Lithium ion battery diaphragm with low transverse hemming rate and preparation method thereof

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly discloses a preparation method of a lithium ion battery diaphragm with a low transverse hemming rate, and the preparation method comprises the following steps: S1, preparing a binder; s2, preparing composite slurry; and S3, preparing the lithium ion battery diaphragm. According to the lithium ion battery diaphragm with the low transverse hemming rate provided by the invention, the components of the diaphragm coatings on the two sides of the battery diaphragm are optimized, and the coating process of coating the diaphragm coating on the diaphragm body is optimized, so that the adhesion between the diaphragm coating and the diaphragm body of the prepared lithium ion battery diaphragm is high; and the transverse hemming rate of the battery diaphragm is reduced, so that the overall performance of the battery diaphragm is optimized.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a lithium ion battery separator with a low transverse curling rate and a preparation method thereof. Background Art

[0002] As a rechargeable battery, lithium-ion batteries rely on the movement of lithium ions between the positive and negative electrodes to work. + Insertion and deinsertion back and forth between the two electrodes: During charging, Li + It is deintercalated from the positive electrode and intercalated into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; the opposite is true during discharge.

[0003] Lithium-ion battery separator plays a vital role in the battery. It not only prevents direct contact between the positive and negative electrodes causing a short circuit, but also allows lithium ions to pass freely between the positive and negative electrodes to form a charge and discharge circuit.

[0004] However, during the production and use of the diaphragm, the lateral curling problem of the diaphragm is relatively common. The lateral curling mainly occurs at the edge of the diaphragm. The main reasons for the lateral curling of the diaphragm are: the unevenness of the diaphragm material, defects in the production process or improper operation during the battery assembly process. The lateral curling of the diaphragm will make the internal structure of the battery uneven, affect the migration of lithium ions, increase the internal resistance of the battery, and thus reduce the battery's charge and discharge efficiency and cycle stability. In addition, the lateral curling problem of the diaphragm will also cause uneven distribution of electrolyte on the surface of the diaphragm, resulting in too much or too little electrolyte in local areas inside the battery, affecting the consistency and safety of the battery. Summary of the invention

[0005] The purpose of the present invention is to overcome the above problems existing in the prior art and to provide a lithium-ion battery separator with a low lateral curling rate. By optimizing the components of the separator coating on both sides of the battery separator and optimizing the coating process of the separator coating on the separator body, the prepared lithium-ion battery separator has strong adhesion between the separator coating and the separator body, and the lateral curling rate of the battery separator is reduced, thereby optimizing the overall performance of the battery separator.

[0006] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0007] An embodiment of the first aspect of the present invention provides a method for preparing a lithium-ion battery separator with a low transverse curling rate, the preparation method comprising the following steps:

[0008] S1: Preparation of binder

[0009] Weighing PVA powder into a mixer, adding a crosslinking agent into the mixer, and mixing uniformly to prepare a mixture, using citric acid to adjust the pH value of the mixture to 3-5 to prepare a binder, and putting the binder into water at 60-100° C. to fully react to prepare a binder;

[0010] S2: Preparation of composite slurry

[0011] Weigh ceramic particles into a second mixer, add a dispersant into the second mixer, mix well to prepare a second mixture, put the second mixture into water to prepare a pre-slurry, put the binder prepared in step S1 into the pre-slurry, mix and stir to prepare a composite slurry;

[0012] S3: Preparation of lithium-ion battery separators

[0013] The composite slurry is coated on both sides of the diaphragm body by using a roller coater, and the diaphragm body coated with the composite slurry is dried to form a diaphragm coating on both sides of the diaphragm body to prepare a lithium ion battery diaphragm.

[0014] Further, in step S1, in step S1, the cross-linking agent is methyl acetoacetate;

[0015] The mass ratio of PVA powder to cross-linking agent is 1:(0.10-0.30);

[0016] The mass ratio of binder to water is 1:(8-10).

[0017] Furthermore, in step S1 and step S2, the water is deionized water.

[0018] Furthermore, in step S2, D50 of the ceramic particles is not greater than 1.2 μm.

[0019] Further, in step S2, the dispersant is any one or more of polyacrylic acid sodium salt and polytetrafluoroethylene mixed in any proportion;

[0020] The mass ratio of the ceramic particles to the dispersant is (100-140):1.

[0021] Further, in step S2, the mass ratio of the second mixture to water is (0.6-1.0):1;

[0022] The mass ratio of the binder to the pre-slurry is 1:(3-5).

[0023] Furthermore, in step S2, during the mixing and stirring process, the mixing and stirring rate is 30-40 rpm / min, and the mixing and stirring time is 30-50 min.

[0024] Further, in step S3, the coating rate of the roller coater is 100-130 m / min;

[0025] In step S3, the coating pressure is 0.5-0.6 MPa, and the coating gap is 3-5 μm.

[0026] Furthermore, in step S3, during the drying process, the drying temperature is 60-70° C., and the drying time is 10-20 min.

[0027] An embodiment of the second aspect of the present invention provides a lithium-ion battery separator with a low transverse curling rate, characterized in that it is prepared by the preparation method of a lithium-ion battery separator with a low transverse curling rate provided by the embodiment of the first aspect of the present invention.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The lithium-ion battery separator with low transverse curling rate provided by the present invention effectively reduces the transverse curling rate. When used in lithium-ion batteries, the overall performance and reliability of the lithium-ion batteries can be improved, thereby promoting the further development of lithium-ion battery technology.

[0030] 2. The present invention provides a lithium-ion battery separator with a low transverse curling rate. By optimizing the components of the separator coating on both sides of the battery separator and optimizing the coating process of the separator coating on the separator body, the prepared lithium-ion battery separator has strong adhesion between the separator coating and the separator body, and the transverse curling rate of the battery separator is reduced, thereby optimizing the overall performance of the battery separator.

[0031] 3. In the present invention, the diaphragm coating is prepared by applying a composite slurry on both sides of the diaphragm body and then drying it; wherein the composite slurry is prepared by mixing a binder and a pre-slurry, the binder is prepared by mixing PVA powder and methyl acetoacetate and then putting it into water, and the pre-slurry is prepared by mixing ceramic particles and a dispersant and then mixing them with water; the long molecular chains of PVA (polyvinyl alcohol) are tightly combined with ceramic particles through physical entanglement, thereby enhancing the adhesion between the particles. At the same time, the rich hydroxyl functional groups on the PVA molecular chains can undergo a grafting reaction with ceramic particles under the action of methyl acetoacetate as an initiator, further improving the adhesion and uniformity of the diaphragm coating. The dual effects of physical entanglement and chemical grafting significantly improve the uniformity of the diaphragm coating, thereby effectively reducing the curling phenomenon that may occur due to uneven surface tension of the diaphragm body, thereby optimizing the overall performance of the diaphragm body.

[0032] 4. In the present invention, by optimizing the coating process when the composite slurry is coated on both sides of the diaphragm body, that is, optimizing the parameters such as the coating speed, coating pressure and coating gap, it is ensured that the composite slurry is evenly coated on the surface of the diaphragm body to form a coating with uniform thickness and smooth surface, thereby avoiding the difference in diaphragm performance caused by uneven coating, thereby significantly improving the lateral curling problem of lithium-ion battery diaphragms and improving the quality and performance of battery diaphragms. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0034] Figure 1 is a schematic diagram of cross-linking formation of the adhesive provided in Example 1 of the present invention;

[0035] Figure 2 It is a schematic diagram of the grafting of ceramic particles and a binder provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] An embodiment of the first aspect of the present invention provides a method for preparing a lithium-ion battery separator with a low transverse curling rate, the preparation method comprising the following steps:

[0038] S1: Preparation of binder

[0039] Weighing PVA powder into a mixer, adding a crosslinking agent into the mixer, and mixing uniformly to prepare a mixture, using citric acid to adjust the pH value of the mixture to 3-5 to prepare a binder, and putting the binder into water at 60-100° C. to fully react to prepare a binder;

[0040] Among them, in mixture 1, the cross-linking agent is methyl acetoacetate;

[0041] The mass ratio of PVA powder to cross-linking agent is 1:(0.10-0.30);

[0042] In the binder, the mass ratio of binder to water is 1:(8-10);

[0043] The cross-linking process of the binder is as follows: Figure 1As shown, that is, the cross-linking reaction process of PVA powder and cross-linking agent methyl acetoacetate;

[0044] S2: Preparation of composite slurry

[0045] Weigh ceramic particles into a mixer 2, add a dispersant into the mixer 2, mix well to prepare a mixture 2, put the mixture 2 into water to prepare a pre-slurry, put the binder prepared in step S1 into the pre-slurry, mix and stir to prepare a composite slurry; during the mixing and stirring process, the mixing and stirring rate is 30-40rpm / min, and the mixing and stirring time is 30-50min;

[0046] The reaction formula of ceramic particles (ceramic materials with alumina (Al2O3) as the main component) and binder is as follows: Figure 2 As shown, it is the grafting reaction process of ceramic particles and binder. In this process, the physical entanglement of the long molecular chain of PVA powder can achieve close combination with ceramic particles and enhance the adhesion between particles. In addition, the hydroxyl functional groups on the PVA molecular chain are used to graft with ceramic particles through methyl acetoacetate initiator to improve adhesion and uniformity.

[0047] Wherein, in step S1 and step S2, the water used is deionized water;

[0048] In step S2, the D50 of the ceramic particles is not greater than 1.2 μm;

[0049] In the second mixture, the dispersant is any one or more of polyacrylic acid sodium salt and polytetrafluoroethylene mixed in any proportion;

[0050] The mass ratio of ceramic particles to dispersant is (100-140):1;

[0051] In the pre-slurry, the mass ratio of the second mixture to water is (0.6-1.0):1;

[0052] In the composite slurry, the mass ratio of the binder to the pre-slurry is 1:(3-5);

[0053] S3: Preparation of lithium-ion battery separators

[0054] The composite slurry is coated on both sides of the diaphragm body by using a roller coater, and the diaphragm body coated with the composite slurry is dried to form a diaphragm coating on both sides of the diaphragm body to prepare a lithium ion battery diaphragm;

[0055] In the process of coating the composite slurry on both sides of the diaphragm body, the coating rate is 120-160 m / min, the coating pressure is 0.5-0.6 MPa, and the coating gap is 3-5 μm.

[0056] PVA plays a dual role in enhancing the performance of lithium-ion battery separators. First, the physical entanglement of the long molecular chains of PVA powder can achieve close bonding with ceramic particles and enhance the adhesion between particles. Second, the hydroxyl functional groups on the PVA molecular chains undergo a grafting reaction with ceramic particles through the methyl acetoacetate initiator to improve adhesion and uniformity.

[0057] Combining the dual action mechanisms of physical winding and chemical grafting mentioned above, the uniformity of the prepared lithium-ion battery separator is significantly improved, thereby effectively reducing the curling phenomenon caused by uneven separator tension, thereby improving the quality and safety of battery manufacturing.

[0058] The embodiment of the second aspect of the present invention provides a lithium-ion battery separator with a low transverse curling rate, and the battery separator is prepared by the preparation method of a lithium-ion battery separator with a low transverse curling rate provided by the embodiment of the first aspect of the present invention;

[0059] Specifically, the lithium-ion battery diaphragm includes a diaphragm body and a diaphragm coating coated on both sides of the diaphragm body. The diaphragm coating is a coating formed by coating a composite slurry on both sides of the diaphragm body and then drying it.

[0060] The following are specific examples. In the following examples, unless otherwise specified, all raw materials can be obtained from commercial sources.

[0061] Example 1

[0062] This embodiment provides a method for preparing a lithium ion battery separator, the preparation method comprising the following steps:

[0063] S1: Preparation of binder

[0064] Weighing PVA powder into a mixer, adding methyl acetoacetate into the mixer, and mixing evenly to prepare a mixture, adjusting the pH value of the mixture to 4 with citric acid to prepare a binder, and putting the binder into deionized water at 80° C., and after sufficient reaction, preparing a binder;

[0065] Among them, in the mixture 1, the mass ratio of PVA powder to methyl acetoacetate is 10:2;

[0066] In the binder, the mass ratio of binder to water is 1:9;

[0067] S2: Preparation of composite slurry

[0068] Weigh ceramic particles into a mixer 2, add sodium polyacrylate into the mixer 2, mix well to prepare a mixture 2, put the mixture 2 into deionized water to prepare a pre-slurry, put the binder prepared in step S1 into the pre-slurry, mix and stir at 35 rpm / min for 40 min, and prepare a composite slurry after mixing and stirring;

[0069] Wherein, in step S2, the D50 of the ceramic particles is 1.2 μm;

[0070] In the second mixture, the mass ratio of ceramic particles to sodium polyacrylate is 120:1;

[0071] In the pre-slurry, the mass ratio of the second mixture to water is 0.75:1;

[0072] In the composite slurry, the mass ratio of binder to pre-slurry is 1:4;

[0073] S3: Preparation of lithium-ion battery separators

[0074] The composite slurry is coated on both sides of the diaphragm body by using a roller coater, and the diaphragm body coated with the composite slurry is dried to form a diaphragm coating on both sides of the diaphragm body to prepare a lithium ion battery diaphragm;

[0075] In the process of coating the composite slurry on both sides of the diaphragm body, the coating rate was 120 m / min, the coating pressure was 0.5 MPa, and the coating gap was 3 μm.

[0076] Example 2

[0077] This embodiment provides a method for preparing a lithium ion battery separator, the preparation method comprising the following steps:

[0078] S1: Preparation of binder

[0079] Weighing PVA powder into a mixer, adding methyl acetoacetate into the mixer, and mixing evenly to prepare a mixture, adjusting the pH value of the mixture to 5 with citric acid to prepare a binder, and putting the binder into deionized water at 100° C. to fully react to prepare a binder;

[0080] Among them, in the mixture 1, the mass ratio of PVA powder to methyl acetoacetate is 10:1;

[0081] In the binder, the mass ratio of binder to water is 1:10;

[0082] S2: Preparation of composite slurry

[0083] Weigh ceramic particles into a second mixer, add sodium polyacrylate into the second mixer, mix well to prepare a second mixture, add the second mixture into deionized water to prepare a pre-slurry, add the binder prepared in step S1 into the pre-slurry, mix and stir at 30 rpm / min for 50 min, and prepare a composite slurry after mixing and stirring;

[0084] Wherein, in step S2, the D50 of the ceramic particles is 1.2 μm;

[0085] In the second mixture, the mass ratio of ceramic particles to sodium polyacrylate is 100:1;

[0086] In the pre-slurry, the mass ratio of the second mixture to water is 0.6:1;

[0087] In the composite slurry, the mass ratio of binder to pre-slurry is 1:5;

[0088] S3: Preparation of lithium-ion battery separators

[0089] The composite slurry is coated on both sides of the diaphragm body by using a roller coater, and the diaphragm body coated with the composite slurry is dried to form a diaphragm coating on both sides of the diaphragm body to prepare a lithium ion battery diaphragm;

[0090] In the process of coating the composite slurry on both sides of the diaphragm body, the coating rate was 130 m / min, the coating pressure was 0.6 MPa, and the coating gap was 5 μm.

[0091] Example 3

[0092] This embodiment provides a method for preparing a lithium ion battery separator, the preparation method comprising the following steps:

[0093] S1: Preparation of binder

[0094] Weighing PVA powder into a mixer, adding methyl acetoacetate into the mixer, and mixing evenly to prepare a mixture, adjusting the pH value of the mixture to 3 with citric acid to prepare a binder, and putting the binder into deionized water at 60° C., and after sufficient reaction, preparing a binder;

[0095] Among them, in the mixture 1, the mass ratio of PVA powder to methyl acetoacetate is 10:3;

[0096] In the binder, the mass ratio of binder to water is 1:8;

[0097] S2: Preparation of composite slurry

[0098] Weigh ceramic particles into a mixer 2, add sodium polyacrylate into the mixer 2, mix well to prepare a mixture 2, put the mixture 2 into deionized water to prepare a pre-slurry, put the binder prepared in step S1 into the pre-slurry, mix and stir at 40 rpm / min for 30 min, and prepare a composite slurry after mixing and stirring;

[0099] Wherein, in step S2, the D50 of the ceramic particles is 1.2 μm;

[0100] In the second mixture, the mass ratio of ceramic particles to sodium polyacrylate is 140:1;

[0101] In the pre-slurry, the mass ratio of the second mixture to water is 1:1;

[0102] In the composite slurry, the mass ratio of binder to pre-slurry is 1:3;

[0103] S3: Preparation of lithium-ion battery separators

[0104] The composite slurry is coated on both sides of the diaphragm body by using a roller coater, and the diaphragm body coated with the composite slurry is dried to form a diaphragm coating on both sides of the diaphragm body to prepare a lithium ion battery diaphragm;

[0105] In the process of coating the composite slurry on both sides of the diaphragm body, the coating rate was 160 m / min, the coating pressure was 0.55 MPa, and the coating gap was 4 μm.

[0106] Example 4

[0107] This embodiment provides a method for preparing a lithium-ion battery separator. Compared with Example 1, in this embodiment, the dispersant is polytetrafluoroethylene, and the remaining operation steps are the same as those in Example 1.

[0108] Comparative Example 1

[0109] This comparative example provides a method for preparing a lithium-ion battery separator. Compared with Example 1, in this comparative example, the crosslinking agent is polyvinylidene fluoride, and the remaining operating steps are the same as those in Example 1.

[0110] Comparative Example 2

[0111] This comparative example provides a method for preparing a lithium-ion battery separator. Compared with Example 1, in this comparative example, the cross-linking agent is an aldehyde compound glutaraldehyde, and the remaining operation steps are the same as those in Example 1.

[0112] Comparative Example 3

[0113] This comparative example provides a method for preparing a lithium-ion battery separator. Compared with Example 1, in this comparative example, the mixing stirring rate is replaced from 35 rpm / min to 20 rpm / min, and the remaining operating steps are the same as those in Example 1.

[0114] Comparative Example 4

[0115] This comparative example provides a method for preparing a lithium-ion battery separator. Compared with Example 1, in this comparative example, the coating rate is replaced from 120 m / min to 60 m / min, and the remaining operating steps are the same as those in Example 1.

[0116] Experimental example

[0117] The thickness deviation and transverse curling rate of the lithium ion battery separators prepared in Examples 1-4 and Comparative Examples 1-4 were detected and calculated, and compared with ordinary ceramic coating separators, and then the thickness deviation change rate (%) and transverse curling rate change rate (%) of the lithium ion battery separators prepared in Examples 1-4 and Comparative Examples 1-4 were calculated, and the calculation formula is as follows:

[0118]

[0119] The calculation results are shown in Table 1;

[0120] Table 1

[0121] Group Thickness deviation change rate / % Transverse hemming rate change rate / % Example 1 28 43 Example 2 24 38 Example 3 24 34 Example 4 25 39 Comparative Example 1 21 30 Comparative Example 2 15 23 Comparative Example 3 18 23 Comparative Example 4 19 25

[0122] According to the data in Table 1, it can be seen that in the present application, the lithium ion battery separator prepared in Example 1 has a thickness deviation reduced by 28% and a lateral curling rate reduced by 43% compared with the ordinary ceramic coating separator; it can also be seen from the data in Table 1 that the data of Examples 1-4 are better than those of Comparative Examples 1-4, indicating that the lithium ion battery separator prepared in the present application can effectively reduce the curling phenomenon of the separator; specifically:

[0123] Comparative Example 1 uses polyvinylidene fluoride as a cross-linking agent. Although it has a certain effect in reducing the transverse curling, the cost of polyvinylidene fluoride is relatively high, and its effect of improving the transverse curling of the lithium-ion battery separator is much less than that of Example 1;

[0124] Comparative Example 2 uses an aldehyde compound as a cross-linking agent, which cannot provide sufficient thermal stability, resulting in an insufficient decrease in the transverse curling rate;

[0125] In Comparative Example 3, the stirring rate was reduced, resulting in uneven mixing of the slurry, affecting the coating quality, and further affecting the quality of the prepared lithium ion battery separator;

[0126] In Comparative Example 4, the coating rate is reduced, which may easily lead to uneven coating during the coating process, thereby affecting the performance of the prepared lithium-ion battery separator.

[0127] The present invention provides a lithium-ion battery separator with a low transverse curling rate, which effectively reduces the transverse curling rate. When used in lithium-ion batteries, the separator can improve the overall performance and reliability of the lithium-ion batteries, thereby promoting the further development of lithium-ion battery technology. The present invention also provides a method for preparing a lithium-ion battery separator with a low transverse curling rate, by optimizing the coating process when the composite slurry is coated on both sides of the separator body, that is, optimizing the coating speed, coating pressure, coating gap and other parameters, ensuring that the composite slurry is evenly coated on the surface of the separator body to form a coating with uniform thickness and smooth surface, avoiding the difference in separator performance caused by uneven coating, thereby significantly improving the transverse curling problem of the lithium-ion battery separator and improving the quality and performance of the battery separator.

[0128] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0129] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a lithium-ion battery separator with a low transverse curling rate, characterized in that: The preparation method comprises the following steps: S1: Preparation of binder Weighing PVA powder into a mixer, adding a crosslinking agent into the mixer, and mixing uniformly to prepare a mixture, using citric acid to adjust the pH value of the mixture to 3-5 to prepare a binder, and putting the binder into water at 60-100° C. to fully react to prepare a binder; S2: Preparation of composite slurry Weigh ceramic particles into a second mixer, add a dispersant into the second mixer, mix well to prepare a second mixture, put the second mixture into water to prepare a pre-slurry, put the binder prepared in step S1 into the pre-slurry, mix and stir to prepare a composite slurry; S3: Preparation of lithium-ion battery separators The composite slurry is coated on both sides of the diaphragm body by using a roller coater, and the diaphragm body coated with the composite slurry is dried to form a diaphragm coating on both sides of the diaphragm body to prepare a lithium ion battery diaphragm.

2. The method for preparing a lithium-ion battery separator with a low transverse curling rate according to claim 1, characterized in that: In step S1, the cross-linking agent is methyl acetoacetate; The mass ratio of PVA powder to cross-linking agent is 1:(0.10-0.30); The mass ratio of binder to water is 1:(8-10).

3. The method for preparing a lithium-ion battery separator with a low transverse curling rate according to claim 1, characterized in that: In step S1 and step S2, the water is deionized water.

4. The method for preparing a lithium-ion battery separator with a low transverse curling rate according to claim 1, characterized in that: In step S2, the D50 of the ceramic particles is not greater than 1.2 μm.

5. The method for preparing a lithium-ion battery separator with a low transverse curling rate according to claim 1, characterized in that: In step S2, the dispersant is any one or more of polyacrylic acid sodium salt and polytetrafluoroethylene mixed in any proportion; The mass ratio of the ceramic particles to the dispersant is (100-140):

1.

6. The method for preparing a lithium-ion battery separator with a low transverse curling rate according to claim 1, characterized in that: In step S2, the mass ratio of the second mixture to water is (0.6-1.0):1; The mass ratio of the binder to the pre-slurry is 1:(3-5).

7. The method for preparing a lithium-ion battery separator with a low transverse curling rate according to claim 1, characterized in that: In step S2, during the mixing and stirring process, the mixing and stirring rate is 30-40 rpm / min, and the mixing and stirring time is 30-50 min.

8. The method for preparing a lithium-ion battery separator with a low transverse curling rate according to claim 1, characterized in that: In step S3, the coating rate of the roller coater is 120-160 m / min; In step S3, the coating pressure is 0.5-0.6 MPa, and the coating gap is 3-5 μm.

9. The method for preparing a lithium-ion battery separator with a low transverse curling rate according to claim 1, characterized in that: In step S3, during the drying process, the drying temperature is 60-70° C. and the drying time is 10-20 min.

10. A lithium-ion battery separator with a low transverse curling rate, characterized in that: The invention is prepared by the method for preparing a lithium-ion battery separator with a low transverse curling rate as described in any one of claims 1 to 9.

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