A negative electrode sheet, a lithium ion battery, and an electronic device

Abstract

The application provides a negative electrode sheet, comprising: a current collector, a first negative electrode coating sheet, a second negative electrode coating sheet and a negative electrode porous sheet, wherein the first negative electrode coating sheet is coated on a first surface of the current collector, the second negative electrode coating sheet is coated on a non-single-surface area of a second surface of the current collector, the first surface of the current collector and the second surface of the current collector are opposite to each other, and the negative electrode porous sheet is coated in a single-surface area of the second surface of the current collector, the non-single-surface area and the single-surface area of the second surface of the current collector are adjacent to each other. The embodiment of the application can increase the roll peel strength of the single-surface area of the negative electrode sheet by arranging the negative electrode porous sheet in the single-surface area of the second surface of the current collector, thereby improving the problem of the single-surface area of the negative electrode sheet being separated from the current collector, and reducing the risk of single-surface lithium precipitation of the negative electrode sheet.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a negative electrode, a lithium-ion battery, and an electronic device. Background Technology

[0002] Lithium-ion batteries are currently the mainstream battery type used in electronic products on the market. With the improvement of electronic product performance, there is a growing demand for higher energy density in lithium-ion batteries. Current technologies utilize high-density and highly compacted electrode sheets to produce lithium-ion batteries with higher energy density. However, in this technology, the single-sided area of ​​the negative electrode is prone to detachment from the current collector during cycling, leading to a problem of excessive single-sided lithium plating on the negative electrode during use.

[0003] It is evident that existing technologies suffer from a significant problem of single-sided lithium plating on the negative electrode. Summary of the Invention

[0004] This invention provides a negative electrode sheet, a lithium-ion battery, and an electronic device to solve the problem of excessive single-sided lithium plating in the prior art.

[0005] To achieve the above objectives, embodiments of the present invention provide a negative electrode sheet, comprising: a current collector, a first negative electrode coating, a second negative electrode coating, and a porous negative electrode sheet, wherein,

[0006] The first negative electrode coating is coated on the first surface of the current collector, and the second negative electrode coating is coated on the non-single-sided area of ​​the second surface of the current collector, wherein the first surface and the second surface of the current collector are opposite to each other;

[0007] The negative electrode porous sheet is coated in a single-sided region on the second surface of the current collector, and the non-single-sided region and the single-sided region on the second surface of the current collector are adjacent.

[0008] As an optional implementation, the porous negative electrode sheet comprises porous nanomaterials and a binder, wherein the content of porous nanomaterials is 85%-95% and the content of binder is 5%-15%.

[0009] As an optional implementation, the thickness of the porous negative electrode sheet is 1 / 10 to 1 / 3 of the thickness of the second negative electrode coating.

[0010] As an optional implementation, the porosity of the negative electrode porous sheet is 30%-60%.

[0011] As an optional implementation, the negative electrode sheet and the positive electrode sheet of the battery are wound together to form a core structure, wherein:

[0012] The single-sided area is located at the starting section in the middle of the core structure. The negative electrode porous sheet includes a first porous sheet and a second porous sheet. The first negative electrode coating, the second negative electrode coating, the first porous sheet and the second porous sheet are all quadrilaterals.

[0013] The first side of the first porous sheet is one side of the starting segment;

[0014] The first side of the first porous sheet and the first side of the second porous sheet are adjacent to each other, the second side of the second porous sheet is adjacent to the first side of the second negative electrode coating, and the first side and the second side of the second porous sheet are opposite to each other.

[0015] As an optional implementation, the first porous sheet and the second porous sheet are adapted in size, and the shapes of the first porous sheet and the second porous sheet are adapted in shape.

[0016] As an optional implementation, in the core structure, the second side of the first porous sheet, the second side of the second porous sheet, and the first side of the second negative electrode coating are located on the same plane, and the first side and the second side of the first porous sheet are opposite to each other;

[0017] The first side of the first negative electrode coating corresponds to the second side of the first porous sheet, the second side of the first negative electrode coating corresponds to the second side of the second negative electrode coating, the first side and the second side of the first negative electrode coating are opposite to each other, and the first side and the second side of the second negative electrode coating are opposite to each other.

[0018] As an optional implementation, the first negative electrode coating and the second negative electrode coating are made of active material, conductive agent, binder and dispersant in a certain proportion.

[0019] This invention also provides a lithium-ion battery, including the aforementioned negative electrode sheet.

[0020] This invention also provides an electronic device including the aforementioned lithium-ion battery.

[0021] One of the above technical solutions has the following advantages or beneficial effects:

[0022] In this embodiment of the invention, by setting a porous negative electrode sheet on a single-sided area of ​​the second surface of the current collector, the rolling peeling force of the single-sided area of ​​the negative electrode sheet can be increased, thereby improving the problem of the single-sided area of ​​the negative electrode sheet detaching from the current collector and reducing the risk of single-sided lithium plating of the negative electrode sheet. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of a planar structure of a negative electrode sheet provided in an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the core structure of a negative electrode sheet provided in an embodiment of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] Please see Figure 1 , Figure 1 This is a schematic diagram of a planar structure of a negative electrode sheet provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the negative electrode includes: a current collector 10, a first negative electrode coating 21, a second negative electrode coating 22, and a porous negative electrode sheet 30, wherein...

[0028] The first negative electrode coating 21 is coated on the first surface of the current collector 10, and the second negative electrode coating 22 is coated on the non-single-sided area of ​​the second surface of the current collector 10. The first surface and the second surface of the current collector 10 are opposite to each other.

[0029] The negative electrode porous sheet 30 is coated in the single-sided area of ​​the second surface of the current collector 10, and the non-single-sided area and the single-sided area of ​​the second surface of the current collector 10 are adjacent.

[0030] In this embodiment, by providing a porous negative electrode sheet 30 on a single-sided area of ​​the second surface of the current collector 10, the rolling peeling force of the single-sided area of ​​the negative electrode sheet can be increased, thereby improving the problem of the single-sided area of ​​the negative electrode sheet detaching from the current collector 10, and thus reducing the risk of single-sided lithium plating of the negative electrode sheet.

[0031] As an optional implementation, the negative electrode porous sheet 30 includes porous nanomaterials and a binder, wherein the content of porous nanomaterials is 85%-95% and the content of binder is 5%-15%.

[0032] In this embodiment, the porous negative electrode sheet 30 has multiple pores, which can store a certain amount of electrolyte. During the later stages of battery cycling, when the battery expands, electrolyte deficiency can easily occur. At this time, the porous negative electrode sheet 30 can release the previously stored electrolyte, thereby compensating for the electrolyte deficiency and improving the battery's cycle performance.

[0033] Among them, the porous sheet for the negative electrode is used to effectively preserve the electrolyte. The porous nanomaterial allows the electrolyte to be deposited after the battery has been used for a long time to maintain the battery's energy density, thereby improving the battery's lifespan.

[0034] Among them, porous nanomaterials can be nano-silica, nano-titanium dioxide, alumina or other silicate minerals, kaolinite, etc., and porous nanomaterials can be one or more of these components.

[0035] Specifically, the first porous sheet 301 and the second porous sheet 302 are made by mixing porous nanomaterials and an adhesive in a certain proportion. In this embodiment of the invention, the proportion of the adhesive is 5%-15%, and the adhesive is styrene-butadiene rubber. The adhesive can effectively improve the adhesion between the first porous sheet 301 and the current collector 10, and between the second porous sheet 302 and the current collector 10, thereby improving the roll-pressing peel force of the single-sided area of ​​the negative electrode sheet.

[0036] As an optional implementation, the thickness of the porous negative electrode sheet 30 is 1 / 10 to 1 / 3 of the thickness of the second negative electrode coating 22.

[0037] In this embodiment, since the porous negative electrode sheet 30 needs to improve the roll-pressing peeling force of the single-sided area of ​​the negative electrode sheet, the porous negative electrode sheet 30 needs to be set to a thickness greater than a certain value. In this embodiment of the invention, the thickness of the porous negative electrode sheet 30 is set to be greater than 1 / 10 of the second negative electrode coating 22. When the porous negative electrode sheet 30 is less than the set minimum thickness, its effect of enhancing the roll-pressing peeling force is poor, and the negative electrode sheet will still exhibit a large amount of lithium plating.

[0038] Furthermore, since the porous negative electrode sheet 30 stores a certain amount of electrolyte, excessive electrolyte storage will lead to a lower energy density of the battery. Therefore, the thickness of the porous negative electrode sheet 30 needs to be set to no more than a certain thickness. In this embodiment of the invention, the thickness of the porous negative electrode sheet 30 is set to be less than 1 / 3 of the thickness of the second negative electrode coating 22. When the thickness of the porous negative electrode sheet 30 is less than the set maximum thickness, the battery energy density can be maintained at a high level.

[0039] As an optional implementation, the porosity of the negative electrode porous sheet 30 is 30%-60%.

[0040] In this embodiment, the porosity of the negative electrode porous sheet 30 is also an important indicator affecting the storage of electrolyte in the negative electrode porous sheet 30. If the porosity is too low, it cannot store electrolyte, while if the porosity is too high, it will store too much electrolyte, resulting in a low battery energy density. In this embodiment of the invention, the porosity of the negative electrode porous sheet 30 is set to be in the range of 30%-60%.

[0041] As an optional implementation, please refer to Figure 2 , Figure 2 This is a schematic diagram of a wound core structure for a negative electrode sheet provided in an embodiment of the present invention, as shown below. Figure 2 As shown, the negative electrode sheet and the positive electrode sheet of the battery are wound together to form a core structure, wherein:

[0042] The single-sided area is located in the starting section at the middle position of the core structure. The negative electrode porous sheet 30 includes a first porous sheet 301 and a second porous sheet 302. The first negative electrode coating 21, the second negative electrode coating 22, the first porous sheet 301 and the second porous sheet 302 are all quadrilaterals.

[0043] The first side of the first porous plate 301 is one side of the starting segment;

[0044] The first side of the first porous sheet 301 and the first side of the second porous sheet 302 are adjacent to each other, the second side of the second porous sheet 302 is adjacent to the first side of the second negative electrode coating 22, and the first side and the second side of the second porous sheet 302 are opposite to each other.

[0045] In this embodiment, the negative electrode is configured as a wound core structure, which is used to combine with the wound core structure of the positive electrode of the lithium-ion battery to form a lithium-ion battery. This allows for the storage of more electrolyte, thereby increasing the energy density of the battery.

[0046] A separator is provided between the negative electrode and the positive electrode of the lithium-ion battery to prevent short circuits.

[0047] As an optional implementation, the sizes of the first porous sheet 301 and the second porous sheet 302 are adapted to each other, and the shapes of the first porous sheet 301 and the second porous sheet 302 are adapted to each other.

[0048] In this embodiment, since the single-sided area of ​​the negative electrode sheet in the wound core structure is a bent structure, such as Figure 2 As shown, the first porous sheet 301 and the second porous sheet 302 need to be shaped to fit this structure. By increasing the rolling peeling force of the single-sided area of ​​the negative electrode sheet at different positions using the first porous sheet 301 and the second porous sheet 302, the lithium plating problem in the single-sided area can be improved.

[0049] As an optional implementation, in the core structure, the second side of the first porous sheet 301, the second side of the second porous sheet 302, and the first side of the second negative electrode coating 22 are located on the same plane, and the first side and the second side of the first porous sheet 301 are opposite to each other.

[0050] The first side of the first negative electrode coating 21 corresponds to the second side of the first porous sheet 301, the second side of the first negative electrode coating 21 corresponds to the second side of the second negative electrode coating 22, the first side and the second side of the first negative electrode coating 21 are opposite to each other, and the first side and the second side of the second negative electrode coating 22 are opposite to each other.

[0051] In this embodiment, due to the bending structure of the single-sided region of the negative electrode sheet, the first porous sheet 301 and the second porous sheet 302 are located in the single-sided region of the negative electrode sheet, while the second negative electrode coating 22 needs to correspond to the non-single-sided region of the first negative electrode coating 21 to realize the function of the lithium-ion battery. This embodiment completes the formation of a negative electrode sheet from the first negative electrode coating 21, the second negative electrode coating 22, the first porous sheet 301, and the second porous sheet 302.

[0052] The shape of the first negative electrode coating 21 is adapted to the shape of the current collector 10, and the size of the first negative electrode coating 21 is adapted to the size of the current collector 10. Since the negative electrode sheet needs to be placed in the inner layer in the lithium-ion battery, the size of the first negative electrode coating 21 needs to be adapted to the size of the first surface of the current collector 10, and the sizes of the second negative electrode coating 22, the first porous sheet 301, and the second porous sheet 302 need to be adapted to the size of the second surface of the current collector 10.

[0053] In addition, such as Figure 2 As shown, the size of the current collector 10 needs to be smaller than the size of the positive electrode of the lithium-ion battery so that the negative electrode can be located inside the battery after it is wound into a battery.

[0054] As an optional implementation, the first negative electrode coating 21 and the second negative electrode coating 22 are made of active material, conductive agent, binder and dispersant in a certain proportion.

[0055] In this embodiment, by mixing the active material, conductive agent, binder and dispersant in a certain proportion to prepare the first negative electrode coating 21 and the second negative electrode coating 22, the negative electrode sheet can have better conductivity.

[0056] The active material is graphite, with a content of 95%-97.5%; the conductive agent is composed of conductive carbon nanotubes and conductive carbon black mixed in a ratio of 0.25-0.5, with a content of 0.5%-2.5%; the binder has a content of 1.5%-2.5%; and the dispersant sodium carboxymethyl cellulose has a content of 0.5%-1.5%.

[0057] In this embodiment of the invention, the following comparative test experiments were conducted to obtain suitable thickness and porosity parameters for the porous negative electrode sheet 30:

[0058] Comparative Example 1: Preparation of a negative electrode without a porous negative electrode sheet 30;

[0059] Comparative Example 2: A negative electrode sheet with a porous negative electrode sheet 30 was prepared, wherein the proportion of porous nanomaterial in the porous negative electrode sheet 30 was 96%, the binder content was 4%, and the thickness of the porous negative electrode sheet was 1 / 4 of the thickness of the second negative electrode coating 22.

[0060] Comparative Example 3: A negative electrode sheet with a porous negative electrode sheet 30 was prepared, wherein the proportion of porous nanomaterial in the porous negative electrode sheet 30 was 90%, the binder content was 10%, and the thickness of the porous negative electrode sheet was 1 / 2 the thickness of the second negative electrode coating 22.

[0061] Comparative Example 4: A negative electrode sheet with a porous negative electrode sheet 30 was prepared, wherein the proportion of porous nanomaterial in the porous negative electrode sheet 30 was 90%, the binder content was 10%, and the thickness of the porous negative electrode sheet was 1 / 11 of the thickness of the second negative electrode coating 22.

[0062] Example 1: A negative electrode sheet with a porous negative electrode sheet 30 is prepared, wherein the proportion of porous nanomaterial in the porous negative electrode sheet 30 is 85%, the binder content is 15%, and the thickness of the porous negative electrode sheet is 1 / 4 of the thickness of the second negative electrode coating 22.

[0063] Example 2: A negative electrode sheet with a porous negative electrode sheet 30 is prepared, wherein the proportion of porous nanomaterial in the porous negative electrode sheet 30 is 90%, the binder content is 10%, and the thickness of the porous negative electrode sheet is 1 / 4 of the thickness of the second negative electrode coating 22.

[0064] Example 3: A negative electrode sheet with a porous negative electrode sheet 30 is prepared, wherein the proportion of porous nanomaterial in the porous negative electrode sheet 30 is 95%, the binder content is 5%, and the thickness of the porous negative electrode sheet is 1 / 4 of the thickness of the second negative electrode coating 22.

[0065] Example 4: A negative electrode sheet with a porous negative electrode sheet 30 is prepared, wherein the proportion of porous nanomaterial in the porous negative electrode sheet 30 is 90%, the binder content is 10%, and the thickness of the porous negative electrode sheet is 1 / 10 of the thickness of the second negative electrode coating 22.

[0066] Example 5: A negative electrode sheet with a porous negative electrode sheet 30 is prepared, wherein the proportion of porous nanomaterial in the porous negative electrode sheet 30 is 90%, the binder content is 10%, and the thickness of the porous negative electrode sheet is 1 / 3 of the thickness of the second negative electrode coating 22.

[0067] The negative electrode sheet prepared above was used to fabricate a lithium-ion battery with a lithium-ion battery positive electrode sheet, and the following performance tests were performed on the fabricated lithium-ion battery:

[0068] Energy density testing was performed on the lithium-ion batteries of the examples and comparative examples using a charge-discharge regime of 0.2C charging, 0.5C discharging, and 0.025C cutoff.

[0069] Cycle capacity retention rate, i.e., the lithium-ion batteries of the examples and comparative examples are cycled for 500T at 25°C with a cycle regime of 2C charging, 0.5C discharging, and 0.025C cutoff.

[0070] Lithium plating condition: Take a battery with the corresponding number of cycles, disassemble it after it is fully charged, observe the lithium plating condition on one side of the negative electrode, and take pictures of the lithium plating condition with a digital camera.

[0071] The residual liquid volume test is calculated by subtracting the weight of the packaged battery from the weight of the battery after double sealing.

[0072] The test results for the different lithium-ion batteries are as follows:

[0073]

[0074] This application also provides a lithium-ion battery, including the above-mentioned negative electrode sheet.

[0075] It should be noted that the implementation method of the above-described negative electrode embodiment is also applicable to the embodiment of this lithium-ion battery and can achieve the same technical effect, so it will not be described again here.

[0076] This application also provides an electronic device including the above-described lithium-ion battery.

[0077] It should be noted that the implementation method of the above-described lithium-ion battery embodiment is also applicable to the embodiment of this electronic device and can achieve the same technical effect, so it will not be described again here.

[0078] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0079] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of the present invention.

Claims

1. A negative electrode sheet, characterized in that, include: The current collector, the first negative electrode coating, the second negative electrode coating, and the porous negative electrode sheet, wherein, The first negative electrode coating is coated on the first surface of the current collector, and the second negative electrode coating is coated on the non-single-sided area of ​​the second surface of the current collector, wherein the first surface and the second surface of the current collector are opposite to each other; The negative electrode porous sheet is coated in a single-sided region on the second surface of the current collector, and the non-single-sided region and the single-sided region on the second surface of the current collector are adjacent. The negative electrode porous sheet includes porous nanomaterials and an adhesive, wherein the adhesive is styrene-butadiene rubber, the content of the adhesive is 5%-15%, the content of the porous nanomaterials is 85%-95%, and the porosity of the negative electrode porous sheet is 30%-60%. The thickness of the porous negative electrode sheet is 1 / 10 to 1 / 3 of the thickness of the second negative electrode coating.

2. The negative electrode sheet according to claim 1, characterized in that, The negative electrode sheet and the positive electrode sheet of the battery are wound together to form a core structure, wherein: The single-sided area is located at the starting section in the middle of the core structure. The negative electrode porous sheet includes a first porous sheet and a second porous sheet. The first negative electrode coating, the second negative electrode coating, the first porous sheet and the second porous sheet are all quadrilaterals. The first side of the first porous sheet is one side of the starting segment; The first side of the first porous sheet and the first side of the second porous sheet are adjacent to each other, the second side of the second porous sheet is adjacent to the first side of the second negative electrode coating, and the first side and the second side of the second porous sheet are opposite to each other.

3. The negative electrode sheet according to claim 2, characterized in that, The first porous sheet and the second porous sheet are matched in size, and the first porous sheet and the second porous sheet are matched in shape.

4. The negative electrode sheet according to claim 2, characterized in that, In the core structure, the second side of the first porous sheet, the second side of the second porous sheet, and the first side of the second negative electrode coating are located on the same plane, and the first side and the second side of the first porous sheet are opposite to each other. The first side of the first negative electrode coating corresponds to the second side of the first porous sheet, the second side of the first negative electrode coating corresponds to the second side of the second negative electrode coating, the first side and the second side of the first negative electrode coating are opposite to each other, and the first side and the second side of the second negative electrode coating are opposite to each other.

5. The negative electrode sheet according to claim 1, characterized in that, The first negative electrode coating and the second negative electrode coating are made of active material, conductive agent, binder and dispersant in a certain proportion.

6. A lithium-ion battery, characterized in that, The lithium-ion battery includes a negative electrode sheet as described in any one of claims 1-5.

7. An electronic device, characterized in that, The electronic device includes the lithium-ion battery as described in claim 6.

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