Pole piece, battery cell and battery

Abstract

The pole piece comprises a current collector and an active material layer, and the current collector comprises a first surface and a second surface which are arranged back to back; the active material layer is arranged on the first surface and / or the second surface of the current collector; wherein a butadiene styrene rubber layer is arranged between the current collector and the active material layer, and the butadiene styrene rubber layer is attached to the surface of the current collector and is wrapped by the active material layer. According to the pole piece provided by the utility model, the migration behavior of the butadiene styrene rubber layer arranged on the surface of the current collector is very weak in the drying process, and enough butadiene styrene rubber can be retained on the surface of the current collector, so that the adhesion strength between the active material layer and the current collector is ensured, and the electrochemical performance of the active material is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium batteries, and particularly relates to an electrode sheet, an electric core and a battery. Background Art

[0002] With the wide application of lithium-ion batteries, higher requirements are put forward for lithium batteries with high energy density. Styrene-butadiene rubber is often used as a binder for lithium-ion batteries because of its advantages of not easily polluting the environment and being easy to process in engineering.

[0003] However, during the drying process of the electrode sheet of the lithium-ion battery, due to the fluidity of the styrene-butadiene rubber, the styrene-butadiene rubber in the active material layer will gradually migrate to the outer surface facing away from the current collector, resulting in poor adhesion strength between the active material layer and the current collector, deteriorating the electrochemical performance of the active material, and thus reducing the energy density of the battery. Summary of the Utility Model

[0004] The main object of the utility model is to propose an electrode sheet, aiming to solve the technical problem that at present, due to the migration of styrene-butadiene rubber in the active material layer to the outer surface facing away from the current collector, the adhesion strength between the active material layer and the current collector becomes poor, deteriorating the electrical performance of the active material, and thus reducing the energy density of the battery.

[0005] To achieve the above object, the utility model proposes an electrode sheet, which includes:

[0006] A current collector, the current collector includes a first surface and a second surface arranged opposite to each other;

[0007] An active material layer, arranged on the first surface and / or the second surface of the current collector;

[0008] Wherein, a styrene-butadiene rubber layer is arranged between the current collector and the active material layer, and the styrene-butadiene rubber layer adheres to the surface of the current collector and is wrapped by the active material layer.

[0009] In some embodiments, the styrene-butadiene rubber layer is composed of at least two spaced-apart styrene-butadiene rubber regions, the spaced-apart direction of the styrene-butadiene rubber regions is perpendicular to the thickness direction of the electrode sheet, and the styrene-butadiene rubber regions adhere to the surface of the current collector and are wrapped by the active material layer.

[0010] In some embodiments, the coating amount of the styrene-butadiene rubber region is 7 ug / cm 2 ~45 ug / cm 2 .

[0011] In some embodiments, along the length direction of the current collector, the spacing between any two adjacent styrene-butadiene rubber regions is equal; and / or,

[0012] Along the width direction of the current collector, the distance between any two adjacent styrene-butadiene rubber regions is equal.

[0013] In some embodiments, the styrene-butadiene rubber regions are evenly distributed on the surface of the current collector.

[0014] In some embodiments, the styrene-butadiene rubber regions are in an island structure.

[0015] In some embodiments, the thickness of the current collector is D1 mm, the thickness of the styrene-butadiene rubber layer is D2 mm, and the thickness of the active material layer is D3 mm, where 5(D1 + D2) mm < D3 mm.

[0016] In some embodiments, the electrode sheet is a negative electrode sheet, and the current collector is a copper foil current collector.

[0017] The present utility model further provides an electrode core, which includes a positive electrode sheet, a separator, and a negative electrode sheet that are stacked and wound with each other, and the separator is disposed between the positive electrode sheet and the negative electrode sheet;

[0018] Wherein, the negative electrode sheet is the electrode sheet described above.

[0019] The present utility model further provides a battery, which includes a housing and the electrode core described above, and the electrode core is disposed in the housing.

[0020] For the electrode sheet provided by the present utility model, the migration behavior of the styrene-butadiene rubber layer disposed on the surface of the current collector during the drying process is very weak, and a sufficient amount of styrene-butadiene rubber can be retained on the surface of the current collector, ensuring the adhesion strength between the active material layer and the current collector and improving the electrochemical performance of the active material. In addition, since the surface of the current collector is already provided with a styrene-butadiene rubber layer, the concentration of the styrene-butadiene rubber binder in the active material layer can be reduced, and the reduction of the concentration can reduce the concentration gradient of the styrene-butadiene rubber binder in the active material layer, so that the binder is evenly distributed in the thickness direction of the active material layer and will not accumulate on the surface of the active material layer facing away from the current collector, thereby avoiding the pore-blocking effect caused by the styrene-butadiene rubber, enabling the smooth migration of lithium ions from the active material layer, and further improving the electrochemical performance of the battery. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of an electrode sheet in an embodiment of the present utility model;

[0022] Figure 2 It is a schematic structural diagram of an electrode sheet in another embodiment of the present utility model;

[0023] Figure 3 It is a schematic structural diagram of an electrode sheet in yet another embodiment of the present utility model;

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

[0025] Label Name Label Name 110 Current collector 120 Active material layer 130 Styrene-butadiene rubber layer 131 Styrene-butadiene rubber area

[0026] The realization, functional features and advantages of the present utility model will be further described in conjunction with embodiments and with reference to the accompanying drawings. Specific embodiments

[0027] Next, the solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying 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 of 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 fall within the scope of protection of the present utility model.

[0028] It should be noted that all 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 positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0029] It should also be noted that when an element is referred to as being "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 being "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time.

[0030] In addition, the descriptions involving "first", "second", etc. in the present utility model are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. 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 scope of protection required by the present utility model.

[0031] The present utility model provides a pole piece, with reference to Figure 1 and Figure 3 , the pole piece includes:

[0032] A current collector 110, the current collector 110 includes a first surface and a second surface disposed opposite to each other;

[0033] An active material layer 120, disposed on the first surface and / or the second surface of the current collector 110;

[0034] In this embodiment, the thickness of the current collector 110 is 4 μm to 22 μm. Among them, the current collector 110 is the main conduction path of the current in the battery. If the current collector 110 is too thin, it will cause an increase in the internal resistance of the battery, and there is a risk of excessive heat generation when the current passes through the current collector 110, which will further cause overheating of the current collector 110 or the surrounding structure, and even pose a danger of fire or explosion, reducing the safety performance of the battery. If the current collector 110 is too thick, it will reduce the volumetric energy density of the battery. Therefore, in this embodiment, when the thickness of the current collector 110 is set to 4 μm to 22 μm, the above situation can be effectively avoided. Preferably, the thickness of the current collector 110 is set to 6 μm to 12 μm.

[0035] The active material layer 120 is disposed on the first surface and / or the second surface of the current collector 110, that is, the active material layer 120 can be disposed on the first surface or the second surface of the current collector 110, or the active material layer 120 can be disposed on the first surface and the second surface of the current collector 110. When the active material layer 120 is disposed on both the first surface and the second surface of the current collector 110, during the production process of the electrode sheet, the active material is first coated on the first surface of the current collector 110, and after the active material is dried, an active material layer 120 is formed. Then, the active material is coated on the second surface of the current collector 110, and after drying, another active material layer 12 is formed.

[0036] Among them, a styrene-butadiene rubber layer 130 is disposed between the current collector 110 and the active material layer 120. The styrene-butadiene rubber layer 130 adheres to the surface of the current collector 110, and the styrene-butadiene rubber layer 130 is wrapped by the active material layer 120. The styrene-butadiene rubber layer 130 is formed by coating a styrene-butadiene rubber emulsion on the surface of the current collector 110 and drying. The setting of the styrene-butadiene rubber layer 130 can increase the adhesion strength between the active material layer 120 and the current collector 110, and improve the electrochemical performance of the electrode sheet. It can be understood that when the styrene-butadiene rubber layer 130 is disposed on both the first surface and the second surface of the current collector 110, corresponding to the active material layers 120 on the opposite sides of the current collector 110, the adhesion strength between the current collector 110 and the active material layers 120 on both sides can be increased together, further improving the electrochemical performance of the electrode sheet.

[0037] For the electrode sheet provided by the present invention, the migration behavior of the styrene-butadiene rubber layer disposed on the surface of the current collector 110 during the drying process is very weak, and a sufficient amount of styrene-butadiene rubber can be retained on the surface of the current collector 110, ensuring the adhesion strength between the active material layer 120 and the current collector 110, and improving the electrochemical performance of the active material.

[0038] In addition, since a styrene-butadiene rubber layer is already provided on the surface of the current collector 110, the concentration of the styrene-butadiene rubber binder in the active material layer 120 can be reduced. The reduced concentration can decrease the concentration gradient of the styrene-butadiene rubber binder in the active material layer 120, so that the binder is uniformly distributed in the thickness direction of the active material layer 120 and does not accumulate on the surface of the active material layer 120 facing away from the current collector 110. Thus, the pore-blocking effect caused by the styrene-butadiene rubber is avoided, and the migration of lithium ions from the active material layer 120 is smooth, further improving the electrochemical performance of the battery.

[0039] In some embodiments, referring to Figure 2 , the styrene-butadiene rubber layer 130 is composed of at least two spaced-apart styrene-butadiene rubber regions 131. The spaced-apart direction of the styrene-butadiene rubber regions 131 is perpendicular to the thickness direction of the electrode plate. The styrene-butadiene rubber regions 131 are attached to the surface of the current collector 110 and are wrapped by the active material layer 120. Specifically, on the current collector 110, the multiple styrene-butadiene rubber regions 131 of the styrene-butadiene rubber layer 130 can be arranged in a matrix. Among them, the styrene-butadiene rubber is sprayed on the current collector 110 by an intermittent spraying method, and the multiple styrene-butadiene rubber regions 131 are formed after the styrene-butadiene rubber dries. Intermittent spraying can accurately control the coating amount and the coating position, ensure the uniformity and consistency of the styrene-butadiene rubber coating amount, reduce the performance differences between different regions. In addition, intermittent coating can also reduce the waste of materials and save resources.

[0040] In some embodiments, the coating amount of the styrene-butadiene rubber region 131 is 7 μg / cm 2 ~45 μg / cm 2 . For example, the coating amount of the styrene-butadiene rubber region 131 is 7 μg / cm 2 , 26 μg / cm 2 , or 45 μg / cm 2 . Among them, the coating amount of the styrene-butadiene rubber region 131 can be set with reference to the specifications of the battery. When the battery specifications are small, the coating amount of the styrene-butadiene rubber region 131 can be 7 μg / cm 2 ; when the battery specifications are medium, the coating amount of the styrene-butadiene rubber region 131 can be 26 μg / cm 2 ; when the battery specifications are large, the coating amount of the styrene-butadiene rubber region 131 can be 45 μg / cm 2 ; preferably, the coating amount of the styrene-butadiene rubber region 131 is 10 μg / cm 2 ~27 μg / cm 2 . That is, the coating amount of the styrene-butadiene rubber region 131 can be set within the range of 10 μg / cm 2 ~27 μg / cm 2 . For example, the coating amount of the styrene-butadiene rubber region 131 is 10 μg / cm 2 , 18.5 μg / cm2 or 27 μg / cm 2 The above data are only exemplary and not restrictive.

[0041] In some embodiments, along the length direction of the current collector 110, the spacing between any two adjacent styrene-butadiene rubber regions 131 is equal; and / or, along the width direction of the current collector 110, the spacing between any two adjacent styrene-butadiene rubber regions 131 is equal. As can be seen from the aforementioned styrene-butadiene rubber regions 131, the styrene-butadiene rubber regions 131 are formed by spraying styrene-butadiene rubber on the surface of the current collector 110 through a coating device. During the spraying process, spraying is performed at the same spacing along the length direction of the current collector 110; and / or, spraying is performed at the same spacing along the width direction of the current collector 110, which can make the styrene-butadiene rubber regions 131 evenly distributed on the current collector 110, so that the adhesion between the active material layer 120 and the current collector 110 is more stable; in addition, the setting and operation of the coating device will also be more convenient, and production personnel can operate according to the preset spacing without complex adjustments during each coating process, thereby improving production efficiency.

[0042] In some embodiments, the styrene-butadiene rubber regions 131 have an island-like structure. When spraying styrene-butadiene rubber on the surface of the current collector 110 through a coating device, the shape of the styrene-butadiene rubber regions 131 can be changed by changing the shape of the nozzle. Specifically, it can be roughly island-like. Herein, the defined island-like can be understood as a shape like an island, usually used to describe some independent objects or regions, like an island surrounded by the surroundings. In addition, the styrene-butadiene rubber regions 131 can also be dot-like, lump-like, etc.

[0043] In some embodiments, the styrene-butadiene rubber regions 131 are evenly distributed on the surface of the current collector 110. When spraying styrene-butadiene rubber on the surface of the current collector 110 through a coating device, spraying can be performed according to the preset coating spacing and coating amount to ensure that the styrene-butadiene rubber regions 131 are evenly distributed on the surface of the current collector 110.

[0044] In other embodiments, the styrene-butadiene rubber layer 130 can be arranged in a strip form on the surface of the current collector 110. For example, the styrene-butadiene rubber layer 130 includes a plurality of styrene-butadiene rubber strips, and the plurality of styrene-butadiene rubber strips are arranged at intervals in sequence along the length direction of the current collector 110, or arranged at intervals in sequence along the width direction of the current collector 110. Or, the styrene-butadiene rubber layer 130 can be arranged in a grid form on the surface of the current collector 110, which is formed by the staggered combination of a plurality of first styrene-butadiene rubber strips arranged at intervals in sequence along the length direction of the current collector 110 and a plurality of second styrene-butadiene rubber strips arranged at intervals in sequence along the width direction of the current collector 110. In addition, the styrene-butadiene rubber layer 130 can also adopt other arrangement forms on the surface of the current collector 110.

[0045] In some embodiments, the thickness of the current collector 110 is D1 mm, the thickness of the styrene-butadiene rubber layer 130 is D2 mm, and the thickness of the active material layer 120 is D3 mm, where 5(D1 + D2) mm < D3 mm. The overall thickness of the current collector 110, the active material layer 120, and the styrene-butadiene rubber layer 130 determines the thickness of the electrode sheet, and the thickness of the electrode sheet affects the energy density of the battery. Among them, the active material layer 120 contains the active materials required for the electrochemical reaction, so the thickness of the active material layer directly affects the energy density of the battery. To ensure the overall performance of the electrode sheet, the overall thickness of the styrene-butadiene rubber layer 130 and the current collector 110 will be limited. When the thicknesses of the styrene-butadiene rubber layer 130, the current collector 110, and the active material layer 120 satisfy 5(D1 + D2) < D3, the thickness of the electrode sheet will not be too thick, and at the same time, the energy density of the battery will not decrease.

[0046] In some embodiments, the electrode sheet is a negative electrode sheet, and the current collector 110 is a copper foil current collector. Among them, the copper current collector has good electrical conductivity and can quickly and effectively transfer charges in the battery, reducing resistance loss. In addition, the current collector 110 can also be other types of metal current collectors.

[0047] The embodiment of the present utility model also provides an electric core, which includes a positive electrode sheet, a separator, and a negative electrode sheet that are stacked and wound with each other, and the separator is disposed between the positive electrode sheet and the negative electrode sheet;

[0048] Among them, the negative electrode sheet is the electrode sheet described above.

[0049] For the specific structure of the electrode sheet, refer to the above embodiments. Since this electric core adopts all the technical solutions of all the above embodiments, it has at least all the technical effects brought by the technical solutions of the above embodiments, which will not be elaborated here one by one.

[0050] The embodiment of the present utility model also provides a battery, which includes a housing and the electric core described above, and the electric core is disposed in the housing. For the specific structure of the electric core, refer to the above embodiments. Since this battery adopts all the technical solutions of all the above embodiments, it has at least all the technical effects brought by the technical solutions of the above embodiments, which will not be elaborated here one by one. Optionally, the battery can be a lithium battery.

[0051] 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: include: A current collector, the current collector comprising a first surface and a second surface disposed opposite to each other; An active material layer, disposed on the first surface and / or the second surface of the current collector; Wherein, a styrene-butadiene rubber layer is arranged between the current collector and the active material layer, and the styrene-butadiene rubber layer is attached to the surface of the current collector and is wrapped by the active material layer.

2. The pole piece according to claim 1, characterized in that: The styrene butadiene rubber layer is composed of at least two styrene butadiene rubber areas distributed at intervals, the spacing distribution direction of the styrene butadiene rubber areas is perpendicular to the thickness direction of the pole piece, and the styrene butadiene rubber areas are attached to the surface of the current collector and are wrapped by the active material layer.

3. The pole piece according to claim 2, characterized in that: The coating amount of the styrene butadiene rubber area is 7ug / cm 2 ~45ug / cm 2 .

4. The pole piece according to claim 2 or 3, characterized in that: The styrene-butadiene rubber area is evenly distributed on the surface of the current collector.

5. The pole piece according to claim 2 or 3, characterized in that: Along the length direction of the current collector, the spacing between any two adjacent styrene-butadiene rubber areas is equal; and / or, Along the width direction of the current collector, the spacing between any two adjacent styrene-butadiene rubber areas is equal.

6. The pole piece according to claim 2 or 3, characterized in that: The styrene-butadiene rubber area presents an island structure.

7. The pole piece according to claim 1, characterized in that: The thickness of the current collector is D1 mm, the thickness of the styrene-butadiene rubber layer is D2 mm, and the thickness of the active material layer is D3 mm, wherein 5(D1+D2) mm<D3 mm.

8. The pole piece according to claim 1, characterized in that: The electrode sheet is a negative electrode sheet, and the current collector is a copper foil current collector.

9. A battery cell, characterized in that: It comprises a positive electrode sheet, a separator and a negative electrode sheet which are stacked and wound one another, wherein the separator is arranged between the positive electrode sheet and the negative electrode sheet; Wherein, the negative electrode sheet is the electrode sheet as described in any one of claims 1-8.

10. A battery, characterized in that: The invention comprises a shell and the battery cell as claimed in claim 9, wherein the battery cell is arranged in the shell.

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