production process relatively simple, the process controllability is good, and the use effect is stable.

[0048] Specifically, the thicker the active material layer of the pole piece 100, the higher the magnetic field required when magnetizing the pole piece 100 to form the magnetized segment 120. When the active material layer becomes thicker, the higher magnetic field can cause the deeper graphite to change its orientation.

[0049] In the embodiment, active material layers are provided on both sides of the current collector. The above-mentioned pole piece 100 meets the requirements of conventional pole pieces 100, resulting in a higher energy density of the battery cell. It is understood that in some embodiments, the active material layer can be provided on only one side of the current collector.

[0050] Specifically, the electrode sheet 100 can be a positive electrode sheet 100 or a negative electrode sheet 100. When the electrode sheet 100 is a positive electrode sheet 100, the current collector is typically made of aluminum foil, and the active material layer may contain, in addition to graphite, active materials such as ternary materials or lithium iron phosphate. When the electrode sheet 100 is a negative electrode sheet 100, the current collector is typically made of copper foil, and the active material layer may contain only graphite or may contain, in addition to graphite, a negative electrode active material such as a silicon-based material.

[0051] In this embodiment, corner regions 400 are provided on opposite sides of the straight region 300. This structure simplifies the winding process of the battery cell. Accordingly, all magnetized segments 120 are also located in the two corner regions 400, meaning that different magnetized segments 120 are located at either end of the straight region 300.

[0052] The utility model also provides a battery using the above-mentioned wound battery cell. Due to the use of the above-mentioned wound battery cell, the problem of lithium plating during the charge and discharge cycle is reduced, and the charge and discharge performance is improved.

[0053] Specifically, the above-mentioned battery is preferably a lithium-ion battery. It is understandable that other types of batteries can also adopt the above-mentioned wound cell structure, which is not limited here.

[0054] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative use of the above terms does 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 any one or more embodiments or examples.

[0055] Although the embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and purpose of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A wound battery cell, characterized in that: include: Two pole pieces (100) and two diaphragms (200), the two pole pieces (100) and the two diaphragms (200) are alternately stacked and wound to form a wound battery core body, the wound battery core body having a straight area (300) and a corner area (400), each pole piece (100) comprising a current collector and an active material layer disposed on the current collector, the active material layer comprising graphite, each pole piece (100) comprising at least two non-magnetized segments (110) and at least two magnetized segments (120), all of the non-magnetized segments (110) and all of the magnetized segments (120) being alternately arranged in sequence along the length direction of the pole piece (100); In each of the pole pieces (100), the non-magnetized segment (110) is located in the straight region (300), the magnetized segment (120) is at least partially located in the corner region (400), and the graphite orientation degree of the magnetized segment (120) is smaller than the graphite orientation degree of the non-magnetized segment (110).

2. The wound battery cell according to claim 1, wherein: One end or both ends of the magnetized segment (120) are located in the straight region (300).

3. The wound battery cell according to claim 2, characterized in that: The length of the magnetized segment (120) is A, and the corner radius corresponding to the magnetized segment (120) is R, satisfying: A=πR+0.5mm.

4. The wound battery cell according to claim 2, wherein: Both ends of the magnetized section (120) respectively have extension portions (121) of the same length, and the extension portions (121) are located in the straight region (300).

5. The wound battery cell according to claim 1, wherein: Along the length direction of the pole piece (100), the length of the magnetized segment (120) increases sequentially.

6. The wound battery cell according to claim 1, wherein: The graphite orientation degree of all the magnetized segments (120) is the same.

7. The wound battery cell according to claim 1, characterized in that: The graphite orientation degree of the same magnetized segment (120) is the same everywhere.

8. The wound battery cell according to claim 1, wherein: The active material layer is disposed on at least one side of the current collector.

9. The wound battery cell according to claim 1, characterized in that: The corner areas (400) are respectively provided on opposite sides of the straight area (300).

10. A battery, characterized in that: The invention comprises the wound battery cell according to any one of claims 1 to 9.

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