Positive pole piece, battery monomer and electric equipment

Abstract

The utility model relates to the technical field of lithium batteries, in particular to a positive pole piece, a battery monomer and electric equipment. The positive pole piece comprises a positive current collector and a coating layer, the positive current collector comprises a coating part and an empty foil part which are sequentially connected along a second direction, and the coating part is provided with a middle part and an edge part connected with the middle part; the coating layer comprises a second active coating arranged on the middle part and a coating layer arranged on the edge part, the thickness of the second active coating is equal to that of the coating layer, and the surface density of the coating layer is smaller than that of the second active coating. According to the positive pole piece, the battery monomer and the electric equipment provided by the invention, the problem that the energy density of the battery is greatly sacrificed by the design thought for integrally improving the NP ratio of the positive pole and the negative pole in order to solve the problem of lithium precipitation in the prior art is solved.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to a positive electrode sheet, a battery cell and an electrical device. Background Art

[0002] When square-shell batteries are fast-charged and cycled, lithium plating is prone to occur at the overhang edge of the negative electrode (corresponding to the 0-3mm range of the positive electrode). The conventional solution is to increase the overall positive-negative electrode NP ratio to increase the lithium insertion vacancy margin at the overhang edge of the negative electrode (for example, increase the overall thickness of the negative electrode), thereby improving the lithium plating problem.

[0003] However, the above-mentioned design idea of ​​improving the NP ratio of positive and negative electrodes will greatly sacrifice the energy density of the battery. Utility Model Content

[0004] The purpose of this application is to provide a positive electrode sheet, a battery cell and an electrical device, thereby solving the problem in the prior art that the design idea of ​​improving the NP ratio of the positive and negative electrodes as a whole in order to solve the lithium plating problem will greatly sacrifice the energy density of the battery.

[0005] According to a first aspect of the present application, a positive electrode plate is provided, comprising a positive electrode current collector and a coating layer, wherein the positive electrode current collector comprises a coating portion and a hollow foil portion sequentially connected along a second direction, wherein the coating portion has a middle portion and an edge portion connected to the middle portion; the coating layer comprises a second active coating layer arranged in the middle portion and a coating layer arranged in the edge portion, wherein the thickness of the second active coating layer is equal to the thickness of the coating layer, and the surface density of the coating layer is less than the surface density of the second active coating layer.

[0006] In any of the above technical solutions, further, the edge portion includes two first edge portions arranged opposite to each other along a first direction, the middle portion connects the two first edge portions; and the first direction and the second direction are perpendicular to each other.

[0007] In any of the above technical solutions, further, the edge portion is a U-shaped structure, the edge portion includes a second edge portion and two third edge portions arranged opposite to each other along the first direction, the middle portion connects the two third edge portions, and the middle portion connects the second edge portion and the empty foil portion, and the first direction and the second direction are perpendicular to each other.

[0008] In any of the above technical solutions, further, the edge portion is a rectangular frame structure, the edge portion includes two fourth edge portions arranged opposite to each other along the first direction and a fifth edge portion arranged opposite to each other along the second direction, the middle portion connects the two fourth edge portions, and the middle portion connects the two fifth edge portions, the fifth edge portion is connected to the empty foil portion, and the first direction and the second direction are perpendicular to each other.

[0009] In any of the above technical solutions, further, the coating layer includes a primer layer arranged at the edge portion and a first active coating layer arranged on the primer layer; the second active coating layer is a second active coating layer, wherein the first active coating layer and the second active coating layer have the same structure; the primer layer is a conductive layer with viscosity.

[0010] In any of the above technical solutions, further, the width of the primer layer is 1 mm to 3 mm.

[0011] In any of the above technical solutions, further, the thickness of the primer layer and the surface density of the coating layer are in a linear relationship.

[0012] In any of the above technical solutions, further, an insulating layer is provided at one end of the hollow foil portion close to the coating layer.

[0013] According to a second aspect of the present application, a battery cell is provided, comprising the positive electrode plate as described above.

[0014] According to a third aspect of the present application, an electrical device is provided, comprising the battery cell described above.

[0015] The positive electrode sheet of the present application includes a positive electrode current collector and a coating layer, the positive electrode current collector (including a coating portion and a hollow foil portion connected in sequence along a second direction, the coating portion having a middle portion and an edge portion connected to the middle portion; the coating layer includes a second active coating layer arranged in the middle portion and a coating layer arranged in the edge portion, the thickness of the second active coating layer is equal to the thickness of the coating layer, and the surface density of the coating layer is less than the surface density of the second active coating layer.

[0016] According to the above technical features, the beneficial effects of this application are:

[0017] In the design of the positive electrode sheet of this application, a second active coating layer is provided in the middle of the coating portion, and a coating layer is provided at the edge of the coating portion, with the coating layer having a lower surface density than the second active coating layer. As a result, the NP ratio between the coating layer of the positive electrode sheet and the corresponding negative electrode sheet is greater than the NP ratio between the second active coating layer of the positive electrode sheet and the corresponding negative electrode sheet, thereby achieving the goal of increasing the local NP ratio.

[0018] In summary, compared with the prior art, the present application adjusts the surface density of the coating layer in the middle and edge parts of the coating part so that the surface density of the coating layer in the edge part is smaller, thereby reducing and adjusting the density of the active material in the edge part, that is, achieving the NP ratio control of the local area of ​​the edge without increasing the NP ratio of the positive and negative electrodes as a whole, resulting in design waste and energy density loss.

[0019] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 A schematic structural diagram of the positive electrode current collector of Example 1 of the present application is shown;

[0022] Figure 2 A schematic structural diagram of the overall positive electrode current collector with a primer layer before cutting according to Example 1 of the present application is shown;

[0023] Figure 3 A schematic structural diagram of the positive electrode sheet before cutting is shown in Example 1 of the present application;

[0024] Figure 4 A schematic structural diagram of the positive electrode sheet of Example 1 of the present application is shown;

[0025] Figure 5 A schematic structural diagram of the positive electrode current collector of Example 2 of the present application is shown;

[0026] Figure 6 A schematic structural diagram of the overall positive electrode current collector with a primer layer before cutting according to Example 2 of the present application is shown;

[0027] Figure 7 A schematic structural diagram of the positive electrode current collector of Example 2 of the present application is shown;

[0028] Figure 8 A schematic structural diagram of the overall positive electrode current collector with a primer layer before cutting according to Example 2 of the present application is shown;

[0029] Figure 9 Show Figure 4 Cross-sectional view in the aa direction.

[0030] icon:

[0031] 100-positive electrode current collector; 110-coating portion; 111-middle portion; 112-first edge portion; 113-second edge portion; 114-third edge portion; 115-fourth edge portion; 116-fifth edge portion; 120-hollow foil portion; 200-coating layer; 210-coating layer; 211-priming layer; 212-first active coating layer; 220-second active coating layer; 300-insulating layer; L1-first direction; L2-second direction. DETAILED DESCRIPTION

[0032] The following detailed description is provided to help the reader gain a comprehensive understanding of the methods, devices, and / or systems described herein. However, various changes, modifications, and equivalents of the methods, devices, and / or systems described herein will be apparent upon understanding the disclosure of this application. For example, the order of operations described herein is merely illustrative and is not limited to the order set forth herein. Rather, except for operations that must occur in a particular order, changes may be made that will be apparent upon understanding the disclosure of this application. Furthermore, descriptions of features known in the art may be omitted for clarity and brevity.

[0033] The features described herein may be implemented in different forms and should not be construed as being limited to the examples described herein. Rather, the examples described herein have been provided merely to illustrate some of the many possible ways to implement the methods, devices, and / or systems described herein that will be apparent upon understanding the disclosure of this application.

[0034] Throughout the specification, when an element (such as a layer, region, or substrate) is described as being “on,” “connected to,” “coupled to,” “over,” or “overlaying” another element, it may be directly “on,” “connected to,” “coupled to,” “over,” or “overlaying” another element, or one or more other elements may be present between them. In contrast, when an element is described as being “directly on,” “directly connected to,” “directly coupled to,” “directly over,” or “directly covering” another element, there may be no other elements intervening therebetween.

[0035] As used herein, the term "and / or" includes any one of the associated listed items and any combination of any two or more items.

[0036] Although terms such as "first," "second," and "third" may be used herein to describe various members, components, regions, layers, or portions, these members, components, regions, layers, or portions are not limited by these terms. Rather, these terms are used only to distinguish one member, component, region, layer, or portion from another member, component, region, layer, or portion. Thus, a first member, component, region, layer, or portion in the examples described herein may also be referred to as a second member, component, region, layer, or portion without departing from the teachings of the examples.

[0037] For ease of description, spatial relational terms such as "above," "upper," "below," and "lower" may be used herein to describe the relationship of one element to another element as shown in the accompanying drawings. Such spatial relational terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the accompanying drawings. For example, if the device in the accompanying drawings is turned over, an element described as being "above" or "upper" relative to another element would subsequently be "below" or "lower" relative to the other element. Thus, the term "above" includes both the orientations "above" and "below," depending on the spatial orientation of the device. The device may also be positioned in other ways (e.g., rotated 90 degrees or in other orientations), and the spatial relational terms used herein will be interpreted accordingly.

[0038] The terms used herein are intended only to describe various examples and are not intended to limit the present disclosure. Unless the context clearly indicates otherwise, the singular is intended to include the plural. The terms "comprise," "include," and "have" list the presence of stated features, quantities, operations, components, elements, and / or combinations thereof, but do not preclude the presence or addition of one or more other features, quantities, operations, components, elements, and / or combinations thereof.

[0039] Due to manufacturing techniques and / or tolerances, variations in the shapes shown in the drawings may occur. Therefore, the examples described herein are not limited to the specific shapes shown in the drawings but include changes in shapes that occur during manufacturing.

[0040] The features of the examples described herein can be combined in various ways that will be apparent after understanding the disclosure of the present application. In addition, although the examples described herein have various configurations, other configurations are possible as will be apparent after understanding the disclosure of the present application.

[0041] In Example 1, during fast charging cycles, square-shell batteries are prone to lithium plating at the overhang edge of the negative electrode (corresponding to the 0-3mm range of the positive electrode). Prior to the present application, the conventional solution in the prior art was to increase the overall positive-negative electrode NP ratio to increase the lithium insertion vacancy margin at the overhang edge of the negative electrode (for example, by increasing the overall thickness of the negative electrode), thereby improving the lithium plating problem. However, the above-mentioned design approach of increasing the overall positive-negative electrode NP ratio will greatly sacrifice the energy density of the battery.

[0042] In view of this, the first aspect of the present application provides a positive electrode sheet, thereby solving the problem in the prior art that the design idea of ​​improving the NP ratio of the positive and negative electrodes as a whole in order to solve the lithium plating problem will greatly sacrifice the energy density of the battery.

[0043] The following will refer to Figures 1 to 9 The positive electrode sheet described in the embodiments of the present application is described in detail.

[0044] like Figure 4 and Figure 9 As shown, the positive electrode sheet of the present application includes a positive electrode collector 100 and a coating layer 200, the positive electrode collector 100 includes a coating portion 110 and a hollow foil portion 120 connected in sequence along the second direction L2, the coating portion 110 has a middle portion 111 and an edge portion connected to the middle portion 111; the coating layer 200 includes a second active coating layer 220 arranged in the middle portion 111 and a coating layer 210 arranged in the edge portion, the thickness of the second active coating layer 220 is equal to the thickness of the coating layer 210, and the surface density of the coating layer 210 is less than the surface density of the second active coating layer 220.

[0045] In the design of the positive electrode sheet of the present application, a second active coating layer 220 is provided in the middle portion 111 of the coating portion 110, and a coating layer 210 is provided at the edge of the coating portion 110. The areal density of the coating layer 210 is less than the areal density of the second active coating layer 220. Since N / P = negative electrode active material gram capacity × negative electrode areal density × negative electrode active material content ratio ÷ (positive electrode active material gram capacity × positive electrode areal density × positive electrode active material content ratio), and since the negative electrode sheet region corresponding to the second active coating layer 220 and the negative electrode sheet region corresponding to the coating layer 210 are equal, the NP ratio between the coating layer 210 of the positive electrode sheet and the corresponding negative electrode sheet region is greater than the NP ratio between the second active coating layer 220 of the positive electrode sheet and the corresponding negative electrode sheet region, thereby achieving the purpose of increasing the local NP ratio.

[0046] In summary, compared with the prior art, the present application adjusts the surface density of the coating layer 210 coated on the middle part 111 and the edge part of the coating part 110, so that the surface density of the edge part is smaller, thereby reducing the density of the active material in the edge part, that is, realizing the NP ratio control of the local area of ​​the edge without increasing the NP ratio of the positive and negative electrode sheets as a whole, resulting in design waste and energy density loss.

[0047] It should be noted that the coating layer 200 is provided on one side surface or both sides surface of the positive electrode current collector 100 , depending on the specific use requirements.

[0048] In the embodiments of the present application, Figure 9 As shown, the coating layer 210 includes a primer layer 211 disposed at the edge portion and a first active coating layer 212 disposed on the primer layer 211. The first active coating layer 212 and the second active coating layer 220 have the same structure. That is, the positive electrode active material content ratio in the first active coating layer 212 and the positive electrode active material content ratio in the second active coating layer 220 are equal, and the positive electrode active material gram capacity in the first active coating layer 212 and the positive electrode active material gram capacity in the second active coating layer 220 are equal. The primer layer 211 is a conductive layer with adhesiveness.

[0049] When designing the positive electrode sheet of the present application, a primer layer 211 is pre-coated on the edge of the positive electrode current collector 100. After the primer layer is completed, the positive electrode coating is performed to obtain the first active coating layer 212 and the second active coating layer 220. In this way, by providing the primer layer 211 on the edge of the positive electrode current collector 100, the surface density of the coating layer 210 is reduced, and the lithium insertion redundancy in the lithium deposition area at the overhang edge of the negative electrode is improved, thereby improving the lithium deposition problem.

[0050] In addition, the base coating is designed to be a conductive layer with viscosity. On the one hand, the base coating with viscosity makes the bonding between the first active coating 212 and the base coating 211 and between the base coating 211 and the positive electrode current collector 100 more stable. On the other hand, the base coating with conductivity reduces the interface resistance between the positive electrode current collector and the first active coating 212, which is conducive to rapid charge transfer.

[0051] In the embodiment of the present application, the edge portion includes two first edge portions 112 oppositely arranged along a first direction L1 , and the middle portion 111 connects the two first edge portions 112 , wherein the first direction L1 and the second direction L2 are perpendicular to each other.

[0052] Specifically, see Figure 1 、 Figure 2 and Figure 3As shown, first, a transverse cutting line and a longitudinal cutting line are preset on the entire positive electrode current collector according to the width and length of the positive electrode sheet, and then a plurality of transverse primer layers are coated on the entire positive electrode current collector by gravure coating according to the edge design. The transverse primer layer here is composed of a first edge portion 112 respectively arranged on both sides of the transverse cutting line and extending along the length direction of the entire positive electrode current collector. Finally, the active slurry is coated on the entire positive electrode current collector to obtain an active coating. The active coating here is composed of a first active coating and a second active coating. The above completes the production of the entire positive electrode sheet, and then the entire positive electrode sheet is cut along the transverse cutting line and the longitudinal cutting line to obtain the positive electrode sheet (see Figure 4 and Figure 9 ).

[0053] In the embodiments of the present application, considering that when the width of the bottom coating layer 211 is too large, the energy density of the battery cell will be significantly deteriorated, and when the width of the bottom coating layer 211 is too small, it will not have the effect of improving the lithium deposition window at the edge. Therefore, the width of the bottom coating layer 211 of the positive electrode sheet is designed to be 1mm to 3mm. Specifically, the width of the bottom coating layer 211 of the positive electrode sheet is 1.3mm or 1.5mm or 1.8mm or 2.1mm or 2.4mm or 2.6mm or 2.9mm.

[0054] In the embodiment of the present application, the thickness of the primer layer 211 and the surface density of the coating layer are linearly related, that is, the surface density of the coating layer = the surface density of the second active coating layer × (the thickness of the second active coating layer L - the thickness of the primer layer 211 X) ÷ the thickness of the second active coating layer L, wherein, since the surface density of the portion of the negative electrode sheet corresponding to the middle portion 111 and the surface density of the portion of the negative electrode sheet corresponding to the edge portion are consistent, therefore, the NP at the corresponding edge portion = the NP at the corresponding middle portion × L ÷ (L-X), that is, the thickness of the primer layer 211 of the positive electrode sheet is determined by the NP ratio required for the overhang edge of the negative electrode sheet, which is convenient for adjustment and control.

[0055] In the embodiment of the present application, an insulating layer 300 is provided at one end of the hollow foil portion 120 near the coating layer. The design of the insulating layer 300 prevents the presence of powder burrs on the edge of the positive electrode tab when the hollow foil portion 120 is die-cut to form the tab. The insulating layer 300 can be made of a ceramic material or insulating tape.

[0056] According to a second aspect of the present application, a battery cell is provided, comprising the positive electrode plate as described above.

[0057] According to a third aspect of the present application, an electrical device is provided, comprising the battery cell described above.

[0058] Example 2 The basic structure of a positive electrode plate of the present application is the same as that of Example 1, except that: Figure 5As shown, the edge portion is a U-shaped structure, including a second edge portion 113 and two third edge portions 114 arranged opposite to each other along a first direction L1, a middle portion 111 connecting the two third edge portions 114, and the middle portion 111 connecting the second edge portion 113 and the hollow foil portion 120. The first direction L1 and the second direction L2 are perpendicular to each other.

[0059] Specifically, see Figure 5 and Figure 6 As shown, first, according to the width and length of the positive electrode sheet, a horizontal cutting line and a vertical cutting line are preset on the entire positive electrode collector, and then according to the edge design, the entire positive electrode collector is coated by gravure coating to obtain multiple horizontal primer layers and a vertical primer layer. The horizontal primer layer here is composed of a third edge portion 114 respectively arranged on both sides of the horizontal cutting line and extending along the length direction of the entire positive electrode collector, and the vertical primer layer is composed of a second edge portion 113 respectively arranged on both sides of the vertical cutting line and extending along the length direction of the entire positive electrode collector. Finally, the active slurry is coated on the entire positive electrode collector to obtain an active coating layer, and the active coating layer here is composed of a first active coating layer and a second active coating layer. The above completes the production of the entire positive electrode sheet, and then the entire positive electrode sheet is cut along the horizontal cutting line and the vertical cutting line to obtain the positive electrode sheet.

[0060] Example 3

[0061] The basic structure of a positive electrode plate of the present application is the same as that of Example 1, except that: Figure 7 As shown, the edge portion is a rectangular frame structure, including two fourth edge portions 115 arranged opposite to each other along the first direction L1 and a fifth edge portion 116 arranged opposite to each other along the second direction L2. The middle portion 111 connects the two fourth edge portions 115, and the middle portion 111 connects the two fifth edge portions 116. The fifth edge portion 116 is connected to the hollow foil portion 120. The first direction L1 and the second direction L2 are perpendicular to each other.

[0062] Specifically, see Figure 7 and Figure 8As shown, first, according to the width and length of the positive electrode sheet, a horizontal cutting line and a vertical cutting line are preset on the entire positive electrode collector. Then, according to the edge design, the entire positive electrode collector is coated by gravure coating to obtain multiple horizontal primer layers, an intermediate vertical primer layer and two edge vertical primer layers. The horizontal primer layer here is composed of a fourth edge portion 115 respectively arranged on both sides of the horizontal cutting line and extending along the length direction of the entire positive electrode collector, the intermediate vertical primer layer is composed of a fifth edge portion 116 respectively arranged on both sides of the vertical cutting line and extending along the length direction of the entire positive electrode collector, and the edge vertical primer layer is composed of a fifth edge portion 116 extending along the length direction of the entire positive electrode collector. Finally, the active slurry is coated on the entire positive electrode collector to obtain an active coating. The active coating here is composed of a first active coating and a second active coating. The above completes the production of the entire positive electrode sheet. Then, the entire positive electrode sheet is cut along the horizontal cutting line and the longitudinal cutting line to obtain the positive electrode sheet.

[0063] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present application, which are used to illustrate the technical solutions of the present application rather than to limit them. The scope of protection of the present application is not limited thereto. Although the present application has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that any technician familiar with this technical field can still modify the technical solutions recorded in the aforementioned embodiments within the technical scope disclosed in the present application, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be covered by the scope of protection of the present application.

Claims

1. A positive electrode plate, characterized in that: The positive electrode sheet comprises a positive electrode current collector (100) and a coating layer (200), wherein the positive electrode current collector (100) comprises a coating portion (110) and a hollow foil portion (120) sequentially connected along a second direction (L2), and the coating portion (110) comprises a middle portion (111) and an edge portion connected to the middle portion (111); The coating layer (200) includes a second active coating layer (220) arranged in the middle portion (111) and a coating layer (210) arranged in the edge portion, the thickness of the second active coating layer (220) is equal to the thickness of the coating layer (210), and the surface density of the coating layer (210) is less than the surface density of the second active coating layer (220).

2. The positive electrode sheet according to claim 1, characterized in that: The edge portion comprises two first edge portions (112) arranged opposite to each other along a first direction (L1), and the middle portion (111) connects the two first edge portions (112); the first direction (L1) and the second direction (L2) are perpendicular to each other.

3. The positive electrode sheet according to claim 1, characterized in that: The edge portion is a U-shaped structure, comprising a second edge portion (113) and two third edge portions (114) arranged opposite to each other along a first direction (L1), the middle portion (111) connecting the two third edge portions (114), and the middle portion (111) connecting the second edge portion (113) and the hollow foil portion (120), and the first direction (L1) and the second direction (L2) are perpendicular to each other.

4. The positive electrode sheet according to claim 1, characterized in that: The edge portion is a rectangular frame structure, comprising two fourth edge portions (115) arranged opposite to each other along a first direction (L1) and a fifth edge portion (116) arranged opposite to each other along a second direction (L2), the middle portion (111) connecting the two fourth edge portions (115), and the middle portion (111) connecting the two fifth edge portions (116), the fifth edge portion (116) connecting the empty foil portion (120), and the first direction (L1) and the second direction (L2) are perpendicular to each other.

5. The positive electrode sheet according to any one of claims 1 to 4, characterized in that: The coating layer (210) comprises a primer layer (211) arranged at an edge portion and a first active coating layer (212) arranged on the primer layer (211); wherein the first active coating layer and the second active coating layer have the same structure; and the primer layer (211) is a conductive layer with adhesiveness.

6. The positive electrode sheet according to claim 5, characterized in that: The width of the primer layer (211) is 1 mm to 3 mm.

7. The positive electrode sheet according to claim 5, characterized in that: The thickness of the primer layer (211) and the surface density of the coating layer (210) are linearly related.

8. The positive electrode sheet according to claim 5, characterized in that: An insulating layer (300) is provided at one end of the hollow foil portion (120) close to the coating layer.

9. A battery cell, characterized in that: The invention comprises a positive electrode sheet as claimed in any one of claims 1 to 8.

10. An electrical device, characterized in that: The battery cell according to claim 9 is included.

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