Battery separator, wound battery cell and secondary battery

Abstract

Battery separator, characterized in that it comprises: a base film, a coating layer and an adhesive particle layer, which are stacked one after the other, wherein a contact angle between the coating layer and the adhesive particle layer is 30° to 90°.

Description

TECHNICAL AREA

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

[0002] In the manufacture of a wound battery cell, a positive electrode plate, a negative electrode plate, and a battery separator are first stacked and wound, then hot-pressed to obtain a wound battery cell with predetermined dimensions. During charging, active ions, such as lithium ions, deintercalate from the positive electrode plate, pass through the battery separator, and intercalate into the negative electrode plate, thereby increasing the thickness of the negative electrode plate. In one direction of thickness, this increase in the thickness of the negative electrode plate is transformed into an expansion in both directions due to the constraints imposed by the compressed positive electrode plate and the battery separator.Due to the small distance between the battery separator and the positive electrode plate, as well as between the battery separator and the negative electrode plate in the region of the R-angle, this bilateral expansion effect is restricted in the region of the R-angle, leading to wrinkles on the large surface of the wound battery cell. The formation of these wrinkles, however, prevents lithium ions from being deposited into the negative electrode plate in a timely manner, thus impairing the performance and safety of the secondary battery. SUMMARY

[0003] The embodiments of the present application provide a battery separator, a wound battery cell and a secondary battery to solve the problem of wrinkling on the surface of the wound battery cell and thereby improve the performance and safety of the secondary battery.

[0004] In a first aspect, the embodiments of the present application provide a battery separator comprising: a base film, a coating layer and an adhesive particle layer stacked one after the other, wherein a contact angle between the coating layer and the adhesive particle layer is 30° to 90°.

[0005] In a second aspect, the embodiments of the present application provide a wound battery cell comprising: a positive electrode plate, a negative electrode plate and the battery separator introduced above in the first aspect, wherein the battery separator is arranged between the positive electrode plate and the negative electrode plate.

[0006] In a third aspect, the embodiments of the present application provide a secondary battery comprising: a housing and the wound battery cell introduced above in the second aspect, wherein the wound battery cell is arranged in the housing.

[0007] The beneficial effects of the present application are as follows: If a coating layer is added to the battery separator, the wound battery cell, and the secondary battery provided by the embodiments of the present application, and the contact angle between the coating layer and the adhesive particle layer is between 30° and 90°, this indicates that the wettability between the adhesive particle layer and the coating layer is relatively low and that the coating layer can act as an adhesive repellent, thus preventing adhesive particles from infiltrating into the coating layer. When such a battery separator is used in the wound battery cell, wrinkles on a large surface area of ​​a negative electrode plate in the wound battery cell can be avoided, thereby improving the performance and safety of the wound battery cell and the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a structural schematic representation of a battery separator provided in embodiments of the present application; Fig. Figure 2 is a schematic representation of a contact angle provided in embodiments of the present application; Fig. Figure 3 is a structural schematic representation of a wound battery cell provided in embodiments of the present application; Fig. Figure 4 shows the double-sided extension of the negative electrode plate in the wound battery cell, which is provided in embodiments of the present application; Fig. Figure 5 is an enlarged view of the local structure within the solid circle 1 in Fig. 4; Fig. Figure 6 is a structural schematic representation of a secondary battery provided in embodiments of the present application.

[0008] Reference symbols: 10-base film, 20-coating layer, 30-adhesive particle layer, 31-adhesive particle, 110-wound battery cell, 120-case, 130-electrolyte, 141-positive terminal, 142-negative terminal, m1-negative electrode plate, m2-battery separator, m3-positive electrode plate, m4-positive tab, m5-negative tab. DETAILED DESCRIPTION OF EXECUTION FORMS

[0009] The specific embodiments of a battery separator, a wound battery cell, and a secondary battery provided by the embodiments of the present application are described in detail with reference to the accompanying drawings. It should be noted that the described embodiments represent only a subset of the embodiments of the present application and not all embodiments. All other embodiments that could be obtained by those skilled in the art based on the embodiments of the present application without any inventive step fall within the scope of protection of the present application.

[0010] The embodiments of the present application provide a separator. As in Fig. 1 and Fig. As shown in Figure 2, the battery separator m2 can comprise: a base film 10, a coating layer 20, and an adhesive particle layer 30, stacked sequentially, with a contact angle between the coating layer 20 and the adhesive particle layer 30 ranging from 30° to 90°. It is understood that the adhesive particle layer 30 contains adhesive particles 31, and the contact angle between the coating layer 20 and the adhesive particle layer 30 is the contact angle A between the adhesive particles 31 and the coating layer 20.

[0011] Therefore, if a coating layer is added to the battery separator and the contact angle between the coating layer and the adhesive particle layer is 30° to 90°, this indicates that the wettability between the adhesive particle layer and the coating layer is low and the coating layer can play an adhesive-repellent role, thus preventing adhesive particles in the adhesive particle layer from infiltrating into the coating layer.

[0012] Furthermore, the adhesive particle layer, due to its presence in the battery separator, can play a fixing role when applied to the wound battery cell, thereby making the structure of the manufactured wound battery cell more stable and preventing loosening of the wound battery cell, which would impair performance. Therefore, this type of battery separator can also be referred to as an adhesive separator.

[0013] Optionally, a material for producing particles in the adhesive particle layer contains a nonpolar substance, and a surface of the coating layer facing the adhesive particle layer has a hydrophilic group, the hydrophilic group being a polar group, so that when the nonpolar substance and the hydrophilic group come into contact, they repel each other, thereby increasing the contact angle between the adhesive particle layer and the coating layer and thus playing an adhesive-repellent role.

[0014] Furthermore, the coating layer contains ceramic particles and a polymer material, and the polymer material contains the hydrophilic group. This means that the hydrophilic group can be provided on the surface of the coating layer by the polymer material and thus plays an adhesion-repellent role.

[0015] The polymer material can include, but is not limited to, the following: molecular fibers, polymer fibers, which can be, but are not limited to, cellulose, aramid, etc., whereby the specific choice of fiber can be determined according to actual requirements and is not restricted here. Common hydrophilic groups include, but are not limited to: carboxyl group, sulfone group, amino group, amine group, hydroxyl group, amide group, etc., which can be determined according to actual requirements and are not specifically restricted here.If the hydrophilic group contains, for example, but is not limited to, a sulfone group and / or a carboxyl group, the polymer material with a sulfone group and / or carboxyl group can improve the thermal stability of the battery separator, so that the hydrophilic group can be selected from a sulfone group and / or carboxyl group to play an adhesion-repellent role and improve the thermal stability of the battery separator.

[0016] Materials for the production of 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.

[0017] Materials used to produce the adhesive particle layer include at least one nonpolar substance such as polytetrafluoroethylene and polymethyl methacrylate. When the nonpolar substance comes into contact with the hydrophilic group, the repulsion between them can increase the contact angle between the adhesive particle layer and the coating layer, thus acting as an adhesive-repellent agent.

[0018] Furthermore, the mass ratio of ceramic particles to polymer material can range from 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, or other values ​​that can be determined according to actual requirements and are not specifically limited here. For example, if the proportion of ceramic particles is too low, this will result in reduced heat resistance of the battery separator, and if the proportion of polymer material is too low, this will result in reduced adhesion repellent properties. Therefore, with a mass ratio of ceramic particles to polymer material within this range, both improved heat resistance and improved adhesion repellent properties can be achieved.

[0019] Alternatively, as in Fig. Figure 1 shows that the thickness d1 of the coating layer can be from 0.5 µm to 2.5 µm, and furthermore, the thickness d1 of the coating layer can be from 1 µm to 2 µm, such as, but not limited to: 1 µm, 1.5 µm, 2 µm or other thicknesses which can be determined according to actual requirements and are not specifically limited here.For example, if the thickness d1 of the coating layer is too great, this leads to an excessive thickness of the battery separator, which impairs the manufacture of the wound battery cell and also leads to reduced distances between the positive electrode plate and the battery separator, as well as between the negative electrode plate and the battery separator, thus reducing the wrinkle removal effect; if the thickness d1 of the coating layer is too small, this can lead to a reduced adhesive-repellent effect; therefore, setting the thickness d1 of the coating layer within a suitable range can increase the adhesive-repellent effect and thereby improve the wrinkle removal effect.

[0020] As in Fig. As shown in Figure 1, the thickness d2 of the adhesive particle layer can be 0.5 µm to 3 µm, and furthermore, the thickness d2 of the adhesive particle layer can be 1 µm to 2 µm, such as, but not limited to: 1 µm, 1.5 µm, 2 µm or other thicknesses which can be determined according to actual requirements and are not specifically limited here.For example, if the thickness d2 of the adhesive particle layer is too large, this leads to an excessive thickness of the battery separator, which impairs the manufacture of the wound battery cell; if the thickness d2 of the adhesive particle layer is too small, the fixing effect may be reduced, and the compressible space is relatively small, which is not conducive to wrinkle removal; therefore, setting the thickness d2 of the adhesive particle layer within a suitable range can both increase the compressible space, enhance the wrinkle removal effect, and improve the manufacturability of the wound battery cell.

[0021] Furthermore, the thickness ratio between the coating layer and the adhesive 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, or other values ​​that can be determined according to actual needs and are not specifically limited here. For example, if the thickness ratio is too large, this indicates that the coating layer is too thick and the adhesive particle layer too thin, which can lead to poor wrinkle removal; if the thickness ratio is too small, this indicates that the coating layer is too thin and the adhesive particle layer too thick, which can lead to negligible adhesive repellency; therefore, setting the thickness ratio within a suitable range can enhance the adhesive repellency and thereby improve the wrinkle removal effect.

[0022] Based on the same inventive concept, the embodiments of the present application provide a wound battery cell. As in Fig. As shown in Figure 3, the wound battery cell 110 comprises: a positive electrode plate m3, a negative electrode plate m1 and the aforementioned battery separator m2, which is provided by the embodiments of the present application, wherein the battery separator m2 is arranged between the positive electrode plate m3 and the negative electrode plate m1.

[0023] With reference to the in Fig. 4 and Fig. The 5 principle diagrams shown illustrate Fig. 4 the bilateral extension of the negative electrode plate m1 in the wound battery cell, wherein the thick white arrows indicate the direction of extension of the negative electrode plate m1, the dashed box 2 indicates the R-angle area of ​​the wound battery cell, the dashed box 3 indicates the large surface area of ​​the wound battery cell and Fig. 5 an enlarged view of the local structure within the circle 1 indicated by a solid line in Fig. 4 is. Since the coating layer in the battery separator m2 offers a better adhesive-repellent effect, which reduces the wettability of the adhesive particles 31 on the coating layer surface, as in Fig. 4 and Fig. Figure 5 shows the actual thickness of the adhesive particle layer, thereby improving a compressible space between the positive electrode plate m3 and the battery separator m2, thereby increasing an expansion space for the negative electrode plate m1 in the R-angle region, allowing the negative electrode plate m1 to expand in various directions in the R-angle region, with the expansion in the R-angle region being Fig. 5 is indicated by dashed arrows. In this way, expansion towards the large surface due to a lack of expansion space in the R-angle region can be avoided, thus preventing wrinkles on the large surface. Therefore, the wound battery cell produced using the aforementioned battery separator m2, provided by the embodiments of the present application, eliminates wrinkles on the large surface, allowing active ions to intercalate conveniently and in a timely manner into the negative electrode, thus improving the performance and safety of the wound battery cell.

[0024] When the wound battery cell is used in a sodium-ion battery, the active ions are sodium ions; when the wound battery cell is used in a lithium-ion battery, the active ions are lithium ions; when the wound battery cell is used in a potassium-ion battery, the active ions are potassium ions.

[0025] Based on the same inventive concept, the embodiments of the present application provide a secondary battery. As in Fig. As shown in Figure 6, the secondary battery can comprise a housing 120 and the aforementioned wound battery cell 110, which is provided by the embodiments of the present application, wherein the wound battery cell 110 is arranged in the housing 120. Due to the improved performance and safety of the wound battery cell 110, the secondary battery thus also exhibits improved performance and safety.

[0026] Alternatively, the secondary battery can be used, as in Fig. Figure 6 shows that the structure also includes other structures besides the wound battery cell 110 and the housing 120, such as, but not limited to: a positive terminal 141, a negative terminal 142, an electrolyte 130, etc., wherein the positive tab m4 in the wound battery cell 110 is connected to the positive terminal 141, the negative tab m5 in the wound battery cell 110 is connected to the negative terminal 142, and the wound battery cell 110 is immersed in the electrolyte 130, thereby realizing the function of the secondary battery.

[0027] Of course, the positions of the positive terminal 141 and the negative terminal 142 are not based on those in Fig. The positions shown are limited to the 6 shown, but can also be located on the left side, the right side, or other places in the Fig.The housing shown in section 6 can be arranged as follows: Accordingly, the positions of the positive tab m4 and the negative tab m5 can be adaptively adjusted, which can be determined according to actual application scenarios and is not specifically restricted here.

[0028] Alternatively, in the embodiments of the present application, the secondary battery can be: a lithium-ion battery, a sodium-ion battery or a potassium-ion battery, which can be determined according to actual needs and is not specifically limited in the present case.

[0029] In summary, in the aforementioned technical solutions provided by the embodiments of the present application, the coating layer in the battery separator contains the polymer material with hydrophilic groups and ceramic particles, thus giving the surface of the coating layer hydrophilic groups. If the adhesive particles use nonpolar substances, such as, but not limited to, polytetrafluoroethylene and polymethyl methacrylate, the hydrophilic groups, being polar groups, repel the nonpolar substances, thereby increasing the contact angle between the coating layer and the adhesive particle layer and reducing the infiltration effect between the adhesive particles and the coating layer, thus increasing the thickness of the actual adhesive particle layer.The wound battery cell, manufactured using such a battery separator, increases the compressible space between the positive electrode plate and the battery separator, thereby increasing the expansion space for the negative electrode plate in the R-angle range, thus avoiding wrinkles on the large surface, thereby improving the performance and safety of the wound battery cell.

[0030] Naturally, a person skilled in the art can make various modifications and variations to the present application without deviating from the fundamental concept and scope of the present application. If these changes and variations of the present application fall within the scope of the claims and their equivalent technologies, the present application shall therefore also encompass these changes and variations.

Claims

[1] Battery separator, characterized by , that it comprises: a base film, a coating layer and an adhesive particle layer stacked one after the other, with a contact angle between the coating layer and the adhesive particle layer being 30° to 90°. [2] Battery separator according to claim 1, characterized by , that a material for producing particles in the adhesive particle layer comprises a nonpolar substance and a surface of the coating layer facing the adhesive particle layer has a hydrophilic group. [3] Battery separator according to claim 2, characterized by , that the coating layer comprises ceramic particles and a polymer material and the polymer material comprises the hydrophilic group; wherein the polymer material comprises: cellulose or aramid; and / or the hydrophilic group comprises a sulfone group and / or a carboxyl group. [4] Battery separator according to claim 3, characterized bythat the ceramic particles comprise aluminium oxide, silicon oxide and / or magnesium hydroxide. [5] Battery separator according to claim 3 or 4, characterized by , that the mass ratio of the ceramic particles to the polymer material is 1.5 to 9. [6] Battery separator according to claim 2, 3, 4 or 5, characterized by , that a material for the production of the adhesive particle layer comprises polytetrafluoroethylene and / or polymethyl methacrylate. [7] Battery separator according to any one of claims 1 to 6, characterized by , that the thickness of the coating layer is 0.5 µm to 2.5 µm. [8] Battery separator according to any one of claims 1 to 7, characterized by , that the thickness of the adhesive particle layer is 0.5 µm to 3 µm. [9] Battery separator according to any one of claims 1 to 8, characterized by , that the thickness ratio of the coating layer to the adhesive particle layer is 0.5 to 3. [10] Wound battery cell, characterized by, comprising: a positive electrode plate, a negative electrode plate and the battery separator according to any one of claims 1 to 9, wherein the battery separator is arranged between the positive electrode plate and the negative electrode plate. [11] Secondary battery, characterized by , comprising: a housing and the wound battery cell according to claim 10, wherein the wound battery cell is arranged in the housing.

Images