Long-circulation sodium-ion battery diaphragm

Abstract

The utility model relates to a long-circulation sodium ion battery diaphragm, which belongs to the field of sodium ion batteries and comprises a diaphragm body, the diaphragm body comprises a diaphragm base layer and a functional layer which are mutually laminated, the functional layer is a non-woven fabric layer, and the thickness of the non-woven fabric functional layer is 2.5-3 times of that of the diaphragm base layer. According to the utility model, the diaphragm base layer adopts a conventional sodium-ion battery diaphragm, the thickness of the diaphragm base layer is about 16 microns, and the purpose of reducing the vacuum baking time of a sodium-ion battery cell using the diaphragm body disclosed by the utility model is achieved by adding the functional layer on the surface of the diaphragm base layer. Besides, the non-woven fabric layer is additionally arranged on the surface of the diaphragm base layer, so that the diaphragm body between the positive plate and the negative plate can accommodate more electrolyte, and the sodium ion battery using the diaphragm body disclosed by the utility model has the characteristic of long circulation.

Description

Technical Field

[0001] The utility model relates to the field of sodium ion batteries, in particular to a long-cycle sodium ion battery diaphragm. Background Art

[0002] Sodium-ion battery is a secondary battery that mainly relies on the movement of sodium ions between the positive and negative electrodes to work, which is similar to the working principle of lithium-ion batteries.

[0003] Compared with lithium-ion batteries, the sodium salt raw materials used in sodium-ion batteries are abundant in reserves, cheap, and have lower manufacturing costs. Since sodium ions are larger than lithium ions, sodium-ion batteries are generally used in scenarios where weight and energy density are not high, such as energy storage scenarios. Among them, when sodium-ion batteries are used in energy storage scenarios, their size is generally designed to be larger, and the diaphragms of existing sodium-ion batteries are generally polyolefin diaphragms, such as PP diaphragms, PE diaphragms, etc. The holes on them for sodium ions to pass through are generally processed by dry uniaxial stretching process, dry biaxial stretching process, wet stretching process, etc., that is, polyolefin diaphragms are only permeable in the direction perpendicular to them. Therefore, in the case of a high height of the sodium-ion battery, its vacuum baking process takes a long time to achieve the purpose of removing moisture from the battery cell. According to the applicant's test, a cylindrical sodium-ion battery with a diameter of 120 mm and a height of 300 mm even takes up to two weeks to completely remove the moisture from the battery cell, which is not conducive to improving production efficiency.

[0004] Based on this, the utility model provides a long-cycle sodium ion battery separator to reduce the time required for vacuum baking of large-size sodium ion batteries, thereby achieving the purpose of improving production efficiency. Utility Model Content

[0005] Based on this, the utility model provides a long-cycle sodium-ion battery separator, comprising a separator body, wherein the separator body comprises a separator base layer and a functional layer stacked on each other, wherein the functional layer is a non-woven fabric layer, and the thickness of the non-woven fabric functional layer is 2.5-3 times the thickness of the separator base layer.

[0006] In the utility model, the diaphragm base layer adopts a conventional sodium ion battery diaphragm with a thickness of about 16 μm. The utility model achieves the purpose of reducing the vacuum baking time of the sodium ion battery cell using the diaphragm body of the utility model by adding a functional layer on the surface of the diaphragm base layer.

[0007] In the utility model, after the diaphragm body and the positive and negative electrode sheets are wound into a battery cell, the diaphragm body will be sandwiched between the positive and negative electrode sheets. At this time, since the structure of the non-woven fabric is mainly a fiber mesh structure, it has good air permeability in all directions. Therefore, during the vacuum baking process, the moisture in the battery cell can enter the non-woven fabric from all directions and flow smoothly in the non-woven fabric. Therefore, the moisture in the battery cell can be quickly dried completely, greatly reducing the vacuum baking time of the sodium ion battery cell. It has been verified that the sodium ion battery cell with a diameter of 120mm and a height of 300mm using the diaphragm body of the utility model can completely remove the moisture in the battery cell within 2-3 days in a vacuum environment of 85°C. It can be seen that the diaphragm body of the utility model can effectively reduce the time required for vacuum baking of large-size sodium ion batteries, thereby achieving the purpose of improving production efficiency. Among them, preferably, the diaphragm base layer is a diaphragm base layer made of PP material, and the functional layer is a non-woven fabric layer made of PP material.

[0008] In addition, in the present invention, since a non-woven fabric layer is added to the surface of the diaphragm base layer, the diaphragm body located between the positive and negative electrode sheets can accommodate more electrolyte, so that the sodium ion battery using the diaphragm body of the present invention can have a long cycle characteristic.

[0009] Furthermore, the width of the functional layer is smaller than the width of the diaphragm base layer, and there are areas not covered by the functional layer at both ends of the diaphragm base layer in the width direction, forming blank areas.

[0010] In the utility model, the thickness of the functional layer is much greater than the thickness of the diaphragm base layer. When the diaphragm body of the utility model is used, most of the electrolyte will be contained in the functional layer, and correspondingly, only a small part of the electrolyte will be contained in the blank area of ​​the diaphragm base layer. Therefore, by making the width of the functional layer consistent with the width of the positive and negative electrode sheets, and aligning the edges of the positive and negative electrode sheets and the functional layer, most of the electrolyte in the sodium ion battery can be located between the positive and negative electrode sheets, thereby effectively promoting the migration of sodium ions between the positive and negative electrodes, and helping to achieve more efficient energy conversion during the charging and discharging process, thereby achieving the purpose of improving the performance of the sodium ion battery.

[0011] Furthermore, connection areas are formed at both end edges in the width direction of the functional layer, the connection areas are arranged along the length direction of the functional layer, and the connection areas are fixedly connected to the diaphragm base layer; the functional layer forms a working area between the connection areas thereon.

[0012] In the utility model, the connection areas formed at the edges of both ends of the functional area in the width direction are used for fixed connection with the diaphragm base layer, thereby realizing the fixed connection between the functional layer and the diaphragm base layer.

[0013] Among them, for the functional layer formed with a connection area, when in use, it is necessary to make the width of the working area of ​​the functional layer consistent with the width of the positive and negative electrode sheets to avoid the connection structure between the connection area and the diaphragm base layer affecting the migration of sodium ions in the diaphragm body.

[0014] The width of the connection area needs to be as small as possible, for example, 0.2-0.5 mm, so as to reduce the amount of electrolyte contained in the connection area.

[0015] Furthermore, a plurality of welding areas are arranged on the connection area, and the welding areas are arranged at equal intervals along the length direction of the connection area. The connection area is fixedly connected to the diaphragm base layer through the welding areas thereon.

[0016] In the utility model, the welding area on the connection area can be fixedly connected to the diaphragm base layer by ultrasonic welding. Since the connection area on the functional layer is located on the outside of the positive and negative electrode sheets when in use, the existence of the welding connection structure will not affect the permeability of the diaphragm body to sodium ions.

[0017] Furthermore, functional layers are disposed on both side surfaces of the diaphragm base layer, and the edges of the functional layers on both sides of the diaphragm base layer are disposed flush with each other.

[0018] In the utility model, functional layers are arranged on both side sheets of the diaphragm base layer, so that both sides of the diaphragm body have good air permeability, which can further reduce the vacuum baking time of the battery cell. At the same time, the presence of functional layers on both sides can further increase the electrolyte holding capacity, thereby further improving the long cycle performance of the sodium ion battery.

[0019] The principle and effect of the present invention are further described below in combination with the above technical solutions and the accompanying drawings:

[0020] In the utility model, after the diaphragm body and the positive and negative electrode sheets are wound into a battery cell, the diaphragm body will be sandwiched between the positive and negative electrode sheets. At this time, since the structure of the non-woven fabric is mainly a fiber mesh structure, it has good air permeability in all directions. Therefore, during the vacuum baking process, the moisture in the battery cell can flow smoothly in the non-woven fabric, so that the moisture in the battery cell can be quickly and completely dried, which greatly reduces the vacuum baking time of the sodium ion battery cell, thereby achieving the purpose of improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the front view of the long cycle sodium ion battery separator according to an embodiment of the utility model;

[0022] Figure 2 The side view structure of the long cycle sodium ion battery separator of the utility model embodiment is shown in FIG. Figure 1 ;

[0023] Figure 3 The side view structure of the long cycle sodium ion battery separator of the utility model embodiment is shown in FIG. Figure 2 .

[0024] Reference numerals

[0025] 1-diaphragm base layer, 11-blank area, 2-functional layer, 21-connection area, 211-welding area. DETAILED DESCRIPTION

[0026] In order to facilitate understanding by those skilled in the art, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0027] like Figure 1-3 A long-cycle sodium-ion battery separator comprises a separator body, wherein the separator body comprises a separator base layer 1 and a functional layer 2 stacked on each other, wherein the functional layer 2 is a non-woven fabric layer, and the thickness of the non-woven fabric functional layer 2 is 2.5-3 times the thickness of the separator base layer.

[0028] In the present invention, the diaphragm base layer 1 adopts a conventional sodium ion battery diaphragm with a thickness of about 16 μm. The present invention achieves the purpose of reducing the vacuum baking time of the sodium ion battery cell using the diaphragm body of the present invention by adding a functional layer 2 on the surface of the diaphragm base layer 1.

[0029] In the utility model, after the diaphragm body and the positive and negative electrode sheets are wound into a battery cell, the diaphragm body will be sandwiched between the positive and negative electrode sheets. At this time, since the structure of the non-woven fabric is mainly a fiber mesh structure, it has good air permeability in all directions. Therefore, during the vacuum baking process, the moisture in the battery cell can enter the non-woven fabric from all directions and flow smoothly in the non-woven fabric, so the moisture in the battery cell can be quickly dried completely, greatly reducing the vacuum baking time of the sodium ion battery cell. It has been verified that the sodium ion battery cell with a diameter of 120mm and a height of 300mm using the diaphragm body of the utility model can completely remove the moisture in the battery cell within 2-3 days in a vacuum environment of 85°C. It can be seen that the diaphragm body of the utility model can effectively reduce the time required for vacuum baking of large-size sodium ion batteries, thereby achieving the purpose of improving production efficiency. Among them, preferably, the diaphragm base layer 1 is a diaphragm base layer 1 made of PP material, and the functional layer 2 is a non-woven fabric layer made of PP material.

[0030] In addition, in the present invention, since a non-woven fabric layer is added to the surface of the diaphragm base layer 1, the diaphragm body located between the positive and negative electrode sheets can accommodate more electrolyte, so that the sodium ion battery using the diaphragm body of the present invention can have a long cycle characteristic.

[0031] In one embodiment, the width of the functional layer 2 is smaller than the width of the diaphragm base layer 1 , and there are areas not covered by the functional layer 2 at both ends of the diaphragm base layer 1 in the width direction, forming blank areas 11 .

[0032] In this embodiment, the thickness of the functional layer 2 is much greater than the thickness of the diaphragm base layer 1. When the diaphragm body of the utility model is used, most of the electrolyte will be contained in the functional layer 2, and correspondingly, only a small part of the electrolyte will be contained in the blank area 11 of the diaphragm base layer 1. Therefore, by making the width of the functional layer 2 consistent with the width of the positive and negative electrode sheets, and aligning the edges of the positive and negative electrode sheets and the functional layer 2, most of the electrolyte in the sodium ion battery can be located between the positive and negative electrode sheets, thereby effectively promoting the migration of sodium ions between the positive and negative electrodes, and helping to achieve more efficient energy conversion during the charging and discharging process, thereby achieving the purpose of improving the performance of the sodium ion battery.

[0033] In one embodiment, connection areas 21 are formed at both end edges of the functional layer 2 in the width direction, the connection areas 21 are arranged along the length direction of the functional layer 2, and the connection areas 21 are fixedly connected to the diaphragm base layer 1; the functional layer 2 forms a working area between the connection areas 21 thereon.

[0034] In this embodiment, the connection areas 21 formed at the edges of both ends of the functional area in the width direction are used for fixed connection with the diaphragm base layer 1 , thereby achieving fixed connection between the functional layer 2 and the diaphragm base layer 1 .

[0035] Among them, for the functional layer 2 formed with the connection area 21, when in use, it is necessary to make the width of the working area of ​​the functional layer 2 consistent with the width of the positive and negative electrode sheets to avoid the connection structure between the connection area 21 and the diaphragm base layer 1 affecting the migration of sodium ions in the diaphragm body.

[0036] The width of the connection area 21 needs to be as small as possible, for example, 0.2-0.5 mm, so as to reduce the amount of electrolyte contained in the connection area 21 .

[0037] In one embodiment, a plurality of welding areas 211 are provided on the connection area 21 , and the welding areas 211 are equally spaced along the length direction of the connection area 21 , and the connection area 21 is fixedly connected to the diaphragm base layer 1 via the welding areas 211 thereon.

[0038] In this embodiment, the welding area 211 on the connection area 21 can be fixedly connected to the diaphragm base layer 1 by ultrasonic welding, wherein, since the connection area 21 on the functional layer 2 is located on the outside of the positive and negative electrode sheets when in use, the existence of the welding connection structure will not affect the permeability of the diaphragm body to sodium ions.

[0039] In one embodiment, functional layers 2 are disposed on both side surfaces of the diaphragm substrate 1 , and the edges of the functional layers 2 on both sides of the diaphragm substrate 1 are flush with each other.

[0040] In this embodiment, functional layers 2 are provided on both side sheets of the diaphragm base layer 1, so that both sides of the diaphragm body have good air permeability, which can further reduce the vacuum baking time of the battery cell. At the same time, the presence of functional layers 2 on both sides can further increase the electrolyte holding capacity, thereby further improving the long cycle performance of the sodium ion battery.

[0041] The above embodiments only express several implementation methods of the utility model, and the descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the utility model patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, which all belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent shall be based on the attached claims.

Claims

1. A long cycle sodium ion battery separator, characterized in that: The invention comprises a diaphragm body, wherein the diaphragm body comprises a diaphragm base layer and a functional layer which are stacked on each other, wherein the functional layer is a non-woven fabric layer, and the thickness of the non-woven fabric functional layer is 2.5-3 times the thickness of the diaphragm base layer.

2. A long cycle sodium ion battery separator according to claim 1, characterized in that: The membrane base layer is a membrane base layer made of PP material, and the functional layer is a non-woven fabric layer made of PP material.

3. A long cycle sodium ion battery separator according to claim 1 or 2, characterized in that: The width of the functional layer is smaller than the width of the diaphragm base layer, and there are areas not covered by the functional layer at both ends of the diaphragm base layer in the width direction, forming blank areas.

4. A long cycle sodium ion battery separator according to claim 3, characterized in that: The functional layer has connection areas formed at both end edges in the width direction. The connection areas are arranged along the length direction of the functional layer and are fixedly connected to the diaphragm base layer. The functional layer forms a working area between the connection areas thereon.

5. A long cycle sodium ion battery separator according to claim 4, characterized in that: The connection area is provided with a plurality of welding areas, and the welding areas are arranged at equal intervals along the length direction of the connection area. The connection area is fixedly connected to the diaphragm base layer through the welding areas thereon.

6. A long cycle sodium ion battery separator according to claim 5, characterized in that: Functional layers are arranged on both side surfaces of the diaphragm base layer, and the edges of the functional layers located on both sides of the diaphragm base layer are arranged flush with each other.

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