A lithium-ion battery core and battery

Abstract

This utility model discloses a lithium-ion battery core and battery, including a positive electrode sheet, a negative electrode sheet, and a separator. The positive electrode sheet, negative electrode sheet, and separator are wound into a core structure. In the core structure, the corner of the innermost first fold of the positive electrode sheet is a blank area of ​​positive electrode powder formed by laser processing, and there is no powder adhering to the blank area. The left side of the blank area is adjacent to the first positive electrode powder area on the positive electrode sheet, and the right side is adjacent to the second positive electrode powder area on the positive electrode sheet. Both the first and second positive electrode powder areas are covered by the negative electrode powder on the negative electrode sheet of the core structure. This utility model reduces the local lithium deposition phenomenon at the corner caused by the imbalance of the N / P ratio of the positive and negative electrode sheets by eliminating the excess positive electrode powder not covered by the negative electrode at the corner, thereby reducing the safety risks caused by lithium deposition at the corner electrode.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, specifically to a lithium-ion battery core and battery. Background Technology

[0002] In lithium-ion batteries, the wound core uses a spiral winding structure where the positive and negative electrodes overlap at the first fold, similar to a snap-fit. The negative electrode sheet at the first fold often cannot be fully inserted into the innermost edge of the core, leaving a gap of 2-5mm between the sheet and the innermost edge. This gap results in the positive electrode powder at the corner not having corresponding negative electrode powder. Simultaneously, after the winding needle is pulled out, the negative electrode sheet tends to retract and fold along the junction of the winding needle's curved and flat surfaces. This retraction and folding also contributes to the gap, specifically manifesting as a lack of corresponding negative electrode coverage in the positive electrode corner powder area, leading to an imbalance in the positive and negative NP ratio. This can cause lithium plating at the corners during long-term charge-discharge use, further resulting in battery surface bulging, a sharp drop in capacity retention, and even fire and explosion. Utility Model Content

[0003] The purpose of this invention is to provide a lithium-ion battery core and battery to solve the above-mentioned problems.

[0004] The technical solution provided by this utility model is:

[0005] A lithium-ion battery core includes a positive electrode sheet, a negative electrode sheet, and a separator, wherein the positive electrode sheet, the negative electrode sheet, and the separator are wound into a core structure.

[0006] In the aforementioned core structure, the corner of the innermost first fold of the positive electrode sheet is a blank area of ​​positive electrode powder formed by laser processing, and there is no powder adhesion on the blank area of ​​positive electrode powder.

[0007] The left side of the blank area of ​​the positive electrode powder is adjacent to the first positive electrode powder area on the positive electrode sheet, and the right side is adjacent to the second positive electrode powder area on the positive electrode sheet. Both the first positive electrode powder area and the second positive electrode powder area are covered by the negative electrode powder on the core structure negative electrode sheet.

[0008] To optimize the above technical solution, the specific measures also include:

[0009] The positive electrode, separator, and negative electrode are spindle-shaped core structures formed by spiral winding, with curved ends and a flat area in the middle.

[0010] In the aforementioned core structure, the distance between the end face of the first fold of the innermost positive electrode sheet and the end face of the first fold of the innermost negative electrode sheet and the vertex of the innermost arc corner of the nearest core structure is 2 to 5 mm.

[0011] The distance between the vertices of the innermost arc corners at both ends of the core structure is 20-110 mm.

[0012] The positive electrode sheet has a thickness of 60–180 μm and a width of 20–140 mm.

[0013] As a preferred embodiment, the blank area of ​​the positive electrode powder is formed by laser removal of a thickness of 22-86 μm on the surface of the positive electrode sheet, and the width of the laser removal is the same as the width of the positive electrode sheet.

[0014] As a preferred embodiment, the length of the blank area of ​​the positive electrode powder is the length of the innermost arc corner at the end of the core structure plus 2 to 4 mm.

[0015] Furthermore, the outermost electrode of the core structure is provided with a finishing tape for securing the core.

[0016] In the described core structure, each stack of positive and negative electrode sheets constitutes a winding layer, and the total number of winding layers in the core structure is greater than or equal to 3 layers and less than or equal to 40 layers.

[0017] This utility model also protects a battery containing the aforementioned lithium-ion battery core.

[0018] Compared with the prior art, the beneficial effects of this utility model are:

[0019] This invention reduces localized lithium plating at corners caused by N / P ratio imbalance due to the removal of excess positive electrode powder not covered by the negative electrode. This lowers the risk of localized battery swelling, bulging, and even fire or explosion caused by lithium plating at corner electrodes. The solution provided by this invention can guide technicians in identifying areas for powder removal, resulting in a more stable and balanced internal battery structure.

[0020] The lithium-ion battery prepared using the core of this invention can be used as a power source for consumer electronics, energy storage systems, and power systems, and is especially suitable for electrical equipment such as aircraft and electric vehicles that require high current and high rate charging and discharging. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the A-structure core before corner powder removal during winding.

[0022] Figure 2 This is a schematic diagram of the A-structure core structure before the corner powder is removed, and the electrode sheet folds after the winding needle is pulled out.

[0023] Figure 3 This is a schematic diagram of the A-structure core after the corner powder has been removed.

[0024] Figure 4This is a schematic diagram of the B-structure core before corner powder removal.

[0025] Figure 5 This is a schematic diagram of the B-structure core after the corner powder has been removed.

[0026] Figure 6 This is a schematic diagram of the C-structure core before corner powder removal.

[0027] Figure 7 This is a schematic diagram of the C-structure core after the corner powder has been removed.

[0028] In the diagram: 1-positive electrode sheet, 2-negative electrode sheet, 3-first protective tape, 4-second protective tape, 5-winding needle, 6-the part of the electrode sheet folded after the winding needle is pulled out, 7-blank area of ​​positive electrode powder, 8-third protective tape. Detailed Implementation

[0029] The present invention will be further described in detail below through embodiments, but it should not be construed as the scope of the present invention being limited to the following embodiments. All technologies implemented based on the present invention fall within the scope of the present invention.

[0030] In the description of this utility model, it should also be noted that:

[0031] The orientations or positional relationships described herein are based on the relationships shown in the accompanying drawings and are only for the purpose of facilitating the description of this utility model and simplifying the description. They are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0032] This utility model provides a lithium-ion battery core, including a positive electrode 1, a negative electrode 2 and a separator, wherein the positive electrode 1, the negative electrode 2 and the separator are wound into a core structure.

[0033] In the core structure, the corner of the innermost first fold of the positive electrode sheet 1 is the blank area 7 of the positive electrode powder formed by laser processing, and there is no powder bonding on the blank area 7 of the positive electrode powder.

[0034] The left side of the blank area 7 of the positive electrode powder is adjacent to the first positive electrode powder area on the positive electrode sheet 1, and the right side is adjacent to the second positive electrode powder area on the positive electrode sheet 1. Both the first positive electrode powder area and the second positive electrode powder area are covered by the negative electrode powder on the negative electrode sheet 2 with the core structure.

[0035] The positive electrode 1, the separator, and the negative electrode 2 are a spindle-shaped core structure formed by spiral winding, with curved structures at both ends and a flat area in the middle.

[0036] In the core structure, the negative electrode sheet often leaves a gap because it cannot be fully inserted into the innermost edge of the core during the first fold. At the same time, after the winding needle is pulled out, the electrode sheet tends to retract and fold along the junction of the curved surface and the plane of the winding needle 5, which also leads to the generation of gaps.

[0037] In some embodiments, in the core structure of this utility model, the distance between the end face of the innermost first folded positive electrode 1 and the end face of the innermost first folded negative electrode 2 and the vertex of the innermost arc corner of the core structure closest to them is 2 to 5 mm.

[0038] The distance between the vertices of the innermost arc corners at both ends of the core structure is 20–110 mm.

[0039] The powder removal of this utility model is achieved by using a laser to remove the powder area at the corner of the positive electrode assembly. After the treatment, a blank area 7 for positive electrode powder is left. The positive electrode powder on both sides of the blank area 7 is located within the area of ​​the negative electrode powder. Preferably, the negative electrode powder of the negative electrode sheet 2 on the left and right sides covers the first positive electrode powder area and the second positive electrode powder area by more than 2-4 mm, respectively, so as to achieve the purpose of negative electrode covering positive electrode.

[0040] In some embodiments, the thickness of the positive electrode 1 is 60–180 μm and the width is 20–140 mm.

[0041] The blank area 7 of the positive electrode powder is formed by laser removal of a thickness of 22 to 86 μm on the surface of the positive electrode sheet 1. The width of the laser removal is the same as the width of the positive electrode sheet 1.

[0042] The length of the blank area 7 of the positive electrode powder is the length of the innermost arc corner at the end of the core structure plus 2 to 4 mm.

[0043] Specifically, the perimeter of the curved portion at the end of the core structure is calculated by fitting a portion of an approximate elliptical curve. In some implementations, it is assumed that the parameter t corresponding to the elliptical curve portion of the spindle is in the range of [t1, t2] (0 ≤ t1 < t2 ≤ 2π), and the perimeter of the curved portion... Let a be the major semi-axis of the elliptic curve, and b be the minor semi-axis; let h be the thickness of the needle coil, then the range of the angle parameter θ corresponding to the curved portion of the needle coil is: Substituting the values ​​into the calculation, we can obtain the circumference C of the curve at one end of the needle.

[0044] In some implementations, the outermost electrode of the core structure is provided with a finishing tape to stabilize the core and prevent electrode displacement.

[0045] In some embodiments, in the core structure, each stack of positive electrode 1 and negative electrode 2 is considered as a winding layer, and the total number of winding layers in the core structure is greater than or equal to 3 layers and less than or equal to 40 layers.

[0046] This utility model also provides a battery containing the above-mentioned lithium-ion battery core.

[0047] This invention is applied to a core where the positive and negative electrode powder areas at the innermost corner are mismatched. After the winding is completed and the needle is pulled out, the inner negative electrode sheet will shrink and curl along the junction of the curved surface and the plane of the winding needle. This shrinkage causes the innermost gap to be generated, and the positive electrode sheet 1 at the inner corner of the core cannot be completely covered by the negative electrode sheet 2. By laser removal of the powder at the corner of the positive electrode sheet according to the above scheme, the negative electrode powder can completely cover the positive electrode powder, which plays a role in stabilizing and balancing the internal structure of the battery during long-term use.

[0048] The following detailed description, in conjunction with specific accompanying drawings and embodiments, further illustrates the following:

[0049] Positive electrode 1 uses 8-15µm aluminum foil as the substrate, coated with positive electrode powder. The thickness of positive electrode 1 is 60-180µm, the cutting width of positive electrode 1 is 20-150mm, and the length of positive electrode powder is 0.6-3m. Negative electrode 2 uses 4-8µm copper foil as the substrate, coated with negative electrode powder. The thickness of negative electrode 2 is 60-180µm, the cutting width of negative electrode 2 is 20-150mm, and the length of negative electrode powder is 0.6-3m.

[0050] The positive electrode 1 powder area has a corresponding negative electrode material. The separator width minus the negative electrode 2 cutting width is 1.5~3.0mm, and the negative electrode 2 cutting width minus the positive electrode 1 cutting width is 1.0~3.0mm. The separator thickness is 5~18um. The corresponding parts of the positive and negative electrode 2 are separated by a separator, which completely covers the positive and negative electrode 2 in both length and width directions.

[0051] The pressurized formation process for battery manufacturing involves a formation temperature of 70–90°C and a formation pressure of (10–22) kgf / cm². 2 The formation time is between 0.5 and 5 hours.

[0052] Example 1

[0053] like Figures 1-3 As shown, core A is spirally wound in the form of positive and negative electrode overlap. The structure of core A includes positive electrode sheet 1, negative electrode sheet 2, diaphragm, first tail protective tape 3 and second tail protective tape 4.

[0054] The powder removal area is located at the first fold corner of the positive electrode, in the gap area created by the coiling and curling of the first fold of the negative electrode after the winding needle is pulled away. The positive electrode powder in the gap area is removed by laser. After the winding process is completed, the operator removes the powder from the gap area. Figure 3 By observing from above, it can be determined whether the position of the blank area 7 of the positive electrode powder is correct.

[0055] The thickness of the blank area 7 of the positive electrode powder is equal to the thickness of the powder on a single positive electrode sheet. The width of the blank area 7 of the positive electrode powder is equal to the width of the positive electrode sheet itself. The length of the blank area 7 of the positive electrode powder is equal to the perimeter of the curved part of the winding needle + (2~4) mm.

[0056] The winding process uses a spinning needle with spindle-shaped elliptical curves at both ends and a straight middle section, with curved sections at both ends.

[0057] Further, in the formation process, the formation temperature is around 85℃, and the battery is activated by charge-discharge, with a formation pressure of 17 kgf / cm². 2 The formation time is 2 hours. During the formation stage, planar pressure is applied to the core. The curled negative electrode sheet is pressed and fixed in this process. After the powder is removed, the positive electrode powder falls completely on the powder area corresponding to the negative electrode sheet. At this time, the core is fixed and clamped during the formation pressure. In this way, the first round of positive electrode powder has a corresponding negative electrode powder, and the NP ratio of the battery is balanced, thereby reducing the occurrence of corner lithium plating and the safety problems caused by it during the later use of the battery.

[0058] Example 2

[0059] like Figure 4 , 5 As shown, core B is spirally wound in a form of interlocking positive and negative electrode overlap. The structure of core B includes a positive electrode sheet 1, a negative electrode sheet 2, a diaphragm, a first tail protective tape 3, and a second tail protective tape 4.

[0060] The powder removal area is located at the first fold corner of the positive electrode. Because the innermost negative electrode sheet of the first fold of the core cannot be fully inserted to the edge of the core, there is a gap between the first fold negative electrode sheet and the edge of the core. This gap causes the positive electrode powder at the innermost corner to not be completely covered by the negative electrode powder. This results in an imbalance of the NP ratio at the corner. In subsequent use of the battery, the excess positive electrode powder at the corner will cause lithium plating, which may lead to side bulging and lithium dendrites piercing the separator, resulting in a short circuit between the positive and negative electrodes.

[0061] like Figure 6The single-powder powder at the first fold of the positive electrode is removed. The thickness of the blank area 7 of the positive electrode powder is equal to the thickness of the single-powder powder on the positive electrode sheet, the width of the blank area 7 of the positive electrode powder is equal to the width of the positive electrode sheet itself, and the length of the blank area 7 of the positive electrode powder is equal to the perimeter of the curve portion of the winding needle + (2~4) mm. The size of the area to be removed is calculated in a similar way to that in Example 1. After the winding process is completed, the operator removes the powder from the blank area. Figure 5 By observing from above, it is possible to determine whether the location of the elimination area is correct and whether the first fold of positive electrode powder is completely matched with the negative electrode powder.

[0062] Example 3

[0063] like Figure 6 , 7 As shown, the core C is spirally wound in a form of interlocking positive and negative electrode overlap. The core C structure includes a positive electrode sheet 1, a negative electrode sheet 2, a diaphragm, and a third protective tape 8.

[0064] The main difference between core C and core B lies in the way they end. Core B ends with the positive electrode at the outermost edge, while core C ends with the negative electrode at the outermost edge.

[0065] The innermost negative electrode first fold of core C cannot be inserted into the edge of the core, which is the same problem as core B. The innermost positive electrode powder has no corresponding negative electrode powder, and the positive and negative NP ratio at the corner is unbalanced.

[0066] Similarly, for the positive electrode at the innermost corner, such as... Figure 7 The powder removal process is shown to form a blank area 7 for the positive electrode powder, thereby avoiding lithium deposition at the corner positive electrode.

[0067] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the present utility model in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the present utility model's technical solution and based on the technical essence of the present utility model shall still fall within the protection scope of the present utility model's technical solution.

Claims

1. A lithium-ion battery jelly-roll, characterized by: It includes a positive electrode sheet, a negative electrode sheet, and a separator, wherein the positive electrode sheet, the negative electrode sheet, and the separator are wound into a core structure; In the aforementioned core structure, the corner of the innermost first fold of the positive electrode sheet is a blank area of ​​positive electrode powder formed by laser processing, and there is no powder adhesion on the blank area of ​​positive electrode powder. The left side of the blank area of ​​the positive electrode powder is adjacent to the first positive electrode powder area on the positive electrode sheet, and the right side is adjacent to the second positive electrode powder area on the positive electrode sheet. Both the first positive electrode powder area and the second positive electrode powder area are covered by the negative electrode powder on the core structure negative electrode sheet.

2. The lithium-ion battery jelly-roll of claim 1, wherein: The positive electrode, separator, and negative electrode are spindle-shaped core structures formed by spiral winding, with curved ends and a flat area in the middle.

3. The lithium-ion battery jelly-roll of claim 1, wherein: In the aforementioned core structure, the distance between the end face of the first fold of the innermost positive electrode sheet and the end face of the first fold of the innermost negative electrode sheet and the vertex of the innermost arc corner of the nearest core structure is 2 to 5 mm.

4. The lithium-ion battery jelly-roll of claim 1, wherein: The distance between the vertices of the innermost arc corners at both ends of the core structure is 20-110 mm.

5. The lithium-ion battery jelly-roll of claim 1, wherein: The positive electrode sheet has a thickness of 60–180 μm and a width of 20–140 mm.

6. The lithium-ion battery jelly-roll of claim 5, wherein: The blank area of ​​the positive electrode powder is formed by laser removal of a thickness of 22-86 μm on the surface of the positive electrode sheet, and the width of the laser removal is the same as the width of the positive electrode sheet.

7. The lithium-ion battery jelly-roll of claim 1, wherein: The length of the blank area of ​​the positive electrode powder is the length of the innermost arc corner at the end of the core structure plus 2 to 4 mm.

8. The lithium-ion battery core according to claim 1, characterized in that: The outermost electrode of the core structure is provided with a finishing tape to secure the core.

9. The lithium-ion battery jelly-roll of claim 1, wherein: In the described core structure, each stack of positive and negative electrode sheets constitutes a winding layer, and the total number of winding layers in the core structure is greater than or equal to 3 layers and less than or equal to 40 layers.

10. A battery, characterized by: It contains a lithium-ion battery core as described in any one of claims 1 to 9.

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