Positive plate and lithium ion battery

Abstract

The utility model relates to a positive plate and a lithium ion battery. The positive plate comprises a current collector, the current collector comprises a first surface and a second surface which are oppositely arranged, the first surface and the second surface are coated with a priming coat, and the surface of the priming coat of the first surface and / or the second surface is coated with an active material layer; wherein the bottom coating is continuously coated in the length direction of the positive plate, and the active material layers are coated at intervals in the length direction of the positive plate. According to the scheme provided by the invention, the positive electrode current collector can be effectively prevented from being in contact with the negative electrode active material, the safety performance of the battery cell can be improved, the time and labor cost of the production process are saved, and the production efficiency is improved.

Description

Technical Field

[0001] The present application relates to the field of new energy technology, and in particular to positive electrode sheets and lithium-ion batteries. Background Art

[0002] As people's requirements for lithium-ion battery energy density, charging speed, etc. continue to increase, battery safety has received more and more attention. There are four main short-circuit failure modes in lithium-ion batteries, namely, contact between the positive current collector and the negative electrode, contact between the positive current collector and the negative electrode active material, contact between the negative electrode and the positive electrode active material, and contact between the negative electrode active material and the positive electrode active material. Among them, the contact between the positive electrode and the negative electrode active material has the highest safety risk, which will cause the internal temperature of the battery to rise rapidly, and even cause the battery to catch fire or explode.

[0003] In the related art, a primer layer is generally coated on one end of the positive current collector and an insulating layer is coated on the other end of the current collector to prevent the positive current collector from contacting the negative electrode active material and causing a short circuit. However, the preparation process of the positive electrode sheet of this structure is complicated and the efficiency is low. Utility Model Content

[0004] In order to solve or partially solve the problems existing in the related art, the present application provides a positive electrode sheet and a lithium-ion battery, which can effectively avoid contact between the positive electrode collector and the negative electrode active material, improve the safety performance of the battery cell, and also save time and labor costs in the production process and improve production efficiency.

[0005] A first aspect of the present application provides a positive electrode sheet, the positive electrode sheet comprising:

[0006] A current collector, the current collector comprising a first surface and a second surface arranged opposite to each other, the first surface and the second surface being coated with a primer layer, and a surface of the primer layer of the first surface and / or the second surface being coated with an active material layer;

[0007] The primer layer is continuously coated in the longitudinal direction of the positive electrode sheet, and the active material layer is coated at intervals in the longitudinal direction of the positive electrode sheet.

[0008] In one embodiment, the positive electrode sheet includes a first region and a second region arranged in the length direction, the first region is the coating location of the active material layer, and the second region is the interval between adjacent active material layers; the thickness of the primer layer in the second region is greater than or equal to the thickness of the primer layer in the first region.

[0009] In one embodiment, the thickness of the primer layer on one side of the first region is 2-20 μm, and the thickness of the primer layer on one side of the second region is 3-22 μm; and / or,

[0010] The single-sided surface density of the primer layer in the first region is 2-22 g / m 2 The single-sided surface density of the primer layer in the second region is 3-25 g / m 2 and / or,

[0011] The single-sided thickness of the primer layer in the first region is D1, and the single-sided thickness of the primer layer in the second region is D2, wherein D2≥D1, and D2-D1<4.

[0012] In one embodiment, the single-side thickness of the active material layer is 20-80 μm.

[0013] In one embodiment, there are thinning areas at both ends of the active material layer along the length direction of the current collector, the thickness of the active material layer in the thinning area is D4, and the thickness of the active material layer outside the thinning area is D5, wherein -7μm≤D4-D5≤3μm.

[0014] In one embodiment, the material of the base coating layer is a mixture of a ceramic material, a conductive agent and a binder.

[0015] In one embodiment, the ceramic material includes at least one of boehmite, alumina, silica, magnesia, titanium oxide, zirconium dioxide, and vanadium dioxide; and / or,

[0016] The conductive agent includes at least one of conductive carbon black, carbon fiber, carbon nanotube, and graphene; and / or,

[0017] The binder includes at least one of polyvinylidene fluoride, polyacrylonitrile, polyacrylic acid, a copolymer of vinylidene fluoride and hexafluoropropylene, and polystyrene.

[0018] In one embodiment, the mass proportion of the ceramic material in the primer layer is greater than or equal to 80%.

[0019] In one embodiment, the current collector is provided with a tab connection position, and the primer layer is coated on a region outside the tab connection position to facilitate positioning when the active material layer is coated.

[0020] A second aspect of the present application provides a lithium ion battery, comprising:

[0021] A battery core, wherein the battery core is formed by winding the positive electrode sheet described in the first aspect.

[0022] The technical solution provided by this application may have the following beneficial effects:

[0023] The positive electrode sheet provided in the present application includes a current collector, the current collector includes a first surface and a second surface arranged opposite to each other, the first surface and the second surface are coated with a primer layer, and the primer layer surface of the first surface and / or the second surface is coated with an active material layer; wherein the primer layer is continuously coated in the length direction of the positive electrode sheet, and the active material layer is coated at intervals in the length direction of the positive electrode sheet. The positive electrode sheet provided in the present application, because the primer layer is coated on the first surface and the second surface of the current collector, can effectively avoid the positive electrode current collector from contacting with the negative electrode active material, can improve the safety performance of the battery cell, and also saves time and labor costs in the production process and improves production efficiency.

[0024] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and other objects, features and advantages of the present application will become more apparent through a more detailed description of exemplary embodiments of the present application in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the present application.

[0026] Figure 1 It is a schematic diagram of the structure of a positive electrode sheet shown in one embodiment of the present application.

[0027] Figure numerals: 10, current collector; 11, undercoat layer; 12, active material layer; 111, first region; 112, second region; 12a, first end; 12b, second end; 001, thinning region. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0029] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The singular forms of "a", "said" and "the" used in this application and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0030] It should be understood that although the terms "first", "second", "third", etc. may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0031] In the description of the present application, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0032] Unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0033] In the related art, a primer layer is generally applied to one end of the current collector, and an insulating layer is applied to the other end of the current collector to prevent the positive current collector from contacting with the negative active material and causing a short circuit. However, the preparation process of the positive electrode sheet of this structure is complicated and inefficient. In view of the above problems, the embodiments of the present application provide a positive electrode sheet and a lithium-ion battery, which can effectively prevent the positive current collector from contacting with the negative active material, improve the safety performance of the battery cell, and also save time and labor costs in the production process and improve production efficiency.

[0034] The technical solution of the embodiments of the present application is described in detail below with reference to the accompanying drawings.

[0035] Figure 1 It is a schematic diagram of the structure of a positive electrode sheet shown in one embodiment of the present application.

[0036] See also Figure 1The present application provides a positive electrode sheet, which includes a current collector 10, the current collector 10 includes a first surface A and a second surface B arranged opposite to each other, the first surface A and the second surface B are respectively located on both sides of the thickness direction Y of the current collector 10, the first surface A and the second surface B are coated with a primer layer 11, and the surface of the primer layer 11 of the first surface A and / or the second surface B is coated with an active material layer 12; wherein the primer layer 11 is continuously coated in the length direction X of the positive electrode sheet, and the active material layer 12 is coated at intervals in the length direction X of the positive electrode sheet.

[0037] The positive electrode sheet provided in the present application can effectively avoid contact between the positive electrode current collector 10 and the negative electrode active material because the primer layer 11 is coated on the first surface A and the second surface B of the current collector 10, thereby improving the safety performance of the battery cell, while also saving time and labor costs in the production process and improving production efficiency.

[0038] In this embodiment, the primer layer 11 is coated on the first surface A and the second surface B of the current collector 10, that is, coated on the two surfaces of the current collector 10, and the active material layer 12 is coated on the primer layer 11 of the first surface A and / or the second surface B, that is, the active material layer 12 is coated on the primer layer 11 of at least one surface of the current collector 10.

[0039] Continue to see Figure 1 In some embodiments, the positive electrode sheet includes a first region 111 and a second region 112 arranged in the length direction X, the first region 111 is the coating area of ​​the active material layer 12, and the second region 112 is the interval between adjacent active material layers 12; the thickness of the primer layer 11 in the second region 112 is greater than or equal to the thickness of the primer layer 11 in the first region 111.

[0040] Since the resistance increases as the thickness of the primer layer 11 increases, by setting the thickness of the primer layer 11 in the second area 112 to be greater than that of the primer layer 11 in the first area 111, that is, increasing the resistance value of the primer layer 11 in the second area 112, it plays the role of coating the positive electrode current collector 10, while ensuring the electrical performance of the battery cell, the safety performance of the battery cell can be improved.

[0041] In this embodiment, the primer layer 11 can be continuously coated on the first surface A and the second surface B of the current collector 10 using a gravure roller device, and by designing different roller depths at different positions on the gravure roller, the thickness of the first area 111 of the primer layer 11 is made smaller than the thickness of the second area 112.

[0042] The current collector 10 is provided with a tab connection position, and the primer layer 11 is applied to the area outside the tab connection position so as to position the active material layer when it is coated. After the primer layer 11 is continuously coated on the first surface A and the second surface B of the current collector 10, the primer layer 11 is removed from a specific position on the second area 112 by a scraper device to form a tab connection position, which is convenient for subsequent welding of the tab connection position and then the tab. In some embodiments, the tab connection position can also be cleaned out on the primer layer 11 by means such as laser cleaning.

[0043] In some embodiments, the thickness of the bottom coating layer 11 of the first region 111 is 2-20 μm, preferably 4-10 μm, and the thickness of the bottom coating layer 11 of the second region 112 is 3-22 μm, preferably 6-12 μm. If the bottom coating layer 11 is too thin, it is easy to cause leakage during the manufacturing process, so that the positive electrode current collector 10 cannot be completely covered, affecting the safety performance; if the bottom coating layer 11 is too thick, it will have a greater impact on the battery energy density. The thickness range of this embodiment can significantly improve the battery safety performance while having a smaller impact on the battery energy density.

[0044] In some embodiments, the single-sided surface density of the primer layer 11 in the first region 111 is 2-22 g / m 2 , preferably 3-12g / m 2 The single-sided surface density of the primer layer 11 in the second region 112 is 3-25 g / m 2 , preferably 6-16g / m 2 If the surface density is too low and the bottom coating 11 is too thin, the phenomenon of foil leakage is likely to occur during the manufacturing process, so that the positive electrode current collector 10 cannot be completely covered, affecting the safety performance; if the surface density is too high and the bottom coating 11 is too thick, it will have a greater impact on the battery energy density. The surface density range of this embodiment can significantly improve the battery safety performance while having a smaller impact on the battery energy density.

[0045] In some embodiments, the thickness of the primer layer 11 of the first region 111 is D1, and the thickness of the primer layer 11 of the second region 112 is D2, wherein D2≥D1, D2-D1<4, wherein the thickness difference between D1 and D2 can be achieved by designing the roller depth at different positions on the gravure roller. Compared with the related art that requires two coatings to coat the primer layer 11 and the insulating layer on the current collector 10, the design of the present application only requires one coating to complete the coating of the ceramic coating, which can effectively improve the production efficiency, and make the current collector 10 at the interval X along the length direction of the active material layer 12 better coated, thereby improving the safety performance of the battery.

[0046] In some embodiments, the thickness of the single side of the active material layer 12 is 20-80 μm. If the active material layer 12 is too thin, it will affect the energy density of the battery; if the active material layer 12 is too thick, it will affect the battery charging rate and other electrical properties. In this embodiment, the thickness of the single side of the active material layer 12 is 20-80 μm, which will not affect the energy density of the battery, nor will it affect the battery charging rate and other electrical properties.

[0047] In some other embodiments, the coating thickness of the primer layer 11 on the first region 111 and the second region 112 of the current collector 10 may be equal, and the tab connection position on the current collector 10 is reserved by a gravure roller device.

[0048] Continue to see Figure 1 In some embodiments, the active material layer 12 has thinning regions 001 at both ends along the length direction X of the current collector 10, the thickness of the active material layer 12 in the thinning region 001 is D4, and the thickness of the area outside the thinning region 001 of the active material layer 12 is D5, wherein -7μm≤D4-D5≤3μm. In this embodiment, each section of the active material layer 12 includes two ends arranged in the length direction X of the current collector 10, respectively, a first end 12a and a second end 12b, and the thinning region 001 is located in the area near the first end 12a and the second end 12b near the bottom coating 11. The thinning regions 001 at both ends of the active material layer 12 can avoid the lithium plating problem caused by the reduction of the thickness at both ends of the negative electrode, thereby improving the safety of the battery.

[0049] In some embodiments, the current collector 10 is aluminum foil, and the material of the bottom coating 11 is a mixture of ceramic material, conductive agent and binder, which can make the coating have good mechanical stability and adhesion, and can improve the safety of the battery while ensuring the electrical performance of the battery. The conductive agent makes the bottom coating 11 have a certain conductivity, which can ensure the electrical performance of the battery.

[0050] Among them, the mass proportion of the ceramic material in the bottom coating 11 is greater than or equal to 80%. The ceramic coating with this proportion is relatively dense and has good mechanical stability. At the same time, it can better protect the positive electrode collector 10 and effectively improve the safety performance of the battery.

[0051] The ceramic material in the undercoat layer 11 of the present embodiment includes at least one of boehmite, alumina, silica, magnesia, titanium oxide, zirconium dioxide, and vanadium dioxide, but is not limited thereto.

[0052] In some embodiments, the conductive agent includes at least one of conductive carbon black, carbon fiber, carbon nanotubes, and graphene; in some embodiments, the binder includes at least one of polyvinylidene fluoride, polyacrylonitrile, polyacrylic acid, a copolymer of vinylidene fluoride and hexafluoropropylene, and polystyrene, but is not limited thereto.

[0053] In some embodiments, the binder includes at least one of polyvinylidene fluoride, polyacrylonitrile, polyacrylic acid, a copolymer of vinylidene fluoride and hexafluoropropylene, and polystyrene, but is not limited thereto.

[0054] The present application also provides a lithium-ion battery, which includes a battery cell, and the battery cell is formed by winding the positive electrode sheet of any of the above embodiments. The structure of the positive electrode sheet refers to the description of the above embodiments and will not be repeated here. The battery cell provided by the present application can effectively avoid contact between the positive electrode collector and the negative electrode active material, and can improve the safety performance of the battery cell. Moreover, the complex process in which the base coating and the insulating layer need to be coated twice in the existing electrode structure is optimized. While improving the performance of the battery cell, it also saves time and labor costs in the production process and improves production efficiency.

[0055] The embodiments of the present application have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A positive electrode sheet, characterized in that: The positive electrode sheet includes a current collector, the current collector includes a first surface and a second surface arranged opposite to each other, the first surface and the second surface are coated with a primer layer, and the primer layer surface of the first surface and / or the second surface is coated with an active material layer; The primer layer is continuously coated in the longitudinal direction of the positive electrode sheet, and the active material layer is coated at intervals in the longitudinal direction of the positive electrode sheet.

2. The positive electrode sheet according to claim 1, characterized in that: The positive electrode sheet includes a first region and a second region arranged in the length direction, the first region is the coating area of ​​the active material layer, and the second region is the interval between adjacent active material layers; the thickness of the primer layer in the second region is greater than or equal to the thickness of the primer layer in the first region.

3. The positive electrode sheet according to claim 2, characterized in that: The thickness of the primer layer on a single side in the first region is 2-20 μm, and the thickness of the primer layer on a single side in the second region is 3-22 μm.

4. The positive electrode sheet according to claim 1, characterized in that: The single-side thickness of the active material layer is 20-80 μm.

5. The positive electrode sheet according to claim 1, characterized in that: The active material layer has thinned areas at both ends along the length direction of the current collector, the thickness of the active material layer in the thinned areas is D4, and the thickness of the active material layer outside the thinned areas is D5, wherein -7μm≤D4-D5≤3μm.

6. The positive electrode sheet according to claim 2, characterized in that: The single-sided surface density of the primer layer in the first region is 2-22 g / m 2 The single-sided surface density of the primer layer in the second region is 3-25 g / m 2 .

7. The positive electrode sheet according to claim 2, characterized in that: The single-sided thickness of the primer layer in the first region is D1, and the single-sided thickness of the primer layer in the second region is D2, wherein D2≥D1, and D2-D1<4.

8. The positive electrode sheet according to claim 1, characterized in that: The current collector is provided with a tab connection position, and the primer layer is coated on the area outside the tab connection position so as to facilitate positioning when the active material layer is coated.

9. A lithium ion battery, characterized in that: include: A battery cell, wherein the battery cell is formed by winding the positive electrode sheet according to any one of claims 1 to 8.

Images