Structure-improved lithium ion battery diaphragm

Abstract

The utility model provides a lithium ion battery diaphragm with an improved structure. The lithium ion battery diaphragm comprises a base membrane matched with an external lithium battery pole piece for use, and a coating layer arranged on the base membrane, a coating gap is formed in the coating layer, water vapor between the lithium battery pole piece and the coating layer is discharged through the coating gap, external electrolyte can also infiltrate the base membrane by virtue of the coating gap, and the base membrane infiltrated by the electrolyte is used for enabling lithium ions to pass between the positive pole piece and the negative pole piece of the lithium battery; in the manufacturing process of the diaphragm, water vapor can be generated due to the influence of environment humidity, the capillary adsorption effect can be generated when the water vapor passes through the coating gap to accelerate discharge, and in the electrolyte injection process, the electrolyte can rapidly infiltrate the diaphragm when flowing through the coating gap, so that the diaphragm is prevented from being damaged. And a gap between the positive electrode and the negative electrode of the lithium ion battery is increased while the liquid absorption speed of the battery cell is increased, so that the electrolyte infiltration efficiency is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of lithium-ion batteries, and particularly discloses a structurally improved lithium-ion battery separator. Background Art

[0002] As an important part of a lithium battery, the lithium-ion battery separator plays a role in preventing short circuit between the positive and negative electrodes of the battery. When overcharged or the temperature rises, the separator will block the current conduction by closing pores to prevent the battery from exploding. Therefore, the performance of the lithium-ion battery separator has a great impact on the battery itself. One of the main methods to improve the performance of the lithium-ion battery separator is to use the separator coating process to improve the heat resistance, mechanical strength, liquid retention and wettability of the separator. In the prior art, methods such as spraying, dipping, and electrospinning technology are generally used to coat inorganic ceramic materials on the surface of the separator to improve the performance of the separator, and most of them use a full coating method to coat the separator. However, the full coating method of the separator will hinder the diffusion and infiltration of the electrolyte on the surface of the separator due to the too large coating thickness and the low surface energy of the coating, or lead to the problem of low infiltration efficiency of the electrolyte on the surface of the separator, which will have an adverse impact on the service life of the lithium battery. Summary of the Utility Model

[0003] In order to overcome the disadvantages and deficiencies in the prior art, the purpose of the utility model is to provide a structurally improved lithium-ion battery separator, which can improve the infiltration efficiency of the electrolyte, optimize the material cost, and extend the service life of the lithium battery.

[0004] To achieve the above purpose, a structurally improved lithium-ion battery separator of the utility model includes a base film used in cooperation with an external lithium battery electrode plate, and a coating layer provided on the base film; there are coating gaps provided on the coating layer, and an included angle is provided between the extending direction of the coating gaps and the extending direction of the base film, and the water vapor between the lithium battery electrode plate and the coating layer is discharged through the coating gaps; the external electrolyte infiltrates the base film through the coating gaps, and the base film infiltrated by the electrolyte enables lithium ions to conduct between the positive and negative electrodes of the lithium battery.

[0005] Further, the coating gaps are in a straight strip shape.

[0006] Further, the coating gaps penetrate through the coating layer along the thickness direction of the coating layer.

[0007] Further, the coating gaps penetrate through the coating layer along the length direction or / and the width direction of the coating layer.

[0008] Further, the included angle between the extending direction of the coating gaps and the extending direction of the base film is 0-90 degrees.

[0009] Further, a plurality of coating gaps are provided, and two adjacent coating gaps are arranged in parallel.

[0010] Further, the width of the coating gap is 0.01 - 5 mm.

[0011] Further, the coating layer is provided on both sides of the base film. When the coating layer is provided on both sides of the base film, the extending directions of the coating gaps on the coating layers located on both sides of the base film are arranged in parallel, and the coating gaps on the coating layer on one side of the base film and the coating gaps on the coating layer on the other side of the base film are asymmetrically arranged relative to the base film.

[0012] Further, the coating gap is formed by a micro - gravure roll through an aqueous coating process. The micro - gravure roll is provided with a coating part and a recessed part. The coating part protrudes from the recessed part. The coating part is used to coat an inorganic polymer on the surface of the base film to form a coating layer, and the cross - sectional area of the recessed part is equal to the cross - sectional area of the coating gap.

[0013] Further, a plurality of coating parts are provided, and the recessed part is between two adjacent coating parts.

[0014] Further, the base film is one of a polyethylene porous film, a polypropylene porous film, and a non - woven fabric.

[0015] The beneficial effects of the present utility model: The present utility model provides a structure - improved lithium - ion battery separator, including a base film for cooperating with the positive and negative electrode plates of an external lithium battery, and a coating layer provided on the surface of the base film; the base film has a microporous structure, the coating layer is located on both sides of the base film, and coating gaps are provided on the coating layer. The water vapor between the lithium - battery electrode plate and the coating layer is discharged through the coating gaps, and the external electrolyte can enter more quickly through the coating gaps and infiltrate the separator through the micropores on the base film. The separator infiltrated by the electrolyte is used to electrically conduct the positive and negative electrode plates of the lithium battery.

[0016] Compared with the prior art, the present solution has the following advantages:

[0017] 1. For the separator coated with such a twill gap, since there are blank areas remaining on the surface of the base film, the coating area is smaller than that of the traditional full - coating method, so the material cost is saved to a certain extent.

[0018] 2. In a lithium battery, a certain amount of gases such as oxygen and carbon dioxide will be generated during the charge - discharge process. If these gases cannot be discharged in time and effectively, it may cause adverse effects such as pressure accumulation and temperature rise inside the battery cell. The coating gap is equivalent to the structure of a capillary. This coating gap can promote the flow and discharge of gases, making it easier for the gases to diffuse and be released through this gap, effectively improving the problem of slow exhaust of the battery cell; in addition, during the processing and manufacturing of lithium batteries, due to the influence of environmental humidity, water vapor will be generated between the coating layer and the lithium - battery electrode plate. The water vapor passing through the coating gap will generate a capillary adsorption effect and be discharged more quickly.

[0019] 3. Since the thickness of the coating layer is in the micron range and considering the setting of the coating gap, at the microscopic level, the striped gap is equivalent to a capillary-like structure. When the electrolyte flows through this gap, capillary adsorption occurs, accelerating its penetration into the separator, thereby enhancing the wetting efficiency of the electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 FIG. is a schematic structural view of the improved-structured lithium-ion battery separator of the present invention;

[0021] Figure 2 FIG. is a schematic structural view when the coating gap of the present invention penetrates through the coating layer;

[0022] Figure 3 FIG. is a schematic structural view when the coating gap of the present invention does not penetrate through the coating layer;

[0023] Figure 4 FIG. is a schematic structural view when the coating layer of the present invention is disposed on both sides of the base film;

[0024] Figure 5 FIG. is a schematic structural view of the microgravure roll for coating the lithium battery separator of the present invention;

[0025] Reference numerals include:

[0026] 1 - Base film, 2 - Coating layer, 3 - Microgravure roll

[0027] 21 - Coating gap, 31 - Coating portion, 32 - Concave portion DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] For the convenience of understanding by those skilled in the art, the present invention will be further described below in conjunction with embodiments and the accompanying drawings. The content mentioned in the embodiments does not limit the present invention.

[0029] Please refer to Figures 1 to 5 As shown, an improved-structured lithium-ion battery separator of the present invention includes a base film 1 for cooperating with external lithium battery electrode plates and a coating layer 2 disposed on the base film 1; a coating gap 21 is provided on the coating layer 2, and an included angle is provided between the extending direction of the coating gap 21 and the extending direction of the base film 1. The water vapor between the external lithium battery electrode plate and the coating layer 2 is discharged through the coating gap 21. The external electrolyte can infiltrate the separator by means of the coating gap 21, and the separator infiltrated by the electrolyte enables lithium ions to conduct between the positive and negative electrodes of the lithium battery.

[0030] When the liquid is a wetting liquid and is in a capillary tube, due to the surface tension of the liquid, the liquid will form a sunken shape in the capillary tube like a taut rubber band. At this time, the liquid on both sides of the sunken area will exert a pulling force on the liquid in the middle of the sunken area, causing the liquid to rise along the wall of the capillary tube; when this phenomenon is applied to the technical field of the present invention, since the electrolyte is a wetting liquid and the coating gap 21 acts as a capillary tube, the liquid level of the wetting liquid in the coating gap 21 is sunken. Therefore, both sides of the electrolyte close to the side wall of the coating gap 21 will exert a pulling force on the sunken area of the electrolyte, promoting the rapid movement of the electrolyte in the coating gap 21, thereby improving the wetting efficiency of the electrolyte.

[0031] In actual production, the material of the base film 1 can be selected from polyethylene, polypropylene or non-woven fabric. Multiple micropores with good air permeability and ion transport characteristics are formed on the base film 1 by processes such as stretching method or salt solvent method. Then, an organic coating or an inorganic coating is applied on the surface of the base film 1 to prevent the direct contact between the positive and negative electrode plates of the lithium battery; an auxiliary structure can also be provided on the coating layer 2. The auxiliary structure can be multiple liquid inlet holes or grooves corresponding to the above micropores opened on the coating layer 2. The external electrolyte can penetrate into the micropores through the grooves or liquid inlet holes to wet the entire separator, so that lithium ions can pass through the coating layer 2. In this solution, the function of the auxiliary structure is realized by setting the coating gap 21 on the coating layer 2, which saves materials while ensuring a good wetting rate of the electrolyte.

[0032] Specifically, the coating gap 21 is in a straight strip shape. Compared with a curved or other non-straight-shaped gap, water vapor or electrolyte will flow more smoothly when flowing through the coating gap 21. Compared with the ceramic separator coated by the full coating method in the prior art, the contact between the separator and the positive and negative electrode plates of the lithium battery is relatively tight, which is not conducive to the discharge of water vapor and the further wetting of the electrolyte. However, the coating gap 21 set on the coating layer in this solution reduces the contact stress between the lithium battery electrode plate and the coating layer 2. When water vapor in the environment enters the coating gap, capillary adsorption will occur to accelerate the discharge. Similarly, the electrolyte will also accelerate the flow due to the setting of the coating gap 21, improving the wetting efficiency of the electrolyte.

[0033] In addition, the setting of the coating gap 21 not only provides a convenient channel for the wetting of the electrolyte, but also reserves an expansion space for the positive and negative electrode plates of the lithium battery, enabling the lithium battery to quickly replenish the electrolyte in a timely manner during the later cycle use; the production of the coating gap 21 will not increase the complexity of the battery system and is easier to achieve mass production.

[0034] Preferably, the coating gap 21 penetrates through the coating layer 2 along the thickness direction of the coating layer 2. After the electrolyte enters the coating gap 21, it directly penetrates into the separator through the microporous structure on the base film, without the transition of other materials in the middle process, which maximally improves the infiltration efficiency of the electrolyte. In actual use, the coating gap 21 may also be arranged without penetrating through the coating layer 2 along the thickness direction of the coating layer 2 (as Figure 3 shown).

[0035] Specifically, the included angle between the extending direction of the coating gap 21 and the extending direction of the base film 1 is 0-90 degrees. Preferably, when the included angle is 60 degrees, the liquid absorption rate and liquid retention rate of the separator are the best.

[0036] Specifically, the coating gap 21 penetrates through the coating layer 2 along the length direction or / and the width direction of the coating layer 2. When the coating gap 21 penetrates through the coating layer 2 along the length direction, the coating gap 21 appears as multiple vertical stripes on the surface of the separator. When the coating gap 21 penetrates through the coating layer 2 along the width direction, the coating gap 21 appears as multiple horizontal stripes on the surface of the separator. In this embodiment, the coating gap 21 penetrates through the coating layer 2 along the length direction and the width direction of the coating layer 2, and a single coating gap 21 presents a continuous and unbroken shape; at this time, the coating gap 21 appears as multiple inclined stripes on the surface of the separator, ensuring the infiltration efficiency of the electrolyte on the premise of minimizing the material cost as much as possible.

[0037] Preferably, a plurality of coating gaps 21 are provided, and two adjacent coating gaps 21 are arranged in parallel. The plurality of coating gaps 21 are arranged in a regular array along the length direction of the base film 1. The purpose of setting the coating gaps 21 in plurality is to appropriately increase the number of coating gaps formed between a single coating gap between the positive and negative electrode plates of the lithium battery and the separator on the original basis, further improving the infiltration efficiency of the electrolyte. The number of coating gaps 21 depends on the size of the lithium battery and the covering area of the coating layer 2 relative to the separator.

[0038] Preferably, the width of the coating gap 21 is 0.01-5 mm. In this embodiment, the coating gap 21 with a width of 0.2 mm is preferably used, and the coating gap 21 divides the coating layer 2 into multiple coating stripes, and the width of the coating stripes is preferably 0.6 mm.

[0039] Specifically, the coating layer 2 is provided on both sides of the base film 1. When the coating layer 2 is provided on both sides of the base film 1, the extending directions of the coating gaps 21 on the coating layers 2 on both sides of the base film 1 are arranged in parallel, and the coating gaps 21 on the coating layer 2 on one side of the base film 1 and the coating gaps 21 on the coating layer 2 on the other side of the base film 1 are arranged in a staggered manner. Preferably, in this embodiment, the coating layer 2 is provided on both sides of the base film 1 (as Figure 3As shown in the figure, the coating gaps 21 on both sides of the base film 1 are asymmetrically arranged relative to the base film, that is, the coating gap 21 on the upper surface of the base film 1 and the coating gap 21 on the lower surface of the base film 1 are staggered. This design enables the two coating gaps 21 on different surfaces to cooperate with each other in space (the staggered arrangement of two capillaries can increase the contact area with the adsorbed substance, thereby enhancing the capillary adsorption effect; when the two capillaries are staggered, the adsorbed substance can enter the capillary from two different directions, improving the capillary adsorption effect), further enhancing the water vapor emission effect between the lithium battery separator and the electrode sheet.

[0040] In actual use, the coating layer 2 can be provided only on one side of the base film. When the coating layer 2 is provided on one side of the base film 1, compared with the scheme of providing it on both sides, this method saves material costs and ensures the overall mechanical strength of the separator. However, the lithium ion transmission rate will also decrease accordingly, which may also lead to a decrease in the battery cycle life. In addition, under high temperature conditions, the thermal stability of the single-sided coated lithium battery separator will also be poor, which may cause risks of separator failure or safety problems.

[0041] Specifically, the base film 1 is one of a polyethylene porous film, a polypropylene porous film, and a non-woven fabric.

[0042] Specifically, (as Figure 5 shown) the coating gap 21 is formed by a micro gravure roll 3 through an aqueous coating process. The micro gravure roll 3 is provided with a coating part 31 and a recessed part 32. The coating part 31 protrudes from the recessed part 32. The coating part 31 is used to coat the inorganic polymer on the surface of the base film 1 to form the coating layer 2. The cross-sectional area of the recessed part 32 is equal to the cross-sectional area of the coating gap 21. Preferably, a plurality of coating parts 31 are provided, and the recessed part 32 is located between two adjacent coating parts 31.

[0043] In this embodiment, micro gravure coating with a customized micro gravure roll 3 enables the inorganic polymer coating to be more evenly coated on the surface of the base film 1, which helps to improve the conductivity of the lithium battery; and the use of an aqueous coating process is because aqueous coatings do not require the use of expensive organic solvents, and the preparation cost is relatively low. Coupled with the gap coating method in this scheme, the material cost is further controlled, and it is easy to realize industrialization. Compared with the high cost in the manufacturing process of lithium battery separators in the prior art, this scheme has significant advantages.

[0044] The above content is only the preferred embodiment of the present invention. For those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. The content of this specification should not be construed as a limitation to the present invention.

Claims

1. An improved-structured lithium-ion battery separator, comprising a base film (1) used in cooperation with external lithium battery electrodes and a coating layer (2) provided on the base film (1); characterized in that: A coating gap (21) is provided on the coating layer (2). An included angle is provided between the extending direction of the coating gap (21) and the extending direction of the base film (1). Moisture between the lithium battery electrode sheet and the coating layer (2) is discharged through the coating gap (21).

2. The improved-structured lithium-ion battery separator according to claim 1, wherein: The coating gap (21) is in a straight strip shape.

3. The improved-structured lithium-ion battery separator according to claim 1, wherein: The included angle between the extending direction of the coating gap (21) and the extending direction of the base film (1) is 0 - 90 degrees.

4. An improved-structured lithium-ion battery separator according to claim 1, wherein: A plurality of coating gaps (21) are provided, and two adjacent coating gaps (21) are arranged in parallel.

5. An improved-structured lithium-ion battery separator according to claim 1, wherein: The width of the coating gap (21) is 0.01 - 5 mm.

6. An improved-structured lithium-ion battery separator according to claim 1, wherein: The coating layer (2) is provided on both sides of the base film (1). The coating gaps (21) on the coating layer (2) on one side of the base film (1) and the coating gaps (21) on the coating layer (2) on the other side of the base film (1) are asymmetrically arranged relative to the base film.

7. An improved-structured lithium-ion battery separator according to any one of claims 1 to 6, characterized in that: The coating gap (21) is formed by a micro - gravure roll (3) through a roll coating method. The micro - gravure roll (3) is provided with a coating part (31) and a recessed part (32). The coating part (31) protrudes from the recessed part (32). The micro - gravure roll (3) is used to coat an external coating slurry on the base film (1) to form the coating layer (2), and the recessed part (32) rolls on the base film (1) to form the coating gap (21).

8. An improved-structured lithium-ion battery separator according to claim 7, characterized in that: A plurality of coating parts (31) are provided, and the recessed part (32) is between two adjacent coating parts (31).

9. The structure-improved lithium-ion battery separator according to claim 1, wherein: The base film (1) is one of a polyethylene porous film, a polypropylene porous film, and a non - woven fabric.

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