Battery diaphragm, winding type battery cell and secondary battery

Abstract

The invention discloses a battery diaphragm, a winding type battery cell and a secondary battery, a coating is added in the battery diaphragm, and when the contact angle of the coating and a colloidal particle layer is 30-90 degrees, the wettability of the colloidal particle layer and the coating is relatively low, and the coating can play a role in dispersing glue, so that colloidal particles in the colloidal particle layer are prevented from being infiltrated in the coating; when the battery diaphragm is applied to the winding type battery cell, the negative plate can be prevented from wrinkling on the large surface of the winding type battery cell, so that the performance and the safety of the winding type battery cell and even a secondary battery can be improved.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery separator, a wound battery cell and a secondary battery. Background Art

[0002] When making a wound cell, the positive electrode sheet, the negative electrode sheet and the battery separator are firstly wound up, and then hot pressed, so that a wound cell of a preset size can be obtained. During the charging process of the wound cell, active ions such as lithium ions escape from the positive electrode sheet and pass through the battery separator and are embedded in the negative electrode sheet, which increases the thickness of the negative electrode sheet. In the thickness direction of the wound cell, due to the constraint of the compacted positive electrode sheet and the battery separator, the thickening of the negative electrode sheet in the thickness direction will be transformed into extension to both sides; since the gap between the battery separator and the positive electrode sheet, and the battery separator and the negative electrode sheet at the R corner is very small, this effect of extending to both sides will be constrained at the R corner, resulting in wrinkles on the large surface of the wound cell. However, the appearance of wrinkles will cause the lithium ions to fail to be embedded in the negative electrode sheet in time, thereby affecting the performance and safety of the secondary battery. Summary of the invention

[0003] The embodiments of the present application provide a battery separator, a wound battery cell and a secondary battery, which are used to solve the problem of wrinkles on the surface of the wound battery cell, thereby improving the performance and safety of the secondary battery.

[0004] In a first aspect, an embodiment of the present application provides a battery separator, comprising: a base film, a coating layer and a colloid layer stacked in sequence, wherein the contact angle between the coating layer and the colloid layer is 30°-90°.

[0005] In a second aspect, an embodiment of the present application provides a wound battery cell, comprising: a positive electrode sheet, a negative electrode sheet, and a battery separator as described in the first aspect above, wherein the battery separator is located between the positive electrode sheet and the negative electrode sheet.

[0006] In a third aspect, an embodiment of the present application provides a secondary battery, comprising: a shell, and a wound battery cell as described in the second aspect above, wherein the wound battery cell is disposed in the shell.

[0007] The beneficial effects of this application are as follows:

[0008] A battery separator, a wound battery cell and a secondary battery provided in the embodiments of the present application, wherein a coating is added to the battery separator, and when the contact angle between the coating and the colloid layer is 30°-90°, it indicates that the wettability between the colloid layer and the coating is low, and the coating can play a role in repelling glue, thereby preventing the colloid particles in the colloid layer from being wetting in the coating; when such a battery separator is used in a wound battery cell, wrinkles on the large surface of the negative electrode sheet on the wound battery cell can be avoided, thereby improving the performance and safety of the wound battery cell and even the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a schematic diagram of the structure of a battery separator provided in an embodiment of the present application;

[0010] Figure 2 A schematic diagram of the contact angle provided in the embodiments of the present application;

[0011] Figure 3 A schematic diagram of the structure of a wound battery cell provided in an embodiment of the present application;

[0012] Figure 4 The negative electrode sheet in the wound battery cell provided in the embodiment of the present application extends to both sides;

[0013] Figure 5 for Figure 4 An enlarged schematic diagram of the local structure in the solid coil 1;

[0014] Figure 6 This is a schematic diagram of the structure of a secondary battery provided in an embodiment of the present application.

[0015] Figure numerals: 10 - base film, 20 - coating, 30 - colloid layer, 31 - colloid, 110 - wound battery cell, 120 - shell, 130 - electrolyte, 141 - positive electrode column, 142 - negative electrode column, m1 - negative electrode sheet, m2 - battery separator, m3 - positive electrode sheet, m4 - positive electrode ear, m5 - negative electrode ear. DETAILED DESCRIPTION

[0016] The following will be combined with the accompanying drawings to describe in detail the specific implementation of a battery separator, a wound battery cell and a secondary battery provided in the embodiments of the present application. It should be noted that the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0017] The present application embodiment provides a battery separator, such as Figure 1 and Figure 2 As shown, the battery separator m2 may include: a base film 10, a coating 20 and a colloid layer 30 stacked in sequence, and the contact angle between the coating 20 and the colloid layer 30 is 30°-90°. It should be understood that the colloid layer 30 includes colloid particles 31, and the contact angle between the coating 20 and the colloid layer 30 is the contact angle A between the colloid particles 31 and the coating 20.

[0018] In this way, when a coating is added to the battery separator and the contact angle between the coating and the colloid layer is 30°-90°, it means that the wettability of the colloid layer and the coating is low. The coating can play a role in repelling glue and prevent the colloid particles in the colloid layer from being infiltrated into the coating.

[0019] In addition, since there is a colloid layer in the battery separator, when it is applied to the wound battery cell, the colloid layer can play a fixing role, making the structure of the wound battery cell more stable, and preventing the wound battery cell from becoming loose and affecting the performance. Therefore, this type of battery separator can also be called a sticky separator.

[0020] Optionally, the material of the colloid particles in the colloid particle layer includes a non-polar substance, and the surface of the coating layer facing the colloid particle layer has a hydrophilic group. The hydrophilic group is a polar group, so the non-polar substance and the hydrophilic group will repel each other when in contact, thereby increasing the contact angle between the colloid particle layer and the coating layer, thereby playing a role in repelling glue.

[0021] Furthermore, the coating includes ceramic particles and polymer materials, and the polymer materials include hydrophilic groups. In other words, the hydrophilic groups on the surface of the coating can be provided by the polymer materials, thereby playing a role of gelatin repelling.

[0022] Among them, the polymer material may include but is not limited to: molecular fibers, polymer fibers may be but are not limited to cellulose, aramid, etc., and the specific selection of which fiber can be set according to actual needs and is not limited here. Common hydrophilic groups include but are not limited to: carboxyl, sulfonic acid, amino, amine, hydroxyl, amide, etc., which can be set according to actual needs and are not specifically limited here. For example, when the hydrophilic group includes but is not limited to at least one of sulfonic acid and carboxyl, the polymer material with at least one of sulfonic acid and carboxyl can improve the thermal stability of the battery separator, so in order to play a role in dispersing glue and improving the thermal stability of the battery separator, the hydrophilic group can be selected from at least one of sulfonic acid and carboxyl.

[0023] The materials used to make the ceramic particles may include, but are not limited to, aluminum oxide, silicon oxide, magnesium hydroxide and other inorganic materials with excellent heat resistance, which can increase the thermal stability of the battery separator.

[0024] The material of the colloid layer includes at least one of non-polar substances such as polytetrafluoroethylene and polymethyl methacrylate. When the non-polar substance contacts the hydrophilic group, the repulsion between the two can increase the contact angle between the colloid layer and the coating, thereby playing a role of dispersing the glue.

[0025] In addition, the mass ratio of ceramic particles to polymer materials can be 1.5 to 9, such as but not limited to 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9 and other values, which can be set according to actual needs and are not specifically limited here. For example, if the proportion of ceramic particles is too small, the heat resistance of the battery separator will be reduced, and if the proportion of polymer materials is too small, the glue-dispersing effect will be reduced. Therefore, when the mass ratio of ceramic particles to polymer materials is high, both good heat resistance and good glue-dispersing effect can be achieved.

[0026] Alternatively, if Figure 1 As shown in , the thickness d1 of the coating can be 0.5μm-2.5μm, and further, the thickness d1 of the coating can be 1μm-2μm, such as but not limited to: 1μm, 1.5μm, 2μm and other thicknesses, which can be set according to actual needs and are not specifically limited here. For example, when the thickness d1 of the coating is too large, the thickness of the battery separator will be too large, which will affect the production of the wound battery cell, and will also cause the gap between the positive electrode sheet and the battery separator, and the gap between the negative electrode sheet and the battery separator to become smaller, reducing the effect of removing wrinkles; if the thickness d1 of the coating is too small, it may cause the glue-dispersing effect to decrease; so setting the thickness d1 of the coating within a suitable range can improve the glue-dispersing effect, thereby improving the effect of removing wrinkles.

[0027] Continue as Figure 1 As shown in , the thickness d2 of the colloid layer can be 0.5μm-3μm, and further, the thickness d2 of the colloid layer can be 1μm-2μm, such as but not limited to: 1μm, 1.5μm, 2μm and other thicknesses, which can be set according to actual needs and are not specifically limited here. For example, when the thickness d2 of the colloid layer is too large, the thickness of the battery separator will be too large, which will affect the production of the wound battery cell; when the thickness d2 of the colloid layer is too small, the fixing effect may be reduced, and the compressible space is small, which is not conducive to removing wrinkles; therefore, setting the thickness d2 of the colloid layer within a suitable range can increase the compressible space, increase the effect of removing wrinkles, and improve the convenience of producing the wound battery cell.

[0028] Moreover, the thickness ratio of the coating layer to the colloid particle layer (i.e., d1 / d2) can be 0.5 to 3, such as but not limited to: 0.5, 1, 1.5, 2, 2.5, 3 and other values, which can be set according to actual needs and are not specifically limited here. For example, when the thickness ratio is too large, it means that the coating layer is too thick and the colloid particle layer is too thin, which may result in a poor wrinkle removal effect; when the thickness ratio is too small, it means that the coating layer is too thin and the colloid particle layer is too thick, which may result in an unclear glue dispersing effect; therefore, setting the thickness ratio within a suitable range can improve the glue dispersing effect and thus improve the wrinkle removal effect.

[0029] Based on the same inventive concept, the present application embodiment provides a wound battery cell, such as Figure 3 As shown, the wound battery cell 110 includes: a positive electrode sheet m3, a negative electrode sheet m1, and the battery separator m2 provided in the embodiment of the present application, and the battery separator m2 is located between the positive electrode sheet m3 and the negative electrode sheet m1.

[0030] Combination Figure 4 and Figure 5 The schematic diagram shown, Figure 4 The negative electrode sheet m1 in the wound cell shown in the figure extends to both sides. Figure 4 The thick white arrow in the figure indicates the extension direction of the negative electrode sheet m1, the dotted frame 2 indicates the R angle of the wound battery cell, and the dotted frame 3 indicates the large surface of the wound battery cell. Figure 5 for Figure 4 A partial enlarged schematic diagram of the solid coil 1 in FIG. Figure 4 and Figure 5 As shown in the figure, since the coating in the battery separator m2 has a good effect of dispersing glue, the wettability of the glue particles 31 on the coating surface is reduced, so that the actual thickness of the glue particle layer is increased, the compressible space between the positive electrode sheet m3 and the battery separator m2 is increased, and the stretching space of the negative electrode sheet m1 at the R corner is increased, so that the negative electrode sheet m1 can extend in all directions at the R corner. Figure 5 Indicated by the dotted arrow, this can avoid stretching to the large surface due to the lack of extension space at the R corner, thereby avoiding the generation of wrinkles on the large surface. The wound battery cell produced by the above-mentioned battery separator m2 provided in the embodiment of the present application eliminates the wrinkles on the large surface, so that the active ions can be easily and timely embedded in the negative electrode, thereby improving the performance and safety of the wound battery cell.

[0031] It should be understood that when the wound cell is used in a sodium ion battery, the active ions are sodium ions; when the wound cell is used in a lithium ion battery, the active ions are lithium ions; when the wound cell is used in a potassium ion battery, the active ions are potassium ions.

[0032] Based on the same inventive concept, the present application embodiment provides a secondary battery, such as Figure 6 As shown, the secondary battery may include: a housing 120, and the wound battery cell 110 as provided in the embodiment of the present application, wherein the wound battery cell 110 is disposed in the housing 120. Thus, on the basis that the wound battery cell 110 has good performance and safety, the secondary battery also has good performance and safety.

[0033] Alternatively, if Figure 6As shown in , the secondary battery may also include other structures besides the wound battery cell 110 and the shell 120, such as but not limited to: a positive electrode column 141, a negative electrode column 142, an electrolyte 130, etc. The positive electrode ear m4 in the wound battery cell 110 is connected to the positive electrode column 141, the negative electrode ear m5 in the wound battery cell 110 is connected to the negative electrode column 142, and the wound battery cell 110 is immersed in the electrolyte 130, thereby realizing the function of a secondary battery.

[0034] Of course, the locations of the positive pole 141 and the negative pole 142 are not limited to Figure 6 , can also be located at Figure 6 The left side, right side, etc. of the shell 120 are shown in the figure. Accordingly, the positions of the positive electrode tab m4 and the negative electrode tab m5 can be adaptively adjusted, and can be specifically set according to the actual application scenario, which is not specifically limited here.

[0035] Optionally, the secondary battery in the embodiment of the present application may be a lithium ion battery, a sodium ion battery or a potassium ion battery, which may be configured according to actual needs and is not specifically limited herein.

[0036] In summary, in the above-mentioned technical scheme provided in the embodiment of the present application, the coating in the battery separator includes a polymer material and ceramic particles with hydrophilic groups, so that the surface of the coating has hydrophilic groups. When the colloid particles use non-polar substances such as but not limited to polytetrafluoroethylene and polymethyl methacrylate, the hydrophilic groups as polar groups repel each other with the non-polar substances, thereby increasing the contact angle between the coating and the colloid particle layer, reducing the wetting effect of the colloid particles and the coating, and increasing the thickness of the actual colloid particle layer; the wound battery cell made of such a battery separator increases the compressible space between the positive electrode sheet and the battery separator, thereby increasing the stretching space of the negative electrode sheet at the R corner, so that wrinkles can be avoided on the large surface, thereby improving the performance and safety of the wound battery cell.

[0037] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A battery separator, characterized in that: include: The base film, the coating layer and the colloid particle layer are stacked in sequence, and the contact angle between the coating layer and the colloid particle layer is 30°-90°.

2. The battery separator according to claim 1, characterized in that The materials for making the colloid particles in the colloid particle layer include non-polar substances, and the surface of the coating layer facing the colloid particle layer has hydrophilic groups.

3. The battery separator according to claim 2, characterized in that The coating comprises ceramic particles and polymer materials, and the polymer materials comprise the hydrophilic groups; The polymer material includes: cellulose or aramid; and / or the hydrophilic group includes at least one of a sulfonic acid group and a carboxyl group.

4. The battery separator according to claim 3, characterized in that The mass ratio of the ceramic particles to the polymer material is 1.5 to 9.

5. The battery separator according to claim 2, characterized in that The material for making the colloid particle layer includes at least one of polytetrafluoroethylene and polymethyl methacrylate.

6. The battery separator according to any one of claims 1 to 5, characterized in that: The coating has a thickness of 0.5 μm-2.5 μm.

7. The battery separator according to any one of claims 1 to 6, characterized in that: The thickness of the colloid particle layer is 0.5 μm-3 μm.

8. The battery separator according to any one of claims 1 to 7, characterized in that: The thickness ratio of the coating layer to the colloidal particle layer is 0.5 to 3.

9. A wound battery cell, characterized in that: include: A positive electrode sheet, a negative electrode sheet, and a battery separator as described in any one of claims 1 to 8, wherein the battery separator is located between the positive electrode sheet and the negative electrode sheet.

10. A secondary battery, characterized in that: The invention comprises: a shell, and the wound battery core as claimed in claim 9, wherein the wound battery core is arranged in the shell.

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