CN113258209A - Low-thermal-shrinkage lithium ion battery diaphragm and preparation method thereof - Google Patents
Low-thermal-shrinkage lithium ion battery diaphragm and preparation method thereof Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention discloses a low-thermal-shrinkage lithium ion battery diaphragm and a preparation method thereof. The lithium ion battery diaphragm comprises the following raw materials: 70-75% of white oil, 10-15% of ultrahigh molecular weight polyethylene, 10-15% of high density polyethylene, 0.1-1% of propylene-ethylene block copolymer, 0.1-0.2% of modifier and 0.1-0.2% of compatilizer in percentage by weight. Has the advantages that: the stability of the membrane in the stretching process is guaranteed through limitation and accurate proportioning of raw materials, the length proportion of a stretching area, a non-stretching area and a retraction area of a transverse-pulling oven is jointly designed through limitation of temperature, stretching ratio and retraction ratio in a primary transverse process and a secondary transverse process, the transverse shrinkage caused in the transverse-pulling process is reduced, the setting temperature is increased in a heat setting area, the thermal shrinkage of the membrane is reduced, the membrane is prevented from shrinking and deforming to generate winding wrinkles when being wound, the thermal shrinkage of the membrane is prevented from being too large, the short circuit risk of the battery is reduced, and the overall performance of the lithium ion battery is improved.
Description
Technical Field
The invention relates to the technical field of battery diaphragms, in particular to a low-thermal-shrinkage lithium ion battery diaphragm and a preparation method thereof.
Background
The lithium ion battery is composed of four parts, namely a positive electrode material, a negative electrode material, a diaphragm and electrolyte. Wherein, the diaphragm is an important component of the lithium battery and plays a role in isolating the positive pole and the negative pole; meanwhile, the battery can limit the rise of current under the condition of overcharge or temperature rise of the battery, and the explosion caused by short circuit of the battery is prevented; therefore, the separator must have high mechanical strength. In addition, the performance of the diaphragm has important influence on the cycle performance and the safety performance of the lithium ion battery, and the thermal shrinkage of the diaphragm is too large, so that adverse effects such as winding rib breaking and the like are easily caused in the base film winding process; in the baking process of the diaphragm and the temperature rise process of the battery, transverse shrinkage is easy to occur to narrow the width, and the positive electrode and the negative electrode are in direct contact to cause short circuit.
In summary, the present patent provides a low thermal shrinkage lithium ion battery separator and a preparation method thereof to solve the above problems. In the preparation process of the diaphragm, the prepared diaphragm has lower thermal shrinkage performance through the optimized adjustment of a processing technology and equipment, the problems that the diaphragm is easy to wind, wrinkle and short circuit when in use are solved, and the safety of the lithium ion battery is improved.
Disclosure of Invention
The invention aims to provide a low-thermal-shrinkage lithium ion battery diaphragm and a preparation method thereof, so as to solve the problems in the background technology.
In order to solve the technical problems, the invention provides the following technical scheme:
a low-thermal-shrinkage lithium ion battery separator is prepared from the following raw materials: 70-75% of white oil, 10-15% of ultrahigh molecular weight polyethylene, 10-15% of high density polyethylene, 0.1-1% of propylene-ethylene block copolymer, 0.1-0.2% of modifier and 0.1-0.2% of compatilizer in percentage by weight.
Optimally, the molecular weight of the ultra-high molecular weight polyethylene is 1200000-4000000; the molecular weight of the high-density polyethylene is 300000-800000; the ethylene content in the propylene-ethylene block copolymer is 5-20%.
Preferably, the modifier is one or a mixture of glass fiber, glass beads, mica and talcum powder; the compatilizer is a beta crystal form nucleating agent.
Preferably, the preparation method of the low thermal shrinkage lithium ion battery diaphragm comprises the following steps:
s1: mixing materials: stirring and mixing the raw materials except the white oil uniformly to form a mixture;
s2: melt extrusion: uniformly mixing the mixture with white oil, melting and extruding to form a sheet;
s3: longitudinal stretching: longitudinally stretching the sheet to obtain a film A;
s4: primary transverse stretching: setting the length proportion of one-time transverse stretching: the ratio of the stretching area to the non-stretching area to the retraction area is (0.8-1.0) to (1.0-1.5), and the film A is transversely stretched for one time to obtain a film B;
s5: and (3) extraction: extracting the membrane B in a solvent to obtain a membrane C;
s6: secondary transverse stretching: setting the length proportion of the secondary transverse stretching: the ratio of the stretching area to the non-stretching area to the retraction area is (0.8-1.0) to (1.2-2.2), and the film C is subjected to secondary stretching to obtain a film D;
s7: heat setting: and carrying out heat setting treatment on the membrane D to obtain the lithium ion battery diaphragm.
Preferably, the method comprises the following steps: in step S2, the extrusion process parameters are: the rotating speed of the screw is 30-40 rmp, and the extrusion temperature is 150-250 ℃.
Preferably, in step S3, the process parameters of the longitudinal stretching are: the stretching temperature is 50-120 ℃, and the stretching ratio is 5-9.
Preferably, in the step S4, the primary transverse stretching temperature is 90-140 ℃; the width direction parameters of the primary transverse stretching are as follows: the stretch ratio is 6 to 10, and the stretch-recovery ratio is 10 to 14.
Preferably, in the step S6, the secondary transverse stretching temperature is 120-140 ℃; the width direction parameters of the secondary transverse stretching are as follows: the stretch ratio is 1.2-2, and the stretch-recovery ratio is 20-26.
Preferably, in step S7, the heat setting temperature is 80-100 ℃.
In the technical scheme, high-density polyethylene, ultrahigh molecular weight polyethylene, white oil, propylene-ethylene block copolymer, a modifier and a compatilizer are melted and blended; and then the low thermal shrinkage lithium ion battery diaphragm is prepared by primary and secondary stretching process. The prepared film has a thickness of 5-20 μm, a porosity of 30-50%, a gas permeability of 130-180 s/100mL, a pore size distribution interval of 0.01-0.1 μm, and a tensile strength of more than 2000kgf/cm2MD heat shrinkage < 3(105 ℃/1h), TD heat shrinkage < 0.5(105 ℃/1 h).
The process aspect is as follows: (1) in the primary and secondary transverse stretching processes, the stretching proportion and the retraction proportion are limited, the length proportion of a stretching area, a non-stretching area and a retraction area of a transverse stretching oven is designed, the transverse shrinkage caused in the transverse stretching process is reduced, the setting temperature is increased in a heat setting area, so that the heat shrinkage of the diaphragm is reduced, the diaphragm is prevented from shrinking and deforming to generate winding wrinkles when being wound, the diaphragm is prevented from excessively shrinking to reduce the short circuit risk of the battery, and the overall performance of the lithium ion battery is improved. (2) By limiting the temperature of primary and secondary transverse stretching, molecular chains with higher orientation degree are subjected to secondary de-orientation at high temperature, and mutual internal stress is released, so that the subsequent thermal shrinkage of MD/TD is reduced. (3) The degree of orientation of the molecular chains is reduced by defining the stretch ratio and the retraction ratio of the primary and secondary transverse stretching, and simultaneously by means of the retraction after TD stretching at high temperature, thereby reducing the thermal shrinkage of the separator in the TD direction. (4) The heat setting temperature is limited to 80-100 ℃, the heat setting effect cannot be achieved due to too low temperature, molecular chains with higher orientation degree are subjected to secondary orientation at high temperature, and mutual internal stress is released, so that the subsequent MD/TD heat shrinkage is reduced.
In the aspect of raw materials: (1) the molecular weights of ultra-high molecular weight polyethylene and high density polyethylene are defined because the larger the molecular weight, the poorer the thermal kinetic energy of the molecule, the weaker the de-orientation ability of the molecular chain, and the smaller the thermal shrinkage rate at the same temperature. However, too high a molecular weight results in too low a crystallization rate to facilitate subsequent processing in MD/TD properties, and too high a viscosity results in difficulty in extrusion. (2) The ethylene content in the propylene-ethylene block copolymer is limited, so that the melting point of the propylene-ethylene block copolymer is close to that of polyethylene resin, and after the propylene-ethylene block copolymer is blended with ultrahigh molecular weight polyethylene, mutual restriction is generated among crystals, the regularity of spherulites of the propylene-ethylene block copolymer is damaged, the orientation degree of molecular chains is reduced, and the thermal shrinkage rate is reduced. (3) The modifier such as mica and talcum powder can improve the rigidity of the diaphragm and reduce the shrinkage of the diaphragm. (4) The compatilizer is a beta crystal form nucleating agent, the spherulite size of the polymer is refined after the beta-nucleating agent is added, and the polymer crystal is ensured not to deform to generate larger gaps in the stretching process, so that the contraction of the diaphragm at high temperature is reduced.
Compared with the prior art, the invention has the following beneficial effects: (1) the length proportion of a stretching area, a non-stretching area and a retraction area of a transverse stretching oven is jointly designed by limiting the temperature, the stretching ratio and the retraction ratio in the primary and secondary transverse processes, so that the transverse shrinkage caused in the transverse stretching process is reduced, and meanwhile, the setting temperature is increased in a heat setting area, so that the heat shrinkage of the diaphragm is reduced, the winding wrinkles caused by the shrinkage deformation of the diaphragm during winding are prevented, the risk of short circuit of the battery is avoided being reduced due to the excessive heat shrinkage of the diaphragm, and the overall performance of the lithium ion battery is improved. (2) The raw materials are limited and accurately proportioned, the stability of the membrane in the stretching process is ensured, the thermal shrinkage rate is reduced, and the low thermal shrinkage lithium ion battery diaphragm is finally obtained by combining the stretching process.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic view of transverse stretch and retraction;
description of the drawings: 1 chain clamp.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1:
s1: mixing materials: stirring and mixing the raw materials except the white oil uniformly to form a mixture;
s2: melt extrusion: uniformly mixing and melting the mixture and white oil, setting the rotating speed of a screw to be 35rmp, the extrusion temperature to be 200 ℃, the casting temperature to be 22 ℃, and extruding to form a sheet;
s3: longitudinal stretching: the process parameters of longitudinal stretching are set as follows: stretching the sheet at a stretching temperature of 105 ℃ and a stretching ratio of 7.5 in the longitudinal direction to obtain a film A;
s4: primary transverse stretching: the technological parameters of one-time transverse stretching are set as follows: stretching temperature is 120 ℃, stretching ratio is 8.7, stretching retraction ratio is 12, the length ratio of a stretching area to a non-stretching area to a retraction area is 1:1:1, and the film A is transversely stretched for one time to obtain a film B;
s5: and (3) extraction: extracting the membrane B in a solvent to obtain a membrane C;
s6: secondary transverse stretching: setting the technological parameters of secondary transverse stretching as follows: stretching temperature is 130 ℃, stretching ratio is 1.6, stretching retraction ratio is 22, length ratio of stretching area to non-stretching area to retraction area is 1:0.8:2, and secondary stretching is carried out on the film C to obtain a film D;
s7: heat setting: setting the setting temperature to be 100 ℃, and carrying out heat setting treatment on the membrane D to obtain the lithium ion battery diaphragm.
In the technical scheme, the lithium ion battery diaphragm comprises the following raw materials: according to weight percentage, 70 percent of white oil, 15 percent of ultra-high molecular weight polyethylene, 14.4 percent of high density polyethylene, 0.4 percent of propylene-ethylene block copolymer, 0.1 percent of modifier and 0.1 percent of compatilizer; the molecular weight of the ultra-high molecular weight polyethylene is 1500000; the molecular weight of the high-density polyethylene is 400000; the ethylene content of the propylene-ethylene block copolymer is 12 percent; the modifier is mica; the compatilizer is a beta crystal form nucleating agent.
Example 2:
s1: mixing materials: stirring and mixing the raw materials except the white oil uniformly to form a mixture;
s2: melt extrusion: uniformly mixing and melting the mixture and white oil, setting the rotating speed of a screw to be 35rmp, the extrusion temperature to be 200 ℃, the casting temperature to be 22 ℃, and extruding to form a sheet;
s3: longitudinal stretching: the process parameters of longitudinal stretching are set as follows: stretching the sheet at a stretching temperature of 105 ℃ and a stretching ratio of 7.5 in the longitudinal direction to obtain a film A;
s4: primary transverse stretching: the technological parameters of one-time transverse stretching are set as follows: stretching temperature is 120 ℃, stretching ratio is 8.5, stretching retraction ratio is 12, the length ratio of a stretching area to a non-stretching area to a retraction area is 1:1:1, and the film A is transversely stretched for one time to obtain a film B;
s5: and (3) extraction: extracting the membrane B in a solvent to obtain a membrane C;
s6: secondary transverse stretching: setting the technological parameters of secondary transverse stretching as follows: stretching temperature is 130 ℃, stretching ratio is 1.5, stretching retraction ratio is 22, length ratio of stretching area to non-stretching area to retraction area is 1:0.8:2, and secondary stretching is carried out on the film C to obtain a film D;
s7: heat setting: setting the setting temperature to be 100 ℃, and carrying out heat setting treatment on the membrane D to obtain the lithium ion battery diaphragm.
In the technical scheme, the lithium ion battery diaphragm comprises the following raw materials: according to weight percentage, 70 percent of white oil, 15 percent of ultra-high molecular weight polyethylene, 14.3 percent of high density polyethylene, 0.5 percent of propylene-ethylene block copolymer, 0.1 percent of modifier and 0.1 percent of compatilizer; the molecular weight of the ultra-high molecular weight polyethylene is 1500000; the molecular weight of the high-density polyethylene is 400000; the ethylene content of the propylene-ethylene block copolymer is 12 percent; the modifier is talcum powder; the compatilizer is a beta crystal form nucleating agent.
Example 3:
s1: mixing materials: stirring and mixing the raw materials except the white oil uniformly to form a mixture;
s2: melt extrusion: uniformly mixing and melting the mixture and white oil, setting the rotating speed of a screw to be 35rmp, the extrusion temperature to be 200 ℃, the casting temperature to be 22 ℃, and extruding to form a sheet;
s3: longitudinal stretching: the process parameters of longitudinal stretching are set as follows: stretching the sheet at a stretching temperature of 105 ℃ and a stretching ratio of 7.5 in the longitudinal direction to obtain a film A;
s4: primary transverse stretching: the technological parameters of one-time transverse stretching are set as follows: stretching temperature is 120 ℃, stretching ratio is 8.6, stretching retraction ratio is 12, the length ratio of a stretching area to a non-stretching area to a retraction area is 1:1:1, and the film A is transversely stretched for one time to obtain a film B;
s5: and (3) extraction: extracting the membrane B in a solvent to obtain a membrane C;
s6: secondary transverse stretching: setting the technological parameters of secondary transverse stretching as follows: stretching temperature is 130 ℃, stretching ratio is 1.55, stretching retraction ratio is 22, length ratio of stretching area to non-stretching area to retraction area is 1:0.8:2, and secondary stretching is carried out on the film C to obtain a film D;
s7: heat setting: setting the setting temperature to be 100 ℃, and carrying out heat setting treatment on the membrane D to obtain the lithium ion battery diaphragm.
In the technical scheme, the lithium ion battery diaphragm comprises the following raw materials: according to weight percentage, 70 percent of white oil, 15 percent of ultra-high molecular weight polyethylene, 14.2 percent of high density polyethylene, 0.06 percent of propylene-ethylene block copolymer, 0.1 percent of modifier and 0.1 percent of compatilizer; the molecular weight of the ultra-high molecular weight polyethylene is 1500000; the molecular weight of the high-density polyethylene is 400000; the ethylene content of the propylene-ethylene block copolymer is 12 percent; the modifier is glass fiber; the compatilizer is a beta crystal form nucleating agent.
Example 4:
s1: mixing materials: stirring and mixing the raw materials except the white oil uniformly to form a mixture;
s2: melt extrusion: uniformly mixing and melting the mixture and white oil, setting the screw rotation speed at 30rmp, the extrusion temperature at 150 ℃ and the casting temperature at 22 ℃, and extruding to form a sheet;
s3: longitudinal stretching: the process parameters of longitudinal stretching are set as follows: stretching the sheet longitudinally at a stretching temperature of 50 ℃ and a stretching ratio of 5 to obtain a film A;
s4: primary transverse stretching: the technological parameters of one-time transverse stretching are set as follows: stretching at 90 ℃, at a stretch ratio of 6 and a stretch-retraction ratio of 10, wherein the length ratio of a stretch zone to a non-stretch zone to a retraction zone is 0.8:0.8:1.2, and performing primary transverse stretching on the film A to obtain a film B;
s5: and (3) extraction: extracting the membrane B in a solvent to obtain a membrane C;
s6: secondary transverse stretching: setting the technological parameters of secondary transverse stretching as follows: stretching temperature is 120 ℃, stretching ratio is 1.2, stretching retraction ratio is 20, length ratio of stretching area to non-stretching area to retraction area is 0.8:1:1.2, and secondary stretching is carried out on the film C to obtain a film D;
s7: heat setting: setting the setting temperature to 80 ℃, and carrying out heat setting treatment on the membrane D to obtain the lithium ion battery diaphragm.
In the technical scheme, the lithium ion battery diaphragm comprises the following raw materials: 72 percent of white oil, 10 percent of ultra-high molecular weight polyethylene, 10 percent of high density polyethylene, 0.1 percent of propylene-ethylene block copolymer, 0.15 percent of modifier and 0.15 percent of compatilizer; the molecular weight of the ultra-high molecular weight polyethylene is 1200000; the high density polyethylene has a molecular weight of 300000; the ethylene content in the propylene-ethylene block copolymer is 5%; the modifier is a mixture of glass fiber and talcum powder; the compatilizer is a beta crystal form nucleating agent.
Example 5:
s1: mixing materials: stirring and mixing the raw materials except the white oil uniformly to form a mixture;
s2: melt extrusion: uniformly mixing and melting the mixture and white oil, setting the rotating speed of a screw at 40rmp, the extrusion temperature at 250 ℃ and the casting temperature at 22 ℃, and extruding to form a sheet;
s3: longitudinal stretching: the process parameters of longitudinal stretching are set as follows: stretching the sheet longitudinally at a stretching temperature of 120 ℃ and a stretching ratio of 9 to obtain a film A;
s4: primary transverse stretching: the technological parameters of one-time transverse stretching are set as follows: stretching temperature is 140 ℃, stretching ratio is 10, stretching retraction ratio is 14, the ratio of stretching area to non-stretching area to retraction area is 0.9:0.9:1.5, and the film A is transversely stretched for one time to obtain a film B;
s5: and (3) extraction: extracting the membrane B in a solvent to obtain a membrane C;
s6: secondary transverse stretching: setting the technological parameters of secondary transverse stretching as follows: stretching the film C at 140 ℃, wherein the stretching ratio is 1.2-2, the stretching retraction ratio is 20-26, the ratio of a stretching area to a non-stretching area to a retraction area is 0.9:0.9:2.2, and performing secondary stretching to obtain a film D;
s7: heat setting: setting the setting temperature to 90 ℃, and carrying out heat setting treatment on the membrane D to obtain the lithium ion battery diaphragm.
In the technical scheme, the lithium ion battery diaphragm comprises the following raw materials: according to weight percentage, 75 percent of white oil, 13 percent of ultra-high molecular weight polyethylene, 15 percent of high density polyethylene, 1 percent of propylene-ethylene block copolymer, 0.2 percent of modifier and 0.2 percent of compatilizer; the molecular weight of the ultra-high molecular weight polyethylene is 4000000; the high density polyethylene has a molecular weight of 800000; the ethylene content in the propylene-ethylene block copolymer is 20%; the modifier is a mixture of glass fiber and glass beads; the compatilizer is a beta crystal form nucleating agent.
Example 6: no propylene-ethylene block copolymer, modifier, compatibilizer were added; the rest is the same as in example 3.
Example 7: the proportion of the stretching area to the non-stretching area to the retraction area of the primary transverse pulling and the secondary transverse pulling is not set; the rest is the same as in example 3.
Experiment: the lithium ion battery diaphragm prepared in the embodiment 1-7 is characterized in that:
the air permeability value of the diaphragm is tested by a Gurley air permeability instrument.
And secondly, calculating the porosity of the diaphragm by adopting a weighing method.
And measuring the tensile strength of the diaphragm by adopting a tensile testing instrument.
Placing the diaphragm in an oven at 105 ℃ for baking for 1 hour to test the size change of the diaphragm, and calculating the thermal shrinkage of the diaphragm by a formula: heat shrinkage (105 ℃/1h) — (original size-size after baking)/original size × 100%.
The data obtained are shown in table 1:
table 1:
and (4) conclusion: from the data of examples 1 to 5, it is clear that: the porosity of the prepared film is more than 35 percent, the air permeability value is more than 160s/100mL, and the tensile strength is more than 2000kgf/cm2The MD heat shrinkage is less than 2, the TD heat shrinkage is less than 0.5, and the performance is excellent.
Comparing the data of example 6 and example 1, it can be found that: the MD/TD heat shrinkage is significantly reduced compared to the previous case because: the modifier such as mica and talcum powder can improve the rigidity of the diaphragm and reduce the shrinkage of the diaphragm. The compatilizer is a beta crystal form nucleating agent, the spherulite size of the polymer is refined after the beta-nucleating agent is added, and the polymer crystal is ensured not to deform to generate larger gaps in the stretching process, so that the contraction of the diaphragm at high temperature is reduced. The compatilizer helps the modifier to increase the biocompatible phase, and the compatilizer and the modifier synergistically improve the tensile strength and reduce the heat shrinkage.
Comparing the data of example 7 and example 3, it can be found that: the porosity, air permeability, tensile strength and the previous values are similar in example 7, but the MD/TD heat shrinkage is significantly higher than before. The reason is that: in the primary and secondary transverse stretching processes, the stretching proportion and the retraction proportion in the width direction are limited, the length proportion of a stretching area, a non-stretching area and a retraction area is accurately designed, the transverse shrinkage caused in the transverse stretching process is reduced, and meanwhile, the setting temperature is increased in a heat setting area, so that the heat shrinkage of the diaphragm is reduced, the diaphragm is prevented from shrinking and deforming to generate winding wrinkles when being wound, the diaphragm is prevented from excessively shrinking to reduce the short circuit risk of the battery, and the overall performance of the lithium ion battery is improved.
In conclusion, the process can prepare the battery diaphragm with low thermal shrinkage on the premise of keeping other performance parameters from changing obviously.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A low thermal contraction lithium ion battery diaphragm is characterized in that: the lithium ion battery diaphragm comprises the following raw materials: 70-75% of white oil, 10-15% of ultrahigh molecular weight polyethylene, 10-15% of high density polyethylene, 0.1-1% of propylene-ethylene block copolymer, 0.1-0.2% of modifier and 0.1-0.2% of compatilizer in percentage by weight.
2. The low thermal shrinkage lithium ion battery separator according to claim 1, wherein: the molecular weight of the ultra-high molecular weight polyethylene is 1200000-4000000; the molecular weight of the high-density polyethylene is 300000-800000; the ethylene content in the propylene-ethylene block copolymer is 5-20%.
3. The low thermal shrinkage lithium ion battery separator according to claim 1, wherein: the modifier is one or a mixture of glass fiber, glass beads, mica and talcum powder; the compatilizer is a beta crystal form nucleating agent.
4. A preparation method of a low thermal shrinkage lithium ion battery diaphragm is characterized by comprising the following steps: the method comprises the following steps:
s1: mixing materials: stirring and mixing the raw materials except the white oil uniformly to form a mixture;
s2: melt extrusion: uniformly mixing the mixture with white oil, melting and extruding to form a sheet;
s3: longitudinal stretching: longitudinally stretching the sheet to obtain a film A;
s4: primary transverse stretching: setting the length proportion of one-time transverse stretching: the ratio of the stretching area to the non-stretching area to the retraction area is (0.8-1.0) to (1.0-1.5), and the film A is transversely stretched for one time to obtain a film B;
s5: and (3) extraction: extracting the membrane B in a solvent to obtain a membrane C;
s6: secondary transverse stretching: setting the length proportion of the secondary transverse stretching: the ratio of the stretching area to the non-stretching area to the retraction area is (0.8-1.0) to (1.2-2.2), and the film C is subjected to secondary stretching to obtain a film D;
s7: heat setting: and carrying out heat setting treatment on the membrane D to obtain the lithium ion battery diaphragm.
5. The preparation method of the low thermal shrinkage lithium ion battery separator according to claim 4, characterized in that: the method comprises the following steps: in step S2, the extrusion process parameters are: the rotating speed of the screw is 30-40 rmp, and the extrusion temperature is 150-250 ℃.
6. The preparation method of the low thermal shrinkage lithium ion battery separator according to claim 4, characterized in that: in step S3, the process parameters of longitudinal stretching are: the stretching temperature is 50-120 ℃, and the stretching ratio is 5-9.
7. The preparation method of the low thermal shrinkage lithium ion battery separator according to claim 4, characterized in that: in the step S4, the primary transverse stretching temperature is 90-140 ℃; the width direction parameters of the primary transverse stretching are as follows: the stretch ratio is 6 to 10, and the stretch-recovery ratio is 10 to 14.
8. The preparation method of the low thermal shrinkage lithium ion battery separator according to claim 4, characterized in that: in the step S6, the secondary transverse stretching temperature is 120-140 ℃; the width direction parameters of the secondary transverse stretching are as follows: the stretch ratio is 1.2-2, and the stretch-recovery ratio is 20-26.
9. The preparation method of the low thermal shrinkage lithium ion battery separator according to claim 4, characterized in that: in step S7, the heat setting temperature is 80-100 ℃.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113809472A (en) * | 2021-08-30 | 2021-12-17 | 重庆恩捷纽米科技股份有限公司 | High-elongation polyolefin microporous membrane, preparation method thereof and battery |
| CN114094284A (en) * | 2021-11-16 | 2022-02-25 | 无锡恩捷新材料科技有限公司 | Novel cross-linked diaphragm and preparation method thereof, battery and electronic equipment |
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2021
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113809472A (en) * | 2021-08-30 | 2021-12-17 | 重庆恩捷纽米科技股份有限公司 | High-elongation polyolefin microporous membrane, preparation method thereof and battery |
| CN113809472B (en) * | 2021-08-30 | 2024-06-25 | 重庆恩捷纽米科技股份有限公司 | High-elongation polyolefin microporous membrane, preparation method thereof and battery |
| CN114094284A (en) * | 2021-11-16 | 2022-02-25 | 无锡恩捷新材料科技有限公司 | Novel cross-linked diaphragm and preparation method thereof, battery and electronic equipment |
| CN114094284B (en) * | 2021-11-16 | 2024-05-10 | 苏州捷力新能源材料有限公司 | Novel crosslinked diaphragm, preparation method thereof, battery and electronic equipment |
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Application publication date: 20210813 |