Winding type battery

Abstract

The utility model relates to the technical field of batteries, in particular to a winding type battery, which comprises a battery cell and a battery shell, the battery cell comprises a positive plate and a negative plate which are wound mutually, the positive plate comprises a positive current collector and positive active material layers coated on two surfaces of the positive current collector in the thickness direction, and the negative plate comprises a negative current collector and a positive active material layer coated on the negative active material layer. The positive electrode current collector comprises an empty foil section and a coating section which are connected with each other, the positive electrode active material layer is arranged on the coating section, the empty foil section is not coated with the positive electrode active material layer and is provided with a positive electrode lug, the distance between the positive electrode lug and the positive electrode active material layer is L, the width of the positive electrode lug is A, the perimeter of the battery cell is D, and L is more than 0 and less than or equal to D / 4-A / 2. And the negative plate is supported by controlling the position of the positive tab, so that the negative plate is prevented from being broken under the action of shearing force when the battery is expanded.

Description

Technical Field

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

[0002] As modern technology becomes better and better, the demand for battery energy density and endurance continues to increase. To this end, technicians are constantly developing batteries that can be embedded with more lithium ions, thereby increasing the energy density of batteries to meet people's needs.

[0003] However, when the battery is embedded with more lithium ions, the battery's expansion rate increases, resulting in the battery breaking after repeated expansion and contraction during charging and discharging, and this breaking phenomenon will cause the battery to fail directly.

[0004] Based on this, it is urgent to invent a wound battery. Utility Model Content

[0005] One of the purposes of the present invention is to provide a wound battery to address the deficiencies of the prior art, which can provide support for the pole pieces and prevent them from breaking when the battery expands.

[0006] To solve the above technical problems, this application adopts the following technical solutions:

[0007] A wound battery is provided, characterized in that it includes a battery cell and a battery casing, wherein the battery cell includes a positive electrode sheet and a negative electrode sheet wound around each other, the positive electrode sheet includes a positive electrode collector and a positive electrode active material layer coated on both surfaces of the positive electrode collector in the thickness direction, the positive electrode collector includes a connected empty foil segment and a coated segment, the positive electrode active material layer is arranged in the coated segment, the empty foil segment is not coated with the positive electrode active material layer and is provided with a positive electrode ear, the distance between the positive electrode ear and the positive electrode active material layer is L, the width of the positive electrode ear is A, and the circumference of the battery cell is D, which satisfy the relationship: 0<L≤D / 4-A / 2.

[0008] Specifically, the width A of the positive electrode tab is 5% to 12% of the circumference D of the battery cell.

[0009] Specifically, adhesive paper is provided on the empty foil segment, and part of the adhesive paper extends from the empty foil segment to the positive electrode active material layer on the surface of the coated segment. The length of the adhesive paper provided on the positive electrode active material layer is 0.1 mm to 2 mm.

[0010] Specifically, a positive electrode active material layer is coated on the coating section, the thickness of the positive electrode sheet at the coating section is d1, the sum of the thicknesses of the positive electrode tab, the positive electrode current collector and the adhesive tape is d2, and they satisfy the relationship: 0.5d1<d2<1.5d1.

[0011] Specifically, a positive electrode active material layer is coated on the coating section, the thickness of the positive electrode sheet at the coating section is d1, the sum of the thicknesses of the positive electrode tab, the positive electrode current collector and the adhesive tape is d2, and they satisfy the relationship: d1=d2.

[0012] Specifically, the distance between the battery casing and the battery core is 0.01 mm to 0.5 mm.

[0013] Specifically, the positive electrode tab is arranged in the middle of the empty foil segment.

[0014] Specifically, the positive electrode tab is arranged on a side of the positive electrode current collector away from the center of the battery cell.

[0015] Specifically, the negative electrode sheet includes a negative electrode current collector, and the negative electrode current collector is a copper foil, and the wound battery ends with the negative electrode current collector.

[0016] Specifically, the positive electrode active material layers coated on both sides of the thickness of the positive electrode current collector are aligned at both ends, and the negative electrode active material layers are coated on both sides of the thickness of the negative electrode current collector. The length of the negative electrode active material layer on the side close to the center of the battery cell is greater than the length of the negative electrode active material layer on the other side; after winding, the outermost circle of the negative electrode active material layer covers the positive electrode active material layer.

[0017] The beneficial effect of the present invention is that the present invention can effectively provide support for the negative electrode sheet by controlling the position of the positive electrode ear, thereby preventing the negative electrode sheet from breaking under the action of shear force when the battery expands, thereby improving the reliability of the battery and extending the service life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0019] Figure 1 This is a schematic structural diagram of the wound battery of the utility model;

[0020] Figure 2 This is one of the structural diagrams of the positive electrode sheet of the utility model;

[0021] Figure 3 This is the second structural diagram of the positive electrode sheet of the utility model

[0022] Among them: 1-positive electrode sheet; 11-positive electrode current collector; 12-positive electrode active material layer; 13-empty foil segment; 14-positive electrode ear; 15-tape; 16-coating segment; 2-negative electrode sheet; 21-negative electrode current collector; 22-negative electrode active material layer; 100-battery cell; 200-battery casing. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present application. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0024] In the description of this utility model, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0025] Although the present application is disclosed as above in terms of a preferred embodiment, it is not intended to limit the claims. Any person skilled in the art may make several possible changes and modifications without departing from the concept of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims of the present application.

[0026] like Figure 1As shown, the applicant found that due to the low insertion speed of lithium ions into the negative electrode during charging and the high-rate charging requirement of the battery, lithium ions are easily precipitated at the negative electrode. Therefore, in order to prevent the CB value (the ratio of the positive-side anode capacity to the cathode capacity) from being too small in the wound battery, which leads to the accumulation and precipitation of lithium ions at the negative electrode, the length of the negative electrode sheet 2 is generally set to be longer than that of the positive electrode sheet 1. Moreover, since the mechanical strength of the active material of the positive electrode sheet 1 is low and the chemical reaction is strong, the positive electrode sheet 1 is generally set between the two negative electrode sheets 2 to prevent the discharge of the two sides from being uneven. Uniform, and the formation of arches causes a large amount of active material to fall off. Therefore, the outermost circle of the wound battery is a longer negative electrode sheet 2, and the second outer circle is a shorter positive electrode sheet 1. At the tail of the positive electrode sheet 1, which is not coated with positive active material, the outermost circle negative electrode sheet 2 is arranged between the second outer circle negative electrode sheet 2 inside the second outer circle positive electrode sheet 1 to form a gap. When the battery expands, the outermost circle negative electrode sheet 2 and the second outer circle negative electrode sheet 2 cannot be supported and will be affected by shear force, which will cause the outermost circle negative electrode sheet 2 and the second outer circle negative electrode sheet 2 to break.

[0027] Therefore, the present application provides support for the negative electrode sheet 2 by setting a positive electrode ear 14 at a position where shear force is generated between the positive electrode sheet 1 of the second outer circle and the negative electrode sheet 2 of the outermost circle, thereby dispersing the shear force and preventing the negative electrode sheet 2 from breaking due to battery expansion.

[0028] like Figure 1-3 As shown, the present application provides a wound battery, characterized in that: it includes a battery cell 100 and a battery casing 200, wherein the battery cell 100 includes a positive electrode sheet 1 and a negative electrode sheet 1 wound with each other, the positive electrode sheet 1 includes a positive electrode collector 11 and a positive electrode active material layer 12 coated on both surfaces of the positive electrode collector 11 in the thickness direction, the positive electrode collector 11 includes a connected empty foil segment 13 and a coated segment 16, the positive electrode active material layer 12 is arranged in the coated segment 16, the empty foil segment 13 is not coated with the positive electrode active material layer 12 and is provided with a positive electrode ear 14, the distance between the positive electrode ear 14 and the positive electrode active material layer 12 is L, the width of the positive electrode ear 14 is A, and the circumference of the battery cell 100 is D, which satisfy the relationship: 0<L≤D / 4-A / 2.

[0029] The tab is the conductive connection part between the internal electrode of the battery and the external circuit. It is usually a flat metal sheet. In order to connect the tab to the current collector, an empty foil segment 13 without active material coating is provided so that the tab can be directly welded to the current collector. Therefore, the thickness of the tab is relatively small at the empty foil segment 13 between the tab and the active material layer. When the battery tab is charged and discharged and lithium ions are inserted and removed, the negative tab 2 in contact with the empty foil segment 13 in the thickness direction of the positive tab 1 cannot be supported, so that the negative tab 2 near these empty foil segments 13 will undergo a large deformation when subjected to the expansion force. After multiple charges and discharges, the negative active material of the negative tab 2 will fall off, or even the negative tab 2 will break, resulting in a decrease in the battery life.

[0030] Among them, when the relationship: 0<L≤D / 4-A / 2 is satisfied, the empty foil segment 13 between the positive electrode ear 14 and the positive electrode active material layer 12 will be affected by the supporting effect of the positive electrode ear 14. When the negative electrode sheet 2 close to the empty foil segment 13 is subjected to an expansion force, it is affected by the supporting effect of the positive electrode ear 14, so that the shear force dispersion deformation of the negative electrode sheet 2 is reduced. When the distance L between the positive electrode ear 14 and the positive electrode active material layer 12 is less than D / 4-A / 2, the angle between the supporting force provided by the positive electrode active material layer 12 at the tail of the positive electrode sheet 1 and the direction of the supporting force provided by the positive electrode ear 14 is less than 90 degrees, so that the negative electrode ear at the empty foil segment 13 between the positive electrode ear 14 and the positive electrode active material layer 12 can be affected by the positive electrode ear 14 and the positive electrode active material layer 12 at the same time, which can disperse the expansion force on the negative electrode sheet, reduce the deformation of the negative electrode sheet, improve the service life of the battery, and prevent belt breakage.

[0031] When the relationship L<0 is satisfied, the positive electrode tab 14 is welded to the positive electrode active material layer 12, which will cause a cold weld and battery performance failure.

[0032] When the relationship L>D / 4-A / 2 is satisfied, the positive electrode tab 14 and the empty foil segment 13 of the positive electrode active material layer will become larger, and the included angle will be greater than 90°, so that the empty foil segment 13 has no tab support function, and the outer negative electrode cannot adhere to the wall, which makes it easier for the inner negative electrode to expand and be stressed. In addition, the shear stress caused by the position of the positive electrode active material on the inner negative electrode is more likely to break.

[0033] As shown in FIG2 , preferably, a tape 15 is provided on the empty foil segment 13. The tape 15 is attached to the surface of the pole ear and the empty foil segment 13 to prevent burrs generated after the pole ear is welded, which puncture the diaphragm and cause a short circuit. A buffer is formed after the tape 15 is attached. The stress generated by the expansion is first transferred to the tape 15 and then to the positive electrode current collector 11, which can disperse the stress on the positive electrode current collector 11. The tape 15 can fill the step formed at the connection between the positive electrode active material layer 12 and the empty foil segment 13, buffering the deformation caused by the thickness difference, increasing the mechanical support of the empty foil segment 13, and improving the current collector fragmentation. The situation is that part of the adhesive paper 15 extends from the empty foil segment 13 to the positive electrode active material layer 12 on the surface of the coating segment 16. The length of the adhesive paper 15 set on the positive electrode active material layer 12 is 0.1mm to 2mm, and the direction of the length is the winding direction of the battery cell 100. Within this range, the adhesive paper 15 will not be too long to block the transmission of lithium ions, ensuring that more active materials can participate in the charging and discharging process of the battery, and the thickness of the adhesive paper 15 will not cause a large gap to be formed between the positive electrode sheet 1 and the negative electrode sheet 2, resulting in uneven stress on the battery cell 100 during the expansion process, thereby causing the electrode sheet to break.

[0034] Illustratively, the length of the adhesive tape 15 disposed on the positive electrode active material layer 12 can be selected from 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm, and 2.0 mm.

[0035] In some embodiments, preferably, the width A of the positive tab 14 is 5% to 12% of the circumference D of the battery cell 100, and the direction of the width of the positive tab 14 is along the winding direction of the battery cell 100. When the width of the positive tab 14 is within the above range, the width of the positive tab 14 will not be too small, resulting in an inability to provide sufficient support for the negative electrode sheet 2 to disperse the stress on the negative electrode sheet 2 when the battery cell 100 expands. The width of the positive tab 14 will not be too large. Since the material of the positive tab 14 is a material with relatively high strength, when the width of the positive tab 14 is too large, the deformation of the positive tab 14 is relatively large during winding. This deformation may cause additional stress between the positive tab 14 and the negative electrode sheet 2, thereby causing the risk of poor contact or short circuit.

[0036] like Figure 3 As shown, preferably, a positive electrode active material layer 12 is coated on the coating section 16, the thickness of the positive electrode sheet 1 at the coating section 16 is d1, and the sum of the thicknesses of the positive electrode ear 14, the positive electrode current collector 11 and the adhesive tape 15 is d2, which satisfy the relationship: 0.5d1<d2<1.5d1. When the thickness d2 of the positive electrode sheet 1 at the positive electrode ear 14 is within the above range, the thickness d2 of the positive electrode sheet 1 at the positive electrode ear 14 will not be too large, thereby reducing the stress generated during expansion due to uneven thickness, and the thickness will not be too small to provide support for the negative electrode sheet 2.

[0037] Preferably, the thickness d1 of the positive electrode sheet 1 at the coating section 16 is equal to the thickness d2 of the positive electrode sheet 1 at the positive tab 14. Since there is no thickness difference, local stress concentration caused by the thickness difference can be effectively avoided, reducing the risk of deformation of the battery cell 100 during charging and discharging.

[0038] Preferably, a battery casing 200 is further included, and the distance between the battery casing 200 and the wound battery is 0.01 mm to 0.5 mm. When the distance between the battery casing 200 and the wound battery is within the above range, it can be ensured that after the battery cell 100 expands, the battery cell 100 can be close to the inner wall of the battery casing 200. When the battery cell 100 is close to the inner wall of the battery casing 200, the battery casing 200 can provide support for the electrode sheet, so that the outermost negative electrode sheet 2 is not easily broken when the battery cell 100 expands.

[0039] like Figure 1 As shown, preferably, the positive electrode ear 14 is arranged in the middle of the empty foil segment 13. This arrangement enables the positive electrode ear 14 to evenly support both sides of the empty foil segment 13, so that the stress generated during the charge and discharge process can be more evenly distributed to the empty foil segment 13, reducing the potential failure caused by stress concentration, thereby reducing the risk of deformation or fracture caused by local stress.

[0040] Preferably, the negative electrode current collector 21 is copper foil, and the wound battery ends with the negative electrode current collector 21. In the wound battery, the outer copper foil can serve as an effective conductive channel to prevent the internal battery material from short-circuiting in the event of a failure, thereby enhancing the safety of the battery.

[0041] Preferably, the positive electrode active material layer 12 coated on both sides of the thickness of the positive electrode collector 11 is aligned at both ends, and the negative electrode active material layer 22 is coated on both sides of the thickness of the negative electrode collector 21. The length of the negative electrode active material layer 22 on one side close to the center of the battery cell 100 is greater than the length of the negative electrode active material layer 22 on the other side; after winding, the negative electrode active material layer 22 of the outermost circle covers the positive electrode active material layer 12, and there is a buffer between the thickness difference between the negative electrode sheet 2 at the empty foil section 13 and the negative electrode sheet 2 at the coated section 16, so that the thickness of the negative electrode sheet 2 is gradually thinned in a step-by-step manner to prevent the thickness difference from being too large and the stress from being too large when the battery cell 100 expands, resulting in the breakage of the electrode sheet. The length of the positive electrode active material layer 12 on the outermost circle of the positive electrode sheet 1 is less than the length of the negative electrode active material layer 22 on the outermost circle of the negative electrode sheet 2 to prevent the CB value (the ratio of the anode capacity to the cathode capacity facing the opposite side) from being too small, resulting in the accumulation and precipitation of lithium ions at the negative electrode.

[0042] Preferably, the positive electrode tab 14 is arranged on the side of the positive electrode current collector 11 away from the center of the battery cell 100. This arrangement is because when the battery casing 200 provides support, the negative electrode sheet 2 in the second outer circle is more likely to break than the negative electrode sheet 2 in the outermost circle. Therefore, this arrangement can better protect the negative electrode sheet 2 in the second outer circle.

[0043] The above description shows and describes several preferred embodiments of the present invention. However, as mentioned above, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. Instead, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the present invention through the above teachings or the techniques or knowledge in the relevant fields. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be protected by the claims appended hereto.

Claims

1. A wound battery, characterized in that: The invention comprises a battery cell (100) and a battery casing (200), wherein the battery cell (100) comprises a positive electrode sheet (1) and a negative electrode sheet (2) wound with each other, the positive electrode sheet (1) comprises a positive electrode current collector (11) and a positive electrode active material layer (12) coated on both surfaces of the positive electrode current collector (11) in the thickness direction, the positive electrode current collector (11) comprises a hollow foil section (13) and a coating section (16) connected to each other, the positive electrode active material layer (12) is arranged in the coating section (16), the hollow foil section (13) is not coated with the positive electrode active material layer (12) and is provided with a positive electrode ear (14), the distance between the positive electrode ear (14) and the positive electrode active material layer (12) is L, the width of the positive electrode ear (14) is A, and the circumference of the battery cell (100) is D, which satisfies the relationship: 0<L≤D / 4-A / 2.

2. The wound battery according to claim 1, wherein: The width A of the positive electrode tab (14) is 5% to 12% of the circumference D of the battery core (100).

3. The wound battery according to claim 1, wherein: A tape (15) is provided on the empty foil segment (13), and part of the tape (15) extends from the empty foil segment (13) to the positive electrode active material layer (12) on the surface of the coating segment (16), and the length of the tape (15) provided on the positive electrode active material layer (12) is 0.1 mm to 2 mm.

4. The wound battery according to claim 3, wherein: The thickness of the positive electrode sheet (1) at the coating section (16) is d1, and the sum of the thicknesses of the positive electrode tab (14), the positive electrode current collector (11) and the adhesive tape (15) is d2, which satisfy the relationship: 0.5d1<d2<1.5d1.

5. The wound battery according to claim 4, wherein: The thickness of the positive electrode sheet (1) at the coating section (16) is d1, and the sum of the thicknesses of the positive electrode tab (14), the positive electrode current collector (11) and the adhesive tape (15) is d2, which satisfy the relationship: d 1＝ d2.

6. The wound battery according to claim 1, wherein: The distance between the battery housing (200) and the battery core (100) is 0.01 mm to 0.5 mm.

7. The wound battery according to claim 1, wherein: The positive electrode tab (14) is arranged in the middle of the empty foil segment (13).

8. The wound battery according to claim 1, wherein: The positive electrode tab (14) is arranged on a side of the positive electrode current collector (11) away from the center of the battery core (100).

9. The wound battery according to claim 1, wherein: The negative electrode sheet (2) comprises a negative electrode current collector (21), and the negative electrode current collector (21) is a copper foil, and the wound battery ends with the negative electrode current collector (21).

10. The wound battery according to claim 9, wherein: The positive electrode active material layer (12) coated on both sides of the thickness of the positive electrode current collector (11) is aligned at both ends, and the negative electrode active material layer (22) is coated on both sides of the thickness of the negative electrode current collector (21), and the length of the negative electrode active material layer (22) on one side close to the center of the battery cell (100) is greater than the length of the negative electrode active material layer (22) on the other side; after winding, the outermost circle of the negative electrode active material layer (22) covers the positive electrode active material layer (12).

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