Pole piece, battery cell and lithium ion battery

Abstract

The utility model discloses a pole piece, a battery cell and a lithium ion battery. The pole piece comprises a current collector, an active coating and protective glue, at least one surface of the current collector is coated with the active coating, a step is formed between the active coating and the current collector in the length direction of the current collector, the step is provided with a first step surface, a second step surface and a third step surface, the first step surface and the second step surface are formed on the surface of the active coating, the third step surface is formed on the surface of the current collector, and the first step surface is adjacent to the second step surface. And the first step surface and the third step surface are arranged in parallel. One end of the protective glue is fixed on the first step surface, the other end of the protective glue is fixed on the third step surface, and a slope is formed between at least the middle part of the protective glue and the second step surface and the third step surface, so that the stress area of the pole piece is increased, and the pressure borne by the current collector and the active coating can be reduced; and the risk that the current collector is deformed or damaged due to overlarge stress in the rolling process is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium - ion battery production, and particularly relates to an electrode sheet, a battery cell and a lithium - ion battery. Background Art

[0002] A lithium - ion battery is a secondary battery (rechargeable battery) that stores energy by the movement of lithium ions between the positive and negative electrodes. The production process includes electrode preparation, electrode assembly, electrolyte injection and encapsulation. During the electrode preparation process, the electrode first goes through a coating process, that is, an active material is coated on a current collector (usually aluminum foil). The purpose of this step is to evenly distribute the active material on the current collector to prepare for subsequent processes. After coating, the electrode sheet does not reach the final required density and thickness uniformity. To enhance the bonding strength between the active material and the current collector, prevent peeling during use, and improve the battery performance, the positive electrode sheet needs to go through a rolling process. Rolling is a process of compressing the electrode sheet to a specified thickness under a certain pressure by two steel rollers.

[0003] However, in the coating process, after the electrode slurry is coated, due to the influence of the fluid characteristics of the slurry during the coating process, it is easy to form a semi - circular feature at the starting point, ending point and both sides of the coating, that is, the thickness of the coating increases at the starting and ending positions and the edges. During the rolling process, due to the concentrated stress points, the current collector is under excessive pressure, which easily causes deformation or damage to the current collector, and there is a risk of the electrode sheet breaking during subsequent cycle tests. Summary of the Utility Model

[0004] The main object of the utility model is to propose an electrode sheet, aiming to reduce the risk that the current collector of the existing electrode sheet is easily deformed or damaged due to excessive force during the rolling process.

[0005] To achieve the above object, the first aspect of the utility model proposes an electrode sheet, including:

[0006] A current collector;

[0007] An active coating, the active coating is coated on at least one surface of the current collector, and a step is formed between the active coating and the current collector along the length direction of the current collector. The step has a first step surface and a second step surface formed on the surface of the active coating, and a third step surface formed on the surface of the current collector. The first step surface and the second step surface are adjacent to each other, and the first step surface and the third step surface are parallel to each other;

[0008] A protective adhesive, one end of the protective adhesive is fixed to the first step surface, the other end of the protective adhesive is fixed to the third step surface, and at least the middle part of the protective adhesive forms a slope with the second step surface and the third step surface.

[0009] In some embodiments, the protective adhesive includes a substrate layer and an adhesive layer, and the substrate layer is adhesively connected to the first step surface, the second step surface, and the third step surface through the adhesive layer.

[0010] In some embodiments, the adhesive layer includes a first adhesive layer, a second adhesive layer, and a third adhesive layer, the substrate layer includes a first substrate layer, a second substrate layer, and a third substrate layer, the first substrate layer is adhesively connected to the first step surface through the first adhesive layer, the second substrate layer is adhesively connected to the second step surface and at least partially the third step surface through the second adhesive layer, and the third substrate layer is adhesively connected to at least partially the third step surface through the third adhesive layer;

[0011] Wherein, the thickness of the second adhesive layer gradually decreases along the length direction of the current collector from the second step surface, so as to form the slope between the second substrate layer and the second step surface and at least partially the third step surface.

[0012] In some embodiments, the surface of the first substrate layer is arranged parallel to the surface of the active coating.

[0013] In some embodiments, the distance between the surface of the first substrate layer facing away from the active coating and the first step surface is greater than or equal to 5 μm and less than or equal to 20 μm.

[0014] In some embodiments, the distance between the surface of the first substrate layer facing away from the active coating and the surface of the current collector is greater than or equal to 30 μm and less than or equal to 80 μm.

[0015] In some embodiments, the material of the substrate layer includes one of thermoplastic polyester, polyethylene, polypropylene, and polyvinyl chloride.

[0016] In some embodiments, the material of the adhesive layer includes one of acrylic resin, polycarbonate, polyurethane, and rubber.

[0017] The second aspect of the present utility model further provides an electric core, including a positive electrode sheet, a negative electrode sheet, and a separator, the separator is arranged between the positive electrode sheet and the negative electrode sheet to separate the positive electrode sheet and the negative electrode sheet;

[0018] Wherein, at least one of the positive electrode sheet and the negative electrode sheet adopts the above-mentioned electrode sheet.

[0019] The third aspect of the present utility model further provides a lithium-ion battery, including a housing and the above-mentioned electric core, and the electric core is arranged in the housing.

[0020] In the pole piece of the present utility model, a protective glue is provided at the step formed between the active coating and the current collector. One end of the protective glue is fixed to the first step surface of the step, the other end of the protective glue is fixed to the third step surface of the step, and at least the middle part of the protective glue forms a slope with the second step surface and the third step surface of the step, so as to increase the stress area of the pole piece. In this way, during the rolling process of the pole piece, the pressure on the current collector and the active coating can be reduced, and the risk of deformation or damage of the current collector due to excessive force during the rolling process can be reduced, thereby reducing the risk of broken pieces during subsequent cycle tests. Description of the Drawings

[0021] Figure 1 It is a partial structural schematic diagram of a pole piece in the prior art;

[0022] Figure 2 It is a structural schematic diagram of an embodiment of the pole piece of the present utility model;

[0023] Figure 3 It is a structural schematic diagram of an embodiment of the pole piece of the present utility model.

[0024] Explanation of the Reference Numerals in the Drawings:

[0025] Label Name Label Name 100 Pole piece 101 Current collector 102 Active coating 110 First stepped surface 111 Second stepped surface 112 Third stepped surface 120 Protective glue 121 Base material layer 122 Adhesive layer 130 First adhesive layer 131 Second adhesive layer 132 Third adhesive layer 133 First base material layer 134 Second base material layer 135 Third base material layer 123 Ramp Detailed Description of the Embodiment

[0026] Next, the solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model.

[0027] It should be noted that all the directional indications (such as up, down, left, right, front, back...) in the embodiments of the present utility model are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0028] It should also be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there may be an intermediate element at the same time. When an element is referred to as "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time.

[0029] In addition, the descriptions involving "first", "second", etc. in the present utility model are only for descriptive purposes and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present utility model.

[0030] A lithium-ion battery is a secondary battery (rechargeable battery) that stores energy by the movement of lithium ions between the positive and negative electrodes. The production process includes electrode preparation, electrode assembly, electrolyte injection, and encapsulation.

[0031] In the process of electrode preparation, first, there is a coating process, that is, a uniformly stirred electrode paste is coated on the current collector surface to form an active coating. The purpose of this step is to evenly distribute the active material on the current collector and prepare for the subsequent processes. After coating, the electrode sheet does not reach the final required density and thickness uniformity, so it appears loose and porous.

[0032] To improve this, enhance the bonding strength between the active material and the current collector, prevent peeling during use, and improve the performance of the battery, the electrode sheet needs to go through a rolling process. Rolling is a process of compressing the electrode sheet to a specified thickness under a certain pressure by two steel rollers. This step can further compact the electrode, reduce the contact resistance between substances, increase the capacity within the battery volume, and at the same time ensure the wetting effect of the electrolyte on the electrode sheet, so that the structure of the battery is more stable and the gap distance between particles is smaller.

[0033] However, due to the influence of the slurry fluid characteristics during the coating process, there is a thickness difference between the trailing edge of the electrode sheet after coating and the current collector. This phenomenon is called the "thick edge" phenomenon. During the rolling process, due to the concentrated stress points at this position, the pressure on the current collector is too large, which easily causes deformation or damage to the current collector and has a risk of electrode breakage during subsequent cycle tests.

[0034] See Figure 1 , the electrode sheet 100 includes a current collector 101 and an active coating 102. The active coating 102 of the electrode sheet 100 is coated on at least one surface of the current collector 101, and a step is formed between the active coating 102 and the current collector 101 along the length direction of the current collector 101. The step has a first step surface 110, a second step surface 111 formed on the surface of the active coating 102, and a third step surface 112 formed on the surface of the current collector 101. The first step surface 110 and the second step surface 111 are adjacent to each other, and the first step surface 110 and the third step surface 112 are parallel to each other.

[0035] In this embodiment, the active coating 102 is coated on two opposite surfaces of the current collector 101. Due to the fluid characteristics of the active coating 102, it is easy to form a step between the active coating 102 and the current collector 101. During the actual coating process, this step may be formed at the starting point, the ending point, or both side edges of the coating.

[0036] Among them, the first step surface 110 is formed on the surface of the active coating 102, the third step surface 112 is formed on the surface of the current collector 101 and is parallel to the first step surface 110, and the second step surface 111 is formed on the surface of the active coating 102 and connects the first step surface 110 and the third step surface 112.

[0037] Of course, the above is only exemplary. The active coating 102 can also be coated on only one surface of the current collector 101 alone, and the embodiments of the present invention do not limit this here.

[0038] To reduce the risk that the current collector 101 is prone to deformation or breakage due to excessive pressure during the rolling process, please refer to Figure 3 , the electrode sheet 100 of the embodiment of the present invention further includes a protective adhesive 120. One end of the protective adhesive 120 is fixed to the first step surface 110, the other end of the protective adhesive 120 is fixed to the third step surface 112, and at least the middle part of the protective adhesive 120 forms a slope 123 with the second step surface 111 and the third step surface 112.

[0039] In this embodiment, one end of the protective adhesive 120 is fixed to the surface of the active coating 102, the other end is fixed to the surface of the current collector 101, and a gentle slope 123 is formed between the protective adhesive 120 and the active coating 102 and the current collector 101. This slope 123 can increase the stress area at the junction of the active coating 102 and the current collector 101, that is, change the original stress point of the electrode sheet 100 into a larger stress surface, which can reduce the risk that the current collector 101 is deformed or damaged due to excessive stress during the rolling process, and further reduce the risk of broken pieces during the subsequent cycle test.

[0040] It should be noted that the slope of the slope 123 can be 30°, 40°, 50°, etc., which is specifically determined by the actual situation, and the present invention does not limit this here.

[0041] As some embodiments, the material of the protective adhesive 120 can be PI and PET, or it can also be silicone pressure-sensitive adhesive, acrylate, rubber pressure-sensitive adhesive, etc., and can be specifically selected and set according to actual needs. The embodiments of the present application do not limit this here.

[0042] Please continue to refer to Figure 2, the protective adhesive 120 includes a substrate layer 121 and an adhesive layer 122. The substrate layer 121 is adhesively connected to the first stepped surface 110, the second stepped surface 111, and the third stepped surface 112 through the adhesive layer 122. In this embodiment, the protective adhesive 120 is adhered to the electrode sheet 100 through the adhesive layer 122 to ensure the connection stability between the protective adhesive 120, the active coating 102, and the current collector 101. At the same time, a substrate layer 121 is adhered above the adhesive layer 122, which can prevent the roller pressing equipment from directly contacting the adhesive layer 122 when roller pressing the electrode sheet 100 and leaving residual glue, thereby affecting the subsequent roller pressing of the electrode sheet 100.

[0043] In some embodiments, the material of the substrate layer 121 includes one of thermoplastic polyester, polyethylene, polypropylene, and polyvinyl chloride. For example, the substrate layer 121 of the embodiment of the present application can be made of polypropylene. Among them, polypropylene is odorless, non-toxic, and lightweight, and will not exert excessive pressure on the active coating 102 and the current collector 101 when applied in the electrode sheet 100. Polypropylene also has excellent mechanical properties, including tensile strength and compressive strength, and can be bent without damage when winding the battery cell. Polypropylene also has good heat resistance and can adapt to the high temperature generated during the charge and discharge process of the battery. Of course, this is only exemplary, and others can also be selected. The embodiments of the present application are not limited herein.

[0044] In some embodiments, the material of the adhesive layer 122 includes one of acrylic resin, polycarbonate, polyurethane, and rubber. For example, the adhesive layer 122 can be made of polycarbonate. Polycarbonate has the characteristics of high strength, high elastic modulus, high impact strength, good fatigue resistance, good dimensional stability, and small creep (rarely changes even under high temperature conditions). When winding the battery cell, it can be easily bent together. Polycarbonate has excellent heat aging resistance and can adapt to the high temperature generated during the charge and discharge process of the battery. Of course, this is only exemplary, and others can also be selected. The embodiments of the present application are not limited herein.

[0045] Please refer to Figure 3 , in this embodiment, the adhesive layer 122 includes a first adhesive layer 130, a second adhesive layer 131, and a third adhesive layer 132. The substrate layer 121 includes a first substrate layer 133, a second substrate layer 134, and a third substrate layer 135. The first substrate layer 133 is adhesively connected to the first stepped surface 110 through the first adhesive layer 130. The second substrate layer 134 is adhesively connected to the second stepped surface 111 and at least partially the third stepped surface 112 through the second adhesive layer 131. The third substrate layer 135 is adhesively connected to at least partially the third stepped surface 112 through the third adhesive layer 132;

[0046] Among them, the thickness of the second adhesive layer 131 gradually decreases along the length direction of the current collector 101 from the second stepped surface 111, so as to form a slope 123 between the second base material layer 134, the second stepped surface 111 and at least a part of the third stepped surface 112. That is, the thickness of the second adhesive layer 131 is uneven, so that the second base material layer 134 can form a slope 123 with the second stepped surface 111 and at least a part of the third stepped surface 112, so that when the electrode sheet 100 is roll-pressed, the external roll-pressing device can roll-press the electrode sheet 100 along the slope 123, reducing the pressure on the current collector 101 and reducing the risk of deformation or damage of the current collector 101 due to excessive force.

[0047] In some embodiments, the surface of the first base material layer 133 is parallel to the surface of the active coating layer 102, so that when the electrode sheet 100 is roll-pressed, the external roll-pressing device can roll-press the electrode sheet 100 along the surface of the first base material layer 133, avoiding the first base material layer 133 from affecting the roll-pressing process, improving the smoothness of the roll-pressing device during roll-pressing, and improving the roll-pressing efficiency.

[0048] In some embodiments, the distance between the surface of the first base material layer 133 facing away from the active coating layer 102 and the first stepped surface 110 is greater than or equal to 5 μm and less than or equal to 20 μm. Among them, the distance between the surface of the first base material layer 133 facing away from the active coating layer 102 and the first stepped surface 110 can be selected and set within the range of 5 μm - 20 μm according to actual conditions. For example, it can be 5 μm, 13 μm or 20 μm. By adopting a suitable spacing, on the one hand, it can stably connect the protective glue 120 to the active coating layer 102, avoiding the protective glue 120 from easily separating from the active coating layer 102; on the other hand, it will not cause a situation where the thickness difference between the protective glue 120 and the active coating layer 102 cannot be formed due to too large a distance.

[0049] In some embodiments, the distance between the surface of the first base material layer 133 facing away from the active coating layer 102 and the surface of the current collector 101 is greater than or equal to 30 μm and less than or equal to 80 μm. Among them, the distance between the surface of the first base material layer 133 facing away from the active coating layer 102 and the current collector 101 can be selected and set within the range of 30 μm - 80 μm according to actual conditions. For example, it can be 30 μm, 55 μm or 80 μm. By adopting a reasonable spacing, on the one hand, it can stably connect the protective glue 120 to the active coating layer 102, avoiding the protective glue 120 from easily separating from the active coating layer 102; on the other hand, it will not cause a situation where the slope 123 has an extremely small slope due to too small a distance, which affects the roll-pressing of the electrode sheet 100 by the external roll-pressing device.

[0050] The present utility model also provides an electric core, including a positive electrode sheet, a negative electrode sheet and a separator. The separator is arranged between the positive electrode sheet and the negative electrode sheet to separate the positive electrode sheet and the negative electrode sheet;

[0051] Among them, at least one of the positive electrode sheet and the negative electrode sheet adopts the above-mentioned electrode sheet 100.

[0052] Since the battery cell adopts all the technical solutions of all the above-mentioned embodiments of the electrode sheet 100, the battery cell of the present utility model also has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be elaborated herein one by one.

[0053] The present utility model also provides a lithium-ion battery, which includes a housing and the above-mentioned battery cell, and the battery cell is arranged inside the housing.

[0054] Since the lithium-ion battery adopts all the technical solutions of all the above-mentioned embodiments of the battery cell, the lithium-ion battery of the present utility model also has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be elaborated herein one by one.

[0055] The above are only partial or preferred embodiments of the present utility model. Whether in terms of text or drawings, the scope of protection of the present utility model cannot be limited thereby. Any equivalent structural transformation made by using the content of the specification and drawings of the present utility model under the overall concept of the present utility model, or any direct / indirect application in other related technical fields is included in the scope of protection of the present utility model.

Claims

1. A pole piece, characterized in that, Comprising: Current collector; Active coating, the active coating is coated on at least one surface of the current collector, and a step is formed between the active coating and the current collector along the length direction of the current collector. The step has a first step surface, a second step surface formed on the surface of the active coating, and a third step surface formed on the surface of the current collector. The first step surface and the second step surface are adjacent to each other, and the first step surface is parallel to the third step surface; Protective adhesive, one end of the protective adhesive is fixed to the first step surface, the other end of the protective adhesive is fixed to the third step surface, and at least the middle part of the protective adhesive forms a slope with the second step surface and the third step surface.

2. The pole piece according to claim 1, characterized in that, The protective adhesive includes a base material layer and an adhesive layer, and the base material layer is adhesively connected to the first step surface, the second step surface and the third step surface through the adhesive layer.

3. The pole piece according to claim 2, characterized in that, The adhesive layer includes a first adhesive layer, a second adhesive layer and a third adhesive layer. The base material layer includes a first base material layer, a second base material layer and a third base material layer. The first base material layer is adhesively connected to the first step surface through the first adhesive layer. The second base material layer is adhesively connected to the second step surface and at least a part of the third step surface through the second adhesive layer. The third base material layer is adhesively connected to at least a part of the third step surface through the third adhesive layer; Wherein, the thickness of the second adhesive layer gradually decreases along the length direction of the current collector from the second step surface, so that a slope is formed between the second base material layer and the second step surface and at least a part of the third step surface.

4. The pole piece according to claim 3, characterized in that, The surface of the first base material layer is parallel to the surface of the active coating.

5. The pole piece according to claim 4, characterized in that, The distance between the surface of the first base material layer facing away from the active coating and the first step surface is greater than or equal to 5 μm and less than or equal to 20 μm.

6. The pole piece according to claim 4, characterized in that, The distance between the surface of the first base material layer facing away from the active coating and the surface of the current collector is greater than or equal to 30 μm and less than or equal to 80 μm.

7. The pole piece according to any one of claims 2 to 6, characterized in that, The material of the base material layer includes one of thermoplastic polyester, polyethylene, polypropylene, and polyvinyl chloride.

8. The pole piece according to any one of claims 2 to 6, characterized in that, The material of the adhesive layer includes one of acrylic resin, polycarbonate, polyurethane, and rubber.

9. A battery cell, characterized in that, Including a positive electrode sheet, a negative electrode sheet and a separator, the separator is disposed between the positive electrode sheet and the negative electrode sheet to separate the positive electrode sheet and the negative electrode sheet; Wherein, at least one of the positive electrode sheet and the negative electrode sheet adopts the electrode sheet according to any one of claims 1 to 8.

10. A lithium-ion battery, characterized in that, Including a housing and the battery cell according to claim 9, the battery cell is disposed in the housing.

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