Wet-process high-strength lithium battery diaphragm and preparation process thereof

Abstract

The invention discloses a wet-process high-strength lithium battery diaphragm and a preparation process thereof.The wet-process high-strength lithium battery diaphragm comprises a matrix film, porous ceramic coatings and tensile net layers, the porous ceramic coatings are arranged on the two opposite sides of the matrix film respectively, the tensile net layers are arranged in the porous ceramic coatings respectively, and the tensile net layers are arranged between the matrix film and the porous ceramic coatings respectively. The tensile net layer comprises a plurality of tensile warps arranged in parallel and a plurality of tensile wefts arranged in parallel, and the tensile warps and the tensile wefts are arranged in a staggered mode. The wet-process lithium battery diaphragm has the effects of improving the structural strength of the wet-process lithium battery diaphragm and improving the use safety of a lithium battery.

Description

Technical Field

[0001] The present application relates to the technical field of lithium battery production, and in particular to a wet-process high-strength lithium battery separator and a preparation process thereof. Background Art

[0002] Lithium battery separator is the inner component of lithium battery. In the structure of lithium battery, separator is one of the key inner components. The performance of separator determines the interface structure and internal resistance of battery, directly affects the capacity, cycle and safety performance of battery, and excellent separator plays an important role in improving the comprehensive performance of battery. The main function of separator is to separate the positive and negative electrodes of battery, prevent the two electrodes from contacting and short circuit or unnecessary energy loss in battery, and also has the function of allowing electrolyte ions to pass. The separator material is non-conductive, and its physical and chemical properties have a great influence on the performance of battery. Through different production methods, lithium battery separator can be divided into dry lithium battery film and wet lithium battery film.

[0003] At present, commonly used lithium battery separators can be divided into dry lithium battery separators and wet lithium battery separators. Among them, wet lithium battery film is used to prevent direct contact between electrons of positive and negative electrodes, while also allowing the transmission of lithium ions in the battery and maintaining the stability and performance of the electrolyte. Wet lithium battery separators are usually made by mixing polyolefin resin and pore former into a uniform solution, extruding it through a die, then stretching it into a film, and then removing the pore former through wet extraction to form micropores. Compared with dry lithium battery films, wet lithium batteries are superior to dry separators in terms of thickness uniformity, mechanical properties, air permeability, physical and chemical properties, etc., and are suitable for high-capacity batteries.

[0004] With respect to the above-mentioned related technologies, the inventors believe that the existing lithium battery separators have low strength and are easily penetrated when impacted, causing internal short circuits in the battery, thus affecting its normal use; moreover, the existing lithium battery separators have defects in high temperature resistance and poor fire resistance. When in use, they are prone to cause battery explosions due to high temperature combustion, posing safety hazards to the use of the battery. Summary of the invention

[0005] In order to improve the structural strength of a wet-process lithium battery separator and improve the safety of lithium battery use, the present application provides a wet-process high-strength lithium battery separator and a preparation process thereof.

[0006] The wet-process high-strength lithium battery separator provided in this application adopts the following technical solution: A wet-process high-strength lithium battery separator comprises a base film, a porous ceramic coating and an anti-tensile mesh layer, wherein the porous ceramic coating is provided with a layer on opposite sides of the base coating, and the anti-tensile mesh layer is provided with one layer in each of the porous ceramic coatings, and the anti-tensile mesh layer comprises a plurality of parallel anti-tensile warp threads and a plurality of parallel anti-tensile weft threads, and the anti-tensile warp threads and the anti-tensile weft threads are staggered.

[0007] By adopting the above technical solution, the porous ceramic coating is arranged on both sides of the base film, which improves the opposite sides of the base film and helps to improve the structural strength of the base film. The tensile mesh layer is arranged inside the porous ceramic coating, which improves the tensile resistance of the base film and reduces the possibility of damage to the base film under external force. Through the mutual cooperation of the base film, the porous ceramic coating and the tensile mesh layer, the structural strength of the wet-process lithium battery separator is improved and the safety of lithium battery use is improved.

[0008] Optionally, a refractory layer is disposed on opposite sides of the base film, and the porous ceramic layer is disposed on a side of the refractory layer away from the base film.

[0009] By adopting the above technical solution, the fire-resistant layer is arranged between the porous ceramic coating and the substrate film, thereby reducing the possibility of combustion of the lithium battery separator.

[0010] Optionally, connecting corrugated surfaces are provided on opposite sides of the base film, and the two sides of the base film are connected to the fire-resistant layer through a first adhesive layer.

[0011] By adopting the above technical solution, the setting of the connecting corrugated surface increases the connection area and connection tightness between the two sides of the base film and the two refractory layers.

[0012] Optionally, a plurality of refractory cavities are opened in parallel in the refractory layer, the refractory cavities are filled with refractory fillers, a connecting cavity is opened in the refractory layer, the connecting cavity is connected to the plurality of refractory cavities at the same time, and a vacuum tube connected to the connecting cavity is provided at the edge of the refractory layer.

[0013] By adopting the above technical solution, a refractory filler is arranged in the refractory cavity. When the lithium battery diaphragm is damaged, the refractory filler reduces the possibility of combustion of the lithium battery diaphragm. The refractory cavity is evacuated by a vacuum tube, which reduces the oxygen content in the refractory cavity and reduces the possibility of combustion of the lithium battery film.

[0014] Optionally, a sealing plug is provided at one end of the vacuum tube away from the refractory layer, and the sealing plug includes a plug-in cylinder and a plug-in cone provided at one end thereof, the diameter of the plug-in cone decreases in a direction away from the plug-in cylinder, and a vacuum groove is provided on the sealing plug, one end of the vacuum groove extends to one end of the plug-in cone away from the plug-in cylinder, and the other end extends to the middle position of the plug-in cylinder, and the diameter of the plug-in cylinder is equal to the inner diameter of the vacuum tube.

[0015] By adopting the above technical solution, when the vacuum tube is used to vacuum the refractory cavity, the plug-in cone is inserted into the vacuum tube, and the end of the vacuum groove away from the plug-in cone is located outside the vacuum tube. The end of the vacuum tube away from the refractory layer is placed in the vacuum device, and when the vacuum operation of the refractory cavity is completed, the plug-in cylinder is completely inserted into the vacuum tube, thereby achieving the blocking of the vacuum tube.

[0016] Optionally, a protective layer is provided on a side of the porous ceramic coating away from the base film, and the protective layer is made of polytetrafluoroethylene.

[0017] By adopting the above technical solution, the protective layer is arranged on the outward side of the porous ceramic coating, which reduces the possibility of external impurities and dust adhering to the surface of the porous ceramic coating and affecting its normal use.

[0018] Optionally, a mounting frame is provided on the outer edge of the base film, and the mounting frame is made of a high thermal conductivity material. The mounting frame includes a connecting frame and a connecting ring cover. A receiving groove for receiving the base film is provided on one side of the connecting frame, and the connecting ring cover is connected to the open end of the connecting frame.

[0019] By adopting the above technical solution, the mounting frame is arranged outside the base film, so as to support the base film and reduce the possibility of damage to the base film. At the same time, since the mounting frame is made of a high thermal conductivity material, it is convenient for the base film to dissipate heat, and reduces the possibility of overheating of the base film during use.

[0020] Optionally, a wet process for preparing a high-strength lithium battery separator comprises the following steps: Prepare raw materials: weigh polyolefin raw materials and white oil according to the proportion; Extrusion: The polyolefin raw material and white oil are heated and mixed, and then extruded using an extrusion device to obtain an extrudate; Cooling and shaping: The extrudate is placed in a calendering device for cooling to obtain a cast sheet; Stretching and cooling: The cast sheet is biaxially stretched to obtain a film, and the white oil obtained during the stretching process is recovered. The stretched film is cooled, trimmed, and rolled up; Extraction and drying: immerse the film in an extraction tank for full extraction to obtain a semi-finished film, and then dry the semi-finished film; Extrusion molding: using a die to extrude both sides of the film to form the connecting corrugated surface; Vacuuming: placing the end of the vacuuming tube away from the refractory layer in the vacuuming device, and inserting the sealing plug into the end of the vacuuming tube, so that the end of the vacuum groove away from the plug-in cone is exposed to the vacuuming tube. After the vacuuming operation of the refractory cavity is completed, the plug-in cylinder is fully inserted into the vacuuming tube to seal it; Additional layer pasting: The refractory layer and the porous ceramic coating are pasted on both sides of the film in sequence, and finally the pasted lithium battery separator is clamped in the installation outer frame.

[0021] In summary, the present application includes at least one of the following beneficial technical effects: 1. Through the cooperation of the base film, the porous ceramic coating and the anti-tension mesh layer, the structural strength of the wet-process lithium battery separator is improved and the safety of lithium battery use is improved; 2. The setting of the connecting corrugated surface increases the connection area and connection tightness between the two sides of the base film and the two refractory layers; 3. The mounting frame is arranged outside the base film, so as to support the base film and reduce the possibility of overheating of the base film during use. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of a wet-process high-strength lithium battery separator used in an embodiment of the present application.

[0023] Figure 2 It is a partial cross-sectional view used to reflect the internal structure of the installation frame in the embodiment of the present application.

[0024] Figure 3 It is a partial cross-sectional view used to illustrate the refractory cavity in the embodiment of the present application.

[0025] Figure 4 yes Figure 2 Enlarged view of part A in the middle.

[0026] Explanation of the reference numerals: 1. Mounting outer frame; 101. Connecting frame; 102. Connecting ring cover; 103. First abutting ring; 104. Second abutting ring; 105. Connecting hole; 106. Sealing ring; 2. Base film; 21. Connecting corrugated surface; 3. Refractory layer; 31. Refractory cavity; 32. Connecting cavity; 33. Connecting port; 4. Porous ceramic coating; 5. Protective layer; 6. First adhesive layer; 7. Second adhesive layer; 8. Vacuum tube; 9. Sealing plug; 91. Abutting cover; 92. Plug-in cylinder; 93. Plug-in cone; 94. Vacuum groove; 10. Anti-tensile mesh layer; 11. Extension block; 12. Accommodating groove. DETAILED DESCRIPTION

[0027] The following is combined with Figure 1-4 The present application is further described in detail. The present application provides a wet-process high-strength lithium battery separator and a preparation process thereof, which has the effect of improving the structural strength of the wet-process lithium battery separator and improving the safety of lithium battery use.

[0028] Reference Figure 1 and Figure 2 A wet-process high-strength lithium battery separator includes a separator body and an installation frame 1. The separator body includes a base film 2, a refractory layer 3, a porous ceramic coating 4 and a protective layer 5. The base film 2 is provided with connecting corrugated surfaces 21 on opposite sides, the refractory layer 3 is provided with a layer on opposite sides of the base film 2, and the refractory layer 3 is connected to the collective film through a first adhesive layer 6. The porous ceramic coating 4 is provided with a layer on each side of the refractory layer 3 away from the base film 2, and the porous ceramic coating 4 is connected to the refractory layer 3 through a second adhesive layer 7.

[0029] Reference Figure 2-4 , a plurality of refractory cavities 31 are provided inside the refractory layer 3, and the plurality of refractory cavities 31 are arranged in parallel. Two connecting cavities 32 are provided in parallel in the refractory layer 3, and the two connecting cavities 32 correspond to and are connected with the two ends of the plurality of refractory cavities 31 one by one. A vacuum tube 8 is provided on the edge of the refractory layer 3, and one end of the vacuum tube 8 is connected with one of the connecting cavities 32. A sealing plug 9 is provided at the other end of the vacuum tube 8, and the sealing plug 9 includes an abutment cover 91, a plug-in cylinder 92 and a plug-in cone 93. The abutment cover 91 and the plug-in cone 93 are coaxially connected to the opposite ends of the plug-in cylinder 92, respectively, the diameter of the abutment cover 91 is equal to the outer diameter of the vacuum tube 8, and the diameter of the plug-in cylinder 92 is equal to the inner diameter of the vacuum tube 8. The diameter of the plug-in cone 93 gradually decreases in the direction away from the plug-in cylinder 92.

[0030] Reference Figure 3 and Figure 4The sealing plug 9 is provided with a plurality of vacuum grooves 94 along the circumferential direction, one end of the vacuum groove 94 extends to the end of the plugging cone 93 away from the plugging cylinder 92, and the other end of the vacuum groove 94 extends to the middle position of the plugging cylinder 92. The refractory cavity 31 and the connecting cavity 32 are filled with refractory fillers.

[0031] Reference Figure 2 and Figure 3 , a tensile mesh layer 10 is arranged inside the porous ceramic coating 4, and the tensile mesh layer 10 includes a plurality of parallel tensile warps and a plurality of parallel tensile wefts. The tensile warps and the tensile wefts are staggered, and the tensile warps and the tensile wefts of the tensile mesh layers 10 in the two porous ceramic coatings 4 are staggered. A plurality of connecting openings 33 are provided on the refractory layer 3, and a plurality of extension blocks 11 are arranged on the side of the porous ceramic coating 4 close to the refractory layer 3, and the plurality of extension blocks 11 correspond to the plurality of connecting openings 33 one by one and are plugged in and matched. A protective layer 5 is arranged on the side of the porous ceramic coating 4 away from the refractory layer 3, and the protective layer 5 used in the embodiment of the present application is made of polytetrafluoroethylene material.

[0032] Reference Figure 1 and Figure 2 The mounting outer frame 1 is arranged outside the diaphragm body, and the mounting outer frame 1 includes a connecting frame 101 and a connecting ring cover 102. A receiving groove 12 for receiving the diaphragm body is provided on one side of the connecting frame 101, and the connecting ring cover 102 is connected to the side of the connecting frame 101 provided with the receiving groove 12 by bolts, and the mounting outer frame 1 is made of a high thermal conductivity material. A first abutment ring 103 is provided along the circumferential direction on the inner bottom wall of the receiving groove 12, and a second abutment ring 104 is provided along the circumferential direction on the side of the connecting ring cover 102 close to the receiving groove 12. The first abutment ring 103 and the second abutment ring 104 are both made of elastic material, and the first abutment ring 103 and the second abutment ring 104 abut against the opposite sides of the diaphragm body. A connecting hole 105 for the vacuum tube 8 to pass through is provided on the connecting frame 101, and a sealing ring 106 is provided on the inner ring wall of the connecting hole 105.

[0033] A wet process for preparing a high-strength lithium battery separator comprises the following steps: Prepare raw materials: weigh polyolefin raw materials and white oil according to a specific ratio and mix them; Extrusion: The mixed polyolefin raw material and white oil are heated to a certain temperature, and extruded through an extrusion device to obtain an extrudate. The extrusion device used in this application is a twin-screw extruder; Cooling and shaping: putting the extruded material into a calender for cooling and shaping to obtain a casting sheet; Stretching and cooling: the cast sheet is sequentially added to an asynchronous transverse stretching machine and an asynchronous longitudinal stretching machine for transverse and longitudinal stretching to obtain a base film 2, and the white oil extruded during the stretching process is recovered; Extraction and drying: Put the film into an extraction tank and use dichloromethane as an extractor to extract white oil, so that micropores are formed in the base film 2, and the excess white oil recovery liquid on the surface is recovered and separated, and the base film 2 is dried by a heating device; Extrusion molding: cutting the base film 2, and using a mold to extrude both sides of the base film 2, so that the two opposite sides form a connected corrugated surface 21; Vacuuming: Place the end of the vacuuming tube 8 away from the refractory layer 3 in the vacuuming device, and insert the sealing plug 9 at the end of the vacuuming tube 8, so that the end of the vacuum groove 94 away from the plug-in cone 93 is exposed to the vacuuming tube 8. After the vacuuming operation of the refractory cavity 31 is completed, the plug-in cylinder 92 is fully inserted into the vacuuming tube 8 so that the abutting cover 91 abuts against the end of the vacuuming tube 8, thereby achieving the sealing of the vacuuming tube 8; Additional layer pasting: The two refractory layers 3 are connected to the opposite sides of the base film 2 through the first adhesive layer 6, and the two porous ceramic coatings 4 are connected to the side of the two refractory layers 3 away from the base film 2 using the second adhesive layer 7. The connected diaphragm body is placed in the receiving groove 12 of the connection frame 101, and the connection ring cover 102 is connected to the open end of the connection frame 101 to achieve the fixation of the diaphragm body.

[0034] Reference Figure 2 and Figure 3 The provision of the refractory layer 3 and the refractory filler reduces the possibility of combustion when the diaphragm body is damaged, which helps to improve the safety of the diaphragm body. The refractory cavity 31 and the connecting cavity 32 are evacuated by the vacuum tube 8, which reduces the oxygen content in the refractory layer 3, further reducing the possibility of combustion of the refractory layer 3.

[0035] Reference Figure 2 and Figure 3 The porous ceramic coating 4 is provided to improve the structural strength of the diaphragm body under the premise of ensuring the existence of micropores. The extension block 11 extends into the refractory layer 3 through the connecting port 33, supports the refractory layer 3, and improves the structural strength of the refractory layer 3. The tensile mesh layer 10 is provided in the porous ceramic layer, and the tensile resistance of the diaphragm body is improved by the staggered arrangement of the tensile warp and the tensile weft, and the possibility of the diaphragm body being damaged by external forces is further reduced. The protective layer 5 made of polytetrafluoroethylene is provided on the outermost layer of the diaphragm body, which reduces the possibility of external impurities adhering to the surface of the diaphragm body.

[0036] Reference Figure 1 The mounting frame 1 is connected to the outside of the diaphragm body to support and protect it, reducing the possibility of damage to the diaphragm body. The mounting frame 1 is made of a high thermal conductivity material, reducing the possibility of overheating of the diaphragm body during use.

[0037] The implementation principle of a wet-process high-strength lithium battery diaphragm and its preparation process in the embodiment of the present application is as follows: the provision of the refractory layer 3 and the refractory filler reduces the possibility of combustion when the diaphragm body is damaged, which helps to improve the safety of the diaphragm body. The provision of the porous ceramic coating 4 improves the structural strength of the diaphragm body while ensuring the existence of micropores. The extension block 11 extends into the refractory layer 3 through the connecting port 33, thereby improving the structural strength of the refractory layer 3. The tensile mesh layer 10 is provided in the porous ceramic layer, thereby improving the tensile properties of the diaphragm body and further reducing the possibility of the diaphragm body being damaged by external forces.

[0038] The mounting frame 1 is connected to the outside of the diaphragm body to support and protect it, reducing the possibility of damage to the diaphragm body. The mounting frame 1 is made of a high thermal conductivity material, reducing the possibility of overheating of the diaphragm body during use.

[0039] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A wet-process high-strength lithium battery separator, characterized in that: The invention comprises a base film (2), a porous ceramic coating (4) and an anti-tensile mesh layer (10), wherein the porous ceramic coating (4) is provided with a layer on opposite sides of the base coating, and the anti-tensile mesh layer (10) is provided in each of the porous ceramic coatings (4). The anti-tensile mesh layer (10) comprises a plurality of parallel anti-tensile warp threads and a plurality of parallel anti-tensile weft threads, and the anti-tensile warp threads and the anti-tensile weft threads are arranged in an alternating manner.

2. A wet-process high-strength lithium battery separator according to claim 1, characterized in that: A refractory layer (3) is provided on opposite sides of the base film (2), and the porous ceramic layer is provided on a side of the refractory layer (3) away from the base film (2).

3. A wet-process high-strength lithium battery separator according to claim 2, characterized in that: The base film (2) is provided with connecting corrugated surfaces (21) on both opposite sides, and the two sides of the base film (2) are connected to the fire-resistant layer (3) via a first adhesive layer (6).

4. A wet-process high-strength lithium battery separator according to claim 3, characterized in that: A plurality of refractory cavities (31) are provided in parallel in the refractory layer (3), the refractory cavities (31) are filled with refractory fillers, a connecting cavity (32) is provided in the refractory layer (3), the connecting cavity (32) is connected to the plurality of refractory cavities (31) at the same time, and a vacuum tube (8) connected to the connecting cavity (32) is provided at the edge of the refractory layer (3).

5. A wet-process high-strength lithium battery separator according to claim 4, characterized in that: A sealing plug (9) is provided at one end of the vacuum tube (8) away from the fire-resistant layer (3), and the sealing plug (9) includes a plug-in cylinder (92) and a plug-in cone (93) provided at one end thereof, the diameter of the plug-in cone (93) decreases along the direction away from the plug-in cylinder (92), and a vacuum groove (94) is provided on the sealing plug (9), one end of the vacuum groove (94) extends to one end of the plug-in cone (93) away from the plug-in cylinder (92), and the other end extends to the middle position of the plug-in cylinder (92), and the diameter of the plug-in cylinder (92) is equal to the inner diameter of the vacuum tube (8).

6. A wet-process high-strength lithium battery separator according to claim 1, characterized in that: A protective layer (5) is provided on the side of the porous ceramic away from the base film (2), and the protective layer (5) is made of polytetrafluoroethylene.

7. A wet-process high-strength lithium battery separator according to claim 5, characterized in that: An outer mounting frame (1) is provided at the outer edge of the base film (2); the outer mounting frame (1) is made of a high thermal conductivity material; the outer mounting frame (1) comprises a connecting frame (101) and a connecting ring cover (102); a receiving groove (12) for receiving the base film (2) is provided on one side of the connecting frame (101); and the connecting ring cover (102) is connected to the open end of the connecting frame (101).

8. The process for preparing a wet-process high-strength lithium battery separator according to claim 7, characterized in that: The following steps are involved: Prepare raw materials: weigh polyolefin raw materials and white oil according to the proportion; Extrusion: The polyolefin raw material and white oil are heated and mixed, and then extruded using an extrusion device to obtain an extrudate; Cooling and shaping: The extrudate is placed in a calendering device for cooling to obtain a cast sheet; Stretching and cooling: The cast sheet is biaxially stretched to obtain a film, and the white oil obtained during the stretching process is recovered. The stretched film is cooled, trimmed, and rolled up; Extraction and drying: immerse the film in an extraction tank for full extraction to obtain a semi-finished film, and then dry the semi-finished film; Extrusion molding: using a mold to extrude both sides of the film to form the connecting corrugated surface (21); Vacuuming: placing the end of the vacuuming tube (8) away from the refractory layer (3) in the vacuuming device, and inserting the sealing plug (9) at the end of the vacuuming tube (8) so that the end of the vacuum groove (94) away from the plug-in cone (93) is exposed from the vacuuming tube (8); after the vacuuming operation of the refractory cavity (31) is completed, the plug-in cylinder (92) is completely inserted into the vacuuming tube (8) to seal it; Additional layer pasting: a refractory layer (3) and a porous ceramic coating (4) are pasted on both sides of the film in sequence, and finally the pasted lithium battery separator is clamped in the installation outer frame (1).

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