Diaphragm and lithium ion battery
By adding the second part of the combined particle structure in the separator, the sharp protrusions generated after the silicon negative electrode laser drilling are alleviated, the problem of increasing battery self-discharge is solved, and the battery performance is improved.
Patent Information
- Application Number
- CN202420210147.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-29
- Publication Date
- 2025-05-30
- Estimated Expiration
- 2034-01-29
AI Technical Summary
The silicon negative electrode particles are relatively hard, and sharp particle protrusions are easily formed after laser drilling, resulting in the separator being pierced, causing a micro-short circuit of the positive and negative electrodes, increasing the battery self-discharge and reducing battery performance.
By optimizing the diaphragm structure, adding the second part of the particle combination structure, alleviating the problem of sharp protrusions, ensuring that the battery energy density is not affected, and at the same time preventing too large or too small thickness from affecting the bonding effect.
It effectively alleviates sharp protrusions caused by laser hole drilling, prevents the diaphragm from being pierced, improves the battery self-discharge problem, and improves battery performance.
Smart Images
Figure CN222927708U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of battery production and manufacturing, and particularly relates to a separator and a lithium-ion battery. Background Art
[0002] As a new type of secondary battery, the lithium-ion battery has the advantages of large energy density and power density, high working voltage, light weight, small volume, long cycle life, good safety, environmental friendliness, etc., and has broad application prospects in portable electrical appliances, electric tools, large-scale energy storage, electric vehicle power sources, etc.
[0003] Compared with the existing carbon negative electrode, the silicon negative electrode has a higher energy density. Existing high-rate lithium battery products basically use silicon negative electrodes and are used in combination with laser drilling technology.
[0004] In the process of implementing the present utility model, the inventors found that there are at least the following problems in the existing technology: the silicon negative electrode particles are relatively hard, and sharp particle protrusions are easily formed after laser drilling. The protrusions will pierce the separator, thereby causing a micro short circuit between the positive and negative electrodes, resulting in an increase in battery self-discharge and a decrease in battery performance. Summary of the Utility Model
[0005] One of the purposes of the present utility model is to provide a separator for the deficiencies of the existing technology. By optimizing the separator structure, the protrusion problem caused by laser drilling of the silicon negative electrode can be improved, which helps to improve the quality of the battery.
[0006] In order to achieve the above purpose, the present utility model adopts the following technical solutions:
[0007] A separator includes a base film layer; a first coating layer and a second coating layer, which are respectively coated on both sides of the base film layer; the thickness of the first coating layer is H1, the second coating layer includes a first part and a second part arranged in sequence, the second part is a particle combination structure, the thickness of the first part is H2, and the thickness of the second part is H3, satisfying the relational expressions: H1 < H2 + H3 ≤ 2H1, H2 < H3 ≤ 2H1.
[0008] Preferably, the relational expression between the thickness of the first coating layer and the thickness of the first part is satisfied: 0 < H2 ≤ 1 / 2H1.
[0009] Preferably, the base film layer has a first side and a second side in its thickness direction, the first coating layer covers the first side, and the second coating layer covers the second side.
[0010] Preferably, the area of the first part is equal to the area of the second part, and the second part covers the first part.
[0011] Preferably, the material of the base film layer is polypropylene or polyethylene.
[0012] Preferably, the material of the first coating layer is the same as that of the first part.
[0013] Preferably, the second part is made of polyolefin particles and polymethyl methacrylate particles.
[0014] Preferably, the base film layer is a single-layer structure or a multi-layer structure.
[0015] Another object of the present invention is to provide a lithium-ion battery, which includes a first electrode sheet, a second electrode sheet and the separator as described above, and the first electrode sheet, the separator and the second electrode sheet are stacked and wound in sequence.
[0016] Preferably, the surface of the first coating layer is close to the first electrode sheet, and the surface of the second coating layer is close to the second electrode sheet.
[0017] One of the above technical solutions has the following beneficial effects
[0018] By optimizing the separator structure and adding the second part of the particle combination structure, the present invention plays a role in alleviating sharp protrusions. By adopting the structure of mixing large and small particles, on the premise of ensuring the energy density of the battery, this structure can correspond to the side of the silicon negative electrode, relieve the sharp protrusions generated on the corresponding negative electrode surface due to laser cleaning, prevent piercing the separator, and further improve the problem of large self-discharge of the battery. In addition, by limiting the thicknesses of the first part and the second part, it is prevented that the thickness is too large and affects the energy density of the battery, and at the same time, it is prevented that the thickness is too small and affects the bonding effect. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The features, advantages and technical effects of the exemplary embodiments of the present invention will be described below with reference to the drawings.
[0020] Figure 1 It is a schematic structural diagram of the present invention.
[0021] Among them, the reference numerals are explained as follows:
[0022] 10 - Base film layer;
[0023] 1 - First coating layer;
[0024] 2 - Second coating layer; 21 - First part; 12 - Second part;
[0025] H - Thickness direction. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0026] As used in the specification and claims, certain terms are used to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. The specification and claims do not distinguish components by the difference in names, but by the difference in functions. As used throughout the specification and claims, the term "comprising" is an open-ended term and should be interpreted as "including but not limited to". "Substantially" means within an acceptable error range, and those skilled in the art can solve technical problems within a certain error range and basically achieve technical effects.
[0027] In addition, terms such as "first", "second", etc. are used only for descriptive purposes and should not be construed as indicating or implying relative importance.
[0028] In a utility model, unless otherwise clearly specified and defined, terms such as "installed", "connected", "joined", "fixed", etc. 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 directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this utility model can be understood according to specific circumstances.
[0029] The following further describes the present utility model in detail with reference to the accompanying drawings, but it is not a limitation to the present utility model.
[0030] Embodiment 1
[0031] A diaphragm, comprising a base film layer 10; a first coating layer 1 and a second coating layer 2, which are respectively coated on both sides of the base film layer 10; the thickness of the first coating layer 1 is H1, the second coating layer 2 includes a first part 21 and a second part 22 arranged in sequence, the second part 22 is a particle composite structure, the thickness of the first part 21 is H2, and the thickness of the second part 22 is H3, satisfying the relationship: H1 < H2 + H3 ≤ 2H1, H2 < H3 ≤ 2H1.
[0032] Since the silicon negative electrode particles are relatively hard, sharp particle protrusions are likely to form after laser drilling. The protrusions will pierce the separator, thereby causing a micro short circuit between the positive and negative electrodes, resulting in an increase in the self-discharge of the battery and a decline in battery performance. By optimizing the separator structure, the present utility model adds the second part 22 of the particle combination structure to relieve the sharp protrusions. With this structure of mixing large and small particles, on the premise of ensuring the energy density of the battery, this structure can correspond to the side of the silicon negative electrode, relieve the sharp protrusions generated on the corresponding negative electrode surface due to laser cleaning, prevent piercing the separator, and thus can improve the problem of large self-discharge of the battery. In addition, the thicknesses of the first part 21 and the second part 22 are limited to prevent the thickness from being too large and affecting the energy density of the battery, and at the same time, prevent the thickness from being too small and affecting the bonding effect.
[0033] It should be noted that: the first coating layer 1 is formed by mixing and coating ceramics, PVDF glue, and a solvent. The thickness of the first coating layer 1 is limited to ensure that the battery has good bonding effect and thermal stability.
[0034] In the separator according to the present utility model, the relationship between the thickness of the first coating layer 1 and the thickness of the first part 21 satisfies the formula: 0 < H2 ≤ 1 / 2H1. Specifically, the thickness of the first part 21 is limited to prevent the first part 21 from being too thick and occupying the internal space of the battery, resulting in the situation that the energy density of the battery is affected.
[0035] In the separator according to the present utility model, the base film layer 10 has a first surface and a second surface in its thickness direction H. The first coating layer 1 covers the first surface, and the second coating layer 2 covers the second surface. In this embodiment, the base film layer 10 can be understood as a substrate. As the main body of the separator, the base film layer 10 mainly plays a role in supporting the entire separator. The two surfaces in its thickness direction are the first surface and the second surface respectively. The first surface and the second surface can both be flat surfaces, or can be rough surfaces to improve the bonding strength with the coating layer. This is not limited here, as long as it meets the normal coating materials.
[0036] In the separator according to the present utility model, the material of the base film layer 10 is one or a mixture of two of polypropylene and polyethylene, but the present utility model is not limited thereto. The material of the base film layer 10 can also be other polyolefin component materials, which are not limited here.
[0037] In the separator according to the present utility model, the second part 22 is polyolefin particles and polymethyl methacrylate particles. In this embodiment, the second part 22 is preferably formed by mixing secondary large particles aggregated by polyolefin particles and PMMA small particles, but the present utility model is not limited thereto. The material of the second part 22 can be adjusted according to actual production requirements.
[0038] The working principle of the present utility model is:
[0039] The utility model optimizes the diaphragm structure and adds the second part 22 of the particle combination structure to relieve sharp protrusions. By adopting the structure of mixing large and small particles, on the premise of ensuring the energy density of the battery, this structure can correspond to the side of the silicon negative electrode, relieve the sharp protrusions generated on the corresponding negative electrode surface due to laser cleaning, prevent piercing the diaphragm, and thus improve the problem of large self-discharge of the battery. In addition, the thicknesses of the first part 21 and the second part 22 are defined to prevent the thickness from being too large and affecting the energy density of the battery, and at the same time prevent the thickness from being too small and affecting the bonding effect.
[0040] Embodiment 2
[0041] The difference from Embodiment 1 is that: the area of the first part 21 and the area of the second part 22 in this embodiment are equal, which relieves the sharp protrusions generated on the corresponding negative electrode surface due to laser cleaning. The second part 22 covers the first part 21, and the material of the first coating layer 1 is the same as the material of the first part 21, that is, the composition of the first part 21 is consistent with the coating of the first coating layer 1, which helps to simplify the production process and reduce the overall production cost of the diaphragm.
[0042] Other structures are the same as those in Embodiment 1 and will not be elaborated here.
[0043] Embodiment 3
[0044] The difference from Embodiment 1 is that: the base film layer 10 in this embodiment is a single-layer structure or a multi-layer structure, which can meet the thickness requirements of different batteries and helps to improve the compatibility of the diaphragm. This embodiment is preferably a single-layer structure, which is not limited here.
[0045] Other structures are the same as those in Embodiment 1 and will not be elaborated here.
[0046] Lithium-ion battery
[0047] The utility model includes the diaphragms of Embodiments 1 to 3.
[0048] Specifically, the lithium-ion battery includes a first electrode plate, a second electrode plate and the diaphragm as described above. The first electrode plate, the diaphragm and the second electrode plate are stacked and wound in sequence. Among them, the first electrode plate is a positive electrode plate, the second electrode plate is a negative electrode plate, and the surface of the first coating layer 1 is close to the first electrode plate, which can be understood as the first side of the diaphragm facing the positive electrode side, and the surface of the second coating layer 2 is close to the second electrode plate, which can be understood as the second side of the diaphragm facing the negative electrode side.
[0049] The two electrode plates are stacked on each other and have opposite polarities. The electrode plates with opposite polarities are respectively the positive electrode plate and the negative electrode plate of the battery. In order to avoid short circuit between the positive and negative electrode plates, a diaphragm is arranged between every two adjacent electrode plates, and the electrode plates with opposite polarities are electrically isolated through the diaphragm.
[0050] In some embodiments, the lithium-ion battery may also be a laminated battery. The electrode sheets with opposite polarities are also electrically isolated by the separator. The first electrode sheet and the second electrode sheet have opposite polarities, and there may be multiple first electrode sheets and second electrode sheets, which are stacked on top of each other.
[0051] In some embodiments, the first electrode sheet may be a positive electrode sheet, and the second electrode sheet may be a negative electrode sheet; or, the first electrode sheet may be a negative electrode sheet, and the second electrode sheet may be a positive electrode sheet, which is not limited here. The battery can be encapsulated with an aluminum-plastic film or a steel shell.
[0052] In addition, the battery containing the separator structure of the present invention can also be used in electrical devices, which can be mobile phones, portable devices, laptop computers, and so on.
[0053] Comparative Example 1
[0054] Different from Example 1: The coating layers on both sides of this embodiment both use the coating material of the first coating layer 1 with a thickness of 1.5H1. Then, the separator, the positive electrode sheet, and the negative electrode sheet are stacked and wound in sequence, and finally a battery is made.
[0055] After the batteries of Example 1 and Comparative Example 1 are left standing for 48 hours, the first voltage is measured, and then after standing for another 48 hours, the second voltage is measured. Dividing the voltage difference between the two measurements by the time difference can obtain the K-value data. The specific test results are shown in Table 1 below.
[0056] Table 1. K-value test results of the batteries of Example 1 and Comparative Example 1
[0057] Group Average K value Example 1 0.083 mV / h Comparative Example 1 0.24 mV / h
[0058] As can be seen from Table 1, the K-value measured for the battery prepared in Example 1 is smaller than the K-value of Comparative Example 1, indicating that under the premise of ensuring the energy density of the battery, the structure of the present invention can effectively alleviate the sharp protrusions generated on the corresponding negative electrode surface due to laser cleaning through the second part 22 of the particle combination structure, prevent the sharp protrusions on the negative electrode surface from piercing the separator, and thus can effectively improve the problem of large self-discharge of the battery.
[0059] It should be noted that in the lithium battery industry or the field of electrochemistry, the K-value represents the voltage drop of the battery per unit time. This indicator is usually used to measure the self-discharge rate of lithium batteries. Generally speaking, the smaller the K-value, the better the performance of the battery.
[0060] Based on the disclosure and teachings of the above specification, those skilled in the art to which the present utility model pertains are also able to make changes and modifications to the above embodiments. Therefore, the present utility model is not limited to the above specific embodiments, and any obvious improvements, substitutions or variations made by those skilled in the art on the basis of the present utility model all fall within the protection scope of the present utility model. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present utility model.
Claims
1. A diaphragm, characterized in that: include: Basement membrane layer (10); A first coating layer (1) and a second coating layer (2) are coated on two sides of the base film layer (10) respectively; The thickness of the first coating layer (1) is H1, the second coating layer (2) comprises a first part (21) and a second part (22) which are arranged in sequence, the second part (22) is a particle combination structure, the thickness of the first part (21) is H2, the thickness of the second part (22) is H3, and the relationship is satisfied: H1<H2+H3≤2H1, H2<H3≤2H1; The second part (22) is polyolefin particles and polymethyl methacrylate particles.
2. A diaphragm according to claim 1, characterized in that: The thickness of the first coating layer (1) and the thickness of the first portion (21) satisfy the relationship: 0<H2≤1 / 2H1.
3. A diaphragm according to claim 2, characterized in that: The base film layer (10) has a first surface and a second surface in the thickness direction (H) thereof, the first coating layer (1) covers the first surface, and the second coating layer (2) covers the second surface.
4. A diaphragm according to any one of claims 1 to 3, characterized in that: The area of the first part (21) is equal to the area of the second part (22), and the second part (22) covers the first part (21).
5. A diaphragm according to any one of claims 1 to 3, characterized in that: The base film layer (10) is made of polypropylene or polyethylene.
6. A diaphragm according to any one of claims 1 to 3, characterized in that: The material of the first coating layer (1) is the same as the material of the first portion (21).
7. A diaphragm according to any one of claims 1 to 3, characterized in that: The base film layer (10) is a single-layer structure or a multi-layer structure.
8. A lithium ion battery, characterized in that: It comprises a first pole piece, a second pole piece and a diaphragm as described in any one of claims 1 to 7, wherein the first pole piece, the diaphragm and the second pole piece are stacked and wound in sequence.
9. A lithium ion battery as claimed in claim 8, characterized in that: The surface of the first coating layer (1) is close to the first pole piece, and the surface of the second coating layer (2) is close to the second pole piece.