Battery separator and preparation method and application thereof

Abstract

The application discloses a battery diaphragm, which comprises polytetrafluoroethylene and polymethyl methacrylate, and is a diaphragm ring used for a needle-shaped battery. The assembly mode of the needle-shaped battery is different, resulting in a gap. The diaphragm ring designed by the application has high adaptability to the needle-shaped battery. The diaphragm ring is integrally pressed and formed, and then is assembled by the assembly mode of the application. After the needle-shaped battery is completed with liquid injection, the diaphragm ring can absorb electrolyte expansion, does not have adverse effects on the performance of the needle-shaped battery, can fasten the contact between various interfaces, increases the storage of electrolyte in the diaphragm ring, and achieves the purpose of improving the performance of the needle-shaped battery. In addition, the diaphragm ring is applied to the needle-shaped battery, the gap between pole pieces is reduced, the cycle stability of the needle-shaped battery is ensured, and the problems of the gap caused by assembly and poor performance of the needle-shaped battery are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of battery material preparation, and more specifically, to a battery separator, its preparation method, and its application. Background Technology

[0002] Both wound and stacked batteries have current collectors, resulting in better contact between electrode materials and electrodes. The wound type can control the tension to ensure tight contact between the separator and the electrode, while the stacked type can achieve good interfacial contact between the separator and the electrode through vertical compression.

[0003] Typical separators are sheet-like. In needle-type batteries, the separator needs to be rolled into a ring before use. However, at the junction of the rings, a portion of the separator overlaps (without this overlap, the battery is prone to short circuits and damage). The overlapping area has two layers of separator, resulting in some areas where the separator is too thick. This thickened section has a longer ion pathway, leading to uneven current distribution within the battery. Gaps also exist near the overlapping separator areas. Combined with this uneven current distribution, this results in a loss of battery capacity in those areas and can also cause safety issues such as lithium plating. Figure 1 As shown.

[0004] Current needle-type batteries are neither wound nor stacked structures. The positive and negative electrodes are formed by compression rings, without current collectors. The positive electrode material is in direct contact with the outer casing, while the negative electrode material is in contact with the central steel needle. The battery is assembled by inserting the battery material into the battery casing ring by ring from the outside to the inside. This makes it difficult to achieve a tight fit between the battery material and the battery casing, which will have a certain impact on the battery performance. Summary of the Invention

[0005] Therefore, in order to solve the problem of poor battery performance caused by the difficulty in sealing the battery material and the battery casing in the prior art, this invention provides a battery separator, its preparation method, and its application. The specific technical solution is as follows:

[0006] A battery separator comprising polytetrafluoroethylene and polymethyl methacrylate, wherein the separator is a separator ring for use in a pin-type battery.

[0007] Further, according to the preparation percentages, the polytetrafluoroethylene is 30%-50% and the polymethyl methacrylate is 50%-70%.

[0008] This application provides a method for preparing a battery separator, comprising the following steps:

[0009] After vacuum baking, polytetrafluoroethylene and polymethyl methacrylate were cooled to room temperature and then sealed for later use.

[0010] The baked polytetrafluoroethylene and polymethyl methacrylate were dry-mixed to obtain mixture A;

[0011] The mixture is subjected to fiberization, then tableting, crushing, and sieving to obtain mixture B.

[0012] The mixture B is subjected to ring pressing to obtain a diaphragm ring.

[0013] Furthermore, the vacuum baking process is carried out at a temperature of 80℃-100℃ for 8 hours.

[0014] Furthermore, the ambient temperature for the dry mixing is 0-5℃, and the dry mixing time is 60 minutes.

[0015] Furthermore, the mesh size of the sieving process is -40 mesh to +100 mesh.

[0016] Furthermore, the temperature of the pressing mold for the ring pressing process is 140℃-170℃, the pressure is 10MPa, and the time is 3min-5min.

[0017] Furthermore, the thickness of the diaphragm ring is 30μm-63μm, and the porosity is 40%-60%.

[0018] The present invention also provides an application of a battery separator, wherein the separator ring is applied in the fabrication of a needle-shaped battery, the fabrication of which includes the following steps:

[0019] Place the diaphragm ring, leak-proof rubber plug, and steel needle in a vacuum drying oven at 90°C and vacuum dry for 5-6 hours.

[0020] After drying, the separator ring, the leak-proof rubber plug, and the steel needle are quickly transferred into a glove box with a humidity of ≤1 ppm. Then, the lithium sheet is cut into small pieces that meet the specifications and rolled onto the steel needle. The separator ring is then rolled onto the surface of the lithium sheet. The steel needle with the lithium sheet and separator ring rolled is then inserted into the positive electrode ring inside the battery casing. Electrolyte is added, the leak-proof rubber plug is put on, and the end is sealed by rolling grooves to obtain a needle-shaped battery.

[0021] In the above-described scheme, the separator ring expands after the battery is filled with electrolyte, absorbing the electrolyte. This not only avoids adversely affecting battery performance but also strengthens the contact between various interfaces, increasing electrolyte storage within the separator ring and thus improving battery performance. Furthermore, applying the separator ring of this application to a needle-type battery reduces the gap between the electrodes, ensuring the cycle stability of the needle-type battery. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the cycling curve of the needle-shaped battery prepared in Application Example 1 of the present invention;

[0023] Figure 2 This is a cross-sectional schematic diagram of the needle-shaped battery prepared in Application Example 1 of the present invention;

[0024] Figure 3 This is a cross-sectional schematic diagram of a battery in the prior art;

[0025] Figure 4 This is a schematic diagram of the overall structure of the battery.

[0026] Explanation of reference numerals in the attached figures:

[0027] 1. Separator; 2. Negative electrode material; 3. Battery casing; 4. Positive electrode material; 5. Negative electrode metal rod; 6. Rubber sealing plug. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] A battery separator according to one embodiment of the present invention comprises polytetrafluoroethylene and polymethyl methacrylate, and the separator is a separator ring, which is used in a needle-type battery.

[0031] In one embodiment, the polytetrafluoroethylene comprises 30%-50% and the polymethyl methacrylate comprises 50%-70% by percentage.

[0032] This application provides a method for preparing a battery separator, comprising the following steps:

[0033] After vacuum baking, polytetrafluoroethylene and polymethyl methacrylate were cooled to room temperature and then sealed for later use.

[0034] The baked polytetrafluoroethylene and polymethyl methacrylate were dry-mixed to obtain mixture A;

[0035] The mixture is subjected to fiberization, then tableting, crushing, and sieving to obtain mixture B.

[0036] The mixture B is subjected to ring pressing to obtain a diaphragm ring.

[0037] In one embodiment, the polymethyl methacrylate can be replaced with any one of PVDF, PAA, PVA, and PEC.

[0038] In one embodiment, the battery separator also includes an electrolyte material.

[0039] In one embodiment, the electrolyte material comprises LLZO.

[0040] In one embodiment, the polytetrafluoroethylene comprises 5%-10% by weight, the polymethyl methacrylate comprises 50%-60%, and the LLZO comprises 10%-30%.

[0041] In one embodiment, the vacuum baking process is performed at a temperature of 80°C-100°C for 8 hours.

[0042] In one embodiment, the ambient temperature for the dry mixing is 0-5°C, and the dry mixing time is 60 minutes.

[0043] In one embodiment, the mesh size of the sieving process is -40 mesh to +100 mesh.

[0044] In one embodiment, the temperature of the pressing mold for the ring pressing process is 140℃-170℃, the pressure is 10MPa, and the time is 3min-5min.

[0045] In one embodiment, the thickness of the diaphragm ring is 30 μm-63 μm, and the porosity is 40%-60%.

[0046] In one embodiment, the battery separator includes the following preparation steps:

[0047] After vacuum baking, polytetrafluoroethylene, LLZO and polymethyl methacrylate were cooled to room temperature and then sealed for later use.

[0048] The baked polytetrafluoroethylene, LLZO and polymethyl methacrylate were dry-mixed to obtain mixture A;

[0049] The mixture is subjected to fiberization, then tableting, crushing, and sieving to obtain mixture B.

[0050] The mixture B is subjected to ring pressing to obtain a diaphragm ring.

[0051] The present invention also provides an application of a battery separator, wherein the separator ring is applied in the fabrication of a needle-shaped battery, the fabrication of which includes the following steps:

[0052] Place the diaphragm ring, leak-proof rubber plug, and steel needle in a vacuum drying oven at 90°C and vacuum dry for 5-6 hours.

[0053] After drying, the separator ring, the leak-proof rubber plug, and the steel needle are quickly transferred into a glove box with a humidity of ≤1 ppm. Then, the lithium sheet is cut into small pieces that meet the specifications and rolled onto the steel needle. The separator ring is then rolled onto the surface of the lithium sheet. The steel needle with the lithium sheet and separator ring rolled is then inserted into the positive electrode ring inside the battery casing. Electrolyte is added, the leak-proof rubber plug is put on, and the end is sealed by rolling grooves to obtain a needle-shaped battery.

[0054] In the above-described scheme, the separator ring expands after the battery is filled with electrolyte, absorbing the electrolyte. This not only avoids adversely affecting battery performance but also strengthens the contact between various interfaces, increasing electrolyte storage within the separator ring and thus improving battery performance. Furthermore, applying the separator ring of this application to a needle-type battery reduces the gap between the electrodes, ensuring the cycle stability of the needle-type battery.

[0055] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0056] Example 1:

[0057] A method for preparing a battery separator includes the following steps:

[0058] According to the mass percentage, 45% polytetrafluoroethylene and 55% polymethyl methacrylate were vacuum baked at 100°C, cooled to room temperature, and then sealed for later use.

[0059] The baked polytetrafluoroethylene and polymethyl methacrylate were dry-mixed at a temperature of 4°C for 60 minutes to obtain mixture A.

[0060] The mixture is subjected to fiberization treatment, then compressed into tablets using a roller tablet press, crushed, and then passed through a -40 mesh to +100 mesh sieve to obtain mixture B;

[0061] The mixture B is subjected to ring pressing treatment. The temperature of the pressing mold for ring pressing treatment is 140°C, the pressure is 10MPa, and the time is 5min to obtain a diaphragm ring.

[0062] The relationship between the immersion time of the diaphragm ring prepared in Example 1 in the electrolyte and the diaphragm thickness is shown in Table 1.

[0063] Table 1:

[0064] Soaking time 0min 15min 30min 1h 2h Diaphragm thickness 40um 50.2um 62.3um 63.1um 63.0um

[0065] Analysis of the data in Table 1 shows that the diaphragm ring prepared in this application expands by 57.5% when immersed in electrolyte, which can greatly solidify the contact between the interfaces and stop expanding after a certain period of time.

[0066] Example 2:

[0067] A method for preparing a battery separator includes the following steps:

[0068] According to the mass percentage, 30% LLZO, 10% polytetrafluoroethylene and 60% polymethyl methacrylate were vacuum baked at 100°C, cooled to room temperature and then sealed for later use.

[0069] The baked LLZO, polytetrafluoroethylene and polymethyl methacrylate were dry-mixed at a temperature of 4°C for 60 minutes to obtain mixture A.

[0070] The mixture is subjected to fiberization treatment, then compressed into tablets using a roller tablet press, crushed, and then passed through a -40 mesh to +100 mesh sieve to obtain mixture B;

[0071] The mixture B is subjected to ring pressing treatment. The temperature of the pressing mold for ring pressing treatment is 140°C, the pressure is 10MPa, and the time is 5min to obtain a diaphragm ring.

[0072] The relationship between the immersion time of the diaphragm ring prepared in Example 2 in the electrolyte and the diaphragm thickness is shown in Table 2.

[0073] Soaking time 0min 15min 30min 1h 2h Diaphragm thickness 35.7um 44.5um 55.0um 55.0um 55.6um

[0074] As can be seen from Table 2, the diaphragm ring in Example 2 expanded by 56.0% when immersed in the electrolyte, which is basically the same as in Example 1. However, the addition of solid electrolyte to the formulation can further improve the ionic conductivity of the diaphragm ring.

[0075] Application Example 1-2:

[0076] Application Example 1 applies the separator ring prepared in Example 1 to the fabrication of a needle-shaped battery. Application Example 2 applies the separator ring prepared in Example 2 to the fabrication of a needle-shaped battery. However, the steps in Application Example 1 and Application Example 2 are the same, specifically including the following steps:

[0077] Place the diaphragm ring, leak-proof rubber plug, and steel needle in a vacuum drying oven at 90°C and vacuum dry for 5 hours.

[0078] After drying, the separator ring, the leak-proof rubber plug, and the steel needle are quickly transferred into a glove box with a humidity of ≤1 ppm. Then, the lithium sheet is cut into small pieces that meet the specifications and rolled onto the steel needle. The separator ring is then rolled onto the surface of the lithium sheet. The steel needle with the lithium sheet and separator ring rolled is then inserted into the positive electrode ring inside the battery casing. Electrolyte is added, the leak-proof rubber plug is put on, and then the casing is sealed by rolling grooves. This yields the needle-type battery of Application Example 1 and the needle-type battery of Application Example 2.

[0079] Performance testing was conducted on the corresponding pin-type battery in test case 1, and the results are as follows: Figure 1 As shown, the internal resistance of a needle-shaped battery using a conventional separator is 35.6Ω, while the internal resistance of a needle-shaped battery using a separator ring is 30.2Ω. Subsequently, the cycle performance of the two batteries was tested simultaneously. The battery using a conventional separator had a retention rate of less than 80% after 50 cycles, while the battery using a separator ring could cycle for more than 200 cycles.

[0080] For use case 2, performance testing was conducted on the pin-shaped battery. The internal resistance of the pin-shaped battery using a standard separator was 35.6Ω, while the internal resistance of the pin-shaped battery using separator rings was 9.6Ω. The cycle performance of both batteries was then tested simultaneously. The battery using a standard separator had a retention rate below 80% after 50 cycles, while the battery using separator rings could cycle for over 500 cycles. The addition of a solid electrolyte to the formulation further improved battery performance. This demonstrates that the addition of a solid electrolyte in this application not only ensures swelling but also provides excellent cycle stability.

[0081] in addition, Figure 1 This is a schematic diagram of the cycling curve of the needle-shaped battery prepared in Application Example 1 of the present invention. It can be seen that the battery separator of the present application can cycle stably and there is no phenomenon of uneven current inside the battery. Figure 2 This is a cross-sectional schematic diagram of the needle-shaped battery prepared in Application Example 1 of the present invention; Figure 3 This is a cross-sectional diagram of a battery in existing technology, for comparison. Figure 2 and Figure 3 It is evident that this application contains no voids and requires no coating; the electrolyte material is uniformly distributed within the diaphragm ring, which is integrally pressed, facilitating assembly and mitigating the risk of short circuits caused by improperly rolled diaphragms. However, Figure 3 With large gaps and overlapping membranes, the separator becomes too thick, leading to battery capacity loss and lithium plating, which also poses a safety hazard.

[0082] Figure 4 This is a schematic diagram of the overall structure of the battery. This application improves the battery separator, which is especially suitable for needle-type battery separator settings. Other structures of the battery will not be described in detail in this application.

[0083] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0084] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A battery separator, characterized in that, The separator comprises polytetrafluoroethylene and polymethyl methacrylate, and the separator is a separator ring, which is used in needle-type batteries; By mass percentage, the polytetrafluoroethylene is 30%-50% and the polymethyl methacrylate is 50%-70%; The method for preparing the battery separator includes the following steps: After vacuum baking, polytetrafluoroethylene and polymethyl methacrylate were cooled to room temperature and then sealed for later use. The baked polytetrafluoroethylene and polymethyl methacrylate were dry-mixed to obtain mixture A; The mixture is subjected to fiberization, then tableting, crushing, and sieving to obtain mixture B. The mixture B is subjected to ring pressing to obtain a diaphragm ring.

2. The battery separator according to claim 1, characterized in that, The vacuum baking process is carried out at a temperature of 80℃-100℃ for 8 hours.

3. The battery separator according to claim 1, characterized in that, The ambient temperature for dry mixing is 0-5℃, and the dry mixing time is 60 minutes.

4. The battery separator according to claim 1, characterized in that, The sieve size is -40 mesh to +100 mesh.

5. The battery separator according to claim 1, characterized in that, The pressing mold temperature for the ring pressing process is 140℃-170℃, the pressure is 10MPa, and the time is 3min-5min.

6. The battery separator according to claim 5, characterized in that, The thickness of the diaphragm ring is 30μm-63μm, and the porosity is 40%-60%.

7. An application of a battery separator, characterized in that, The battery separator is the separator ring as described in any one of claims 1-6.

8. The application according to claim 7, characterized in that, The application involves using a separator ring in the fabrication of a needle-shaped battery, the fabrication of which includes the following steps: Place the diaphragm ring, leak-proof rubber plug, and steel needle in a vacuum drying oven at 90°C and vacuum dry for 5-6 hours. After drying, the separator ring, the leak-proof rubber plug, and the steel needle are quickly transferred into a glove box with a humidity of ≤ 1 ppm. Then, the lithium sheet is cut into small pieces that meet the specifications and rolled onto the steel needle. The separator ring is then rolled onto the surface of the lithium sheet. The steel needle with the lithium sheet and separator ring rolled is then inserted into the positive electrode ring inside the battery casing. Electrolyte is added, the leak-proof rubber plug is put on, and then the end is sealed by rolling grooves to obtain a needle-shaped battery.

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