Battery roll core and cylindrical battery

Abstract

The utility model relates to lithium battery technical field discloses a battery roll core and cylindrical battery, this battery roll core includes the positive sheet, first diaphragm, negative sheet and second diaphragm of laminated setting and swelling layer, first diaphragm is equipped between positive sheet with negative sheet, and the one end of first diaphragm is close to winding center and is coated with swelling layer, second diaphragm is equipped at the side of negative sheet and is away from positive sheet, and the one end of second diaphragm is close to winding center and is coated with swelling layer. The utility model has the beneficial effects that: avoid the deformation of center hole and the protrusion of pole piece into center hole to cause lithium precipitation, improve the service life and security of battery.

Description

Technical Field

[0001] This utility model relates to the field of lithium battery technology, and in particular to a battery core and a cylindrical battery. Background Technology

[0002] During the charging and discharging process of a lithium-ion cylindrical battery, lithium ions migrate between the positive and negative electrodes, causing changes in the volume of the electrode sheets. After multiple cycles, the electrode sheet thickness expands and increases, leading to an increase in the diameter of the core. However, the core of the cylindrical battery is constrained by the steel shell and cannot continue to expand outward. This eventually causes pressure to be released towards the center hole of the core, squeezing the center hole and causing it to deform. It can even cause the electrode sheet to bulge into the center hole, resulting in lithium plating, which affects the battery's lifespan and cell safety. Utility Model Content

[0003] The purpose of this invention is to provide a battery core and cylindrical battery that avoids deformation of the center hole and lithium plating caused by the electrode plates protruding into the center hole, thereby improving the battery's lifespan and safety.

[0004] To achieve the above objectives, this utility model provides a battery core, comprising a positive electrode sheet, a first separator, a negative electrode sheet, and a second separator stacked together, as well as a swelling layer;

[0005] The first separator is disposed between the positive electrode and the negative electrode, and the swelling layer is coated on one end of the first separator near the winding center.

[0006] The second separator is disposed on the side of the negative electrode sheet facing away from the positive electrode sheet, and the end of the second separator near the winding center is coated with the swelling layer.

[0007] Furthermore, at least one side of the first diaphragm near the winding center is coated with the swelling layer.

[0008] Furthermore, at least one side of the second diaphragm near the winding center is coated with the swelling layer.

[0009] Furthermore, the positive electrode, the first separator, the negative electrode, and the second separator extend in a first direction and a second direction, with the first direction intersecting the second direction perpendicularly. The length of the swollen layer in the first direction is L1, where 10mm ≤ L1 ≤ 1000mm.

[0010] Furthermore, the length of the swollen layer in the second direction is L2, where 5mm ≤ L2 ≤ 1000mm.

[0011] Furthermore, the thickness of the swollen layer is W, where 1mm ≤ W ≤ 20mm.

[0012] Furthermore, the distance between the projection of the swollen layer on the first diaphragm in the first direction and the projection of the positive electrode in the first direction is L3, where 0 < L3 ≤ 3 mm.

[0013] Furthermore, the overlap length between the projection of the swollen layer on the first diaphragm and the second diaphragm in the first direction and the projection of the negative electrode sheet in the first direction is L4, where 5mm≤L4≤20mm.

[0014] Furthermore, the volume expansion rate of the swollen layer is 100%-500%.

[0015] This utility model also provides a cylindrical battery, comprising the battery core described in any of the above claims.

[0016] Compared with the prior art, the battery core and cylindrical battery of this utility model embodiment have the following advantages: the first separator is disposed between the positive electrode and the negative electrode, and the end of the first separator near the winding center is coated with a swelling layer; the second separator is disposed on the side of the negative electrode facing away from the positive electrode, and the end of the second separator near the winding center is coated with a swelling layer. When the core is formed, the swelling layer absorbs the electrolyte volume and expands after the battery is filled with electrolyte, filling the central hole of the core, avoiding the deformation of the central hole under stress and the lithium plating phenomenon caused by the electrode protruding into the central hole, thereby improving the battery's service life and safety. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the winding of the battery core according to an embodiment of the present invention;

[0018] Figure 2 This is a top view of the battery core of this utility model when it is unfolded.

[0019] In the diagram, 1 is the positive electrode; 2 is the first separator; 3 is the negative electrode; 4 is the second separator; 5 is the swollen layer; X is the first direction; Y is the second direction. Detailed Implementation

[0020] The specific embodiments of this utility model will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this utility model, but are not intended to limit its scope.

[0021] In the description of this utility model, it should be understood that the terms "upper", "lower", "front", "rear", "inner", "outer" and other terms used in this utility model to indicate the orientation or positional relationship are based on the positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device and element 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.

[0022] In the description of this utility model, it should be understood that the terms "first," "second," etc., are used to describe various information, but this information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this utility model, "first" information can also be referred to as "second" information, and similarly, "second" information can also be referred to as "first" information.

[0023] like Figure 1 , Figure 2 As shown, a preferred embodiment of the present invention provides a battery core comprising a positive electrode 1, a first separator 2, a negative electrode 3, a second separator 4, and a swelling layer 5. The positive electrode 1, the first separator 2, the negative electrode 3, and the second separator 4 are stacked. The first separator 2 is disposed between the positive electrode 1 and the negative electrode 3, and the end of the first separator 2 near the winding center is coated with the swelling layer 5. The second separator 4 is disposed on the side of the negative electrode 3 facing away from the positive electrode 1, and the end of the second separator 4 near the winding center is coated with the swelling layer 5. Because the first separator 2 and the second separator 4 have the swelling layer 5 at their ends near the winding center, when the positive electrode 1, the first separator 2, the negative electrode 3, and the second separator 4 are stacked and wound to form a core, the swelling layer 5 absorbs the electrolyte and expands after the battery is filled with electrolyte. This fills the central hole of the core, preventing deformation of the central hole due to stress and lithium plating caused by the electrode protruding into the central hole, thus improving the battery's lifespan and safety. That is, after the first diaphragm 2 and the second diaphragm 4 are wound, the swelling layer 5 forms the inner wall of the central hole of the core. When the swelling layer 5 absorbs the electrolyte, its volume expands and fills the central hole.

[0024] Furthermore, to facilitate the application of the swelling layer 5 on the first separator 2, at least one side of the first separator 2 near the winding center is coated with the swelling layer 5. Similarly, at least one side of the second separator 4 near the winding center is coated with the swelling layer 5. That is, either the first separator 2 or the second separator 4 near the winding center has one side coated with the swelling layer 5, or both sides are coated with the swelling layer 5. This is adjusted synchronously according to the size of the battery and the size of the central hole. In this embodiment, both sides of the first separator 2 and the second separator 4 near the winding center are provided with the swelling layer 5 to meet the design requirements of filling the central hole.

[0025] See Figure 1 , Figure 2 The positive electrode 1, the first separator 2, the negative electrode 3, and the second separator 4 extend in the first direction X and the second direction Y, respectively. The first direction X intersects the second direction Y perpendicularly. For ease of explanation, the length direction of the first separator 2 is defined as the first direction X, and the width direction of the first separator 2 is defined as the second direction Y. Figure 1As shown, the length of the swelling layer 5 in the first direction X is L1, where 10mm ≤ L1 ≤ 1000mm. The length L1 of the swelling layer 5 is adjusted according to the size of the core and the charging and discharging requirements. Preferably, in this embodiment, L1 = 50mm. When L1 is less than 10mm, the size of the swelling layer 5 is too small, and it cannot completely fill the central hole after absorbing the electrolyte. There is still a risk that the central hole will deform and the electrode will bulge into the central hole, leading to lithium plating. When L1 is greater than 1000mm, the size of the swelling layer 5 is too large, increasing the diameter of the core, which is not conducive to installing the core into the steel shell. At the same time, after the swelling layer 5 absorbs the swelling liquid, the expansion volume at the central hole is too large, and the swelling layer 5 squeezes the electrode outward, causing the electrode to deform and leading to lithium plating. Similarly, the length of the swelling layer 5 in the second direction Y is L2, and the size of L2 needs to be limited, where 5mm ≤ L2 ≤ 1000mm. Preferably, in this embodiment, L2 = 40mm. The dimensions of L2 can be adjusted to meet actual design requirements.

[0026] Similarly, the thickness of the swelling layer 5 is W, and its dimensions also need to be limited: 1mm ≤ W ≤ 20mm. Preferably, in this embodiment, W = 10mm.

[0027] Furthermore, in order to facilitate the control of the volume expansion of the swelling layer 5, the swelling layer 5 is composed of one or more of polyacrylic acid, polyacrylamide and polyacrylate. The volume expansion rate of the swelling layer 5 is 100%-500%, that is, after the swelling layer 5 absorbs the electrolyte, the volume expands by 2 to 6 times. It can be adapted to the specifications and dimensions of the battery. In this embodiment, preferably, the volume expansion rate of the swelling layer 5 is 200%, that is, after the swelling layer 5 absorbs the electrolyte, the volume expands by 3 times.

[0028] See Figure 1 During winding, the positive electrode 1 is located in the innermost layer of the core, and the second diaphragm 4 is located in the outermost layer of the core, abutting against the inner wall of the steel shell. To make the expansion layer at the center hole expand more uniformly after absorbing liquid, in some other embodiments, the volume expansion rate of the swelling layer 5 on the second diaphragm 4 and the first diaphragm 2 increases in the direction closer to the center of the core. That is, the volume expansion rate of the swelling layer 5 on each side of the first diaphragm 2 and the second diaphragm 4 is not equal, and increases in the direction closer to the center hole.

[0029] At the start of winding, because the end of the negative electrode 3 near the center of the winding core needs to wrap the end of the positive electrode 1 near the center of the winding core, and the length of the negative electrode 3 is greater than that of the negative electrode 3, when the swelling layer 5 expands, the spacing between the positive electrode 1 and the negative electrode 3 changes. (See [reference needed]). Figure 1The spacing between the swollen layer 5 and the positive electrode 1 needs to be controlled. The distance between the projection of the swollen layer 5 on the first separator 2 in the first direction X and the projection of the positive electrode 1 in the first direction X is L3, where 0 < L3 ≤ 3 mm. Preferably, in this embodiment, L3 = 2 mm, which can be adaptively adjusted according to the actual design requirements of the battery. Similarly, the overlap length between the projection of the swollen layer 5 on the first separator 2 and the second separator 4 in the first direction X and the projection of the negative electrode 3 in the first direction X is L4, where 5 mm ≤ L4 ≤ 20 mm. Preferably, in this embodiment, L4 = 10 mm.

[0030] This utility model provides a cylindrical battery, including the battery core mentioned above, and a steel shell. After the battery core is inserted into the steel shell, electrolyte is injected, the swelling layer 5 expands and fills the central hole, and then the steel shell is sealed to obtain the finished cylindrical battery.

[0031] In summary, this utility model embodiment provides a battery core and a cylindrical battery. The first separator 2 is disposed between the positive electrode 1 and the negative electrode 3, and the end of the first separator 2 near the winding center is coated with a swelling layer 5. The second separator 4 is disposed on the side of the negative electrode 3 facing away from the positive electrode 1, and the end of the second separator 4 near the winding center is coated with a swelling layer 5. When the core is formed, the swelling layer 5 absorbs the electrolyte and expands after the battery is filled with electrolyte, filling the central hole of the core. This avoids the deformation of the central hole due to stress and the lithium plating phenomenon caused by the electrode bulging into the central hole, thereby improving the battery's service life and safety.

[0032] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present utility model, and these improvements and substitutions should also be considered within the protection scope of the present utility model.

Claims

1. A battery core, characterized in that: It includes a positive electrode sheet, a first separator, a negative electrode sheet, and a second separator stacked together, as well as a swollen layer; The first separator is disposed between the positive electrode and the negative electrode, and the swelling layer is coated on one end of the first separator near the winding center. The second separator is disposed on the side of the negative electrode sheet facing away from the positive electrode sheet, and the end of the second separator near the winding center is coated with the swelling layer.

2. The battery core as described in claim 1, characterized in that: The swelling layer is coated on at least one side of the first diaphragm near the center of winding.

3. The battery core as described in claim 1, characterized in that: The second diaphragm has at least one side coated with the swelling layer at one end near the center of winding.

4. The battery core as described in claim 1, characterized in that: The positive electrode, the first separator, the negative electrode, and the second separator extend in a first direction and a second direction, with the first direction intersecting the second direction perpendicularly. The length of the swollen layer in the first direction is L1, where 10mm ≤ L1 ≤ 1000mm.

5. The battery core as described in claim 4, characterized in that: The length of the swollen layer in the second direction is L2, where 5mm ≤ L2 ≤ 1000mm.

6. The battery core as described in claim 4, characterized in that: The thickness of the swelling layer is W, where 1mm ≤ W ≤ 20mm.

7. The battery core as described in claim 4, characterized in that: The distance between the projection of the swollen layer on the first diaphragm in the first direction and the projection of the positive electrode in the first direction is L3, where 0 < L3 ≤ 3 mm.

8. The battery core as described in claim 4, characterized in that: The overlap length between the projection of the swollen layer on the first diaphragm and the second diaphragm in the first direction and the projection of the negative electrode sheet in the first direction is L4, where 5mm≤L4≤20mm.

9. The battery core as described in claim 1, characterized in that: The volume expansion rate of the swollen layer is 100%-500%.

10. A cylindrical battery, characterized in that: Includes the battery core as described in any one of claims 1-9.

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