CN112981722B - Method for preparing lithium ion battery diaphragm by sea island COPET-PP composite negative pressure spinning - Google Patents
Method for preparing lithium ion battery diaphragm by sea island COPET-PP composite negative pressure spinning Download PDFInfo
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- 239000002131 composite material Substances 0.000 title claims abstract description 105
- 238000009987 spinning Methods 0.000 title claims abstract description 49
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 37
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 37
- 238000000034 method Methods 0.000 title claims abstract description 23
- 239000000835 fiber Substances 0.000 claims abstract description 65
- 239000007788 liquid Substances 0.000 claims abstract description 19
- 239000012528 membrane Substances 0.000 claims abstract description 19
- 238000005507 spraying Methods 0.000 claims abstract description 17
- 229920006240 drawn fiber Polymers 0.000 claims abstract description 12
- 239000003513 alkali Substances 0.000 claims abstract description 10
- 238000001035 drying Methods 0.000 claims abstract description 10
- 230000008018 melting Effects 0.000 claims abstract description 10
- 238000002844 melting Methods 0.000 claims abstract description 10
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 14
- 239000000155 melt Substances 0.000 claims description 8
- 238000002791 soaking Methods 0.000 claims description 4
- 208000016261 weight loss Diseases 0.000 claims description 2
- 239000013585 weight reducing agent Substances 0.000 claims description 2
- 230000032683 aging Effects 0.000 claims 1
- 239000000126 substance Substances 0.000 abstract description 2
- 230000008569 process Effects 0.000 description 5
- 238000010025 steaming Methods 0.000 description 3
- 239000012752 auxiliary agent Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 238000002955 isolation Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000003915 cell function Effects 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
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- D—TEXTILES; PAPER
- D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
- D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
- D04H3/00—Non-woven fabrics formed wholly or mainly of yarns or like filamentary material of substantial length
- D04H3/005—Synthetic yarns or filaments
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/08—Melt spinning methods
- D01D5/098—Melt spinning methods with simultaneous stretching
- D01D5/0985—Melt spinning methods with simultaneous stretching by means of a flowing gas (e.g. melt-blowing)
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/28—Formation of filaments, threads, or the like while mixing different spinning solutions or melts during the spinning operation; Spinnerette packs therefor
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- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
- D06M11/00—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising
- D06M11/32—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising with oxygen, ozone, ozonides, oxides, hydroxides or percompounds; Salts derived from anions with an amphoteric element-oxygen bond
- D06M11/36—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with inorganic substances or complexes thereof; Such treatment combined with mechanical treatment, e.g. mercerising with oxygen, ozone, ozonides, oxides, hydroxides or percompounds; Salts derived from anions with an amphoteric element-oxygen bond with oxides, hydroxides or mixed oxides; with salts derived from anions with an amphoteric element-oxygen bond
- D06M11/38—Oxides or hydroxides of elements of Groups 1 or 11 of the Periodic Table
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention belongs to the technical field of chemical fiber composite spinning, and discloses a method for preparing a lithium ion battery diaphragm by sea-island COPET-PP composite negative pressure spinning, which comprises the following steps: A. drying COPET, putting the COPET into a screw extruder for melting and feeding, and then feeding the COPET into a metering pump for metering; B. drying PP, putting the PP into a screw extruder for melting and feeding, and then feeding into a metering pump for metering; C. injecting the COPET serving as a sea component and the PP serving as an island component into a sea-island spinning device; D. ejecting the COPET and the PP from the sea island spinning device to form a composite spinning solution; E. carrying out negative pressure traction and stretching on the composite silk spraying liquid to form composite stretched fibers; F. receiving the composite drawn fibers by using a receiving plate, and simultaneously swinging left and right and moving forwards to form a non-woven composite fiber membrane; G. collecting the non-woven composite fiber membrane after the non-woven composite fiber membrane is flattened; H. and carrying out alkali decrement treatment on the collected non-woven composite fiber membrane, and removing the sea component to obtain the compact lithium ion battery diaphragm.
Description
Technical Field
The invention relates to the technical field of chemical fiber composite spinning, in particular to a method for preparing a lithium ion battery diaphragm by sea island COPET-PP composite negative pressure spinning.
Background
In the construction of lithium ion batteries, the separator is one of the key internal layer components. The diaphragm can isolate the positive and negative electrodes of the battery to prevent short circuit; it is also possible to block the current conduction in the cell by a closed cell function when the cell overheats. The performance of the diaphragm determines the interface structure, internal resistance and the like of the battery, directly influences the capacity, cycle performance, safety performance and other characteristics of the battery, and the diaphragm with excellent performance plays an important role in improving the comprehensive performance of the battery. The high-end diaphragm material, in particular to the diaphragm material for power lithium ion batteries, has extremely high requirements on the consistency of products, and has very high requirements on the uniformity of the size and the distribution of micropores of the diaphragm besides the basic requirements of thickness, surface density and mechanical properties. The diaphragm industry in China has been developed for more than ten years, although the gap between the diaphragm industry and the high-end technology in foreign countries is gradually reduced. But still have many problems in terms of process and product requirements. Such as insufficient strength of the membrane, uneven pores, no high temperature resistance, and the like. With the popularization of new energy electric vehicles and the trend of replacing other energy sources with electric power in the future, whether the development of lithium ion battery separators can keep up with the requirements of social development or not becomes a difficult problem and challenge of industry development.
Disclosure of Invention
The invention aims to solve the problems of limited stretching of the existing composite fiber, insufficient compactness of a lithium ion battery diaphragm, poor strength and the like.
In order to solve the technical problems, the invention adopts the following technical scheme:
a method for preparing a lithium ion battery diaphragm by sea island COPET-PP composite negative pressure spinning comprises the following steps:
A. drying COPET, putting the COPET into a screw extruder for melting and feeding, and then feeding the COPET into a metering pump for metering;
B. drying PP, putting the PP into a screw extruder for melting and feeding, and then feeding into a metering pump for metering;
C. injecting the COPET serving as a sea component and the PP serving as an island component into a sea-island spinning device;
D. ejecting the COPET and the PP from the sea island spinning device to form a composite spinning solution;
E. carrying out negative pressure traction and stretching on the composite silk spraying liquid to form composite stretched fibers;
F. the composite drawn fibers are received by a receiving plate, and the receiving plate swings left and right and moves forwards at the same time to form a non-woven composite fiber film;
G. collecting the non-woven composite fiber membrane after the non-woven composite fiber membrane is flattened;
H. and carrying out alkali decrement treatment on the collected non-woven composite fiber membrane, and removing the sea component to obtain the compact lithium ion battery diaphragm.
The sea island COPET-PP composite fiber is prepared by dispersing PP in COPET, wherein the dispersed phase is in an island state in the cross section of the fiber, the COPET is equivalent to sea, and the island and sea components are continuously, densely and uniformly distributed in the axial direction of the fiber. In the production process, it has the fineness of conventional fiber, but the sea component is dissolved away by using a solvent, so that the superfine fiber bundle in a bundle shape can be obtained.
Preferably, the operation of the negative pressure traction stretching is as follows: and forming negative pressure suction by utilizing hot air flow, keeping the structure of the composite spinning solution unchanged, drawing the composite spinning solution into a corresponding flow passage, drawing the composite spinning solution in the flow passage, and gradually solidifying the composite spinning solution into the composite drawn fiber.
The negative pressure is utilized for traction and stretching, and the traditional traction roller stretching can be replaced. On one hand, the drawing of the drawing roll can be carried out only after the composite fiber is cooled and solidified slightly, the auxiliary agent needs to be added, but the rigidity modulus of the fiber is increased rapidly in the solidification process, the drawing amount of the fiber is greatly reduced, and the maximum fineness of the finished fiber is severely limited. On the other hand, when the traction roller is in contact with the composite fiber, the internal structure of the composite fiber is deformed to a certain extent without being avoided, and the stretching generated by friction force is difficult to ensure that the whole fiber is uniformly stressed, so that the stretching amount and the structural characteristics of the composite fiber are further influenced.
The negative pressure suction is formed on the composite spinning liquid by utilizing the flow of hot air, and the composite spinning can be carried out under the condition that the composite fibers are kept in a molten liquid state. The non-contact traction and stretching can avoid the influence caused by friction force. In the corresponding flow channel, the internal structure of the composite fiber is kept unchanged, integral stretching is carried out, no auxiliary agent is needed, the stretching amount is kept to the maximum extent because the stretching is carried out in a molten liquid state, and thinner filaments can be drawn on the premise of keeping the characteristics of the composite structure. The lithium ion battery diaphragm prepared by the filament has higher compactness, obviously improved strength and puncture resistance and better isolation effect.
The ejection temperature of the composite silk-spraying liquid is 250-300 ℃, the pressure of the hot air is 1.5-4 bar, and the temperature is 260-320 ℃.
Preferably, the composite drawn fiber comprises COPET fiber and PP fiber which are distributed in a sea island manner, wherein the COPET fiber accounts for 30-40 wt%, and the PP fiber accounts for 60-70 wt%.
Preferably, the linear density of the COPET fiber is 0.39-0.78 Um, and the linear density of the PP fiber is 0.2-0.45 Um.
Preferably, the horizontal swinging speed of the bearing plates is 1-5 m/min, and the forward running speed is 500-800 m/min.
Preferably, the COPET has a melt index of 1000 to 1500g/10min.
Preferably, the PP has a melt index of 1000 to 1500g/10min.
Preferably, the alkali weight reduction treatment is performed by: and soaking and dissolving the sea component in 10-15 g/L sodium hydroxide alkali liquor at the steaming temperature of 100-110 ℃ for 10-15 minutes to completely dissolve the sea component, thereby preparing the compact lithium ion battery diaphragm.
The lithium ion battery diaphragm is prepared by the method for preparing the lithium ion battery diaphragm by sea island COPET-PP composite negative pressure spinning.
Compared with the prior art, the implementation of the invention has the following beneficial effects:
the brand new non-contact drawing mode of negative pressure drawing and drawing is used, so that the drawing quality of the composite fiber is improved in multiples, and the linear density (fineness) is further improved while the characteristics of the composite structure are maintained. The filament is used to prepare the battery diaphragm, the sea component is washed off after the preparation is finished, and the characteristic of the sea-island fiber is utilized to obtain the compact battery diaphragm, thereby effectively enhancing the isolation performance of the diaphragm.
Drawings
FIG. 1 is a schematic top view of a negative pressure traction stretching device;
FIG. 2 isbase:Sub>A sectional view taken along line A-A of FIG. 1;
FIG. 3 is an enlarged view of a portion B of FIG. 2;
FIG. 4 is a schematic structural view of a top plate of the negative pressure traction stretching device;
FIG. 5 is a schematic diagram of a plate structure in a negative pressure traction stretching device;
FIG. 6 is a schematic structural diagram of a bottom plate of the negative pressure traction stretching device; .
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.
Example 1
A method for preparing a lithium ion battery diaphragm by sea island COPET-PP composite negative pressure spinning comprises the following steps:
A. drying COPET with the melt index of 1500g/10min, putting the COPET into a screw extruder for melting and feeding, and then feeding into a metering pump for metering;
B. drying PP with the melt index of 1500g/10min, putting the PP into a screw extruder for melting and feeding, and then feeding into a metering pump for metering;
C. injecting COPET as sea component and PP as island component into sea-island spinning device according to the proportion of 30wt% of COPET fiber and 70wt% of PP fiber;
D. heating COPET and PP to 250 ℃ and spraying out from the sea island spinneret device to form a composite spinneret liquid;
E. carrying out negative pressure traction and stretching on the composite silk-spraying liquid, and specifically operating as follows: utilizing hot air (4 bar) flowing at 260 ℃ to form negative pressure suction, keeping the structure of the composite spinning solution unchanged, drawing the composite spinning solution into a corresponding flow channel, drawing the composite spinning solution in the flow channel, and gradually solidifying the composite spinning solution into composite drawn fibers, wherein the linear density of COPET fibers is 0.39Um, and the linear density of PP fibers is 0.2Um;
as shown in fig. 1 to 6, the negative pressure traction and stretching device includes: the top plate 1, the middle plate 2 and the bottom plate 3 which are connected together are overlapped from top to bottom in sequence.
The top plate 1 is provided with a plurality of connecting threaded holes 11, the middle plate 2 is provided with a plurality of connecting through holes 21, and the bottom plate 3 is provided with a plurality of counter bores 31. The connecting threaded holes 11, the connecting through holes 21 and the counter bores 31 correspond one to one. Connecting bolts (not shown) are sequentially passed through the counter bores 31 and the connecting through holes 21 and screwed into the connecting threaded holes 11, so that the top plate 1, the middle plate 2 and the bottom plate 3 are overlapped and connected together.
For convenience of installation, the embodiment of the present invention preferably provides a plurality of first, second and third positioning pin holes 12, 22 and 32 on the top plate 1, the middle plate 2 and the bottom plate 3, respectively. During installation, the positioning pins (not shown in the figure) are simultaneously inserted into the first, second and third positioning pin holes 12, 22 and 32.
The top surface of the top plate 1 is provided with a plurality of rows of first wire feeding through holes 13 which are coaxially and annularly distributed.
The bottom surface of the middle plate 2 is provided with a plurality of rows of bosses 23 which are coaxially and annularly distributed, and the bottom surface of each boss 23 is respectively provided with a second wire feeding through hole 24. Each row of bosses 23 is also provided with a row of air holes 25 distributed annularly on both sides.
The top plate 1 has a plurality of first ring grooves 14 on the bottom surface. Each first ring groove 14 corresponds to one exhaust hole 25 and is located right above the corresponding exhaust hole 25, and each first ring groove 14 is communicated with all the exhaust holes 25 in the corresponding row.
The top plate 1 also has a radial groove 15 on the bottom surface that communicates with all of the first ring grooves 14.
The top plate 1 and/or the middle plate 2 and/or the bottom plate 3 are/is further provided with an air inlet channel communicated with the radial groove 15, the bottom surface of the middle plate 2 is provided with an air inlet through hole 26 and the bottom surface of the bottom plate 3 is provided with an air pipe connecting hole 33, the air inlet through hole 26 is respectively communicated with the air hole connecting hole 33 and the radial groove 15, and the air inlet through hole 26 and the air pipe connecting hole 33 are matched to form the air inlet channel.
The top surface of the bottom plate 3 is further provided with a plurality of second annular grooves 34, and each second annular groove 34 corresponds to one row of bosses 23 and is communicated with all the air holes 25 on two sides of the corresponding row of bosses 23. The second annular groove 34 is located directly below the row of bosses 23 and the air holes 26 on both sides thereof.
The bottom of the second annular groove 34 is provided with a plurality of concave positions 35 for accommodating the bosses 23, and the bottom surface of each concave position 35 is provided with a third wire feeding through hole 36. A gap for communicating the second ring groove 34 and the third wire feeding through hole 36 is formed between the outer wall of the boss 23 and the inner wall of the concave position 35.
Each of the first, second and third yarn feeding through holes 13, 24 and 36 are communicated with each other in a one-to-one correspondence manner to form a drafting channel.
The shape of the convex 23 and concave 35 is preferably an inverted circular truncated cone.
Firstly, high-speed hot air is continuously introduced through the air pipe connecting hole 33, flows through the air pipe connecting hole 33, the air inlet through hole 26, the radial groove 15, the first ring groove 14, the air hole 25 and the second ring groove 34 in sequence, flows into the third wire inlet through hole 36 through a gap between the boss 23 and the concave position 35, flows downwards along the third wire inlet through hole 36 after entering the third wire inlet through hole 36, and finally flows out of the third wire inlet through hole; when the high-speed hot air flows out downwards along the third filament inlet through hole 36, negative pressure is formed in the first filament inlet through hole 13 and the second filament inlet through hole 24, so that composite filament spraying liquid to be drawn and stretched is sucked in at the top end of the first filament inlet through hole 13, and the composite filament spraying liquid is continuously sucked and downwards moved along the first filament inlet through hole 13 and the second filament inlet through hole 24 to enter the third filament inlet through hole 36; after entering the third filament inlet through hole 36, the composite filament spraying liquid moves downwards under the clamping and traction of the high-speed airflow and finally passes out of the third filament inlet through hole 36 along with the high-speed airflow; the composite filament spraying liquid is stretched and thinned under the clamping and drawing of high-speed hot air in the process of being sucked into the first filament inlet through hole 13 and then passing out of the third filament inlet through hole 36, and composite drawn fibers are formed.
F. Bearing the composite drawn fibers by using a bearing plate, wherein the bearing plate swings left and right and moves forwards simultaneously, the left and right swinging speed is 5 m/min, and the forward running speed is 800 m/min, so that a non-woven composite fiber membrane is formed;
G. collecting the non-woven composite fiber membrane after the non-woven composite fiber membrane is flattened;
H. and (3) carrying out alkali decrement treatment on the collected non-woven composite fiber membrane, and specifically operating as follows: soaking and dissolving the sea component for 15 minutes in 15g/L sodium hydroxide alkali liquor at the steaming temperature of 100 ℃ to completely dissolve the sea component, thereby preparing the compact lithium ion battery diaphragm.
A lithium ion battery diaphragm is prepared by the method for preparing the lithium ion battery diaphragm by sea island COPET-PP composite negative pressure spinning.
Example 2
A method for preparing a lithium ion battery diaphragm by sea island COPET-PP composite negative pressure spinning comprises the following steps:
A. drying COPET with the melt index of 1000g/10min, putting the COPET into a screw extruder for melting and feeding, and then feeding into a metering pump for metering;
B. drying PP with the melt index of 1000g/10min, putting the PP into a screw extruder for melting and feeding, and then feeding into a metering pump for metering;
C. injecting COPET as sea component and PP as island component into sea-island spinning device according to the proportion of 40wt% COPET fiber and 60wt% PP fiber;
D. heating COPET and PP to 300 ℃ and spraying out from the sea island spinneret device to form a composite spinneret liquid;
E. the composite silk-spraying liquid is drawn and stretched under negative pressure, and the operation is as follows: utilizing hot air (1.5 bar) with the temperature of more than 320 ℃ to flow to form negative pressure suction, keeping the structure of the composite spinning solution unchanged, drawing the composite spinning solution into a corresponding flow passage, drawing the composite spinning solution in the flow passage and gradually solidifying the composite spinning solution into composite drawn fibers, wherein the linear density of COPET fibers is 0.78Um, and the linear density of PP fibers is 0.45Um;
as shown in fig. 1 to 6, firstly, high-speed hot air is continuously introduced through the air pipe connecting hole 33, the high-speed hot air sequentially flows through the air pipe connecting hole 33, the air inlet through hole 26, the radial groove 15, the first ring groove 14, the air hole 25 and the second ring groove 34, and flows into the third wire inlet through hole 36 through a gap between the boss 23 and the concave position 35, and the high-speed hot air flows downwards along the third wire inlet through hole 36 after entering the third wire inlet through hole 36 and finally flows out of the third wire inlet through hole; when the high-speed hot air flows out downwards along the third filament inlet through hole 36, negative pressure is formed in the first filament inlet through hole 13 and the second filament inlet through hole 24, so that composite filament spraying liquid to be drawn and stretched is sucked in at the top end of the first filament inlet through hole 13, and the composite filament spraying liquid is continuously sucked and downwards moved along the first filament inlet through hole 13 and the second filament inlet through hole 24 to enter the third filament inlet through hole 36; after entering the third filament inlet through hole 36, the composite filament spraying liquid moves downwards under the clamping and traction of high-speed airflow and finally passes out of the third filament inlet through hole 36 along with the high-speed airflow; the composite filament spraying liquid is stretched and thinned under the clamping and drawing of high-speed hot air in the process of being sucked into the first filament inlet through hole 13 and then passing out of the third filament inlet through hole 36, and composite drawn fibers are formed.
F. Bearing the composite drawn fibers by using a bearing plate, wherein the bearing plate swings left and right and moves forwards simultaneously, the left and right swinging speed is 1 m/min, and the forward running speed is 500 m/min, so that a non-woven composite fiber membrane is formed;
G. collecting the non-woven composite fiber membrane after the non-woven composite fiber membrane is flattened;
H. and (3) carrying out alkali decrement treatment on the collected non-woven composite fiber membrane, and specifically operating as follows: the sea component is completely dissolved by soaking and dissolving 10g/L sodium hydroxide lye at the steaming temperature of 110 ℃ for 10 minutes to prepare the compact lithium ion battery diaphragm.
A lithium ion battery diaphragm is prepared by the method for preparing the lithium ion battery diaphragm by sea island COPET-PP composite negative pressure spinning.
Example 3
Researchers use the traditional traction roller to stretch the composite fiber in the earlier stage, the stretching amount is greatly reduced, the structural characteristics are easy to damage, and the traditional traction roller can not be matched with a bearing plate which swings left and right and moves forwards, so that the film can not be prepared.
Example 4
The lithium ion battery separators obtained in example 1 and example 2 were subjected to a performance test, and a commercially available PP lithium ion battery separator was used as a comparative example, and the results are shown in table 1.
TABLE 1
As can be seen from Table 1, compared with a common PP film, the lithium ion battery diaphragm prepared by the process provided by the invention has the advantages of unexpected performance improvement, better tensile strength and puncture strength, and more excellent elongation at break.
The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the scope of the present invention, therefore, the present invention is not limited by the appended claims.
Claims (8)
1. A method for preparing a lithium ion battery diaphragm by sea island COPPETPP composite negative pressure spinning is characterized by comprising the following steps:
A. drying COPET, putting the COPET into a screw extruder for melting and feeding, and then feeding the COPET into a metering pump for metering;
B. drying PP, putting into a screw extruder for melting and feeding, and then feeding into a metering pump for metering;
C. injecting the COPET serving as a sea component and the PP serving as an island component into a sea-island spinning device;
D. ejecting the COPET and the PP from the sea island spinning device to form a composite spinning solution;
E. carrying out negative pressure traction and stretching on the composite silk spraying liquid to form composite stretched fibers;
F. the composite drawn fibers are received by a receiving plate, and the receiving plate swings left and right and moves forwards at the same time to form a non-woven composite fiber film;
G. collecting the non-woven composite fiber membrane after the non-woven composite fiber membrane is flattened;
H. carrying out alkali decrement treatment on the collected non-woven composite fiber membrane, and removing the sea component to prepare a compact lithium ion battery diaphragm;
the negative pressure traction stretching operation comprises the following steps: forming negative pressure suction by utilizing hot air flow, keeping the structure of the composite spinning solution unchanged, drawing the composite spinning solution into corresponding runners, and drawing and gradually solidifying the composite spinning solution into the composite drawn fibers in the runners;
the speed of the horizontal swinging of the bearing plate is 1-5 m/min, and the speed of the forward running is 500-800 m/min.
2. The method for preparing the lithium ion battery diaphragm by sea island COPPETPP composite negative pressure spinning according to claim 1, wherein the spraying temperature of the composite spinning solution is 250-300 ℃, the pressure of the hot air is 1.5-4 bar, and the temperature is 260-320 ℃.
3. The method for preparing the lithium ion battery diaphragm through sea-island COPTPPP composite negative pressure spinning according to claim 1, wherein the composite tensile fiber comprises COPET fiber and PP fiber which are distributed in a sea-island manner, the COPET fiber accounts for 30-40 wt%, and the PP fiber accounts for 60-70 wt%.
4. The method for preparing the lithium ion battery diaphragm by sea island COPPETPP composite negative pressure spinning according to claim 3, wherein the linear density of the COPET fiber is 0.39-0.78 Um, and the linear density of the PP fiber is 0.2-0.45 Um.
5. The method for preparing the lithium ion battery separator by sea island COPPETPP composite negative pressure spinning according to claim 1, wherein the melt index of COPET is 1000-1500 g/10min.
6. The method for preparing the lithium ion battery separator by sea island COPPETPP composite negative pressure spinning according to claim 1, wherein the melt index of the PP is 1000-1500 g/10min.
7. The method for preparing the lithium ion battery diaphragm by sea island COPPETPP composite negative pressure spinning according to claim 1, wherein the alkali weight reduction treatment is carried out by the following operations: and soaking and dissolving the sea component for 10 to 15 minutes at the ageing temperature of 100 to 110 ℃ by 10 to 15g/L of sodium hydroxide alkali liquor to completely dissolve the sea component to prepare the compact lithium ion battery diaphragm.
8. The lithium ion battery separator prepared by the method for preparing the lithium ion battery separator by sea island COPPETPP composite negative pressure spinning according to claim 1.
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