Pole piece and battery cell

Abstract

The utility model relates to battery technology field discloses a kind of pole piece and electric core, the pole piece includes foil material, the foil material includes main body part and the protection part being arranged on the upper and lower sides of the main body part, two surfaces of the main body part are equipped with coating, two surfaces of the protection part are equipped with protective layer, one of the protective layer is equipped with gap for setting tab, the protective layer is insulating adhesive layer.The utility model not only improves the thermal stability of diaphragm, realizes inhibition diaphragm in the shrinkage of heating process, prevents the short circuit between positive and negative pole of electric core due to diaphragm shrinkage.Moreover, even if diaphragm shrinks because of temperature is too high, but due to the protective layer has certain width, when diaphragm part shrinks into positive and negative pole, the protective layer will isolate positive and negative pole, due to the protective layer insulation, to prevent the occurrence of electric core short circuit phenomenon, guarantee the safety performance of battery.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and in particular to an electrode sheet and a battery cell. Background Technology

[0002] In lithium-ion batteries, the separator is one of the key inner components. Its main function is to separate the positive and negative electrodes of the battery and prevent the two electrodes from coming into contact and short-circuiting. Therefore, the performance of the separator directly determines the safety performance of the battery.

[0003] However, in actual use, it was found that under normal conditions, the diaphragm 400 can completely isolate the positive electrode 200 and the negative electrode 300 (e.g. Figure 1 (as shown); however, when the battery temperature rises (130 degrees or above), the separator 400 will gradually shrink, and eventually the width of the separator 400 will be smaller than the width of the positive electrode 200 (as shown). Figure 2 This short circuit, caused by contact between the positive electrode 200 and the negative electrode 300, results in a momentary discharge within the battery cell, generating a large amount of heat and potentially leading to serious hazards such as fire or explosion. Targeted improvements are urgently needed to address this issue. Utility Model Content

[0004] To solve the above-mentioned technical problems, this utility model provides an electrode sheet and a battery cell that can effectively suppress the shrinkage of the separator and effectively isolate the positive and negative electrodes when the separator shrinks, thereby preventing the occurrence of short circuit in the battery cell and ensuring the safety performance of the battery.

[0005] The technical solution adopted by this utility model to solve its technical problem is:

[0006] A battery electrode includes a foil, the foil comprising a main body and protective portions disposed on the upper and lower sides of the main body, both surfaces of the main body being coated, and both surfaces of the protective portions being protected layers, one of the protective layers having a notch for mounting an electrode tab, the protective layer being an insulating adhesive layer.

[0007] Preferably, the foil is symmetrical about a first axis of symmetry along its length, and the main body is symmetrical about the first axis of symmetry.

[0008] Preferably, the height of the main body is h, and the height of the foil is H, where h:H = 0.92 to 0.98.

[0009] Preferably, the protective portions located on both sides of the main body are a first protective portion and a second protective portion, and the first protective portion and the second protective portion have different heights.

[0010] Preferably, the surface of the protective layer is flush with the surface of the coating, and an active material layer is provided between the protective part and the protective layer. The thickness of the protective layer is 1-10 μm, and the thickness of the active material layer is 90-199 μm.

[0011] Preferably, one end of the tab is disposed within the notch and welded to the foil material, the width of the tab is W, the spacing of the notch is L, and W = (0.4~0.6)L.

[0012] Preferably, the protective layer is made of any one of modified polyacrylate, epoxy resin, silica filler, hydrogenated petroleum resin, silane coupling agent, and antioxidant.

[0013] Preferably, the protective layer is composed of a plurality of uniformly distributed protective particles.

[0014] Preferably, the coating material is a positive electrode active material used to form a positive electrode sheet;

[0015] Alternatively, the coating material may be a negative electrode active material used to form a negative electrode sheet.

[0016] A battery cell includes a positive electrode, a negative electrode, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode.

[0017] Both the positive electrode and the negative electrode are the electrodes described above.

[0018] The beneficial effects of this utility model are as follows:

[0019] By setting protective sections on both sides of the main body of the foil, and providing protective layers on both surfaces of the protective sections, which are adhesive to the diaphragm, the protective layers will adhere to the diaphragm after the electrode and the diaphragm are hot-pressed together, thereby improving the thermal stability of the diaphragm, suppressing the shrinkage of the diaphragm during the heating process, and preventing short circuits between the positive and negative electrodes of the battery cell caused by the shrinkage of the diaphragm.

[0020] On the other hand, even if the separator shrinks due to excessive temperature, the protective layer has a certain width. When the separator partially shrinks into the space between the positive and negative electrodes, the protective layer will isolate the positive and negative electrodes. Because the protective layer is insulating, it prevents the occurrence of short circuits in the battery cell and ensures the safety performance of the battery.

[0021] In addition, since one of the protective layers has a notch for setting the tabs, it will not affect the normal setting of the tabs. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of an existing battery cell.

[0023] Figure 2 for Figure 1Schematic diagram of diaphragm contraction.

[0024] Figure 3 This is a schematic diagram of the electrode structure in Example 1.

[0025] Figure 4 This is a schematic diagram of the battery cell structure of this utility model.

[0026] Figure 5 for Figure 4 Schematic diagram of diaphragm contraction.

[0027] Figure 6 for Figure 5 A sectional view.

[0028] Figure 7 for Figure 3 A magnified view of A in the middle.

[0029] Figure 8 This is a schematic diagram of the electrode structure in Example 2.

[0030] Wherein: 1-foil, 11-main body, 12-protective part, 13-first axis of symmetry, 2-protective layer, 21-notch, 3-tab;

[0031] 10 - Positive electrode, 20 - Negative electrode, 30 - Separator, 100 - Cell, 200 - Positive electrode, 300 - Negative electrode, 400 - Separator. Detailed Implementation

[0032] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0033] 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.

[0034] like Figure 3-7As shown, a preferred embodiment of the present invention provides a battery cell comprising a positive electrode 10, a negative electrode 20, and a separator 30, wherein the separator 30 is disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10 and the negative electrode 20 have the same structure, differing only in the active material they are coated with; for ease of description, they are both referred to as electrodes below. Each electrode includes a foil 1, which comprises a main body 11 and protective portions 12 disposed on the upper and lower sides of the main body 11. Both surfaces of the main body 11 are coated. When the coating material is a positive electrode active material, a positive electrode 10 is formed; when the coating material is a negative electrode active material, a negative electrode 20 is formed.

[0035] Both surfaces of the protective part 12 are provided with protective layers 2, one of which has a notch 21 for setting the tab 3. When the electrode is a positive electrode 10, a positive tab is set in the notch 21; when the electrode is a negative electrode 20, a negative tab is set in the notch 21. During connection, one end of the tab 3 is located in the notch 21 and is welded to the foil 1. Meanwhile, to ensure proper welding between the tab 3 and the foil 1, the width of the notch 21 must be greater than the width of the tab 3. Specifically, if the width of the tab 3 is W and the spacing of the notches 21 is L, then W = (0.4~0.6)L, such as 0.41L, 0.42L, 0.43L, 0.44L, 0.45L, 0.46L, 0.47L, 0.48L, 0.49L, 0.5L, 0.51L, 0.52L, 0.53L, 0.54L, 0.55L, 0.56L, 0.57L, 0.58L, 0.59L, etc. The height of the notch 21 can be the same as or less than the width of the protective layer 2, but the end of the notch 21 away from the main body 11 must extend to the side of the foil 1.

[0036] The insulating adhesive layer, i.e., the protective layer 2, is insulating and adhesive to the diaphragm 30. Preferably, the insulating adhesive layer can form an adhesive force of ≥10N / m to the diaphragm 30 to ensure a good interface in the later stage. For example, its material can be any one or more of modified polyacrylate, epoxy resin, silica filler, hydrogenated petroleum resin, silane coupling agent, and antioxidant.

[0037] In the specific manufacturing of the battery cell 100, the protective layer 2 only needs to be set on one type of electrode, that is, only on the positive electrode 10 or only on the negative electrode 20, preferably on the positive electrode 10.

[0038] The foil material 1 can be selected from copper foil, aluminum foil, or composite foil; the coating material can be selected from positive electrode material (a mixture of active material lithium cobalt oxide, conductive agent conductive carbon black, and binder polyvinylidene fluoride mixed with N-methylpyrrolidone in a certain proportion) or negative electrode material (a mixture of active material graphite, binder styrene-butadiene rubber, and sodium carboxymethyl cellulose mixed with deionized water in a certain proportion); the tab can be selected from aluminum tab, nickel tab, or copper-plated nickel tab, etc.

[0039] Based on the above-mentioned technical features, the battery cell 100 has protective portions 12 on both sides of the main body 11 of the foil 1. Both surfaces of the protective portions 12 are provided with protective layers 2, which are adhesive to the separator 30. When the electrode and separator 30 are hot-pressed together, the protective layer 2 adheres to the separator 30, thereby improving the thermal stability of the separator 30, suppressing its shrinkage during heating, and preventing short circuits between the positive and negative electrodes of the battery cell 100 caused by separator shrinkage. Simultaneously, the adhesiveness of the protective layer 2 to the separator 30 also prevents poor adhesion at the cell overhang (in lithium-ion batteries, the negative electrode is designed to be larger than the positive electrode in both length and width, forming a redundant area extending beyond the positive electrode edge), which could affect the cell interface and prevent OH lithium deposition at the overhang (poor adhesion at the overhang can easily lead to OH lithium deposition during cycling).

[0040] like Figure 5-6 As shown, on the other hand, even if the separator 30 shrinks due to excessive temperature, the protective layer 2 has a certain width. When the separator 30 partially shrinks into the space between the positive and negative electrodes, the protective layer 2 will isolate the positive and negative electrodes. Since the protective layer 2 is insulating, it prevents the cell 100 from short-circuiting and ensures the safety performance of the battery.

[0041] Generally, the foil 1 is rectangular, meaning that the foil 1 is symmetrical about the first axis of symmetry 13 along its length. The main body 11 may or may not be symmetrical about the first axis of symmetry 13. Specifically:

[0042] Example 1

[0043] The main body 11 is also symmetrical about the first axis of symmetry 13, that is, the main body 11 is located in the exact center of the foil 1. In a specific configuration, the active material can be coated onto the foil 1 first, then the area where the protective layer 2 needs to be coated can be thinned. After thinning, the protective layer 2 is coated, and the surface of the protective layer 2 is flush with the surface of the coating layer, thereby ensuring good adhesion between the protective layer and the separator 30 during the hot-pressing process. This avoids affecting the cell interface at the cell overhang. The thickness of the protective layer 2 can be set to 1–10 μm, such as 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, etc.

[0044] As described above, the protective layer 2 is disposed on both sides of the foil 1. Given a fixed width of the foil 1, determining the width of the protective layer 2 determines the width of the main body 11. The main body 11 directly determines the energy density of the battery cell 100. If the protective layer 2 is wider, the main body 11 will be narrower, resulting in a decrease in the energy density of the battery cell 100. If the protective layer 2 is too narrow, it will not be able to isolate the positive and negative electrodes when the separator 30 contracts significantly. Therefore, the width of the protective layer 2 is crucial. Preferably, if the height of the main body 11 is h and the height of the foil 1 is H, h:H = 0.92 to 0.98, such as h:H = 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, etc.

[0045] In addition, during the actual manufacturing process, the active material is first coated onto the foil 1, and then the area where the protective layer 2 needs to be coated is thinned. After thinning, the protective layer 2 is coated. Therefore, there is an active material layer between the protective part and the protective layer, and the thickness of the active material layer is 90-199um, such as 95um, 100um, 110um, 115um, 120um, 125um, 130um, 135um, 140um, 145um, 150um, 155um, 160um, 165um, 170um, 175um, 180um, 185um, 190um, 195um, etc.

[0046] Of course, it is also possible to not coat the protective part 12 with an active material, but to directly set the protective layer 2.

[0047] Example 2

[0048] like Figure 8As shown, in this embodiment, the main body 11 is not symmetrical about the first axis of symmetry 13. For ease of description, the protective portions 12 located on both sides of the main body 11 are referred to as the first protective portion 121 and the second protective portion 122, respectively, and the heights of the first protective portion 121 and the second protective portion 121 are different. In actual use, the shrinkage degree of the separator at the positive electrode of the battery cell is generally greater than that at the negative electrode. Therefore, in specific settings, the protective portion can be set according to the positive and negative electrodes of the battery cell, with the height of the protective portion corresponding to the positive electrode being larger and the height of the protective portion corresponding to the negative electrode being smaller. For example, if the first protective portion 121 corresponds to the positive electrode of the battery cell, then the height of the first protective portion 121 is greater than the height of the second protective portion 122.

[0049] In this embodiment, the structure of the protective layer 2 does not affect the wetting of the electrolyte, which can enter through the diaphragm 30 during the wetting process. However, if the protective layer 2 is composed of several uniformly distributed protective particles, the electrolyte can pass between the protective particles, thus improving the wetting effect. Therefore, the protective layer can be configured as a non-porous or porous structure, as long as it can separate the positive and negative electrodes and prevent direct conduction of electrons between them.

[0050] To address the aforementioned technical problems, this application also provides a battery, including a casing, the aforementioned battery cell 100, and a cap. The casing is made of stainless steel, preferably nickel-plated stainless steel, and has an opening. The battery cell 100 is disposed inside the casing through the opening. The tab of the positive electrode is connected to a positive current collector, and the tab of the negative electrode is connected to a negative current collector, which is connected to the bottom wall of the casing. The cap is connected to the casing to cover the opening, and the positive current collector is connected to the cap.

[0051] The battery of this application can not only effectively suppress the shrinkage of the separator 30, but also effectively isolate the positive and negative electrodes when the separator 30 shrinks, thereby preventing the occurrence of short circuit in the cell 100 and ensuring the safety performance of the battery.

[0052] 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 electrode, characterized in that: The foil includes a main body and protective portions disposed on the upper and lower sides of the main body. Both surfaces of the main body are coated, and both surfaces of the protective portions are protected layers. One of the protective layers has a notch for mounting tabs. The protective layer is an insulating adhesive layer.

2. The battery electrode as described in claim 1, characterized in that: Along the length of the foil, the foil is symmetrical about a first axis of symmetry, and the main body is symmetrical about the first axis of symmetry.

3. The battery electrode as described in claim 2, characterized in that: The height of the main body is h, and the height of the foil is H, where h:H = 0.92 to 0.

98.

4. The battery electrode as described in claim 2, characterized in that: The protective portions located on both sides of the main body are a first protective portion and a second protective portion, and the first protective portion and the second protective portion have different heights.

5. The battery electrode as described in claim 1, characterized in that: The surface of the protective layer is flush with the surface of the coating, and an active material layer is provided between the protective part and the protective layer. The thickness of the protective layer is 1-10 μm, and the thickness of the active material layer is 90-199 μm.

6. The battery electrode sheet according to any one of claims 1-5, characterized in that: One end of the electrode tab is located in the notch and welded to the foil. The width of the electrode tab is W, and the spacing of the notch is L, where W = (0.4~0.6)L.

7. The battery electrode sheet according to any one of claims 1-5, characterized in that: The protective layer is made of any one of the following: modified polyacrylate, epoxy resin, silica filler, hydrogenated petroleum resin, silane coupling agent, or antioxidant.

8. The battery electrode sheet according to any one of claims 1-5, characterized in that: The protective layer consists of several uniformly distributed protective particles.

9. The battery electrode sheet according to any one of claims 1-5, characterized in that: The coating material is a positive electrode active material, used to form a positive electrode sheet; Alternatively, the coating material may be a negative electrode active material used to form a negative electrode sheet.

10. A battery cell, characterized in that: It includes a positive electrode, a negative electrode, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode; both the positive electrode and the negative electrode are the electrodes as described in claim 9.

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