Pole piece, battery cell and battery

Abstract

The utility model discloses a pole piece, a battery cell and a battery. The pole piece comprises a current collector, a first active layer and a second active layer, the current collector comprises a first end and a second end, and the pole piece is rolled in the direction from the first end to the second end; the first active layer is coated on one side of the current collector along the thickness direction; the second active layer is coated on the other side of the current collector along the thickness direction; wherein the first active layer comprises a protruding part, the protruding part protrudes out of the second active layer at the first end in the length direction of the current collector, and the protruding part is provided with an insulating glue layer. According to the pole piece disclosed by the utility model, the active layers are arranged in a staggered manner, so that the initial pressure of a roller on the pole piece is greatly reduced, and the belt breakage risk is reduced.

Description

Technical Field

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

[0002] Lithium-ion batteries are widely used in various digital products and mobile devices due to their advantages such as high energy density, low self-discharge, wide operating temperature range, and no environmental pollution. With the rapid development of electronic products and their increasing usage frequency, consumers have higher and higher demands for lithium-ion batteries.

[0003] To improve the performance of lithium-ion batteries, the electrode sheets are often rolled during the manufacturing process to achieve a high compaction density of the active material layer on the substrate. However, during the electrode coating process, due to equipment and process limitations, the active material layer thickness may be too thick at the initial coating position. Furthermore, because the active material layers on both sides of the electrode are aligned, the pressure on the electrode can suddenly increase when the roller moves from the empty foil section to the coating section, thus posing a risk of strip breakage. Utility Model Content

[0004] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes an electrode sheet that, by staggering the active layers, greatly reduces the initial pressure of the rolls on the electrode sheet, thereby reducing the risk of strip breakage.

[0005] This utility model also proposes a battery cell having the above-mentioned electrode plates.

[0006] This utility model also proposes a battery having the above-mentioned battery cell.

[0007] The electrode sheet according to a first aspect embodiment of the present invention includes:

[0008] A current collector, the current collector having a first end and a second end, wherein the electrode is rolled from the first end to the second end;

[0009] A first active layer is coated on one side of the current collector along the thickness direction;

[0010] A second active layer is coated on the other side of the current collector along the thickness direction;

[0011] The first active layer includes a protrusion that protrudes from the second active layer at the first end along the length direction of the current collector, and the protrusion is provided with an insulating adhesive layer.

[0012] The electrode sheet according to the embodiment of this utility model has at least the following beneficial effects:

[0013] The electrode sheet in this application has a significantly smaller thickness in the initial stage of rolling compared to electrodes in related technologies. This greatly reduces the pressure exerted by the rolls on the electrode sheet. The protrusions facilitate a gradual increase in pressure, allowing the electrode sheet sufficient time to adapt. This results in a smoother change in its internal structure, leading to better compaction and preventing breakage caused by sudden pressure increases. Furthermore, to prevent lithium deposition caused by the protrusions, an insulating adhesive layer is applied to the protrusions to inhibit lithium ion migration. This insulating adhesive layer also exhibits good wear resistance and flexibility, making it less susceptible to damage during rolling.

[0014] According to some embodiments of the present invention, the first active layer further includes a main body portion, the protrusion portion is located at the end of the main body portion, the thickness of the protrusion portion is less than the thickness of the main body portion, and the thickness difference between the main body portion and the protrusion portion is in the range of 10 μm to 25 μm.

[0015] According to some embodiments of the present invention, the protrusion includes a first surface, the first surface being disposed parallel to the surface of the current collector, the insulating adhesive layer including a first insulating portion disposed on the first surface, the thickness of the first insulating portion being in the range of 5% to 10% of the thickness difference between the main body portion and the protrusion.

[0016] According to some embodiments of the present invention, the protrusion further includes a second surface, which is disposed intersecting with the surface of the current collector and located at the end of the protrusion along the length direction of the current collector. The insulating adhesive layer further includes a second insulating portion disposed on the second surface, which is connected to the first insulating portion.

[0017] According to some embodiments of the present invention, the first active layer further includes a main body portion, the protrusion portion is located at the end of the main body portion, the protrusion portion includes a first surface, the first surface is inclined relative to the surface of the current collector, and the distance from the first surface to the surface of the current collector gradually decreases along the direction away from the main body portion.

[0018] According to some embodiments of the present invention, the thickness of the larger end of the protrusion is less than the thickness of the main body, and the thickness difference between the main body and the larger end of the protrusion is in the range of 10 μm to 25 μm.

[0019] According to some embodiments of the present invention, the protrusion has a dimension of 2 mm to 5 mm along the length direction of the current collector.

[0020] According to some embodiments of the present invention, the insulating adhesive layer is made of polyurethane material.

[0021] The battery cell according to a second aspect of the present invention includes the electrode sheet described in any of the above embodiments.

[0022] The battery according to a third aspect of the present invention includes the battery cell described in any of the above embodiments.

[0023] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0025] Figure 1 This is a schematic diagram of an electrode in a related technology;

[0026] Figure 2 This is a schematic diagram of the electrode structure according to an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of the structure of the electrode sheet in a further embodiment of the present invention;

[0028] Figure 4 for Figure 3 Enlarged view of region A in the middle;

[0029] Figure 5 for Figure 3 An enlarged schematic diagram of another implementation method;

[0030] Figure 6 This is a graph showing the trend of battery capacity changing with the number of cycles when the electrode sheet of this utility model is applied in the battery.

[0031] Figure 7 This is a graph showing the trend of the expansion rate of the electrode in a battery as a function of the number of cycles, according to an embodiment of the present invention.

[0032] Figure label:

[0033] Current collector 100; First end 101; Second end 102;

[0034] First active layer 200; protrusion 210; first surface 211; second surface 212; main body 220;

[0035] Second active layer 300;

[0036] Insulating adhesive layer 400; First insulating part 410; Second insulating part 420; Detailed Implementation

[0037] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0038] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0039] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0040] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0041] In the description of this utility model, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0042] Lithium-ion batteries are widely used in various digital products and mobile devices due to their advantages such as high energy density, low self-discharge, wide operating temperature range, and no environmental pollution. With the rapid development of electronic products and their increasing usage frequency, consumers have higher and higher demands for lithium-ion batteries.

[0043] To improve the performance of lithium-ion batteries, the electrode sheets are often rolled during the manufacturing process to achieve a high compaction density of the active material layer on the substrate. However, during the electrode coating process, due to equipment and process limitations, the active material layer thickness may be too thick at the initial coating position. Furthermore, because the active material layers on both sides of the electrode are aligned, the pressure on the electrode can suddenly increase when the roller moves from the empty foil section to the coating section, thus posing a risk of strip breakage.

[0044] To address the aforementioned problems, the first aspect of this application proposes an electrode sheet comprising a current collector 100, a first active layer 200, and a second active layer 300. The current collector 100 primarily functions to concentrate current, provide mechanical support, and dissipate heat. During the chemical reaction in the battery, the current collector 100 receives and conducts electrons, thereby forming a converged current to ensure normal power output. In lithium-ion batteries, copper foil is typically chosen for the negative electrode current collector 100, and aluminum foil for the positive electrode current collector 100. Alternatively, composite foil can be used to make the current collector 100. Composite foil often includes a substrate made of a polymer material and a conductive layer made of a metal material, providing good chemical properties while ensuring the mechanical strength of the current collector 100.

[0045] Along the length of the current collector 100, the two ends of the current collector 100 are respectively designated as the first end 101 and the second end 102. It should be noted that during the rolling process, the electrode sheet is conveyed toward the roller along the direction from the second end 102 to the first end 101, so that the first end 101 of the electrode sheet first contacts the roller, and the contact point gradually moves toward the second end 102. That is, the electrode sheet is rolled from the first end 101 to the second end 102.

[0046] The first active layer 200 and the second active layer 300 are coated on both sides of the current collector 100. Specifically, the first active layer 200 is coated on one side of the current collector 100 along its thickness direction, and the second active layer 300 is coated on the other side of the current collector 100 along its thickness direction. The active layers typically consist of active materials, conductive agents, and binders. The active material is the main component of the positive electrode, determining the battery's energy density and charge / discharge efficiency. Common positive electrode active materials include lithium iron phosphate, lithium nickel cobalt manganese oxide (NMC), and lithium nickel cobalt aluminum oxide (NCA). The conductive agent improves the battery's electronic conductivity; common conductive agents include carbon black, graphite, and conductive polymers. The binder is used to bond the active material and conductive agent together while maintaining the battery's structural stability. Common binders include polyvinylidene fluoride (PVDF) and polyacrylate (PAA). The negative electrode also consists of active materials, conductive agents, and binders. Graphite is commonly used as the negative electrode active material because of its high electrochemical stability and good ion conductivity.

[0047] The thickness of the electrode is typically A1+A2+B, where A1 is the normal thickness of the first active layer 200, A2 is the normal thickness of the second active layer 300, and B is the normal thickness of the current collector 100. It should be noted that in related technologies, such as... Figure 1 As shown, the first active layer 200 is coated from the first end 101 to the second end 102, and then the second active layer 300 is coated on the other side of the current collector 100 along the direction from the second end 102 to the first end 101. The first active layer 200 and the second active layer 300 are flush with the first end 101. Under normal circumstances, due to the limitations of the coating equipment, the thickness of the active layer will inevitably be thicker at the beginning of the coating process, and then gradually return to the normal thickness as the coating progresses. Thus, as... Figure 1 As shown, there is a protrusion at the starting end of the first active layer 200. It should be explained that... Figure 1 The protrusions shown are quite prominent and are only for ease of understanding; the size and shape of the protrusions may vary in actual production. The thickness of the electrode at the first end 101 is actually A1'+A2+B, where A1' is the thickness of the first active layer 200 at the beginning of the rolling process, and A1' is greater than A1.

[0048] Therefore, the actual thickness of the electrode at the first end 101 is greater than the thickness at other locations on the electrode. Consequently, when the electrode at the first end 101 contacts the roll, the pressure on the electrode increases sharply to its maximum, and then decreases as the electrode thickness decreases. It is understandable that when the electrode is subjected to a large impact force in a short period of time, its internal structure will undergo drastic changes, and the surge in pressure may cause the current collector 100 to break. Therefore, the electrode is more prone to strip breakage at the initial stage of contact with the roll.

[0049] To address this issue, the electrode in this application has undergone improvements to the coating process, resulting in the following: Figures 2 to 5 The electrode shown is an example of a coating process where, specifically, during the coating of the first active layer 200, the starting point of the coating of the first active layer 200 is offset from the ending point of the coating of the second active layer 300, so that the first active layer 200 extends out of the first end 101 relative to the second active layer 300, thereby forming an electrode on the first active layer 200 as shown in the diagram. Figure 2 The protrusion 210 shown protrudes from the second active layer 300 at the first end 101 along the length direction of the current collector 100.

[0050] Therefore, by moving the coating start end of the first active layer 200 forward, the thickness of the electrode sheet transitions from A1'+B to A1+A2+B along the direction from the first end 101 to the second end 102. Since the second active layer 300 is not coated on the other side of the coating start end of the first active layer 200, the thickest part of the first active layer 200 is avoided, thereby reducing the thickness of the first end 101 of the electrode sheet to A1'+B and the maximum thickness of the electrode sheet to A1+A2+B. The thickness of the electrode sheet in the initial stage of rolling is much smaller than that of the electrode sheet in the initial stage of rolling in the related art, which greatly reduces the pressure of the roller on the electrode sheet. The transition is achieved through the protrusion 210, allowing the pressure of the roller on the electrode sheet to gradually increase. The electrode sheet has enough time to gradually adapt to the increase in pressure, and its internal structure changes more smoothly, thereby achieving a better compaction effect and avoiding the situation where a sudden increase in pressure causes the electrode sheet to break.

[0051] In addition, to prevent lithium plating caused by the protrusion 210, an insulating adhesive layer 400 is attached to the protrusion 210 to prevent lithium ion migration. It should be understood that the insulating adhesive layer 400 can be a coating layer formed on the protrusion 210 through processes such as coating or spraying. Alternatively, the insulating adhesive layer 400 can be a separately manufactured component such as tape, attached to the surface of the protrusion 210 by means of adhesion or bonding. It should be noted that the insulating adhesive layer 400 can be made of polyurethane material, which has good wear resistance and flexibility, and is not easily damaged when passing through the rollers.

[0052] In some embodiments, the first active layer 200 further includes a main body 220. It is understood that the main body 220 is the active layer formed by stable coating using a coating apparatus, and thus the thickness of the main body 220 is equal to the normal thickness A1 of the first active layer 200. A protrusion 210 is located at the end of the main body 220 and is integrally formed with the main body 220. For example... Figures 3 to 5 As shown, a groove is cut into the top surface of the protrusion 210 to thin it, so that the thickness of the protrusion 210 is less than the thickness of the main body 220. It should be noted that the thickness difference between the main body 220 and the protrusion 210 is in the range of 10μm to 25μm. That is, after coating, the protrusion 210 is thinned by 10μm to 25μm. On the one hand, this can avoid tape breakage caused by the protrusion 210 being too thick, and on the other hand, the groove can be opened to accommodate the insulating adhesive layer 400, preventing the insulating adhesive layer 400 from protruding from the surface of the electrode sheet.

[0053] Furthermore, the protrusion 210 includes a first surface 211, such as Figure 4As shown, the first surface 211 is disposed parallel to the surface of the current collector 100, and the insulating adhesive layer 400 includes a first insulating portion 410 disposed on the first surface 211. It should be noted that the thickness of the first insulating portion 410 needs to be maintained within the range of 5% to 10% of the thickness difference between the main body portion 220 and the protrusion 210. If the first insulating portion 410 is too thin, its barrier properties against lithium ions will be poor, and if lithium ions can pass through the first insulating portion 410, it will easily lead to lithium plating problems. If the first insulating portion 410 is too thick, it will easily protrude from the electrode surface after the electrode is rolled, thus affecting the flatness of the electrode.

[0054] Furthermore, the protrusion 210 also includes a second surface 212, which intersects with the surface of the current collector 100 and is located at the end of the protrusion 210 along the length of the current collector 100. The insulating adhesive layer 400 also includes a second insulating portion 420, which is disposed on the second surface 212 to isolate lithium-ion transport on the second surface 212. The second insulating portion 420 and the first insulating portion 410 can be integrally formed, for example, as an integral tape, with the two parts respectively attached to the first surface 211 and the second surface 212, thereby wrapping the protrusion 210. It is understood that the thickness of the second insulating portion 420 can be consistent with the thickness of the first insulating portion 410.

[0055] To verify the impact of the insulating adhesive layer 400 and its thickness on the battery's electrical performance, this application conducted the following three sets of comparative experiments:

[0056] Example 1: The first active layer 200 includes a protrusion 210, and the protrusion 210 is provided with an insulating adhesive layer 400. The thickness of the insulating adhesive layer 400 is 5% of the thickness difference between the main body 220 and the protrusion 210.

[0057] Comparative Example 1: The first active layer 200 includes a protrusion 210, and the protrusion 210 is provided with an insulating adhesive layer 400. The thickness of the insulating adhesive layer 400 is 3% of the thickness difference between the main body 220 and the protrusion 210.

[0058] Comparative Example 2: The first active layer 200 includes a protrusion 210, and the protrusion 210 is not provided with an insulating adhesive layer 400;

[0059] Experimental environment: Charge at 2.8C constant current and constant voltage to 4.25V, cutoff rate 1.8C; charge at 1.8C constant current and constant voltage to 4.4V, cutoff rate 1.5C; charge at 1.5C constant current and constant voltage to 4.53V, cutoff rate 0.05C; the above constitutes one cycle, repeated 800 times.

[0060] Experimental qualification requirements: After 300 cycles, the battery capacity must be ≥92% and the battery expansion rate must be ≤8%.

[0061] Experimental results are as follows Figure 6 and Figure 7 As shown, where, Figure 6 The figure shown is a graph illustrating the change in battery capacity. Figure 7 The graph shows the variation of the battery expansion rate, where line A represents the battery parameters of Example 1, line B represents the battery parameters of Comparative Example 1, and line C represents the battery parameters of Comparative Example 2. It can be observed that... Figure 6 In the 300-cycle test, only the battery of Example 1 met the battery capacity requirements. Figure 7 Of these, only the battery in Example 1 met the expansion rate requirement.

[0062] In other embodiments, such as Figure 5 As shown, when slotting the top surface of the protrusion 210, an oblique groove is formed. That is, the first surface 211 of the protrusion 210 is inclined relative to the surface of the current collector 100, and the distance from the first surface 211 to the current collector 100 gradually decreases in the direction away from the main body 220. Therefore, when the roller contacts the protrusion 210, the pressure applied by the roller to the protrusion 210 gradually increases, thereby achieving a better transition effect and further reducing the probability of electrode breakage.

[0063] Furthermore, since the grooved protrusion 210 needs to accommodate the insulating adhesive layer 400, the distance from the large end of the protrusion 210 to the current collector 100 (i.e., the thickness of the large end of the protrusion 210) is less than the distance from the main body 220 to the current collector 100 (i.e., the thickness of the main body 220). Preferably, the thickness difference between the main body 220 and the large end of the protrusion 210 is in the range of 10μm to 25μm.

[0064] In some embodiments, the protrusion 210 has a dimension of 2 mm to 5 mm along the length direction of the current collector 100. When the size is smaller than this range, the transition effect of the protrusion 210 on the electrode is not obvious. When the size is larger than this range, the arrangement of the protrusion 210 will affect the energy density of the electrode.

[0065] A second aspect of this application also provides a battery cell comprising the electrode plates mentioned in any of the foregoing embodiments. It is understood that the electrode plates in the foregoing embodiments can be either positive or negative electrodes. Therefore, the battery cell of the second aspect embodiment can have only the positive electrode plate using the above structure, only the negative electrode plate using the above structure, or both the positive and negative electrode plates using the above structure.

[0066] A third aspect of this application also proposes a battery comprising the cells mentioned in the above embodiments.

[0067] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. An electrode, characterized in that, include: A current collector, the current collector having a first end and a second end, wherein the electrode is rolled from the first end to the second end; A first active layer is coated on one side of the current collector along the thickness direction; A second active layer is coated on the other side of the current collector along the thickness direction; The first active layer includes a protrusion that protrudes from the second active layer at the first end along the length of the current collector. The electrode also includes an insulating adhesive layer that covers the protrusion.

2. The electrode sheet according to claim 1, characterized in that, The first active layer further includes a main body portion, the protrusion portion being located at the end of the main body portion, the thickness of the protrusion portion being less than the thickness of the main body portion, and the thickness difference between the main body portion and the protrusion portion being in the range of 10 μm to 25 μm.

3. The electrode sheet according to claim 2, characterized in that, The protrusion includes a first surface, which is disposed parallel to the surface of the current collector. The insulating adhesive layer includes a first insulating portion disposed on the first surface. The thickness of the first insulating portion is in the range of 5% to 10% of the thickness difference between the main body portion and the protrusion.

4. The electrode sheet according to claim 3, characterized in that, The protrusion further includes a second surface, which intersects with the surface of the current collector and is located at the end of the protrusion along the length direction of the current collector. The insulating adhesive layer further includes a second insulating portion disposed on the second surface, which is connected to the first insulating portion.

5. The electrode sheet according to claim 1, characterized in that, The first active layer further includes a main body portion, and the protrusion portion is located at the end of the main body portion. The protrusion portion includes a first surface, which is inclined relative to the surface of the current collector. Along the direction away from the main body portion, the distance between the first surface and the surface of the current collector gradually decreases.

6. The electrode sheet according to claim 5, characterized in that, The thickness of the larger end of the protrusion is less than the thickness of the main body, and the thickness difference between the main body and the larger end of the protrusion is in the range of 10 μm to 25 μm.

7. The electrode sheet according to claim 1, characterized in that, The protrusion has a length of 2 mm to 5 mm along the length of the current collector.

8. The electrode sheet according to claim 1, characterized in that, The insulating adhesive layer is made of polyurethane material.

9. A battery cell, characterized in that, Including the electrode as described in any one of claims 1 to 8.

10. A battery, characterized in that, Including the battery cell as described in claim 9.

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