CN113285174B - Sea-island polyphenylene sulfide composite battery diaphragm and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of battery diaphragm manufacturing, and discloses a sea-island type polyphenylene sulfide composite battery diaphragm and a preparation method thereof. Polyphenylene sulfide composite fibers, and then heat-treated sea-island-type polyphenylene sulfide composite fibers are cut short, and then mixed with nanofibers. diaphragm. The preparation process of the invention is simple and convenient, does not need to use an organic solvent, is suitable for large-scale production, improves the electrolyte absorption of the battery diaphragm, and the prepared sea-island type polyphenylene sulfide composite battery diaphragm has good thermal stability and chemical stability. properties, mechanical properties and flame retardancy. The preparation method of the invention is suitable for preparing the separator of the sea-island type polyphenylene sulfide composite battery, and the prepared sea-island type polyphenylene sulfide composite battery separator is suitable for the lithium battery.

Description

Sea-island type polyphenylene sulfide composite battery separator and preparation method thereof

technical field

The invention belongs to the technical field of battery diaphragm manufacturing, and relates to polyphenylene sulfide composite fibers, in particular to a sea-island type polyphenylene sulfide composite battery diaphragm and a preparation method thereof.

Background technique

Lithium-ion batteries have become the representative of high-performance batteries because of their advantages such as high energy density, small self-discharge, long cycle life, no memory effect, and low environmental pollution. They are used in smartphones, notebook computers, digital cameras, MP3 And other small household appliances have been widely used. In the composition of lithium-ion batteries, the diaphragm occupies a very important position, which directly affects the performance and safety of lithium-ion batteries. At present, polyolefin separators occupy a dominant position in the separator market due to their stable chemical properties, low cost, and uniform pore size distribution. However, polyolefin separators also have disadvantages such as poor electrolyte wettability and poor thermal stability. In order to meet the high-temperature dimensional stability and electrolyte absorption performance requirements of high-power lithium-ion batteries, the development of high-performance separators has become the focus of researchers.

Polyphenylene sulfide (PPS) is a polymer containing repeating structural units of p-phenylene sulfide in the molecule. It is a new type of functional engineering plastic with good heat resistance, excellent chemical resistance and flame retardancy. , which can serve as a promising substitute for lithium-ion battery separators.

The invention patent of China Patent No. CN104795525A discloses "a melt-blown polyphenylene sulfide non-woven lithium battery separator and its preparation method". Then, the superfine fiber web is subjected to hot rolling and heat setting treatment to obtain a melt-blown polyphenylene sulfide non-woven lithium battery separator. The PPS non-woven fabric substrate prepared by the melt-blown method forms a three-dimensional fiber network structure through entangled fibers. This structure provides high porosity for the lithium-ion battery separator, but the fibers prepared by the melt-blown method have low strength, The diaphragm pore size is large and unevenly distributed. The invention patent of Chinese Patent No. CN112054146A discloses "a method for producing battery separators made of PPS materials and the film made thereof". The preparation method in this patent is to add PPS materials in a weight ratio of 1%-70% into PP and PE, and then produce a film filled with PPS material with rich nano-scale pores according to the PE film-forming process through steps such as extrusion, stretching, and extension. However, this method is complicated in process, technically difficult, and not suitable for Mass production.

Contents of the invention

The purpose of the present invention is to provide a sea-island type polyphenylene sulfide composite battery separator and its preparation method, so as to overcome the shortcomings in the prior art.

The present invention is for realizing the above object, and the technical method adopted is as follows:

A method for preparing a sea-island type polyphenylene sulfide composite battery diaphragm, comprising the following steps:

S1. Preparation of sea-island polyphenylene sulfide composite fibers: mixing polyphenylene sulfide and alkali-soluble polyester and then melt-spinning to obtain sea-island polyphenylene sulfide composite fibers;

S2. Preparation of sea-island type polyphenylene sulfide composite battery separator: the sea-island type polyphenylene sulfide composite fiber is cut short after heat treatment, and then mixed with nanofibers, dispersed and beaten, thawed, paper-making, and hot-pressed to obtain the sea-island type Polyphenylene sulfide composite battery separator.

As a limitation: the melt index of polyphenylene sulfide in step S1 is 50-500g/10min, the melt index of alkali-soluble polyester is 10-50g/10min, and the polyphenylene sulfide and alkali-soluble polyester are dried before mixing. The temperature is 80-160°C, and the drying time is 12-24h.

As a further limitation: the mass ratio of polyphenylene sulfide to alkali-soluble polyester is 3:7-7:3.

As a further limitation: the fineness of the sea-island type polyphenylene sulfide composite fiber prepared in step S1 is 0.9-5 μm, and its fiber is round; the length of the sea-island type polyphenylene sulfide composite fiber cut short in step S2 is 5 The mass fraction of sea-island polyphenylene sulfide composite fibers of -8mm is 0-25%, the mass fraction of sea-island polyphenylene sulfide composite fibers of 1-2mm length is 0-25%, and the sea-island polyphenylene sulfide composite fibers of 2-5mm The mass fraction of the phenylene sulfide composite fiber is 50-100%.

As another limitation: the heat treatment temperature in step S2 is 80-150° C., and the heat treatment time is 10-60 min.

As a limitation: the nanofibers in step S2 are aromatic nanofibers, which are cut by electrospinning and high-speed carding machine, and the fibers are round, with a diameter of 100-1000nm and a fiber length of 1- 3mm, the mass fraction of chopped polyphenylene sulfide composite fibers in the mixture of aromatic nanofibers and chopped polyphenylene sulfide composite fibers is 80-95%, the rest is aromatic nanofibers, and the dispersion medium is water , the beating concentration is 3-5%wt, the stirring impeller speed is 3000-3500rad/min during the flaking process, the flaking time is 10-15min, the online concentration is 0.03-0.8% in the papermaking process, and the hot pressing pressure in the hot pressing process is 10-20MPa, hot pressing temperature is 150-230℃.

As another limitation: the nanofibers in step S2 are natural nanofibers, which are cut by a dissolution method and a high-speed carding machine, and the fibers are round, with a diameter of 100-1000nm and a fiber length of 1- 3mm, the mass fraction of chopped polyphenylene sulfide composite fibers in the mixture of natural nanofibers and chopped polyphenylene sulfide composite fibers is 80-95%, the rest is natural nanofibers, the dispersion medium is water, and beating The concentration is 3-5%wt, the rotation speed of the stirring impeller is 3000-3500rad/min during the decompression process, the decompression time is 10-15min, the online concentration is 0.03-0.8% during the papermaking process, and the hot pressing pressure during the hot pressing process is 10- 20MPa, hot pressing temperature is 150-230℃.

As another limitation: the nanofibers in step S2 are inorganic nanofibers, which are cut by a flame method and a high-speed carding machine, and the fibers are round, with a diameter of 100-1000nm and a fiber length of 1- 3mm, the mass fraction of chopped polyphenylene sulfide composite fibers in the mixture of inorganic nanofibers and chopped polyphenylene sulfide composite fibers is 80-95%, the rest is inorganic nanofibers, the dispersion medium is water, and the beating The concentration is 3-5%wt, the rotation speed of the stirring impeller is 3000-3500rad/min during the decompression process, the decompression time is 10-15min, the online concentration is 0.03-0.8% during the papermaking process, and the hot pressing pressure during the hot pressing process is 10- 20MPa, hot pressing temperature is 150-230℃.

The present invention also provides the sea-island type polyphenylene sulfide composite battery diaphragm obtained by the above-mentioned preparation method of the sea-island type PPS composite battery diaphragm. The prepared sea-island type polyphenylene sulfide composite battery diaphragm has a porosity of 40-70%, and 0.1-1μm, thickness 10-30μm, electrolyte absorption rate 250-350%, tensile strength 15-50MPa, limiting oxygen index 38-40.

The present invention has adopted above-mentioned scheme, compared with prior art, the beneficial effect that obtains is:

(1) The preparation method of the sea-island type polyphenylene sulfide composite battery diaphragm provided by the present invention, polyphenylene sulfide (PPS) has good heat resistance, excellent chemical corrosion resistance and flame retardancy, and aromatic nanofibers have Excellent thermal stability, mechanical properties, chemical stability, corrosion resistance and other properties, natural nanofibers have excellent mechanical properties, good biodegradability and other properties, inorganic nanofibers have excellent thermal stability, flame retardant Sea-island type polyphenylene sulfide composite battery separator has excellent mechanical strength and uniformity by mixing sea-island polyphenylene sulfide composite fibers with nanofibers, dispersing and beating, dispersing, papermaking, and hot pressing. , flame retardancy, puncture resistance, thermal stability, chemical stability and other properties, and the preparation process is simple and convenient, without the use of organic solvents, suitable for large-scale production;

(2) The island-in-the-sea type polyphenylene sulfide composite battery separator provided by the present invention and the preparation method thereof, by preliminarily regulating the porosity, pore diameter and thickness of the battery separator by using island-in-sea type polyphenylene sulfide composite fibers of different lengths and deniers, Then mix a small amount of nanofibers to further realize the homogenization and miniaturization of the pore size of the battery diaphragm, and at the same time, improve the electrolyte liquid absorption of the battery diaphragm;

(3) The sea-island type polyphenylene sulfide composite battery diaphragm prepared by the preparation method provided by the present invention has high electrolyte liquid absorption, and has good thermal stability, chemical stability, mechanical properties and flame retardancy, etc. , to meet the needs of lithium-ion battery separators, improve the safety of lithium-ion batteries and prolong their service life.

In summary, the preparation method of the sea-island type polyphenylene sulfide composite battery diaphragm provided by the present invention is simple and convenient in the preparation process, does not need to use organic solvents, is suitable for large-scale production, regulates the battery diaphragm, and improves the electrolyte of the battery diaphragm. Liquid absorption, the prepared sea-island polyphenylene sulfide composite battery separator has good thermal stability, chemical stability, mechanical properties and flame retardancy, which improves the safety of lithium-ion batteries and prolongs their service life .

The preparation method of the invention is suitable for preparing the sea-island type polyphenylene sulfide composite battery diaphragm, and the prepared sea-island type polyphenylene sulfide composite battery diaphragm is suitable for lithium batteries.

Description of drawings

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Figure 1a and Figure 1b are scanning electron micrographs of polyphenylene sulfide ultrafine fibers, Figure 1c and Figure 1d are scanning electron micrographs of polyimide nanofibers, and Figure 1e and Figure 1f are sea-islands prepared in Example 1 of the present invention The scanning electron microscope image of the type polyphenylene sulfide composite battery separator;

Fig. 2 is the mapping diagram of the sea-island type polyphenylene sulfide composite battery separator prepared in Example 1 of the present invention;

Fig. 3a-e is the thermal stability performance comparison diagram of the island-in-the-sea polyphenylene sulfide composite battery diaphragm prepared in Example 1 of the present invention and Celgard commercial film;

Fig. 4a and Fig. 4b are the flame retardant performance test diagrams of Celgard commercial film; Fig. 4c and Fig. 4d are the flame retardant performance test diagrams of the island-in-the-sea polyphenylene sulfide composite battery diaphragm prepared in Example 1 of the present invention;

Figure 5a and Figure 5b are scanning electron micrographs of polyphenylene sulfide ultrafine fibers, Figure 5c and Figure 5d are scanning electron micrographs of cellulose nanofibers, Figure 5e and Figure 5f are island-in-the-sea polymers prepared in Example 7 of the present invention. Scanning electron microscope image of phenylene sulfide composite battery separator;

Fig. 6 is a mapping diagram of the sea-island polyphenylene sulfide composite battery separator prepared in Example 7 of the present invention;

Figure 7a-e is a comparison chart of the thermal stability performance of the sea-island type polyphenylene sulfide composite battery separator prepared in Example 7 of the present invention and Celgard's commercial film;

Figure 8a and Figure 8b are the flame retardant performance test charts of Celgard commercial membranes; Figure 8c and Figure 8d are the flame retardant performance test charts of the sea-island polyphenylene sulfide composite battery separator prepared in Example 7 of the present invention;

Figure 9a and Figure 9b are scanning electron micrographs of polyphenylene sulfide ultrafine fibers, Figure 9c and Figure 9d are scanning electron micrographs of glass nanofibers, Figure 9e and Figure 9f are sea-island polyphenylene sulfide prepared in Example 13 of the present invention Scanning electron microscope image of thioether composite battery separator;

Figure 10 is a mapping diagram of the sea-island type polyphenylene sulfide composite battery separator prepared in Example 13 of the present invention;

Figures 11a-e are comparison diagrams of the thermal stability of the sea-island type polyphenylene sulfide composite battery separator prepared in Example 13 of the present invention and Celgard's commercial film;

Figure 12a and Figure 12b are the flame retardant performance test charts of Celgard's commercial film; Figure 12c and Figure 12d are the flame retardant performance test charts of the sea-island type polyphenylene sulfide composite battery separator prepared in Example 13 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the examples, but those skilled in the art should understand that the present invention is not limited to the following examples, and any improvements and equivalent changes made on the basis of the specific examples of the present invention are within the scope of the present invention within the scope of the claims.

Example 1-6 Preparation method of sea-island polyphenylene sulfide composite battery diaphragm

Examples 1-6 are respectively a preparation method of a sea-island type polyphenylene sulfide composite battery diaphragm, and the process parameters in the preparation process are shown in Table 1. The specific preparation process includes the following steps:

S1. Preparation of sea-island polyphenylene sulfide composite fibers: dry polyphenylene sulfide (PPS) with a melt index of 50-500g/10min and alkali-soluble polyester (PET) with a melt index of 10-50g/10min , the drying temperature is 80-160°C, the drying time is 12-24h, and then mixed at a mass ratio of 3:7-7:3, and melt-spun to obtain islands with a fineness of 0.9-5μm and round fibers Type polyphenylene sulfide composite fiber; during the melt spinning process, the extrusion temperature of the screw is 315-325°C, the melting pressure of the screw is 60-120bar, the temperature of the spinning box is 315-325°C, and the pressure of the spinning assembly is less than 60kgf/ cm ² , the spinning speed is 600-1000m/min, and the draft ratio is 3.6-4.3 times.

S2. Preparation of sea-island polyphenylene sulfide composite battery diaphragm: heat-treat the sea-island polyphenylene sulfide composite fiber and cut it short. Relevant data Weigh the sea-island type polyphenylene sulfide composite fiber with a length of 5-8mm in the mass fraction of 0-25% in the shortened sea-island type polyphenylene sulfide composite fiber, and the sea-island type polyphenylene sulfide with a length of 1-2mm The mass fraction of composite fibers is 0-25%, the mass fraction of sea-island polyphenylene sulfide composite fibers with a length of 2-5mm is 50-100%, and the chopped sea-island polyphenylene sulfide composite fibers are combined with electrospinning It is mixed with aromatic nanofibers cut by a high-speed carding machine, the fibers are round, the diameter is 100-1000nm, and the fiber length is 1-3mm, and the mass fraction of the chopped polyphenylene sulfide composite fiber is 80 -95%, and the rest are aromatic nanofibers, which are dispersed and beaten with a water level dispersion medium. Papermaking is carried out with a concentration of 0.03-0.8%, and finally hot-pressed, with a hot-pressing pressure of 10-20MPa and a hot-pressing temperature of 150-230°C, to obtain a sea-island type polyphenylene sulfide composite battery separator.

The aromatic nanofibers in Examples 1-6 are one of polyimide nanofibers, polysulfone nanofibers, aramid nanofibers, and polyether ether ketone nanofibers.

Table 1 Process parameters in the preparation of sea-island polyphenylene sulfide composite battery separators in Examples 1-6

See Table 2 for specific performance indicators of the sea-island type polyphenylene sulfide composite battery separator prepared by the above preparation method.

Table 2 The performance index of the sea-island type polyphenylene sulfide composite battery separator prepared in Examples 1-6

It can be seen from Table 2 that the island-in-the-sea type polyphenylene sulfide composite battery separator prepared in Examples 1-6 has a porosity of 40-70%, a pore diameter of 0.1-1 μm, and a thickness of 10-30 μm. The liquid absorption rate is 250-350%, the electrolyte liquid absorption performance is high, the tensile strength is 15-50MPa, and the mechanical properties are good. In addition, the limiting oxygen index of the sea-island type polyphenylene sulfide composite battery diaphragm obtained in Examples 1-6 is 38-40, and the limiting oxygen index of the existing Celgard commercial film is 18, so the obtained in Examples 1-6 of the present invention The sea-island polyphenylene sulfide composite battery separator has good flame retardancy.

Fig. 1a and Fig. 1b are the scanning electron micrographs of polyphenylene sulfide ultrafine fibers, Fig. 1c and Fig. 1d are the scanning electron micrographs of polyimide nanofibers, Fig. 1e and Fig. 1f are the island-in-the-sea polymers prepared in Example 1. The scanning electron microscope image of the phenylene sulfide composite battery separator, as can be seen from Figure 1, the pore size of the sea-island polyphenylene sulfide composite battery separator is reduced after adding polyimide nanofibers. The mapping diagram of the sea-island type polyphenylene sulfide composite battery diaphragm prepared in Example 1 is shown in Figure 2, and the thermal stability performance comparison between the sea-island type polyphenylene sulfide composite battery diaphragm and the Celgard commercial film is shown in Figure 3. In 3, a-e are the dimensional changes of sea-island polyphenylene sulfide composite battery separators and Celgard commercial membranes at 25°C, 150°C, 175°C, 200°C, and 230°C, Celgard means Celgard commercial membranes, and PSS/PI means Example 1 Island-in-the-sea polyphenylene sulfide composite battery separator, in which PSS is polyphenylene sulfide and PI is polyimide. It can be seen from Figure 3 that the island-in-sea polyphenylene sulfide composite battery separator is at 25°C, 150°C, and 175°C , 200°C, and 230°C have little change in size, while the size of Celgard commercial membranes changes significantly at 5°C, 150°C, 175°C, 200°C, and 230°C, so the thermal stability of sea-island polyphenylene sulfide composite battery separators Better than Celgard commercial membrane; the flame retardant performance comparison of sea-island polyphenylene sulfide composite battery separator and Celgard commercial membrane is shown in Figure 4, Figure 4a is the Celgard commercial membrane before combustion, and Figure 4b is the Celgard commercial membrane after combustion , Figure 4c is the island-in-sea polyphenylene sulfide composite battery separator before combustion, and Figure 4d is the island-in-sea polyphenylene sulfide composite battery separator after combustion. The performance is better than that of Celgard commercial film, and the performance of the sea-island type polyphenylene sulfide composite battery separator prepared in Examples 2-6 is similar to that of the sea-island type polyphenylene sulfide composite battery separator prepared in Example 1.

Example 7-12 Preparation method of sea-island polyphenylene sulfide composite battery diaphragm

Examples 7-12 are respectively a preparation method of a sea-island type polyphenylene sulfide composite battery diaphragm, and the process parameters in the preparation process are shown in Table 3. The specific preparation process includes the following steps:

S1. Preparation of sea-island polyphenylene sulfide composite fibers: dry polyphenylene sulfide (PPS) with a melt index of 50-500g/10min and alkali-soluble polyester (PET) with a melt index of 10-50g/10min , the drying temperature is 80-160°C, the drying time is 12-24h, and then mixed at a mass ratio of 3:7-7:3, and melt-spun to obtain islands with a fineness of 0.9-5μm and round fibers Type polyphenylene sulfide composite fiber; during the melt spinning process, the extrusion temperature of the screw is 315-325°C, the melting pressure of the screw is 60-120bar, the temperature of the spinning box is 315-325°C, and the pressure of the spinning assembly is less than 60kgf/ cm ² , the spinning speed is 600-1000m/min, and the draft ratio is 3.6-4.3 times.

S2. Preparation of sea-island polyphenylene sulfide composite battery diaphragm: heat-treat the sea-island polyphenylene sulfide composite fiber and cut it short. Relevant data Weigh the sea-island type polyphenylene sulfide composite fiber with a length of 5-8mm in the mass fraction of 0-25% in the shortened sea-island type polyphenylene sulfide composite fiber, and the sea-island type polyphenylene sulfide with a length of 1-2mm The mass fraction of the composite fiber is 0-25%, the mass fraction of the sea-island type polyphenylene sulfide composite fiber with a length of 2-5mm is 50-100%, and the sea-island type polyphenylene sulfide composite fiber after being chopped is combined with the dissolution method and Cut by a high-speed carding machine, the fiber is round, the diameter is 100-1000nm, and the fiber length is 1-3mm mixed with natural nanofibers, wherein the mass fraction of the chopped polyphenylene sulfide composite fiber is 80-95 %, the rest are natural nanofibers, and the water level dispersion medium is used for dispersing and beating. Papermaking is carried out at a concentration of 0.8%, and finally hot-pressed with a hot-pressing pressure of 10-20MPa and a hot-pressing temperature of 150-230°C to obtain a sea-island type polyphenylene sulfide composite battery separator.

The natural nanofibers in Examples 7-12 are one of cellulose nanofibers, chitin nanofibers and lignin nanofibers.

Table 3 Process parameters and performance indicators in the preparation of sea-island polyphenylene sulfide composite battery separators in Examples 7-12

For the sea-island type polyphenylene sulfide composite battery separator prepared by the above preparation method, see Table 4 for specific performance indicators.

The performance index of the sea-island type polyphenylene sulfide composite battery diaphragm that table 4 embodiment 7-12 makes

It can be seen from Table 4 that the island-in-the-sea type polyphenylene sulfide composite battery separator prepared in Examples 7-12 has a porosity of 40-70%, a pore diameter of 0.1-1 μm, and a thickness of 10-30 μm. The liquid absorption rate is 250-350%, the electrolyte liquid absorption performance is high, the tensile strength is 15-50MPa, and the mechanical properties are good. In addition, the limiting oxygen index of the sea-island type polyphenylene sulfide composite battery diaphragm obtained in Examples 7-12 is 38-40, and the limiting oxygen index of the existing Celgard commercial film is 18, so the obtained in Examples 7-12 of the present invention The sea-island polyphenylene sulfide composite battery separator has good flame retardancy.

Figure 5a and Figure 5b are scanning electron micrographs of polyphenylene sulfide ultrafine fibers, Figure 5c and Figure 5d are scanning electron micrographs of cellulose nanofibers, and Figure 5e and Figure 5f are sea-island polyphenylene sulfide prepared in Example 7 The scanning electron microscope image of the ether composite battery separator. It can be seen from Figure 5 that the pore size of the sea-island polyphenylene sulfide composite battery separator is reduced after adding cellulose nanofibers. The mapping diagram of the sea-island type polyphenylene sulfide composite battery diaphragm prepared in Example 7 is shown in Figure 6, and the thermal stability performance comparison between the sea-island type polyphenylene sulfide composite battery diaphragm and the Celgard commercial film is shown in Figure 7. In 7, a-e are the dimensional changes of sea-island polyphenylene sulfide composite battery separators and Celgard commercial membranes at 25°C, 150°C, 175°C, 200°C, and 230°C, Celgard means Celgard commercial membranes, and PSS/CNF means Example 7 The island-in-the-sea polyphenylene sulfide composite battery separator, in which PSS is polyphenylene sulfide, and CNF is cellulose nanofiber. It can be seen from Figure 7 that the island-in-sea polyphenylene sulfide composite battery separator is °C, 200 °C, and 230 °C have almost no change in size, while the size of Celgard commercial membranes changes significantly at 5 °C, 150 °C, 175 °C, 200 °C, and 230 °C, so the thermal stability of the sea-island polyphenylene sulfide composite battery separator The performance is better than that of Celgard commercial film; the flame retardant performance comparison of sea-island polyphenylene sulfide composite battery separator and Celgard commercial film is shown in Figure 8, Figure 8a is the Celgard commercial film before combustion, and Figure 8b is the Celgard commercial film after combustion Figure 8c is the separator of the sea-island type polyphenylene sulfide composite battery before combustion, and Figure 8d is the diaphragm of the sea-island type polyphenylene sulfide composite battery after combustion. Combustibility is better than Celgard commercial film, and the performance of the sea-island polyphenylene sulfide composite battery separator prepared in Examples 8-12 is similar to that of the sea-island polyphenylene sulfide composite battery separator prepared in Example 7.

Example 13-18 Preparation method of sea-island polyphenylene sulfide composite battery diaphragm

Examples 13-18 are respectively a preparation method of a sea-island type polyphenylene sulfide composite battery separator. The process parameters during the preparation process are shown in Table 5. The specific preparation process includes the following steps:

S1. Preparation of sea-island polyphenylene sulfide composite fibers: dry polyphenylene sulfide (PPS) with a melt index of 50-500g/10min and alkali-soluble polyester (PET) with a melt index of 10-50g/10min , the drying temperature is 80-160°C, the drying time is 12-24h, and then mixed at a mass ratio of 3:7-7:3, and melt-spun to obtain islands with a fineness of 0.9-5μm and round fibers Type polyphenylene sulfide composite fiber; during the melt spinning process, the extrusion temperature of the screw is 315-325°C, the melting pressure of the screw is 60-120bar, the temperature of the spinning box is 315-325°C, and the pressure of the spinning assembly is less than 60kgf/ cm ² , the spinning speed is 600-1000m/min, and the draft ratio is 3.6-4.3 times.

S2. Preparation of sea-island polyphenylene sulfide composite battery diaphragm: heat-treat the sea-island polyphenylene sulfide composite fiber and cut it short. Relevant data Weigh the sea-island type polyphenylene sulfide composite fiber with a length of 5-8mm in the mass fraction of 0-25% in the shortened sea-island type polyphenylene sulfide composite fiber, and the sea-island type polyphenylene sulfide with a length of 1-2mm The mass fraction of composite fibers is 0-25%, the mass fraction of sea-island polyphenylene sulfide composite fibers with a length of 2-5mm is 50-100%, and the chopped sea-island polyphenylene sulfide composite fibers are combined with flame method and Cut by a high-speed carding machine, the fiber is round, the diameter is 100-1000nm, and the fiber length is 1-3mm Inorganic nanofiber mix, wherein, the mass fraction of the polyphenylene sulfide composite fiber after cutting is 80-95 %, the rest are inorganic nanofibers, and the water level dispersion medium is used for dispersing and beating. Papermaking is carried out at a concentration of 0.8%, and finally hot-pressed with a hot-pressing pressure of 10-20MPa and a hot-pressing temperature of 150-230°C to obtain a sea-island type polyphenylene sulfide composite battery separator.

The inorganic nanofibers in Examples 7-12 are one of glass nanofibers, ceramic nanofibers, quartz nanofibers, and silicon boron nitrogen nanofibers.

Table 5 Process parameters and performance indicators in the preparation of sea-island polyphenylene sulfide composite battery separators in Examples 13-18

For the sea-island type polyphenylene sulfide composite battery separator prepared by the above preparation method, see Table 6 for specific performance indicators.

The performance index of the sea-island type polyphenylene sulfide composite battery diaphragm that table 6 embodiment 13-18 makes

It can be seen from Table 6 that the island-in-the-sea type polyphenylene sulfide composite battery separator prepared in Examples 13-18 has a porosity of 40-70%, a pore diameter of 0.1-1 μm, and a thickness of 10-30 μm. The liquid absorption rate is 250-350%, the electrolyte liquid absorption performance is high, the tensile strength is 15-50MPa, and the mechanical properties are good. In addition, the limiting oxygen index of the sea-island type polyphenylene sulfide composite battery diaphragm obtained in Examples 13-18 is 38-40, and the limiting oxygen index of the existing Celgard commercial film is 18, so the obtained in Examples 13-18 of the present invention The sea-island polyphenylene sulfide composite battery separator has good flame retardancy.

Figure 9a and Figure 9b are scanning electron micrographs of polyphenylene sulfide ultrafine fibers, Figure 9c and Figure 9d are scanning electron micrographs of glass nanofibers, and Figure 9e and Figure 9f are sea-island polyphenylene sulfide prepared in Example 13 The scanning electron microscope image of the composite battery separator, as can be seen from Figure 9, the pore size of the sea-island type polyphenylene sulfide composite battery separator is reduced after adding polyimide nanofibers. The mapping diagram of the sea-island type polyphenylene sulfide composite battery diaphragm prepared in Example 13 is shown in Figure 10, and the thermal stability performance comparison between the sea-island type polyphenylene sulfide composite battery diaphragm and Celgard commercial membrane is shown in Figure 11, Fig. In 11, a-e are the dimensional changes of sea-island polyphenylene sulfide composite battery separators and Celgard commercial membranes at 25°C, 150°C, 175°C, 200°C, and 230°C, Celgard means Celgard commercial membranes, and PSS/GNF means Example 13 The sea-island type polyphenylene sulfide composite battery separator, in which PSS is polyphenylene sulfide, and GNF is glass nanofiber. It can be seen from Figure 11 that the sea-island type polyphenylene sulfide composite battery separator is at , 200°C, and 230°C have little change in size, while the size of Celgard commercial membranes changes significantly at 5°C, 150°C, 175°C, 200°C, and 230°C, so the thermal stability of sea-island polyphenylene sulfide composite battery separators Better than Celgard commercial membrane; the flame retardant performance comparison of island-type polyphenylene sulfide composite battery separator and Celgard commercial membrane is shown in Figure 12, Figure 12a is the Celgard commercial membrane before combustion, and Figure 12b is the Celgard commercial membrane after combustion , Figure 12c is the island-in-sea polyphenylene sulfide composite battery separator before combustion, and Figure 12d is the island-in-sea polyphenylene sulfide composite battery separator after combustion. The performance is better than that of Celgard commercial film, and the performance of the sea-island type polyphenylene sulfide composite battery separator prepared in Examples 14-18 is similar to that of the sea-island type polyphenylene sulfide composite battery separator prepared in Example 13.

Claims (5)

1. A preparation method of a sea-island polyphenylene sulfide composite battery diaphragm is characterized by comprising the following steps:

s1, preparing sea-island polyphenylene sulfide composite fibers: the preparation method comprises the following steps of drying and mixing polyphenylene sulfide and alkali-soluble polyester, and carrying out melt spinning after mixing to obtain the sea-island type polyphenylene sulfide composite fiber; the prepared sea-island polyphenylene sulfide composite fiber is circular; the melt index of the polyphenylene sulfide is 50-500g/10min, the melt index of the alkali-soluble polyester is 10-50g/10min, the drying temperature of the polyphenylene sulfide and the alkali-soluble polyester is 80-160 ℃, and the drying time is 12-24h; the mass ratio of the polyphenylene sulfide to the alkali-soluble polyester is 3;

s2, preparing the sea-island type polyphenylene sulfide composite battery diaphragm: cutting the sea-island polyphenylene sulfide composite fiber after heat treatment, mixing with the nanofiber, and obtaining the sea-island polyphenylene sulfide composite battery diaphragm through dispersion pulping, defibering, papermaking and hot pressing; wherein the mass fraction of the chopped polyphenylene sulfide composite fiber in the mixture of the nano fiber and the chopped polyphenylene sulfide composite fiber is 80-95%; the mass fraction of the sea-island polyphenylene sulfide composite fiber with the length of 5-8mm in the cut sea-island polyphenylene sulfide composite fiber is 0-25%, the mass fraction of the sea-island polyphenylene sulfide composite fiber with the length of 1-2mm is 0-25%, and the mass fraction of the sea-island polyphenylene sulfide composite fiber with the length of 2-5mm is 50-100%; the heat treatment temperature is 80-150 deg.C, and the heat treatment time is 10-60min.

2. The method for preparing a sea-island type polyphenylene sulfide composite battery separator according to claim 1, wherein the nanofibers in step S2 are aromatic nanofibers, the aromatic nanofibers are one of polyimide nanofibers, polysulfonamide nanofibers, aramid nanofibers, and polyetheretherketone nanofibers, the aromatic nanofibers are cut by electrospinning and a high-speed carding machine, the fibers are round, the diameter is 100 to 1000nm, the fiber length is 1 to 3mm, the mass fraction of the polyphenylene sulfide composite fibers cut from a mixture of the aromatic nanofibers and the cut polyphenylene sulfide composite fibers is 80 to 95%, the rest is the aromatic nanofibers, the dispersion medium is water, the beating concentration is 3 to 5 wt, the rotation speed of a stirring impeller in the beating process is 3000 to 3500rad/min, the defibering time is 10 to 15min, the web concentration in the paper making process is 0.03 to 0.8%, the hot-pressing pressure in the hot-pressing process is 10 to 20MPa, and the hot-pressing temperature is 150 to 230 ℃.

3. The method of claim 1, wherein the nanofibers are formed by cutting the nanofibers into a circular shape having a diameter of 100-1000nm and a length of 1-3mm by a dissolution method and a high speed carding machine, the diameter of the fibers is 100-1000nm, the mass fraction of the chopped polyphenylene sulfide composite fibers in the mixture of the natural nanofibers and the chopped polyphenylene sulfide composite fibers is 80-95%, the remainder is the natural nanofibers, the dispersion medium is water, the beating concentration is 3-5 wt, the rotation speed of the impeller is 3000-3500rad/min during the beating, the beating time is 10-15min, the web concentration is 0.03-0.8% during the paper making, the hot pressing pressure is 10-20MPa during the hot pressing, and the hot pressing temperature is 150-230 ℃.

4. The method of claim 1, wherein the nanofibers in step S2 are made of inorganic nanofibers selected from the group consisting of glass nanofibers, ceramic nanofibers, quartz nanofibers, and silicon boron nitrogen nanofibers, the inorganic nanofibers are cut by a flame method and a high speed carding machine, the fibers are round, the diameter is 100 to 1000nm, the fiber length is 1 to 3mm, the mass fraction of the polyphenylene sulfide composite fibers cut from a mixture of the inorganic nanofibers and the cut polyphenylene sulfide composite fibers is 80 to 95%, the balance is the inorganic nanofibers, the dispersion medium is water, the beating concentration is 3 to 5 wt%, the rotational speed of the impeller during the beating process is 3000 to 3500rad/min, the beating time is 10 to 15min, the web concentration during the paper making process is 0.03 to 0.8%, the hot pressing pressure during the hot pressing process is 10 to 20MPa, and the hot pressing temperature is 150 to 230 ℃.

5. The sea-island type polyphenylene sulfide composite battery separator prepared by the method for preparing a sea-island type polyphenylene sulfide composite battery separator according to any one of claims 1 to 4, wherein the sea-island type polyphenylene sulfide composite battery separator is prepared with a porosity of 40 to 70%, a pore diameter of 0.1 to 1 μm, a thickness of 10 to 30 μm, an electrolyte imbibition rate of 250 to 350%, a tensile strength of 15 to 50MPa, and a limiting oxygen index of 38 to 40.

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