Battery cell structure and battery

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a battery cell structure and a battery. The negative plate comprises a first negative straight area, a second negative straight area and a fourth negative straight area. And the positive plate comprises a positive first straight region positioned between the negative second straight region and the negative fourth straight region. The first cathode straight area is provided with a first cathode active material section, so that the thickness difference defect of the head of the battery cell is overcome, and the flatness of the battery cell structure is improved. The invention also provides a battery.

Description

Technical Field

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

[0002] Lithium-ion batteries are a new type of chemical power source with advantages such as high energy density, high power density, and long life. They are widely used in electric vehicles, mobile communications, portable electronic devices, and other fields. A common form of lithium-ion battery electrode assembly is the wound cell. During its production, the positive electrode sheet, negative electrode sheet, and separator are wound together using a winding machine. Adjacent positive and negative electrode sheets are isolated by the separator. Wound cells offer advantages such as compact structure, low cost, and high production efficiency. However, the overhang design of the head causes the negative electrode sheet to extend beyond the positive electrode sheet in the longitudinal direction, affecting the flatness of the cell. The negative electrode sheet on the inner winding is prone to excessive bending, resulting in powder loss.

[0003] Therefore, how to effectively avoid lithium deposition in the arc area of the wound battery cell has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0004] In order to solve the problems and shortcomings of the prior art, the present invention provides a battery cell structure and a battery. The battery cell structure includes a positive electrode sheet, a negative electrode sheet, and a separator, wherein the separator is used to separate the positive electrode sheet from the negative electrode sheet. The positive electrode sheet, the negative electrode sheet, and the separator are wound into a battery cell structure having a straight area and a bent area; The negative electrode sheet has an A side and a B side, wherein the A side is located outside the winding of the negative electrode sheet, and the B side is located inside the winding of the negative electrode sheet; the negative electrode sheet includes a first negative straight region, a first negative bent region, a second negative straight region, a second negative bent region, a third negative straight region, a third negative bent region, and a fourth negative straight region, which are arranged in sequence from the head thereof; The positive electrode sheet includes a first positive straight area, the first positive straight area is located at the head of the positive electrode sheet; the first positive straight area is located between the second negative straight area and the fourth negative straight area; The A surface of the negative electrode first straight area has a first negative electrode active material segment, and the projection of the first negative electrode active material segment on the negative electrode second straight area is located between the projection of the head of the positive electrode first straight area on the negative electrode second straight area and the negative electrode first bending area.

[0005] Optionally, the projection of the first straight region of the negative electrode on the second straight region of the negative electrode is partially located within the range of the projection of the first straight region of the positive electrode on the second straight region of the negative electrode; Optionally, the B surface of the third flat region of the negative electrode has a second negative electrode active material segment, and the projection of the second negative electrode active material segment on the fourth flat region of the negative electrode is located between the projection of the head of the first flat region of the positive electrode on the fourth flat region of the negative electrode and the third bent region of the negative electrode.

[0006] Optionally, the length of the first negative electrode active material segment is 60% to 100% of the distance from the head of the first flat region of the positive electrode to the first bent region of the negative electrode.

[0007] Optionally, the B surfaces of the first flat region of the negative electrode and the second flat region of the negative electrode are not coated with negative electrode active material; Except for the part where the second negative electrode active material segment is provided, the B surface of the third flat region of the negative electrode is not coated with negative electrode active material; Except for the part where the first negative electrode active material segment is provided, the A surface of the first flat region of the negative electrode is not coated with negative electrode active material.

[0008] Optionally, the B surfaces of the first bent region of the negative electrode, the second bent region of the negative electrode, and the third bent region of the negative electrode are not coated with negative electrode active material; The A surface of the first bent region of the negative electrode is not coated with negative electrode active material.

[0009] Optionally, the thickness of the negative electrode active material layer on the A surfaces of the second bent region and the third bent region of the negative electrode is less than the thickness of the negative electrode active material layer on the A surface of the flat region of the negative electrode sheet.

[0010] Optionally, the thickness of the negative electrode active material layer on the A surfaces of the second bent region and the third bent region of the negative electrode sheet is 30% to 90% of the thickness of the negative electrode active material layer on the A surface of the flat region of the negative electrode sheet.

[0011] Optionally, the thickness of the negative electrode active material layer on the A surfaces of the second bent region and the third bent region of the negative electrode sheet is 70% to 90% of the thickness of the negative electrode active material layer on the A surface of the flat region of the negative electrode sheet.

[0012] The present invention also provides a battery, and the battery includes the battery cell structure described in any one of the above.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: By adopting the Overhang design at the head of the battery cell, the negative electrode sheet extends beyond the positive electrode sheet in the length direction. While ensuring sufficient position for lithium intercalation, a first negative electrode active material segment is provided in the first flat region of the negative electrode to make up for the thickness difference defect at the head of the battery cell and improve the flatness of the battery cell structure.

[0014] Those skilled in the art will better understand the above and other objects, advantages and features of the present invention from the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings. Description of the Drawings

[0015] Some specific embodiments of the present invention will be described in detail hereinafter with reference to the accompanying drawings in an exemplary but not limiting manner. The same reference numerals in the drawings denote the same or similar components or parts. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 is a schematic structural view of a cell structure according to an embodiment of the present invention; Figure 2 is a partial structural view of a cell structure according to an embodiment of the present invention; Figure 3 is a view of the B side of a negative electrode sheet according to an embodiment of the present invention; Figure 4 is a view of the A side of a negative electrode sheet according to an embodiment of the present invention.

[0016] In the figure: 10 - negative electrode sheet, 10A - A side, 10B - B side, 11 - first flat region of the negative electrode, 111 - first negative electrode active material segment, 112 - first bending region of the negative electrode, 13 - second flat region of the negative electrode, 14 - second bending region of the negative electrode, 15 - third flat region of the negative electrode, 151 - second negative electrode active material segment, 16 - third bending region of the negative electrode, 17 - fourth flat region of the negative electrode; 20 - positive electrode sheet, 21 - first flat region of the positive electrode. Detailed Embodiments

[0017] The following will refer to Figures 1 to 4 to describe the cell structure and battery of the embodiments of the present invention. In the description of this embodiment, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features, that is, including one or more of such features. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined. When a certain feature "includes or contains" a certain or certain features it covers, unless otherwise specifically described, this indicates that other features are not excluded and other features may be further included.

[0018] In the description of this embodiment, the descriptions with reference to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0019] The length of the positive electrode sheet of the winding head needs to be about 3 mm shorter than that of the negative electrode sheet to ensure that there is enough space for lithium ions to embed during the charging process. However, this suspension will bring flatness defects to the wound battery cell, and the thicker the positive electrode sheet, the more serious the defects in the suspended area of the head. It is not conducive to the formation of a stable and uniform interface film during the hot pressing and formation of the battery cell, and problems such as lithium deposition are likely to occur during long-term charge and discharge at high energy density and high rate, which need to be improved.

[0020] For the first three folds of the inner winding of the wound battery cell, due to almost being folded in half, powder falling is likely to occur. During the repeated vacuum pumping in the liquid injection process, the powder falling will be transferred between the winding core and the aluminum-plastic film to form bumps, resulting in poor appearance of the battery cell.

[0021] Figure 1 is a schematic diagram of the battery cell structure according to an embodiment of the present invention. As Figure 1 shown, and in combination with Figures 2 to 4 , the present invention provides a battery cell structure and a battery. The above battery cell structure includes a positive electrode sheet 20, a negative electrode sheet 10, and a separator. The positive electrode sheet 20 and the negative electrode sheet 10 are spaced apart by the separator, and the positive electrode sheet 20, the negative electrode sheet 10, and the separator are wound into a battery cell structure with a flat area and a bent area. The negative electrode sheet 10 has an A surface 10A and a B surface 10B. The A surface 10A is located on the outer side of the winding of the negative electrode sheet 10 (i.e., the side of the negative electrode sheet 10 wrapped by the positive electrode sheet 20), and the B surface 10B is located on the inner side of the winding of the negative electrode sheet 10 (i.e., the side of the negative electrode sheet 10 wrapping the positive electrode sheet 20); the negative electrode sheet 10 includes a first negative electrode flat area 11, a first negative electrode bent area 12, a second negative electrode flat area 13, a second negative electrode bent area 14, a third negative electrode flat area 15, a third negative electrode bent area 16, and a fourth negative electrode flat area 17 arranged in sequence from its head. The positive electrode sheet 20 includes a first positive electrode flat area 21, and the first positive electrode flat area 21 is located at the head of the positive electrode sheet 20; the first positive electrode flat area 21 is located between the second negative electrode flat area 13 and the fourth negative electrode flat area 17. The A surface 10A of the first negative electrode flat area 11 has a first negative electrode active material section 111, and the projection of the first negative electrode active material section 111 on the second negative electrode flat area 13 is located between the projection of the head of the first positive electrode flat area 21 on the second negative electrode flat area 13 and the first negative electrode bent area 12.

[0022] Specifically, when winding to prepare the battery cell structure, the negative electrode sheet 10 is pre-wound to obtain a first flat region 11 of the negative electrode, a first bending region 12 of the negative electrode, a second flat region 13 of the negative electrode, and a second bending region 14 of the negative electrode. The positive electrode sheet 20 is wound. The first flat region at the starting end of the winding of the positive electrode sheet 20 is the first flat region 21 of the positive electrode, and the head of the positive electrode sheet 20 is located behind the winding of the second bending region 14 of the negative electrode along the winding direction. A first negative electrode active material segment 111 is provided in the first flat region 11 of the negative electrode, and the projection of the first negative electrode active material segment 111 on the second flat region of the negative electrode is located between the projection of the head of the first flat region 21 of the positive electrode on the second flat region 13 of the negative electrode and the first bending region 12 of the negative electrode.

[0023] In this embodiment, by providing the first negative electrode active material segment 111 in the first bending region 12 of the negative electrode, the gap formed by the suspension of the second flat region 13 of the negative electrode sheet 10 between the head of the positive electrode sheet 20 and the first bending region 12 of the negative electrode can be filled, the flatness defect of the battery cell can be improved, which is beneficial to the formation of a stable and uniform interface film during hot pressing and formation of the battery cell structure, and the lithium deposition during long-term charge and discharge at high energy density and high rate of the battery cell structure can be improved.

[0024] In some embodiments of the present invention, the projection of the first flat region 11 of the negative electrode on the second flat region 13 of the negative electrode is partially located within the projection range of the first flat region 21 of the positive electrode on the second flat region 13 of the negative electrode.

[0025] In this embodiment, the projection of the head of the first flat region 11 of the negative electrode on the second flat region 13 of the negative electrode is located within the projection range of the first flat region 21 of the positive electrode on the second flat region 13 of the negative electrode. That is to say, there is partial overlap between the projections of the first flat region 11 of the negative electrode and the first flat region 21 of the positive electrode on the second flat region 13 of the negative electrode. A partial empty foil region is reserved at the head of the first flat region 11 of the negative electrode to prevent powder dropping at the head of the negative electrode sheet 10.

[0026] In some embodiments of the present invention, the B surface 10B of the third flat region 15 of the negative electrode has a second negative electrode active material segment 151, and the projection of the second negative electrode active material segment 151 on the fourth flat region 17 of the negative electrode is located between the projection of the head of the first flat region 21 of the positive electrode on the fourth flat region 17 of the negative electrode and the third bending region 16 of the negative electrode.

[0027] In this embodiment, by providing the second negative electrode active material segment 151 on the B surface 10B of the third flat region 15 of the negative electrode, the gap formed by the suspension of the second flat region 13 of the negative electrode sheet 10 between the head of the positive electrode sheet 20 and the first bending region 12 of the negative electrode is further filled, so as to better improve the flatness of the battery cell structure.

[0028] In some embodiments of the present invention, the length of the first negative electrode active material segment 111 is 60% to 100% of the distance from the head of the first straight region 21 of the positive electrode to the first bent region 12 of the negative electrode.

[0029] In this embodiment, the length of the first negative electrode active material segment 111 is 60% to 100% of the distance from the head of the first straight region 21 of the positive electrode to the first bent region 12 of the negative electrode. Specifically, it can be any value between 60% and 100%, such as 60%, 70%, 80%, 95%, 100%, etc. If the length of the first negative electrode active material segment 111 is too short, it cannot fill the space between the head of the first straight region 21 of the positive electrode and the first bent region 12 of the negative electrode, and cannot well improve the flatness of the battery cell structure. If the length of the first negative electrode active material segment 111 is too long, exceeding the distance between the head of the first straight region 21 of the positive electrode and the first bent region 12 of the negative electrode, the first negative electrode active material segment 111 will be opposite to the first straight region 21 of the positive electrode, and the thickness of the battery cell structure at the relative position of the first negative electrode active material segment 111 and the first straight region 21 of the positive electrode will increase, and a step will be formed at the relative part of the first negative electrode active material segment 111 and the first straight region 21 of the positive electrode, and the flatness of the battery cell structure cannot be improved.

[0030] In some embodiments of the present invention, the B surface 10B of the first straight region 11 of the negative electrode, and the A surface 10A and B surface 10B of the second straight region 13 of the negative electrode are not coated with negative electrode active material. The B surface 10B of the third straight region 15 of the negative electrode is not coated with negative electrode active material except for the part where the second negative electrode active material segment 151 is provided. The A surface 10A of the first straight region 11 of the negative electrode is not coated with negative electrode active material except for the part where the first negative electrode active material segment 111 is provided.

[0031] In this embodiment, the A surface 10A of the first straight region 11 of the negative electrode, the B surface 10B of the first straight region 11 of the negative electrode, the A surface 10A and B surface 10B of the second straight region 13 of the negative electrode, and the B surface 10B of the third straight region 15 of the negative electrode do not correspond to the positive electrode active material layer of the positive electrode sheet. Therefore, these parts are not coated or less coated with negative electrode active material, which not only avoids waste of negative electrode active material, but also helps to improve the energy density of the battery cell structure. The arrangement of the first negative electrode active material segment 111 and the second negative electrode active material segment 151 can fill the gap between the head of the first straight region 21 of the positive electrode and the second bent region 14 of the negative electrode, and fill this part of the space. Thereby improving the flatness of the battery cell structure.

[0032] In some embodiments of the present invention, the B surface 10B of the first bent region 12 of the negative electrode, the B surface 10B of the second bent region 14 of the negative electrode, and the B surface 10B of the third bent region 16 of the negative electrode are not coated with negative electrode active material. The A surface 10A of the first bent region 12 of the negative electrode is not coated with negative electrode active material.

[0033] The first three folds of the negative electrode sheet 10 during the inner winding process are also prone to powder shedding because they are nearly folded in half. In this embodiment, the B-side 10B of the negative electrode first bend region 12, the B-side 10B of the negative electrode second bend region 14, the B-side 10B of the negative electrode third bend region 16, and the A-side 10A of the negative electrode first bend region 12 are not coated with negative electrode active material. This can reduce powder shedding, thereby avoiding the formation of convex spots due to powder shedding, which can cause poor appearance of the battery cell structure. The A-side 10A of the negative electrode first bend region 12 has no positive electrode active material facing it, and the fact that the negative electrode first bend region 12 is not coated with negative electrode active material also helps avoid waste of negative electrode active material and helps improve the energy density of the battery cell structure.

[0034] In some embodiments of the present invention, the thickness of the negative active material layer on the A surface 10A of the negative second bending region 14 and the negative third bending region 16 is smaller than the thickness of the negative active material layer on the A surface 10A of the straight region of the negative electrode sheet 10 .

[0035] In this embodiment, the negative electrode active material layer on the A side 10A of the negative electrode second bending area 14 and the negative electrode third bending area 16 is thinned to release the stress at the bending part of the electrode sheet, reduce the powder loss during the winding of the battery cell structure, and solve the problem of convex spots on the battery cell appearance caused by powder loss during winding.

[0036] In some embodiments of the present invention, the thickness of the negative active material layer on the A surface 10A of the negative second bending region 14 and the negative third bending region 16 is 30% to 90% of the thickness of the negative active material layer on the A surface 10A of the straight region of the negative electrode sheet 10 .

[0037] In this embodiment, the thickness of the negative electrode active material layer on the A-side 10A of the negative electrode second bend region 14 and the negative electrode third bend region 16 is reduced by any value between 10% and 90%, such as 10%, 20%, 40%, 65%, 85%, etc. If the thickness is reduced too much, sufficient embedding space cannot be provided for the lithium ions on the opposing positive electrode sheet 20, resulting in lithium deposition. If the thickness is reduced too little, the stress at the bend of the electrode sheet cannot be released, and powder loss during winding of the battery cell structure cannot be reduced, nor can the problem of bumps on the battery cell caused by powder loss during winding be resolved.

[0038] In some embodiments of the present invention, the thickness of the negative active material layer on the A surface 10A of the negative second bending region 14 and the negative third bending region 16 is 70% to 90% of the thickness of the negative active material layer on the A surface 10A of the straight region of the negative electrode sheet 10 .

[0039] In some embodiments of the present invention, by etching or cleaning the negative electrode active material layer on the A surface 10A of the second negative electrode bending region 14 and the third negative electrode bending region 16, the thickness of the negative electrode active material layer on the A surface 10A of the second negative electrode bending region 14 and the A surface 10A of the third negative electrode bending region 16 is made smaller than the thickness of the negative electrode active material layer on the A surface 10A of the negative electrode flat region.

[0040] In this embodiment, 70% - 90% of the thickness of the negative electrode active material layer on the A surface 10A of the flat region of the negative electrode sheet 10 is used to avoid a reduction in the energy density of the cell structure due to excessive reduction of the negative electrode active material.

[0041] In some embodiments of the present invention, the thinning of the negative electrode active material layer on the A surface 10A of the second negative electrode bending region 14 and the third negative electrode bending region 16 can be obtained by etching or cleaning.

[0042] The present invention also provides a battery, which includes a cell structure as described in any of the above embodiments. The battery of the present application includes a lithium - ion battery, but is not limited to lithium - ion batteries, and is also applicable to other batteries with problems such as the flatness of the cell being affected by the head Overhang design, or the negative electrode sheet of the winding inner ring being easily over - bent resulting in powder falling off.

[0043] The present invention also provides a battery module, which includes a plurality of batteries as described in any of the above embodiments, and the plurality of batteries are connected in series.

[0044] The number of batteries included in the battery module of the present application is multiple, effectively expanding the capacity of the battery module and the application range of the battery module. Those skilled in the art can select an appropriate number according to the application and capacity of the battery module.

[0045] The present invention also provides a battery module, which includes a plurality of batteries as described in any of the above embodiments, and the plurality of batteries are connected in parallel.

[0046] In this embodiment, when the plurality of batteries are connected in parallel, the battery module can obtain a higher battery capacity, and when one battery runs out of energy or fails, it does not affect the continuous power supply of other batteries in the battery module, thus ensuring the continuous operation of the electrical equipment.

[0047] Design the battery module according to the actual situation to make the battery module have more efficient energy transfer.

[0048] The above-mentioned battery can be applied to any electrical device known in the prior art. The electrical device may include, but is not limited to, electronic cigarettes, electronic vaping devices, wireless earphones, floor cleaning robots, drones, laptop computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, head-mounted stereo earphones, video recorders, liquid crystal televisions, hand-held cleaners, portable CD players, mini discs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorized bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0049] The above-mentioned battery module can be applied to any electrical device known in the prior art.

[0050] At this point, those skilled in the art should recognize that although multiple exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications that conform to the principles of the present invention can still be directly determined or derived from the content disclosed in 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 determined to cover all these other variations or modifications.

Claims

1. A battery cell structure, comprising a positive electrode sheet, a negative electrode sheet and a separator, characterized in that, The positive electrode sheet, the negative electrode sheet, and the separator are wound into a battery cell structure having a flat region and a bent region; The negative electrode sheet has an A surface and a B surface. The A surface is located on the outer side of the winding of the negative electrode sheet, and the B surface is located on the inner side of the winding of the negative electrode sheet; the negative electrode sheet includes a first flat region of the negative electrode, a first bent region of the negative electrode, a second flat region of the negative electrode, a second bent region of the negative electrode, a third flat region of the negative electrode, a third bent region of the negative electrode, and a fourth flat region of the negative electrode, which are sequentially arranged from its head; The positive electrode sheet includes a first flat region of the positive electrode, and the first flat region of the positive electrode is located at the head of the positive electrode sheet; the flat region of the positive electrode is located between the second flat region of the negative electrode and the fourth flat region of the negative electrode; The A surface of the first flat region of the negative electrode has a first negative electrode active material segment, and the projection of the first negative electrode active material segment on the second flat region of the negative electrode is located between the projection of the head of the first flat region of the positive electrode on the second flat region of the negative electrode and the first bent region of the negative electrode.

2. The battery cell structure according to claim 1, wherein The projection of the first flat region of the negative electrode on the second flat region of the negative electrode is partially located within the range of the projection of the first flat region of the positive electrode on the second flat region of the negative electrode.

3. The battery cell structure according to claim 1, wherein The B surface of the third flat region of the negative electrode has a second negative electrode active material segment, and the projection of the second negative electrode active material segment on the fourth flat region of the negative electrode is located between the projection of the head of the first flat region of the positive electrode on the fourth flat region of the negative electrode and the third bent region of the negative electrode.

4. The battery cell structure according to claim 1, wherein The length of the first negative electrode active material segment is 60% - 100% of the distance from the head of the first flat region of the positive electrode to the first bent region of the negative electrode.

5. The battery cell structure according to claim 1, wherein Neither the B surface of the first flat region of the negative electrode nor the B surface of the second flat region of the negative electrode is coated with negative electrode active material; Except for the part where the second negative electrode active material segment is provided, the B surface of the third flat region of the negative electrode is not coated with negative electrode active material; Except for the part where the first negative electrode active material segment is provided, the A surface of the first flat region of the negative electrode is not coated with negative electrode active material.

6. The battery cell structure according to claim 1, wherein Neither the B surface of the first bent region of the negative electrode, the B surface of the second bent region of the negative electrode, nor the B surface of the third bent region of the negative electrode is coated with negative electrode active material; The A surface of the first bent region of the negative electrode is not coated with negative electrode active material.

7. The battery cell structure according to claim 1, wherein The thickness of the negative electrode active material layer on the A surface of the second bent region of the negative electrode and the third bent region of the negative electrode is less than the thickness of the negative electrode active material layer on the A surface of the flat region of the negative electrode sheet.

8. The battery cell structure according to claim 1, wherein The thickness of the negative electrode active material layer on the A surface of the second bent region of the negative electrode sheet and the third bent region of the negative electrode sheet is 30% - 90% of the thickness of the negative electrode active material layer on the A surface of the flat region of the negative electrode sheet.

9. The battery cell structure according to claim 1, wherein The thickness of the negative active material layer on the A side of the second bending area and the third bending area of the negative electrode sheet is 70% to 90% of the thickness of the negative active material layer on the A side of the flat area of the negative electrode sheet.

10. A battery, characterized in that, The battery includes the battery cell structure described in any one of claims 1 to 9.

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